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* printk: Update @console_may_schedule in console_trylock_spinning()John Ogness2024-04-031-0/+6
| | | | | | | | | | | | | | | | | | [ Upstream commit 8076972468584d4a21dab9aa50e388b3ea9ad8c7 ] console_trylock_spinning() may takeover the console lock from a schedulable context. Update @console_may_schedule to make sure it reflects a trylock acquire. Reported-by: Mukesh Ojha <quic_mojha@quicinc.com> Closes: https://lore.kernel.org/lkml/20240222090538.23017-1-quic_mojha@quicinc.com Fixes: dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes") Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Mukesh Ojha <quic_mojha@quicinc.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/875xybmo2z.fsf@jogness.linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
* serial: Lock console when calling into driver before registrationPeter Collingbourne2024-04-031-3/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 801410b26a0e8b8a16f7915b2b55c9528b69ca87 ] During the handoff from earlycon to the real console driver, we have two separate drivers operating on the same device concurrently. In the case of the 8250 driver these concurrent accesses cause problems due to the driver's use of banked registers, controlled by LCR.DLAB. It is possible for the setup(), config_port(), pm() and set_mctrl() callbacks to set DLAB, which can cause the earlycon code that intends to access TX to instead access DLL, leading to missed output and corruption on the serial line due to unintended modifications to the baud rate. In particular, for setup() we have: univ8250_console_setup() -> serial8250_console_setup() -> uart_set_options() -> serial8250_set_termios() -> serial8250_do_set_termios() -> serial8250_do_set_divisor() For config_port() we have: serial8250_config_port() -> autoconfig() For pm() we have: serial8250_pm() -> serial8250_do_pm() -> serial8250_set_sleep() For set_mctrl() we have (for some devices): serial8250_set_mctrl() -> omap8250_set_mctrl() -> __omap8250_set_mctrl() To avoid such problems, let's make it so that the console is locked during pre-registration calls to these callbacks, which will prevent the earlycon driver from running concurrently. Remove the partial solution to this problem in the 8250 driver that locked the console only during autoconfig_irq(), as this would result in a deadlock with the new approach. The console continues to be locked during autoconfig_irq() because it can only be called through uart_configure_port(). Although this patch introduces more locking than strictly necessary (and in particular it also locks during the call to rs485_config() which is not affected by this issue as far as I can tell), it follows the principle that it is the responsibility of the generic console code to manage the earlycon handoff by ensuring that earlycon and real console driver code cannot run concurrently, and not the individual drivers. Signed-off-by: Peter Collingbourne <pcc@google.com> Reviewed-by: John Ogness <john.ogness@linutronix.de> Link: https://linux-review.googlesource.com/id/I7cf8124dcebf8618e6b2ee543fa5b25532de55d8 Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Cc: stable@vger.kernel.org Link: https://lore.kernel.org/r/20240304214350.501253-1-pcc@google.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
* printk: Use prb_first_seq() as base for 32bit seq macrosJohn Ogness2024-03-262-5/+5
| | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 90ad525c2d9a8a6591ab822234a94b82871ef8e0 ] Note: This change only applies to 32bit architectures. On 64bit architectures the macros are NOPs. Currently prb_next_seq() is used as the base for the 32bit seq macros __u64seq_to_ulseq() and __ulseq_to_u64seq(). However, in a follow-up commit, prb_next_seq() will need to make use of the 32bit seq macros. Use prb_first_seq() as the base for the 32bit seq macros instead because it is guaranteed to return 64bit sequence numbers without relying on any 32bit seq macros. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20240207134103.1357162-4-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
* printk: Adjust mapping for 32bit seq macrosSebastian Andrzej Siewior2024-03-261-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 418ec1961c07d84293cc3cd54d67b90bbeba7feb ] Note: This change only applies to 32bit architectures. On 64bit architectures the macros are NOPs. __ulseq_to_u64seq() computes the upper 32 bits of the passed argument value (@ulseq). The upper bits are derived from a base value (@rb_next_seq) in a way that assumes @ulseq represents a 64bit number that is less than or equal to @rb_next_seq. Until now this mapping has been correct for all call sites. However, in a follow-up commit, values of @ulseq will be passed in that are higher than the base value. This requires a change to how the 32bit value is mapped to a 64bit sequence number. Rather than mapping @ulseq such that the base value is the end of a 32bit block, map @ulseq such that the base value is in the middle of a 32bit block. This allows supporting 31 bits before and after the base value, which is deemed acceptable for the console sequence number during runtime. Here is an example to illustrate the previous and new mappings. For a base value (@rb_next_seq) of 2 2000 0000... Before this change the range of possible return values was: 1 2000 0001 to 2 2000 0000 __ulseq_to_u64seq(1fff ffff) => 2 1fff ffff __ulseq_to_u64seq(2000 0000) => 2 2000 0000 __ulseq_to_u64seq(2000 0001) => 1 2000 0001 __ulseq_to_u64seq(9fff ffff) => 1 9fff ffff __ulseq_to_u64seq(a000 0000) => 1 a000 0000 __ulseq_to_u64seq(a000 0001) => 1 a000 0001 After this change the range of possible return values are: 1 a000 0001 to 2 a000 0000 __ulseq_to_u64seq(1fff ffff) => 2 1fff ffff __ulseq_to_u64seq(2000 0000) => 2 2000 0000 __ulseq_to_u64seq(2000 0001) => 2 2000 0001 __ulseq_to_u64seq(9fff ffff) => 2 9fff ffff __ulseq_to_u64seq(a000 0000) => 2 a000 0000 __ulseq_to_u64seq(a000 0001) => 1 a000 0001 [ john.ogness: Rewrite commit message. ] Reported-by: Francesco Dolcini <francesco@dolcini.it> Reported-by: kernel test robot <oliver.sang@intel.com> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20240207134103.1357162-3-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
* printk: Disable passing console lock owner completely during panic()Petr Mladek2024-03-261-0/+29
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit d04d5882cd678b898a9d7c5aee6afbe9e6e77fcd ] The commit d51507098ff91 ("printk: disable optimistic spin during panic") added checks to avoid becoming a console waiter if a panic is in progress. However, the transition to panic can occur while there is already a waiter. The current owner should not pass the lock to the waiter because it might get stopped or blocked anytime. Also the panic context might pass the console lock owner to an already stopped waiter by mistake. It might happen when console_flush_on_panic() ignores the current lock owner, for example: CPU0 CPU1 ---- ---- console_lock_spinning_enable() console_trylock_spinning() [CPU1 now console waiter] NMI: panic() panic_other_cpus_shutdown() [stopped as console waiter] console_flush_on_panic() console_lock_spinning_enable() [print 1 record] console_lock_spinning_disable_and_check() [handover to stopped CPU1] This results in panic() not flushing the panic messages. Fix these problems by disabling all spinning operations completely during panic(). Another advantage is that it prevents possible deadlocks caused by "console_owner_lock". The panic() context does not need to take it any longer. The lockless checks are safe because the functions become NOPs when they see the panic in progress. All operations manipulating the state are still synchronized by the lock even when non-panic CPUs would notice the panic synchronously. The current owner might stay spinning. But non-panic() CPUs would get stopped anyway and the panic context will never start spinning. Fixes: dbdda842fe96 ("printk: Add console owner and waiter logic to load balance console writes") Signed-off-by: John Ogness <john.ogness@linutronix.de> Link: https://lore.kernel.org/r/20240207134103.1357162-12-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
* printk: ringbuffer: Skip non-finalized records in panicJohn Ogness2024-03-261-2/+26
| | | | | | | | | | | | | | | | | | | | | | [ Upstream commit b1c4c67a5e90db8fbdb5b5504fe16e17b564cca8 ] Normally a reader will stop once reaching a non-finalized record. However, when a panic happens, writers from other CPUs (or an interrupted context on the panic CPU) may have been writing a record and were unable to finalize it. The panic CPU will reserve/commit/finalize its panic records, but these will be located after the non-finalized records. This results in panic() not flushing the panic messages. Extend _prb_read_valid() to skip over non-finalized records if on the panic CPU. Fixes: 896fbe20b4e2 ("printk: use the lockless ringbuffer") Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20240207134103.1357162-11-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
* printk: ringbuffer: Cleanup reader terminologyJohn Ogness2024-03-261-7/+9
| | | | | | | | | | | | | | | | | | | | [ Upstream commit 584528d621459d1a5c31da7a591218ad3bb96d6c ] With the lockless ringbuffer, it is allowed that multiple CPUs/contexts write simultaneously into the buffer. This creates an ambiguity as some writers will finalize sooner. The documentation for the prb_read functions is not clear as it refers to "not yet written" and "no data available". Clarify the return values and language to be in terms of the reader: records available for reading. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20240207134103.1357162-9-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Stable-dep-of: b1c4c67a5e90 ("printk: ringbuffer: Skip non-finalized records in panic") Signed-off-by: Sasha Levin <sashal@kernel.org>
* printk: Add this_cpu_in_panic()John Ogness2024-03-262-20/+24
| | | | | | | | | | | | | | | | | [ Upstream commit 36652d0f3bf34899e82d31a5fa9e2bdd02fd6381 ] There is already panic_in_progress() and other_cpu_in_panic(), but checking if the current CPU is the panic CPU must still be open coded. Add this_cpu_in_panic() to complete the set. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20240207134103.1357162-8-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Stable-dep-of: b1c4c67a5e90 ("printk: ringbuffer: Skip non-finalized records in panic") Signed-off-by: Sasha Levin <sashal@kernel.org>
* printk: Wait for all reserved records with pr_flush()John Ogness2024-03-263-1/+107
| | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit ac7d7844c64d15603daa3e905a311ddcfbb4bc91 ] Currently pr_flush() will only wait for records that were available to readers at the time of the call (using prb_next_seq()). But there may be more records (non-finalized) that have following finalized records. pr_flush() should wait for these to print as well. Particularly because any trailing finalized records may be the messages that the calling context wants to ensure are printed. Add a new ringbuffer function prb_next_reserve_seq() to return the sequence number following the most recently reserved record. This guarantees that pr_flush() will wait until all current printk() messages (completed or in progress) have been printed. Fixes: 3b604ca81202 ("printk: add pr_flush()") Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20240207134103.1357162-10-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
* printk: ringbuffer: Do not skip non-finalized records with prb_next_seq()John Ogness2024-03-262-41/+127
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 5f72e52ba959e50680b8d83599da1368cd7a6ee2 ] Commit f244b4dc53e5 ("printk: ringbuffer: Improve prb_next_seq() performance") introduced an optimization for prb_next_seq() by using best-effort to track recently finalized records. However, the order of finalization does not necessarily match the order of the records. The optimization changed prb_next_seq() to return inconsistent results, possibly yielding sequence numbers that are not available to readers because they are preceded by non-finalized records or they are not yet visible to the reader CPU. Rather than simply best-effort tracking recently finalized records, force the committing writer to read records and increment the last "contiguous block" of finalized records. In order to do this, the sequence number instead of ID must be stored because ID's cannot be directly compared. A new memory barrier pair is introduced to guarantee that a reader can always read the records up until the sequence number returned by prb_next_seq() (unless the records have since been overwritten in the ringbuffer). This restores the original functionality of prb_next_seq() while also keeping the optimization. For 32bit systems, only the lower 32 bits of the sequence number are stored. When reading the value, it is expanded to the full 64bit sequence number using the 32bit seq macros, which fold in the value returned by prb_first_seq(). Fixes: f244b4dc53e5 ("printk: ringbuffer: Improve prb_next_seq() performance") Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20240207134103.1357162-5-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Sasha Levin <sashal@kernel.org>
* printk: nbcon: Relocate 32bit seq macrosJohn Ogness2024-03-262-37/+37
| | | | | | | | | | | | | | | | | | | | | | | | | | [ Upstream commit 5b73e706f00f3553e1a4efbb31951ce9fe18f2dc ] The macros __seq_to_nbcon_seq() and __nbcon_seq_to_seq() are used to provide support for atomic handling of sequence numbers on 32bit systems. Until now this was only used by nbcon.c, which is why they were located in nbcon.c and include nbcon in the name. In a follow-up commit this functionality is also needed by printk_ringbuffer. Rather than duplicating the functionality, relocate the macros to printk_ringbuffer.h. Also, since the macros will be no longer nbcon-specific, rename them to __u64seq_to_ulseq() and __ulseq_to_u64seq(). This does not result in any functional change. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20240207134103.1357162-2-john.ogness@linutronix.de Signed-off-by: Petr Mladek <pmladek@suse.com> Stable-dep-of: 5f72e52ba959 ("printk: ringbuffer: Do not skip non-finalized records with prb_next_seq()") Signed-off-by: Sasha Levin <sashal@kernel.org>
* Merge tag 'tty-6.7-rc1' of ↵Linus Torvalds2023-11-031-2/+10
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty Pull tty and serial updates from Greg KH: "Here is the big set of tty/serial driver changes for 6.7-rc1. Included in here are: - console/vgacon cleanups and removals from Arnd - tty core and n_tty cleanups from Jiri - lots of 8250 driver updates and cleanups - sc16is7xx serial driver updates - dt binding updates - first set of port lock wrapers from Thomas for the printk fixes coming in future releases - other small serial and tty core cleanups and updates All of these have been in linux-next for a while with no reported issues" * tag 'tty-6.7-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (193 commits) serdev: Replace custom code with device_match_acpi_handle() serdev: Simplify devm_serdev_device_open() function serdev: Make use of device_set_node() tty: n_gsm: add copyright Siemens Mobility GmbH tty: n_gsm: fix race condition in status line change on dead connections serial: core: Fix runtime PM handling for pending tx vgacon: fix mips/sibyte build regression dt-bindings: serial: drop unsupported samsung bindings tty: serial: samsung: drop earlycon support for unsupported platforms tty: 8250: Add note for PX-835 tty: 8250: Fix IS-200 PCI ID comment tty: 8250: Add Brainboxes Oxford Semiconductor-based quirks tty: 8250: Add support for Intashield IX cards tty: 8250: Add support for additional Brainboxes PX cards tty: 8250: Fix up PX-803/PX-857 tty: 8250: Fix port count of PX-257 tty: 8250: Add support for Intashield IS-100 tty: 8250: Add support for Brainboxes UP cards tty: 8250: Add support for additional Brainboxes UC cards tty: 8250: Remove UC-257 and UC-431 ...
| * printk: Constify name for add_preferred_console()Tony Lindgren2023-10-171-2/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | While adding a preferred console handling for serial_core for serial port hardware based device addressing, Jiri suggested we constify name for add_preferred_console(). The name gets copied anyways. This allows serial core to add a preferred console using serial drv->dev_name without copying it. Note that constifying options causes changes all over the place because of struct console for match(). Suggested-by: Jiri Slaby <jirislaby@kernel.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Tony Lindgren <tony@atomide.com> Link: https://lore.kernel.org/r/20231012064300.50221-2-tony@atomide.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
| * printk: Check valid console index for preferred consoleTony Lindgren2023-10-171-2/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Let's check for valid console index values for preferred console to avoid bogus console index numbers from kernel command line. Let's also return an error for negative index numbers for the preferred console. Unlike for device drivers, a negative index is not valid for the preferred console. Let's also constify idx while at it. Signed-off-by: Tony Lindgren <tony@atomide.com> Link: https://lore.kernel.org/r/20231012064300.50221-1-tony@atomide.com Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* | Merge branch 'rework/nbcon-base' into for-linusPetr Mladek2023-11-024-50/+1134
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| * | printk: fix illegal pbufs access for !CONFIG_PRINTKJohn Ogness2023-09-211-26/+18
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When CONFIG_PRINTK is not set, PRINTK_MESSAGE_MAX is 0. This leads to a zero-sized array @outbuf in @printk_shared_pbufs. In console_flush_all() a pointer to the first element of the array is assigned with: char *outbuf = &printk_shared_pbufs.outbuf[0]; For !CONFIG_PRINTK this leads to a compiler warning: warning: array subscript 0 is outside array bounds of 'char[0]' [-Warray-bounds] This is not really dangerous because printk_get_next_message() always returns false for !CONFIG_PRINTK, which leads to @outbuf never being used. However, it makes no sense to even compile these functions for !CONFIG_PRINTK. Extend the existing '#ifdef CONFIG_PRINTK' block to contain the formatting and emitting functions since these have no purpose in !CONFIG_PRINTK. This also allows removing several more !CONFIG_PRINTK dummies as well as moving @suppress_panic_printk into a CONFIG_PRINTK block. Reported-by: kernel test robot <lkp@intel.com> Closes: https://lore.kernel.org/oe-kbuild-all/202309201724.M9BMAQIh-lkp@intel.com/ Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230920155238.670439-1-john.ogness@linutronix.de
| * | printk: nbcon: Allow drivers to mark unsafe regions and check stateThomas Gleixner2023-09-181-0/+75
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | For the write_atomic callback, the console driver may have unsafe regions that need to be appropriately marked. Provide functions that accept the nbcon_write_context struct to allow for the driver to enter and exit unsafe regions. Also provide a function for drivers to check if they are still the owner of the console. Co-developed-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230916192007.608398-9-john.ogness@linutronix.de
| * | printk: nbcon: Add emit function and callback function for atomic printingThomas Gleixner2023-09-183-8/+113
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Implement an emit function for nbcon consoles to output printk messages. It utilizes the lockless printk_get_next_message() and console_prepend_dropped() functions to retrieve/build the output message. The emit function includes the required safety points to check for handover/takeover and calls a new write_atomic callback of the console driver to output the message. It also includes proper handling for updating the nbcon console sequence number. A new nbcon_write_context struct is introduced. This is provided to the write_atomic callback and includes only the information necessary for performing atomic writes. Co-developed-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230916192007.608398-8-john.ogness@linutronix.de
| * | printk: nbcon: Add sequence handlingThomas Gleixner2023-09-183-7/+132
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add an atomic_long_t field @nbcon_seq to the console struct to store the sequence number for nbcon consoles. For nbcon consoles this will be used instead of the non-atomic @seq field. The new field allows for safe atomic sequence number updates without requiring any locking. On 64bit systems the new field stores the full sequence number. On 32bit systems the new field stores the lower 32 bits of the sequence number, which are expanded to 64bit as needed by folding the values based on the sequence numbers available in the ringbuffer. For 32bit systems, having a 32bit representation in the console is sufficient. If a console ever gets more than 2^31 records behind the ringbuffer then this is the least of the problems. Co-developed-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230916192007.608398-7-john.ogness@linutronix.de
| * | printk: nbcon: Add ownership state functionsThomas Gleixner2023-09-181-1/+122
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Provide functions that are related to the safe handover mechanism and allow console drivers to dynamically specify unsafe regions: - nbcon_context_can_proceed() Invoked by a console owner to check whether a handover request is pending or whether the console has been taken over by another context. If a handover request is pending, this function will also perform the handover, thus cancelling its own ownership. - nbcon_context_enter_unsafe()/nbcon_context_exit_unsafe() Invoked by a console owner to denote that the driver is about to enter or leave a critical region where a take over is unsafe. The exit variant is the point where the current owner releases the lock for a higher priority context which asked for the friendly handover. The unsafe state is stored in the console state and allows a new context to make informed decisions whether to attempt a takeover of such a console. The unsafe state is also available to the driver so that it can make informed decisions about the required actions and possibly take a special emergency path. Co-developed-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230916192007.608398-6-john.ogness@linutronix.de
| * | printk: nbcon: Add buffer managementThomas Gleixner2023-09-183-15/+92
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In case of hostile takeovers it must be ensured that the previous owner cannot scribble over the output buffer of the emergency/panic context. This is achieved by: - Adding a global output buffer instance for the panic context. This is the only situation where hostile takeovers can occur and there is always at most 1 panic context. - Allocating an output buffer per non-boot console upon console registration. This buffer is used by the console owner when not in panic context. (For boot consoles, the existing shared global legacy output buffer is used instead. Boot console printing will be synchronized with legacy console printing.) - Choosing the appropriate buffer is handled in the acquire/release functions. Co-developed-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230916192007.608398-5-john.ogness@linutronix.de
| * | printk: Make static printk buffers available to nbconJohn Ogness2023-09-182-4/+11
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The nbcon boot consoles also need printk buffers that are available very early. Since the nbcon boot consoles will also be serialized by the console_lock, they can use the same static printk buffers that the legacy consoles are using. Make the legacy static printk buffers available outside of printk.c so they can be used by nbcon.c. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230916192007.608398-4-john.ogness@linutronix.de
| * | printk: nbcon: Add acquire/release logicThomas Gleixner2023-09-181-0/+497
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Add per console acquire/release functionality. The state of the console is maintained in the "nbcon_state" atomic variable. The console is locked when: - The 'prio' field contains the priority of the context that owns the console. Only higher priority contexts are allowed to take over the lock. A value of 0 (NBCON_PRIO_NONE) means the console is not locked. - The 'cpu' field denotes on which CPU the console is locked. It is used to prevent busy waiting on the same CPU. Also it informs the lock owner that it has lost the lock in a more complex scenario when the lock was taken over by a higher priority context, released, and taken on another CPU with the same priority as the interrupted owner. The acquire mechanism uses a few more fields: - The 'req_prio' field is used by the handover approach to make the current owner aware that there is a context with a higher priority waiting for the friendly handover. - The 'unsafe' field allows to take over the console in a safe way in the middle of emitting a message. The field is set only when accessing some shared resources or when the console device is manipulated. It can be cleared, for example, after emitting one character when the console device is in a consistent state. - The 'unsafe_takeover' field is set when a hostile takeover took the console in an unsafe state. The console will stay in the unsafe state until re-initialized. The acquire mechanism uses three approaches: 1) Direct acquire when the console is not owned or is owned by a lower priority context and is in a safe state. 2) Friendly handover mechanism uses a request/grant handshake. It is used when the current owner has lower priority and the console is in an unsafe state. The requesting context: a) Sets its priority into the 'req_prio' field. b) Waits (with a timeout) for the owning context to unlock the console. c) Takes the lock and clears the 'req_prio' field. The owning context: a) Observes the 'req_prio' field set on exit from the unsafe console state. b) Gives up console ownership by clearing the 'prio' field. 3) Unsafe hostile takeover allows to take over the lock even when the console is an unsafe state. It is used only in panic() by the final attempt to flush consoles in a try and hope mode. Note that separate record buffers are used in panic(). As a result, the messages can be read and formatted without any risk even after using the hostile takeover in unsafe state. The release function simply clears the 'prio' field. All operations on @console::nbcon_state are atomic cmpxchg based to handle concurrency. The acquire/release functions implement only minimal policies: - Preference for higher priority contexts. - Protection of the panic CPU. All other policy decisions must be made at the call sites: - What is marked as an unsafe section. - Whether to spin-wait if there is already an owner and the console is in an unsafe state. - Whether to attempt an unsafe hostile takeover. The design allows to implement the well known: acquire() output_one_printk_record() release() The output of one printk record might be interrupted with a higher priority context. The new owner is supposed to reprint the entire interrupted record from scratch. Co-developed-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230916192007.608398-3-john.ogness@linutronix.de
| * | printk: Add non-BKL (nbcon) console basic infrastructureThomas Gleixner2023-09-184-4/+89
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The current console/printk subsystem is protected by a Big Kernel Lock, (aka console_lock) which has ill defined semantics and is more or less stateless. This puts severe limitations on the console subsystem and makes forced takeover and output in emergency and panic situations a fragile endeavour that is based on try and pray. The goal of non-BKL (nbcon) consoles is to break out of the console lock jail and to provide a new infrastructure that avoids the pitfalls and also allows console drivers to be gradually converted over. The proposed infrastructure aims for the following properties: - Per console locking instead of global locking - Per console state that allows to make informed decisions - Stateful handover and takeover As a first step, state is added to struct console. The per console state is an atomic_t using a 32bit bit field. Reserve state bits, which will be populated later in the series. Wire it up into the console register/unregister functionality. It was decided to use a bitfield because using a plain u32 with mask/shift operations resulted in uncomprehensible code. Co-developed-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: John Ogness <john.ogness@linutronix.de> Signed-off-by: Thomas Gleixner (Intel) <tglx@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230916192007.608398-2-john.ogness@linutronix.de
* | | Merge branch 'rework/misc-cleanups' into for-linusPetr Mladek2023-11-021-13/+13
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| * | | printk: Reduce pr_flush() pooling timePetr Mladek2023-10-111-13/+13
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | pr_flush() does not guarantee that all messages would really get flushed to the console. The best it could do is to wait with a given timeout.[*] The current interval 100ms for checking the progress might seem too long in some situations. For example, such delays are not appreciated during suspend and resume especially when the consoles have been flushed "long" time before the check. On the other hand, the sleeping wait might be useful in other situations. Especially, it would allow flushing the messages using printk kthreads on the same CPU[*]. Use msleep(1) as a compromise. Also measure the time using jiffies. msleep() does not guarantee precise wakeup after the given delay. It might be much longer, especially for times < 20s. See Documentation/timers/timers-howto.rst for more details. Note that msecs_to_jiffies() already translates a negative value into an infinite timeout. [*] console_unlock() does not guarantee flushing the consoles since the commit dbdda842fe96f893 ("printk: Add console owner and waiter logic to load balance console writes"). It would be possible to guarantee it another way. For example, the spinning might be enabled only when the console_lock has been taken via console_trylock(). But the load balancing is helpful. And more importantly, the flush with a timeout has been added as a preparation step for introducing printk kthreads. Signed-off-by: Petr Mladek <pmladek@suse.com> Reviewed-by: John Ogness <john.ogness@linutronix.de> Link: https://lore.kernel.org/r/20231006082151.6969-3-pmladek@suse.com
* | | | Merge branch 'for-6.7' into for-linusPetr Mladek2023-11-021-2/+0
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| * | | printk: printk: Remove unnecessary statements＇len = 0;＇Li kunyu2023-10-241-2/+0
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | In the following two functions, len has already been assigned a value of 0 when defining the variable, so remove 'len=0;'. Signed-off-by: Li kunyu <kunyu@nfschina.com> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20231023062359.130633-1-kunyu@nfschina.com
* | | | Merge branch 'rework/misc-cleanups' into for-linusPetr Mladek2023-10-111-1/+7
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| * | printk: flush consoles before checking progressJohn Ogness2023-10-091-1/+7
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Commit 9e70a5e109a4 ("printk: Add per-console suspended state") removed console lock usage during resume and replaced it with the clearly defined console_list_lock and srcu mechanisms. However, the console lock usage had an important side-effect of flushing the consoles. After its removal, consoles were no longer flushed before checking their progress. Add the console_lock/console_unlock dance to the beginning of __pr_flush() to actually flush the consoles before checking their progress. Also add comments to clarify this additional usage of the console lock. Note that console_unlock() does not guarantee flushing all messages since the commit dbdda842fe96f89 ("printk: Add console owner and waiter logic to load balance console writes"). Reported-by: Todd Brandt <todd.e.brandt@intel.com> Closes: https://bugzilla.kernel.org/show_bug.cgi?id=217955 Fixes: 9e70a5e109a4 ("printk: Add per-console suspended state") Co-developed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Signed-off-by: John Ogness <john.ogness@linutronix.de> Link: https://lore.kernel.org/r/20231006082151.6969-2-pmladek@suse.com
* | | Revert "printk: export symbols for debug modules"Christoph Hellwig2023-09-071-2/+0
| |/ |/| | | | | | | | | | | | | | | | | | | | | This reverts commit 3e00123a13d824d63072b1824c9da59cd78356d9. No, we never export random symbols for out of tree modules. Signed-off-by: Christoph Hellwig <hch@lst.de> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Acked-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230905081902.321778-1-hch@lst.de
* | Merge tag 'printk-for-6.6' of ↵Linus Torvalds2023-09-044-74/+154
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux Pull printk updates from Petr Mladek: - Do not try to get the console lock when it is not need or useful in panic() - Replace the global console_suspended state by a per-console flag - Export symbols needed for dumping the raw printk buffer in panic() - Fix documentation of printf formats for integer types - Moved Sergey Senozhatsky to the reviewer role - Misc cleanups * tag 'printk-for-6.6' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: printk: export symbols for debug modules lib: test_scanf: Add explicit type cast to result initialization in test_number_prefix() printk: ringbuffer: Fix truncating buffer size min_t cast printk: Rename abandon_console_lock_in_panic() to other_cpu_in_panic() printk: Add per-console suspended state printk: Consolidate console deferred printing printk: Do not take console lock for console_flush_on_panic() printk: Keep non-panic-CPUs out of console lock printk: Reduce console_unblank() usage in unsafe scenarios kdb: Do not assume write() callback available docs: printk-formats: Treat char as always unsigned docs: printk-formats: Fix hex printing of signed values MAINTAINERS: adjust printk/vsprintf entries
| * | Merge branch 'rework/misc-cleanups' into for-linusPetr Mladek2023-09-043-73/+151
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| | * printk: Rename abandon_console_lock_in_panic() to other_cpu_in_panic()John Ogness2023-07-202-7/+10
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently abandon_console_lock_in_panic() is only used to determine if the current CPU should immediately release the console lock because another CPU is in panic. However, later this function will be used by the CPU to immediately release other resources in this situation. Rename the function to other_cpu_in_panic(), which is a better description and does not assume it is related to the console lock. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230717194607.145135-8-john.ogness@linutronix.de
| | * printk: Add per-console suspended stateJohn Ogness2023-07-201-30/+44
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently the global @console_suspended is used to determine if consoles are in a suspended state. Its primary purpose is to allow usage of the console_lock when suspended without causing console printing. It is synchronized by the console_lock. Rather than relying on the console_lock to determine suspended state, make it an official per-console state that is set within console->flags. This allows the state to be queried via SRCU. Remove @console_suspended. Console printing will still be avoided when suspended because console_is_usable() returns false when the new suspended flag is set for that console. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230717194607.145135-7-john.ogness@linutronix.de
| | * printk: Consolidate console deferred printingJohn Ogness2023-07-202-14/+30
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Printing to consoles can be deferred for several reasons: - explicitly with printk_deferred() - printk() in NMI context - recursive printk() calls The current implementation is not consistent. For printk_deferred(), irq work is scheduled twice. For NMI und recursive, panic CPU suppression and caller delays are not properly enforced. Correct these inconsistencies by consolidating the deferred printing code so that vprintk_deferred() is the top-level function for deferred printing and vprintk_emit() will perform whichever irq_work queueing is appropriate. Also add kerneldoc for wake_up_klogd() and defer_console_output() to clarify their differences and appropriate usage. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230717194607.145135-6-john.ogness@linutronix.de
| | * printk: Do not take console lock for console_flush_on_panic()John Ogness2023-07-201-9/+19
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently console_flush_on_panic() will attempt to acquire the console lock when flushing the buffer on panic. If it fails to acquire the lock, it continues anyway because this is the last chance to get any pending records printed. The reason why the console lock was attempted at all was to prevent any other CPUs from acquiring the console lock for printing while the panic CPU was printing. But as of the previous commit, non-panic CPUs will no longer attempt to acquire the console lock in a panic situation. Therefore it is no longer strictly necessary for a panic CPU to acquire the console lock. Avoiding taking the console lock when flushing in panic has the additional benefit of avoiding possible deadlocks due to semaphore usage in NMI context (semaphores are not NMI-safe) and avoiding possible deadlocks if another CPU accesses the semaphore and is stopped while holding one of the semaphore's internal spinlocks. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230717194607.145135-5-john.ogness@linutronix.de
| | * printk: Keep non-panic-CPUs out of console lockJohn Ogness2023-07-201-19/+26
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When in a panic situation, non-panic CPUs should avoid holding the console lock so as not to contend with the panic CPU. This is already implemented with abandon_console_lock_in_panic(), which is checked after each printed line. However, non-panic CPUs should also avoid trying to acquire the console lock during a panic. Modify console_trylock() to fail and console_lock() to block() when called from a non-panic CPU during a panic. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230717194607.145135-4-john.ogness@linutronix.de
| | * printk: Reduce console_unblank() usage in unsafe scenariosJohn Ogness2023-07-201-0/+28
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | A semaphore is not NMI-safe, even when using down_trylock(). Both down_trylock() and up() are using internal spinlocks and up() might even call wake_up_process(). In the panic() code path it gets even worse because the internal spinlocks of the semaphore may have been taken by a CPU that has been stopped. To reduce the risk of deadlocks caused by the console semaphore in the panic path, make the following changes: - First check if any consoles have implemented the unblank() callback. If not, then there is no reason to take the console semaphore anyway. (This check is also useful for the non-panic path since the locking/unlocking of the console lock can be quite expensive due to console printing.) - If the panic path is in NMI context, bail out without attempting to take the console semaphore or calling any unblank() callbacks. Bailing out is acceptable because console_unblank() would already bail out if the console semaphore is contended. The alternative of ignoring the console semaphore and calling the unblank() callbacks anyway is a bad idea because these callbacks are also not NMI-safe. If consoles with unblank() callbacks exist and console_unblank() is called from a non-NMI panic context, it will still attempt a down_trylock(). This could still result in a deadlock if one of the stopped CPUs is holding the semaphore internal spinlock. But this is a risk that the kernel has been (and continues to be) willing to take. Signed-off-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230717194607.145135-3-john.ogness@linutronix.de
| * | printk: export symbols for debug modulesEnlin Mu2023-08-161-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | the module is out-of-tree, it saves kernel logs when panic Signed-off-by: Enlin Mu <enlin.mu@unisoc.com> Acked-by: Petr Mladek <pmladek@suse.com> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230815020711.2604939-1-yunlong.xing@unisoc.com
| * | printk: ringbuffer: Fix truncating buffer size min_t castKees Cook2023-08-141-1/+1
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | If an output buffer size exceeded U16_MAX, the min_t(u16, ...) cast in copy_data() was causing writes to truncate. This manifested as output bytes being skipped, seen as %NUL bytes in pstore dumps when the available record size was larger than 65536. Fix the cast to no longer truncate the calculation. Cc: Petr Mladek <pmladek@suse.com> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: John Ogness <john.ogness@linutronix.de> Reported-by: Vijay Balakrishna <vijayb@linux.microsoft.com> Link: https://lore.kernel.org/lkml/d8bb1ec7-a4c5-43a2-9de0-9643a70b899f@linux.microsoft.com/ Fixes: b6cf8b3f3312 ("printk: add lockless ringbuffer") Cc: stable@vger.kernel.org Signed-off-by: Kees Cook <keescook@chromium.org> Tested-by: Vijay Balakrishna <vijayb@linux.microsoft.com> Tested-by: Guilherme G. Piccoli <gpiccoli@igalia.com> # Steam Deck Reviewed-by: Tyler Hicks (Microsoft) <code@tyhicks.com> Tested-by: Tyler Hicks (Microsoft) <code@tyhicks.com> Reviewed-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230811054528.never.165-kees@kernel.org
* | seqlock/latch: Provide raw_read_seqcount_latch_retry()Peter Zijlstra2023-06-051-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The read side of seqcount_latch consists of: do { seq = raw_read_seqcount_latch(&latch->seq); ... } while (read_seqcount_latch_retry(&latch->seq, seq)); which is asymmetric in the raw_ department, and sure enough, read_seqcount_latch_retry() includes (explicit) instrumentation where raw_read_seqcount_latch() does not. This inconsistency becomes a problem when trying to use it from noinstr code. As such, fix it by renaming and re-implementing raw_read_seqcount_latch_retry() without the instrumentation. Specifically the instrumentation in question is kcsan_atomic_next(0) in do___read_seqcount_retry(). Loosing this annotation is not a problem because raw_read_seqcount_latch() does not pass through kcsan_atomic_next(KCSAN_SEQLOCK_REGION_MAX). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Reviewed-by: Petr Mladek <pmladek@suse.com> Tested-by: Michael Kelley <mikelley@microsoft.com> # Hyper-V Link: https://lore.kernel.org/r/20230519102715.233598176@infradead.org
* | Merge tag 'mm-stable-2023-04-27-15-30' of ↵Linus Torvalds2023-04-271-0/+2
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Pull MM updates from Andrew Morton: - Nick Piggin's "shoot lazy tlbs" series, to improve the peformance of switching from a user process to a kernel thread. - More folio conversions from Kefeng Wang, Zhang Peng and Pankaj Raghav. - zsmalloc performance improvements from Sergey Senozhatsky. - Yue Zhao has found and fixed some data race issues around the alteration of memcg userspace tunables. - VFS rationalizations from Christoph Hellwig: - removal of most of the callers of write_one_page() - make __filemap_get_folio()'s return value more useful - Luis Chamberlain has changed tmpfs so it no longer requires swap backing. Use `mount -o noswap'. - Qi Zheng has made the slab shrinkers operate locklessly, providing some scalability benefits. - Keith Busch has improved dmapool's performance, making part of its operations O(1) rather than O(n). - Peter Xu adds the UFFD_FEATURE_WP_UNPOPULATED feature to userfaultd, permitting userspace to wr-protect anon memory unpopulated ptes. - Kirill Shutemov has changed MAX_ORDER's meaning to be inclusive rather than exclusive, and has fixed a bunch of errors which were caused by its unintuitive meaning. - Axel Rasmussen give userfaultfd the UFFDIO_CONTINUE_MODE_WP feature, which causes minor faults to install a write-protected pte. - Vlastimil Babka has done some maintenance work on vma_merge(): cleanups to the kernel code and improvements to our userspace test harness. - Cleanups to do_fault_around() by Lorenzo Stoakes. - Mike Rapoport has moved a lot of initialization code out of various mm/ files and into mm/mm_init.c. - Lorenzo Stoakes removd vmf_insert_mixed_prot(), which was added for DRM, but DRM doesn't use it any more. - Lorenzo has also coverted read_kcore() and vread() to use iterators and has thereby removed the use of bounce buffers in some cases. - Lorenzo has also contributed further cleanups of vma_merge(). - Chaitanya Prakash provides some fixes to the mmap selftesting code. - Matthew Wilcox changes xfs and afs so they no longer take sleeping locks in ->map_page(), a step towards RCUification of pagefaults. - Suren Baghdasaryan has improved mmap_lock scalability by switching to per-VMA locking. - Frederic Weisbecker has reworked the percpu cache draining so that it no longer causes latency glitches on cpu isolated workloads. - Mike Rapoport cleans up and corrects the ARCH_FORCE_MAX_ORDER Kconfig logic. - Liu Shixin has changed zswap's initialization so we no longer waste a chunk of memory if zswap is not being used. - Yosry Ahmed has improved the performance of memcg statistics flushing. - David Stevens has fixed several issues involving khugepaged, userfaultfd and shmem. - Christoph Hellwig has provided some cleanup work to zram's IO-related code paths. - David Hildenbrand has fixed up some issues in the selftest code's testing of our pte state changing. - Pankaj Raghav has made page_endio() unneeded and has removed it. - Peter Xu contributed some rationalizations of the userfaultfd selftests. - Yosry Ahmed has fixed an issue around memcg's page recalim accounting. - Chaitanya Prakash has fixed some arm-related issues in the selftests/mm code. - Longlong Xia has improved the way in which KSM handles hwpoisoned pages. - Peter Xu fixes a few issues with uffd-wp at fork() time. - Stefan Roesch has changed KSM so that it may now be used on a per-process and per-cgroup basis. * tag 'mm-stable-2023-04-27-15-30' of git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm: (369 commits) mm,unmap: avoid flushing TLB in batch if PTE is inaccessible shmem: restrict noswap option to initial user namespace mm/khugepaged: fix conflicting mods to collapse_file() sparse: remove unnecessary 0 values from rc mm: move 'mmap_min_addr' logic from callers into vm_unmapped_area() hugetlb: pte_alloc_huge() to replace huge pte_alloc_map() maple_tree: fix allocation in mas_sparse_area() mm: do not increment pgfault stats when page fault handler retries zsmalloc: allow only one active pool compaction context selftests/mm: add new selftests for KSM mm: add new KSM process and sysfs knobs mm: add new api to enable ksm per process mm: shrinkers: fix debugfs file permissions mm: don't check VMA write permissions if the PTE/PMD indicates write permissions migrate_pages_batch: fix statistics for longterm pin retry userfaultfd: use helper function range_in_vma() lib/show_mem.c: use for_each_populated_zone() simplify code mm: correct arg in reclaim_pages()/reclaim_clean_pages_from_list() fs/buffer: convert create_page_buffers to folio_create_buffers fs/buffer: add folio_create_empty_buffers helper ...
| * | printk: export console trace point for kcsan/kasan/kfence/kmsanPavankumar Kondeti2023-04-181-0/+2
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The console tracepoint is used by kcsan/kasan/kfence/kmsan test modules. Since this tracepoint is not exported, these modules iterate over all available tracepoints to find the console trace point. Export the trace point so that it can be directly used. Link: https://lkml.kernel.org/r/20230413100859.1492323-1-quic_pkondeti@quicinc.com Signed-off-by: Pavankumar Kondeti <quic_pkondeti@quicinc.com> Cc: Alexander Potapenko <glider@google.com> Cc: Andrey Konovalov <andreyknvl@gmail.com> Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: John Ogness <john.ogness@linutronix.de> Cc: Marco Elver <elver@google.com> Cc: Petr Mladek <pmladek@suse.com> Cc: Sergey Senozhatsky <senozhatsky@chromium.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Vincenzo Frascino <vincenzo.frascino@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
* | | Merge tag 'modules-6.4-rc1' of ↵Linus Torvalds2023-04-271-1/+1
|\ \ \ | |_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux Pull module updates from Luis Chamberlain: "The summary of the changes for this pull requests is: - Song Liu's new struct module_memory replacement - Nick Alcock's MODULE_LICENSE() removal for non-modules - My cleanups and enhancements to reduce the areas where we vmalloc module memory for duplicates, and the respective debug code which proves the remaining vmalloc pressure comes from userspace. Most of the changes have been in linux-next for quite some time except the minor fixes I made to check if a module was already loaded prior to allocating the final module memory with vmalloc and the respective debug code it introduces to help clarify the issue. Although the functional change is small it is rather safe as it can only *help* reduce vmalloc space for duplicates and is confirmed to fix a bootup issue with over 400 CPUs with KASAN enabled. I don't expect stable kernels to pick up that fix as the cleanups would have also had to have been picked up. Folks on larger CPU systems with modules will want to just upgrade if vmalloc space has been an issue on bootup. Given the size of this request, here's some more elaborate details: The functional change change in this pull request is the very first patch from Song Liu which replaces the 'struct module_layout' with a new 'struct module_memory'. The old data structure tried to put together all types of supported module memory types in one data structure, the new one abstracts the differences in memory types in a module to allow each one to provide their own set of details. This paves the way in the future so we can deal with them in a cleaner way. If you look at changes they also provide a nice cleanup of how we handle these different memory areas in a module. This change has been in linux-next since before the merge window opened for v6.3 so to provide more than a full kernel cycle of testing. It's a good thing as quite a bit of fixes have been found for it. Jason Baron then made dynamic debug a first class citizen module user by using module notifier callbacks to allocate / remove module specific dynamic debug information. Nick Alcock has done quite a bit of work cross-tree to remove module license tags from things which cannot possibly be module at my request so to: a) help him with his longer term tooling goals which require a deterministic evaluation if a piece a symbol code could ever be part of a module or not. But quite recently it is has been made clear that tooling is not the only one that would benefit. Disambiguating symbols also helps efforts such as live patching, kprobes and BPF, but for other reasons and R&D on this area is active with no clear solution in sight. b) help us inch closer to the now generally accepted long term goal of automating all the MODULE_LICENSE() tags from SPDX license tags In so far as a) is concerned, although module license tags are a no-op for non-modules, tools which would want create a mapping of possible modules can only rely on the module license tag after the commit 8b41fc4454e ("kbuild: create modules.builtin without Makefile.modbuiltin or tristate.conf"). Nick has been working on this *for years* and AFAICT I was the only one to suggest two alternatives to this approach for tooling. The complexity in one of my suggested approaches lies in that we'd need a possible-obj-m and a could-be-module which would check if the object being built is part of any kconfig build which could ever lead to it being part of a module, and if so define a new define -DPOSSIBLE_MODULE [0]. A more obvious yet theoretical approach I've suggested would be to have a tristate in kconfig imply the same new -DPOSSIBLE_MODULE as well but that means getting kconfig symbol names mapping to modules always, and I don't think that's the case today. I am not aware of Nick or anyone exploring either of these options. Quite recently Josh Poimboeuf has pointed out that live patching, kprobes and BPF would benefit from resolving some part of the disambiguation as well but for other reasons. The function granularity KASLR (fgkaslr) patches were mentioned but Joe Lawrence has clarified this effort has been dropped with no clear solution in sight [1]. In the meantime removing module license tags from code which could never be modules is welcomed for both objectives mentioned above. Some developers have also welcomed these changes as it has helped clarify when a module was never possible and they forgot to clean this up, and so you'll see quite a bit of Nick's patches in other pull requests for this merge window. I just picked up the stragglers after rc3. LWN has good coverage on the motivation behind this work [2] and the typical cross-tree issues he ran into along the way. The only concrete blocker issue he ran into was that we should not remove the MODULE_LICENSE() tags from files which have no SPDX tags yet, even if they can never be modules. Nick ended up giving up on his efforts due to having to do this vetting and backlash he ran into from folks who really did *not understand* the core of the issue nor were providing any alternative / guidance. I've gone through his changes and dropped the patches which dropped the module license tags where an SPDX license tag was missing, it only consisted of 11 drivers. To see if a pull request deals with a file which lacks SPDX tags you can just use: ./scripts/spdxcheck.py -f \ $(git diff --name-only commid-id | xargs echo) You'll see a core module file in this pull request for the above, but that's not related to his changes. WE just need to add the SPDX license tag for the kernel/module/kmod.c file in the future but it demonstrates the effectiveness of the script. Most of Nick's changes were spread out through different trees, and I just picked up the slack after rc3 for the last kernel was out. Those changes have been in linux-next for over two weeks. The cleanups, debug code I added and final fix I added for modules were motivated by David Hildenbrand's report of boot failing on a systems with over 400 CPUs when KASAN was enabled due to running out of virtual memory space. Although the functional change only consists of 3 lines in the patch "module: avoid allocation if module is already present and ready", proving that this was the best we can do on the modules side took quite a bit of effort and new debug code. The initial cleanups I did on the modules side of things has been in linux-next since around rc3 of the last kernel, the actual final fix for and debug code however have only been in linux-next for about a week or so but I think it is worth getting that code in for this merge window as it does help fix / prove / evaluate the issues reported with larger number of CPUs. Userspace is not yet fixed as it is taking a bit of time for folks to understand the crux of the issue and find a proper resolution. Worst come to worst, I have a kludge-of-concept [3] of how to make kernel_read*() calls for modules unique / converge them, but I'm currently inclined to just see if userspace can fix this instead" Link: https://lore.kernel.org/all/Y/kXDqW+7d71C4wz@bombadil.infradead.org/ [0] Link: https://lkml.kernel.org/r/025f2151-ce7c-5630-9b90-98742c97ac65@redhat.com [1] Link: https://lwn.net/Articles/927569/ [2] Link: https://lkml.kernel.org/r/20230414052840.1994456-3-mcgrof@kernel.org [3] * tag 'modules-6.4-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/mcgrof/linux: (121 commits) module: add debugging auto-load duplicate module support module: stats: fix invalid_mod_bytes typo module: remove use of uninitialized variable len module: fix building stats for 32-bit targets module: stats: include uapi/linux/module.h module: avoid allocation if module is already present and ready module: add debug stats to help identify memory pressure module: extract patient module check into helper modules/kmod: replace implementation with a semaphore Change DEFINE_SEMAPHORE() to take a number argument module: fix kmemleak annotations for non init ELF sections module: Ignore L0 and rename is_arm_mapping_symbol() module: Move is_arm_mapping_symbol() to module_symbol.h module: Sync code of is_arm_mapping_symbol() scripts/gdb: use mem instead of core_layout to get the module address interconnect: remove module-related code interconnect: remove MODULE_LICENSE in non-modules zswap: remove MODULE_LICENSE in non-modules zpool: remove MODULE_LICENSE in non-modules x86/mm/dump_pagetables: remove MODULE_LICENSE in non-modules ...
| * | Change DEFINE_SEMAPHORE() to take a number argumentPeter Zijlstra2023-04-181-1/+1
| |/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Fundamentally semaphores are a counted primitive, but DEFINE_SEMAPHORE() does not expose this and explicitly creates a binary semaphore. Change DEFINE_SEMAPHORE() to take a number argument and use that in the few places that open-coded it using __SEMAPHORE_INITIALIZER(). Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> [mcgrof: add some tribal knowledge about why some folks prefer binary sempahores over mutexes] Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Davidlohr Bueso <dave@stgolabs.net> Signed-off-by: Luis Chamberlain <mcgrof@kernel.org>
* / printk: Remove obsoleted check for non-existent "user" objectStanislav Kinsburskii2023-04-031-12/+1
|/ | | | | | | | | | | | | | | | | | | | | | | The original check for non-null "user" object was introduced by commit e11fea92e13f ("kmsg: export printk records to the /dev/kmsg interface") when "user" could be NULL if /dev/ksmg was opened for writing. Subsequent change 750afe7babd1 ("printk: add kernel parameter to control writes to /dev/kmsg") made "user" context required for files opened for write, but didn't remove now redundant checks for it to be non-NULL. This patch removes the dead code while preserving the current logic. Signed-off-by: Stanislav Kinsburskii <stanislav.kinsburski@gmail.com> CC: Petr Mladek <pmladek@suse.com> CC: Sergey Senozhatsky <senozhatsky@chromium.org> CC: Steven Rostedt <rostedt@goodmis.org> CC: John Ogness <john.ogness@linutronix.de> CC: linux-kernel@vger.kernel.org Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Reviewed-by: Petr Mladek <pmladek@suse.com> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/167929571877.2810.9926967619100618792.stgit@skinsburskii.localdomain
* Merge tag 'printk-for-6.3' of ↵Linus Torvalds2023-02-233-130/+225
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux Pull printk updates from Petr Mladek: - Refactor printk code for formatting messages that are shown on consoles. This is a preparatory step for introducing atomic consoles which could not share the global buffers - Prevent memory leak when removing printk index in debugfs - Dump also the newest printk message by the sample gdbmacro - Fix a compiler warning * tag 'printk-for-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux: printf: fix errname.c list kernel/printk/index.c: fix memory leak with using debugfs_lookup() printk: Use scnprintf() to print the message about the dropped messages on a console printk: adjust string limit macros printk: use printk_buffers for devkmsg printk: introduce console_prepend_dropped() for dropped messages printk: introduce printk_get_next_message() and printk_message printk: introduce struct printk_buffers console: Document struct console console: Use BIT() macros for @flags values printk: move size limit macros into internal.h docs: gdbmacros: print newest record
| * Merge branch 'rework/buffers-cleanup' into for-linusPetr Mladek2023-02-212-129/+224
| |\
| | * printk: Use scnprintf() to print the message about the dropped messages on a ↵Petr Mladek2023-01-181-1/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | console Use scnprintf() for printing the message about dropped messages on a console. It returns the really written length of the message. It prevents potential buffer overflow when the returned length is later used to copy the buffer content. Note that the previous code was safe because the scratch buffer was big enough and the message always fit in. But scnprintf() makes it more safe, definitely. Reported-by: coverity-bot <keescook+coverity-bot@chromium.org> Addresses-Coverity-ID: 1530570 ("Memory - corruptions") Fixes: c4fcc617e148 ("printk: introduce console_prepend_dropped() for dropped messages") Link: https://lore.kernel.org/r/202301131544.D9E804CCD@keescook Reviewed-by: John Ogness <john.ogness@linutronix.de> Reviewed-by: Sergey Senozhatsky <senozhatsky@chromium.org> Signed-off-by: Petr Mladek <pmladek@suse.com> Link: https://lore.kernel.org/r/20230117161031.15499-1-pmladek@suse.com
generated by cgit v1.2.3 (git 2.25.1) at 2025-03-19 00:08:21 +0000