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* rcu/trace: Add tracing for how segcb list changesJoel Fernandes (Google)2021-01-061-0/+26
| | | | | | | | | | | | | | This commit adds tracing to track how the segcb list changes before/after acceleration, during queuing and during dequeuing. This tracing helped discover an optimization that avoided needless GP requests when no callbacks were accelerated. The tracing overhead is minimal as each segment's length is now stored in the respective segment. Reviewed-by: Frederic Weisbecker <frederic@kernel.org> Reviewed-by: Neeraj Upadhyay <neeraju@codeaurora.org> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu/trace: Print negative GP numbers correctlyJoel Fernandes (Google)2020-08-241-27/+27
| | | | | | | | | | | | GP numbers start from -300 and gp_seq numbers start of -1200 (for a shift of 2). These negative numbers are printed as unsigned long which not only takes up more text space, but is rather confusing to the reader as they have to constantly expend energy to truncate the number. Just print the negative numbering directly. Cc: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
*-. Merge branches 'doc.2020.06.29a', 'fixes.2020.06.29a', ↵Paul E. McKenney2020-06-291-9/+10
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 'kfree_rcu.2020.06.29a', 'rcu-tasks.2020.06.29a', 'scale.2020.06.29a', 'srcu.2020.06.29a' and 'torture.2020.06.29a' into HEAD doc.2020.06.29a: Documentation updates. fixes.2020.06.29a: Miscellaneous fixes. kfree_rcu.2020.06.29a: kfree_rcu() updates. rcu-tasks.2020.06.29a: RCU Tasks updates. scale.2020.06.29a: Read-side scalability tests. srcu.2020.06.29a: SRCU updates. torture.2020.06.29a: Torture-test updates.
| | * rcu: Rename *_kfree_callback/*_kfree_rcu_offset/kfree_call_*Uladzislau Rezki (Sony)2020-06-291-4/+4
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | The following changes are introduced: 1. Rename rcu_invoke_kfree_callback() to rcu_invoke_kvfree_callback(), as well as the associated trace events, so the rcu_kfree_callback(), becomes rcu_kvfree_callback(). The reason is to be aligned with kvfree() notation. 2. Rename __is_kfree_rcu_offset to __is_kvfree_rcu_offset. All RCU paths use kvfree() now instead of kfree(), thus rename it. 3. Rename kfree_call_rcu() to the kvfree_call_rcu(). The reason is, it is capable of freeing vmalloc() memory now. Do the same with __kfree_rcu() macro, it becomes __kvfree_rcu(), the goal is the same. Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Co-developed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
| * trace: events: rcu: Change description of rcu_dyntick trace eventMadhuparna Bhowmik2020-06-291-5/+6
|/ | | | | | | | | | | | | | | | The different strings used for describing the polarity are Start, End and StillNonIdle. Since StillIdle is not used in any trace point for rcu_dyntick, it can be removed and StillNonIdle can be added in the description. Because StillNonIdle is used in a few tracepoints for rcu_dyntick. Similarly, USER, IDLE and IRQ are used for describing context in the rcu_dyntick tracepoints. Since, "KERNEL" is not used for any of the rcu_dyntick tracepoints, remove it from the description. Signed-off-by: Madhuparna Bhowmik <madhuparnabhowmik10@gmail.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
*-. Merge branches 'doc.2020.02.27a', 'fixes.2020.03.21a', ↵Paul E. McKenney2020-03-211-0/+29
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 'kfree_rcu.2020.02.20a', 'locktorture.2020.02.20a', 'ovld.2020.02.20a', 'rcu-tasks.2020.02.20a', 'srcu.2020.02.20a' and 'torture.2020.02.20a' into HEAD doc.2020.02.27a: Documentation updates. fixes.2020.03.21a: Miscellaneous fixes. kfree_rcu.2020.02.20a: Updates to kfree_rcu(). locktorture.2020.02.20a: Lock torture-test updates. ovld.2020.02.20a: Updates to callback-overload handling. rcu-tasks.2020.02.20a: RCU-tasks updates. srcu.2020.02.20a: SRCU updates. torture.2020.02.20a: Torture-test updates.
| | * rcu: Add a trace event for kfree_rcu() use of kfree_bulk()Uladzislau Rezki (Sony)2020-02-201-0/+28
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | | | The event is given three parameters, first one is the name of RCU flavour, second one is the number of elements in array for free and last one is an address of the array holding pointers to be freed by the kfree_bulk() function. To enable the trace event your kernel has to be build with CONFIG_RCU_TRACE=y, after that it is possible to track the events using ftrace subsystem. Signed-off-by: Uladzislau Rezki (Sony) <urezki@gmail.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
| * rcu: Make rcu_barrier() account for offline no-CBs CPUsPaul E. McKenney2020-03-211-0/+1
|/ | | | | | | | | | | | | | | | | | | Currently, rcu_barrier() ignores offline CPUs, However, it is possible for an offline no-CBs CPU to have callbacks queued, and rcu_barrier() must wait for those callbacks. This commit therefore makes rcu_barrier() directly invoke the rcu_barrier_func() with interrupts disabled for such CPUs. This requires passing the CPU number into this function so that it can entrain the rcu_barrier() callback onto the correct CPU's callback list, given that the code must instead execute on the current CPU. While in the area, this commit fixes a bug where the first CPU's callback might have been invoked before rcu_segcblist_entrain() returned, which would also result in an early wakeup. Fixes: 5d6742b37727 ("rcu/nocb: Use rcu_segcblist for no-CBs CPUs") Signed-off-by: Paul E. McKenney <paulmck@kernel.org> [ paulmck: Apply optimization feedback from Boqun Feng. ] Cc: <stable@vger.kernel.org> # 5.5.x
*---. Merge branches 'doc.2019.12.10a', 'exp.2019.12.09a', 'fixes.2020.01.24a', ↵Paul E. McKenney2020-01-241-24/+16
|\ \ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | 'kfree_rcu.2020.01.24a', 'list.2020.01.10a', 'preempt.2020.01.24a' and 'torture.2019.12.09a' into HEAD doc.2019.12.10a: Documentations updates exp.2019.12.09a: Expedited grace-period updates fixes.2020.01.24a: Miscellaneous fixes kfree_rcu.2020.01.24a: Batch kfree_rcu() work list.2020.01.10a: RCU-protected-list updates preempt.2020.01.24a: Preemptible RCU updates torture.2019.12.09a: Torture-test updates
| | | * rcu: Make PREEMPT_RCU be a modifier to TREE_RCULai Jiangshan2019-12-091-2/+2
| |_|/ |/| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Currently PREEMPT_RCU and TREE_RCU are mutually exclusive Kconfig options. But PREEMPT_RCU actually specifies a kind of TREE_RCU, namely a preemptible TREE_RCU. This commit therefore makes PREEMPT_RCU be a modifer to the TREE_RCU Kconfig option. This has the benefit of simplifying several of the #if expressions that formerly needed to check both, but now need only check one or the other. Signed-off-by: Lai Jiangshan <laijs@linux.alibaba.com> Signed-off-by: Lai Jiangshan <jiangshanlai@gmail.com> Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
| | * rcu: Remove kfree_rcu() special casing and lazy-callback handlingJoel Fernandes (Google)2020-01-241-20/+12
| |/ |/| | | | | | | | | | | | | | | | | | | | | | | This commit removes kfree_rcu() special-casing and the lazy-callback handling from Tree RCU. It moves some of this special casing to Tiny RCU, the removal of which will be the subject of later commits. This results in a nice negative delta. Suggested-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org> [ paulmck: Add slab.h #include, thanks to kbuild test robot <lkp@intel.com>. ] Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
| * rcu: Fix data-race due to atomic_t copy-by-valueMarco Elver2019-12-091-2/+2
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | This fixes a data-race where `atomic_t dynticks` is copied by value. The copy is performed non-atomically, resulting in a data-race if `dynticks` is updated concurrently. This data-race was found with KCSAN: ================================================================== BUG: KCSAN: data-race in dyntick_save_progress_counter / rcu_irq_enter write to 0xffff989dbdbe98e0 of 4 bytes by task 10 on cpu 3: atomic_add_return include/asm-generic/atomic-instrumented.h:78 [inline] rcu_dynticks_snap kernel/rcu/tree.c:310 [inline] dyntick_save_progress_counter+0x43/0x1b0 kernel/rcu/tree.c:984 force_qs_rnp+0x183/0x200 kernel/rcu/tree.c:2286 rcu_gp_fqs kernel/rcu/tree.c:1601 [inline] rcu_gp_fqs_loop+0x71/0x880 kernel/rcu/tree.c:1653 rcu_gp_kthread+0x22c/0x3b0 kernel/rcu/tree.c:1799 kthread+0x1b5/0x200 kernel/kthread.c:255 <snip> read to 0xffff989dbdbe98e0 of 4 bytes by task 154 on cpu 7: rcu_nmi_enter_common kernel/rcu/tree.c:828 [inline] rcu_irq_enter+0xda/0x240 kernel/rcu/tree.c:870 irq_enter+0x5/0x50 kernel/softirq.c:347 <snip> Reported by Kernel Concurrency Sanitizer on: CPU: 7 PID: 154 Comm: kworker/7:1H Not tainted 5.3.0+ #5 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 Workqueue: kblockd blk_mq_run_work_fn ================================================================== Signed-off-by: Marco Elver <elver@google.com> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Josh Triplett <josh@joshtriplett.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com> Cc: Joel Fernandes <joel@joelfernandes.org> Cc: Ingo Molnar <mingo@redhat.com> Cc: Dmitry Vyukov <dvyukov@google.com> Cc: rcu@vger.kernel.org Cc: linux-kernel@vger.kernel.org Reviewed-by: Joel Fernandes (Google) <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu: Update descriptions for rcu_future_grace_period tracepointPaul E. McKenney2019-10-301-5/+5
| | | | Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu: Update descriptions for rcu_nocb_wake tracepointPaul E. McKenney2019-10-301-14/+21
| | | | Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu: Remove obsolete descriptions for rcu_barrier tracepointPaul E. McKenney2019-10-301-2/+0
| | | | Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
* rcu/nocb: Use rcu_segcblist for no-CBs CPUsPaul E. McKenney2019-08-131-1/+0
| | | | | | | | | | | | | | | | | | | | | | Currently the RCU callbacks for no-CBs CPUs are queued on a series of ad-hoc linked lists, which means that these callbacks cannot benefit from "drive-by" grace periods, thus suffering needless delays prior to invocation. In addition, the no-CBs grace-period kthreads first wait for callbacks to appear and later wait for a new grace period, which means that callbacks appearing during a grace-period wait can be delayed. These delays increase memory footprint, and could even result in an out-of-memory condition. This commit therefore enqueues RCU callbacks from no-CBs CPUs on the rcu_segcblist structure that is already used by non-no-CBs CPUs. It also restructures the no-CBs grace-period kthread to be checking for incoming callbacks while waiting for grace periods. Also, instead of waiting for a new grace period, it waits for the closest grace period that will cause some of the callbacks to be safe to invoke. All of these changes reduce callback latency and thus the number of outstanding callbacks, in turn reducing the probability of an out-of-memory condition. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* rcu/nocb: Rename and document no-CB CB kthread sleep trace eventPaul E. McKenney2019-08-131-1/+2
| | | | | | | | | The nocb_cb_wait() function traces a "FollowerSleep" trace_rcu_nocb_wake() event, which never was documented and is now misleading. This commit therefore changes "FollowerSleep" to "CBSleep", documents this, and updates the documentation for "Sleep" as well. Signed-off-by: Paul E. McKenney <paulmck@linux.ibm.com>
* Merge tag 'trace-v5.2' of ↵Linus Torvalds2019-05-151-56/+25
|\ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace Pull tracing updates from Steven Rostedt: "The major changes in this tracing update includes: - Removal of non-DYNAMIC_FTRACE from 32bit x86 - Removal of mcount support from x86 - Emulating a call from int3 on x86_64, fixes live kernel patching - Consolidated Tracing Error logs file Minor updates: - Removal of klp_check_compiler_support() - kdb ftrace dumping output changes - Accessing and creating ftrace instances from inside the kernel - Clean up of #define if macro - Introduction of TRACE_EVENT_NOP() to disable trace events based on config options And other minor fixes and clean ups" * tag 'trace-v5.2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace: (44 commits) x86: Hide the int3_emulate_call/jmp functions from UML livepatch: Remove klp_check_compiler_support() ftrace/x86: Remove mcount support ftrace/x86_32: Remove support for non DYNAMIC_FTRACE tracing: Simplify "if" macro code tracing: Fix documentation about disabling options using trace_options tracing: Replace kzalloc with kcalloc tracing: Fix partial reading of trace event's id file tracing: Allow RCU to run between postponed startup tests tracing: Fix white space issues in parse_pred() function tracing: Eliminate const char[] auto variables ring-buffer: Fix mispelling of Calculate tracing: probeevent: Fix to make the type of $comm string tracing: probeevent: Do not accumulate on ret variable tracing: uprobes: Re-enable $comm support for uprobe events ftrace/x86_64: Emulate call function while updating in breakpoint handler x86_64: Allow breakpoints to emulate call instructions x86_64: Add gap to int3 to allow for call emulation tracing: kdb: Allow ftdump to skip all but the last few entries tracing: Add trace_total_entries() / trace_total_entries_cpu() ...
| * rcu: validate arguments for rcu tracepointsYafang Shao2019-04-081-56/+25
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | When CONFIG_RCU_TRACE is not set, all these tracepoints are defined as do-nothing macro. We'd better make those inline functions that take proper arguments. As RCU_TRACE() is defined as do-nothing marco as well when CONFIG_RCU_TRACE is not set, so we can clean it up. Link: http://lkml.kernel.org/r/1553602391-11926-4-git-send-email-laoar.shao@gmail.com Reviewed-by: Paul E. McKenney <paulmck@linux.ibm.com> Signed-off-by: Yafang Shao <laoar.shao@gmail.com> Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
* | treewide: Switch printk users from %pf and %pF to %ps and %pS, respectivelySakari Ailus2019-04-091-2/+2
|/ | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | %pF and %pf are functionally equivalent to %pS and %ps conversion specifiers. The former are deprecated, therefore switch the current users to use the preferred variant. The changes have been produced by the following command: git grep -l '%p[fF]' | grep -v '^\(tools\|Documentation\)/' | \ while read i; do perl -i -pe 's/%pf/%ps/g; s/%pF/%pS/g;' $i; done And verifying the result. Link: http://lkml.kernel.org/r/20190325193229.23390-1-sakari.ailus@linux.intel.com Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: linux-arm-kernel@lists.infradead.org Cc: sparclinux@vger.kernel.org Cc: linux-um@lists.infradead.org Cc: xen-devel@lists.xenproject.org Cc: linux-acpi@vger.kernel.org Cc: linux-pm@vger.kernel.org Cc: drbd-dev@lists.linbit.com Cc: linux-block@vger.kernel.org Cc: linux-mmc@vger.kernel.org Cc: linux-nvdimm@lists.01.org Cc: linux-pci@vger.kernel.org Cc: linux-scsi@vger.kernel.org Cc: linux-btrfs@vger.kernel.org Cc: linux-f2fs-devel@lists.sourceforge.net Cc: linux-mm@kvack.org Cc: ceph-devel@vger.kernel.org Cc: netdev@vger.kernel.org Signed-off-by: Sakari Ailus <sakari.ailus@linux.intel.com> Acked-by: David Sterba <dsterba@suse.com> (for btrfs) Acked-by: Mike Rapoport <rppt@linux.ibm.com> (for mm/memblock.c) Acked-by: Bjorn Helgaas <bhelgaas@google.com> (for drivers/pci) Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com> Signed-off-by: Petr Mladek <pmladek@suse.com>
* rcu: Eliminate ->rcu_qs_ctr from the rcu_dynticks structurePaul E. McKenney2018-08-301-3/+2
| | | | | | | | | | | | | | | | | The ->rcu_qs_ctr counter was intended to allow providing a lightweight report of a quiescent state to all RCU flavors. But now that there is only one flavor of RCU in any one running kernel, there is no point in having this feature. This commit therefore removes the ->rcu_qs_ctr field from the rcu_dynticks structure and the ->rcu_qs_ctr_snap field from the rcu_data structure. This results in the "rqc" option to the rcu_fqs trace event no longer being used, so this commit also removes the "rqc" description from the header comment. While in the neighborhood, this commit also causes the forward-progress request .rcu_need_heavy_qs be set one jiffies_till_sched_qs interval later in the grace period than the first setting of .rcu_urgent_qs. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Inline _rcu_barrier() into its sole remaining callerPaul E. McKenney2018-08-301-10/+10
| | | | | | | | Because rcu_barrier() is a one-line wrapper function for _rcu_barrier() and because nothing else calls _rcu_barrier(), this commit inlines _rcu_barrier() into rcu_barrier(). Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Remove CPU-hotplug failsafe from force-quiescent-state code pathPaul E. McKenney2018-07-121-5/+5
| | | | | | | | | | | Now that quiescent states for newly offlined CPUs are reported either when that CPU goes offline or at the end of grace-period initialization, the CPU-hotplug failsafe in the force-quiescent-state code path is no longer needed. This commit therefore removes this failsafe. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Rename the grace-period-request variables and parametersJoel Fernandes2018-07-121-7/+8
| | | | | | | | | | | | | The name 'c' is used for variables and parameters holding the requested grace-period sequence number. However it is no longer very meaningful given the conversions from ->gpnum and (especially) ->completed to ->gp_seq. This commit therefore renames 'c' to 'gp_seq_req'. Previous patch discussion is at: https://patchwork.kernel.org/patch/10396579/ Signed-off-by: Joel Fernandes <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Don't funnel-lock above leaf node if GP in progressPaul E. McKenney2018-07-121-2/+2
| | | | | | | | | | | | | | The old grace-period start code would acquire only the leaf's rcu_node structure's ->lock if that structure believed that a grace period was in progress. The new code advances to the leaf's parent in this case, needlessly acquiring then leaf's parent's ->lock. This commit therefore checks the grace-period state after marking the leaf with the need for the specified grace period, and if the leaf believes that a grace period is in progress, takes an early exit. Reported-by: Joel Fernandes <joel@joelfernandes.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> [ paulmck: Add "Startedleaf" tracing as suggested by Joel Fernandes. ]
* rcu: Convert rcu_fqs tracepoint to ->gp_seqPaul E. McKenney2018-07-121-6/+6
| | | | | | This commit makes the rcu_fqs tracepoint use ->gp_seq instead of ->gpnum. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Convert rcu_quiescent_state_report tracepoint to ->gp_seqPaul E. McKenney2018-07-121-6/+6
| | | | | | | This commit makes the rcu_quiescent_state_report tracepoint use ->gp_seq instead of ->gpnum. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Convert rcu_unlock_preempted_task tracepoint to ->gp_seqPaul E. McKenney2018-07-121-6/+6
| | | | | | | This commit makes the rcu_unlock_preempted_task tracepoint use ->gp_seq instead of ->gpnum. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Convert rcu_preempt_task tracepoint to ->gp_seqPaul E. McKenney2018-07-121-6/+6
| | | | | | | This commit makes the rcu_preempt_task tracepoint use ->gp_seq instead of ->gpnum. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Convert rcu_grace_period_init tracepoint to gp_seqPaul E. McKenney2018-07-121-6/+6
| | | | | | | This commit makes the rcu_grace_period_init tracepoint use gp_seq instead of ->gpnum. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Convert rcu_future_grace_period tracepoint to gp_seqPaul E. McKenney2018-07-121-13/+9
| | | | | | | This commit makes the rcu_future_grace_period tracepoint use gp_seq instead of ->gpnum and ->completed. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Convert rcu_grace_period tracepoint to gp_seqPaul E. McKenney2018-07-121-6/+7
| | | | | | | | | This commit makes the rcu_grace_period tracepoint use gp_seq instead of ->gpnum or ->completed. It also introduces a "cpuofl-bgp" string to less obscurely indicate when a CPU has gone offline while a grace period is waiting on it. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Update list of rcu_future_grace_period() trace eventsPaul E. McKenney2018-05-151-6/+7
| | | | | | | | | Reworking grace-period initiation and funnel locking added new rcu_future_grace_period() trace events, so this commit updates the rcu_future_grace_period() trace event's header comment accordingly. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Tested-by: Nicholas Piggin <npiggin@gmail.com>
* rcu: Trace expedited GP delays due to transitioning CPUsPaul E. McKenney2018-02-201-0/+1
| | | | | | | | | If a CPU is transitioning to or from offline state, an expedited grace period may undergo a timed wait. This timed wait can unduly delay grace periods, so this commit adds a trace statement to make it visible. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Add more tracing of expedited grace periodsPaul E. McKenney2018-02-201-0/+3
| | | | | | | This commit adds more tracing of expedited grace periods to enable improved debugging of slowdowns. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
*-. Merge branches 'cond_resched.2017.12.04a', 'dyntick.2017.11.28a', ↵Paul E. McKenney2017-12-111-55/+20
|\ \ | | | | | | | | | | | | | | | | | | | | | | | | | | | 'fixes.2017.12.11a', 'srbd.2017.12.05a' and 'torture.2017.12.11a' into HEAD cond_resched.2017.12.04a: Convert cond_resched_rcu_qs() to cond_resched() dyntick.2017.11.28a: Make RCU dynticks handle interrupts from NMI fixes.2017.12.11a: Miscellaneous fixes srbd.2017.12.05a: Remove now-redundant smp_read_barrier_depends() torture.2017.12.11a: Torture-testing update
| | * tracing, rcu: Hide trace event rcu_nocb_wake when not usedSteven Rostedt (VMware)2017-12-111-0/+2
| |/ |/| | | | | | | | | | | | | | | | | | | The trace event rcu_nocb_wake is only used when CONFIG_RCU_NOCB_CPU is defined. But the trace event is defined regardless. As defined trace events take up memory, it is a waste to have it defined when not used. Surround the trace event with an #ifdef to have it only defined when it is used. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| * tracing, rcu: Remove no longer used trace event rcu_prep_idleSteven Rostedt (VMware)2017-11-281-40/+0
| | | | | | | | | | | | | | | | | | | | | | Commit c0f4dfd4f90 ("rcu: Make RCU_FAST_NO_HZ take advantage of numbered callbacks") removed the only instances of trace_rcu_prep_idle, but did not remove the TRACE_EVENT() that creates it. As defined trace events take up memory within the kernel even when they are not used, this is a waste of space. Remove the obsolete event. Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| * rcu: Simplify rcu_eqs_{enter,exit}() non-idle task debug codePaul E. McKenney2017-11-281-7/+5
| | | | | | | | | | | | | | | | | | | | The code that checks for non-idle non-nohz_idle-usermode tasks invoking rcu_eqs_enter() and rcu_eqs_exit() prints a considerable quantity of helpful information. However, these checks fire rarely, so the extra complexity is no longer worth it. This commit therefore replaces this debug code with simple WARN_ON_ONCE() statements. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| * rcu: Add ->dynticks field to rcu_dyntick trace eventPaul E. McKenney2017-11-281-5/+8
| | | | | | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| * rcu: Shrink ->dynticks_{nmi_,}nesting from long long to longPaul E. McKenney2017-11-281-4/+4
| | | | | | | | | | | | | | | | | | | | Because the ->dynticks_nesting field now only contains the process-based nesting level instead of a value encoding both the process nesting level and the irq "nesting" level, we no longer need a long long, even on 32-bit systems. This commit therefore changes both the ->dynticks_nesting and ->dynticks_nmi_nesting fields to long. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
| * rcu: Add tracing to irq/NMI dyntick-idle transitionsPaul E. McKenney2017-11-281-6/+8
|/ | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* License cleanup: add SPDX GPL-2.0 license identifier to files with no licenseGreg Kroah-Hartman2017-11-021-0/+1
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | Many source files in the tree are missing licensing information, which makes it harder for compliance tools to determine the correct license. By default all files without license information are under the default license of the kernel, which is GPL version 2. Update the files which contain no license information with the 'GPL-2.0' SPDX license identifier. The SPDX identifier is a legally binding shorthand, which can be used instead of the full boiler plate text. This patch is based on work done by Thomas Gleixner and Kate Stewart and Philippe Ombredanne. How this work was done: Patches were generated and checked against linux-4.14-rc6 for a subset of the use cases: - file had no licensing information it it. - file was a */uapi/* one with no licensing information in it, - file was a */uapi/* one with existing licensing information, Further patches will be generated in subsequent months to fix up cases where non-standard license headers were used, and references to license had to be inferred by heuristics based on keywords. The analysis to determine which SPDX License Identifier to be applied to a file was done in a spreadsheet of side by side results from of the output of two independent scanners (ScanCode & Windriver) producing SPDX tag:value files created by Philippe Ombredanne. Philippe prepared the base worksheet, and did an initial spot review of a few 1000 files. The 4.13 kernel was the starting point of the analysis with 60,537 files assessed. Kate Stewart did a file by file comparison of the scanner results in the spreadsheet to determine which SPDX license identifier(s) to be applied to the file. She confirmed any determination that was not immediately clear with lawyers working with the Linux Foundation. Criteria used to select files for SPDX license identifier tagging was: - Files considered eligible had to be source code files. - Make and config files were included as candidates if they contained >5 lines of source - File already had some variant of a license header in it (even if <5 lines). All documentation files were explicitly excluded. The following heuristics were used to determine which SPDX license identifiers to apply. - when both scanners couldn't find any license traces, file was considered to have no license information in it, and the top level COPYING file license applied. For non */uapi/* files that summary was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 11139 and resulted in the first patch in this series. If that file was a */uapi/* path one, it was "GPL-2.0 WITH Linux-syscall-note" otherwise it was "GPL-2.0". Results of that was: SPDX license identifier # files ---------------------------------------------------|------- GPL-2.0 WITH Linux-syscall-note 930 and resulted in the second patch in this series. - if a file had some form of licensing information in it, and was one of the */uapi/* ones, it was denoted with the Linux-syscall-note if any GPL family license was found in the file or had no licensing in it (per prior point). Results summary: SPDX license identifier # files ---------------------------------------------------|------ GPL-2.0 WITH Linux-syscall-note 270 GPL-2.0+ WITH Linux-syscall-note 169 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-2-Clause) 21 ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause) 17 LGPL-2.1+ WITH Linux-syscall-note 15 GPL-1.0+ WITH Linux-syscall-note 14 ((GPL-2.0+ WITH Linux-syscall-note) OR BSD-3-Clause) 5 LGPL-2.0+ WITH Linux-syscall-note 4 LGPL-2.1 WITH Linux-syscall-note 3 ((GPL-2.0 WITH Linux-syscall-note) OR MIT) 3 ((GPL-2.0 WITH Linux-syscall-note) AND MIT) 1 and that resulted in the third patch in this series. - when the two scanners agreed on the detected license(s), that became the concluded license(s). - when there was disagreement between the two scanners (one detected a license but the other didn't, or they both detected different licenses) a manual inspection of the file occurred. - In most cases a manual inspection of the information in the file resulted in a clear resolution of the license that should apply (and which scanner probably needed to revisit its heuristics). - When it was not immediately clear, the license identifier was confirmed with lawyers working with the Linux Foundation. - If there was any question as to the appropriate license identifier, the file was flagged for further research and to be revisited later in time. In total, over 70 hours of logged manual review was done on the spreadsheet to determine the SPDX license identifiers to apply to the source files by Kate, Philippe, Thomas and, in some cases, confirmation by lawyers working with the Linux Foundation. Kate also obtained a third independent scan of the 4.13 code base from FOSSology, and compared selected files where the other two scanners disagreed against that SPDX file, to see if there was new insights. The Windriver scanner is based on an older version of FOSSology in part, so they are related. Thomas did random spot checks in about 500 files from the spreadsheets for the uapi headers and agreed with SPDX license identifier in the files he inspected. For the non-uapi files Thomas did random spot checks in about 15000 files. In initial set of patches against 4.14-rc6, 3 files were found to have copy/paste license identifier errors, and have been fixed to reflect the correct identifier. Additionally Philippe spent 10 hours this week doing a detailed manual inspection and review of the 12,461 patched files from the initial patch version early this week with: - a full scancode scan run, collecting the matched texts, detected license ids and scores - reviewing anything where there was a license detected (about 500+ files) to ensure that the applied SPDX license was correct - reviewing anything where there was no detection but the patch license was not GPL-2.0 WITH Linux-syscall-note to ensure that the applied SPDX license was correct This produced a worksheet with 20 files needing minor correction. This worksheet was then exported into 3 different .csv files for the different types of files to be modified. These .csv files were then reviewed by Greg. Thomas wrote a script to parse the csv files and add the proper SPDX tag to the file, in the format that the file expected. This script was further refined by Greg based on the output to detect more types of files automatically and to distinguish between header and source .c files (which need different comment types.) Finally Greg ran the script using the .csv files to generate the patches. Reviewed-by: Kate Stewart <kstewart@linuxfoundation.org> Reviewed-by: Philippe Ombredanne <pombredanne@nexb.com> Reviewed-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
* rcutorture: Place event-traced strings into trace bufferPaul E. McKenney2017-07-241-2/+5
| | | | | | | | | | | Strings used in event tracing need to be specially handled, for example, being copied to the trace buffer instead of being pointed to by the trace buffer. Although the TPS() macro can be used to "launder" pointed-to strings, this might not be all that effective within a loadable module. This commit therefore copies rcutorture's strings to the trace buffer. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Steven Rostedt <rostedt@goodmis.org>
* rcu: Prevent rcu_barrier() from starting needless grace periodsPaul E. McKenney2017-06-081-0/+1
| | | | | | | | | | | | | | | Currently rcu_barrier() uses call_rcu() to enqueue new callbacks on each CPU with a non-empty callback list. This works, but means that rcu_barrier() forces grace periods that are not otherwise needed. The key point is that rcu_barrier() never needs to wait for a grace period, but instead only for all pre-existing callbacks to be invoked. This means that rcu_barrier()'s new callbacks should be placed in the callback-list segment containing the last pre-existing callback. This commit makes this change using the new rcu_segcblist_entrain() function. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Check cond_resched_rcu_qs() state less often to reduce GP overheadPaul E. McKenney2017-01-231-5/+5
| | | | | | | | | | | | | | | | | | | | | Commit 4a81e8328d37 ("rcu: Reduce overhead of cond_resched() checks for RCU") moved quiescent-state generation out of cond_resched() and commit bde6c3aa9930 ("rcu: Provide cond_resched_rcu_qs() to force quiescent states in long loops") introduced cond_resched_rcu_qs(), and commit 5cd37193ce85 ("rcu: Make cond_resched_rcu_qs() apply to normal RCU flavors") introduced the per-CPU rcu_qs_ctr variable, which is frequently polled by the RCU core state machine. This frequent polling can increase grace-period rate, which in turn increases grace-period overhead, which is visible in some benchmarks (for example, the "open1" benchmark in Anton Blanchard's "will it scale" suite). This commit therefore reduces the rate at which rcu_qs_ctr is polled by moving that polling into the force-quiescent-state (FQS) machinery, and by further polling it only after the grace period has been in effect for at least jiffies_till_sched_qs jiffies. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Reviewed-by: Josh Triplett <josh@joshtriplett.org>
* torture: Trace long read-side delaysPaul E. McKenney2016-11-141-1/+4
| | | | | | | | | | | Although rcutorture will occasionally do a 50-millisecond grace-period delay, these delays are quite rare. And rightly so, because otherwise the read rate would be quite low. Thie means that it can be important to identify whether or not a given run contained a long-delay read. This commit therefore inserts a trace_rcu_torture_read() event to flag runs containing long delays. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Enforce expedited-GP fairness via funnel wait queuePaul E. McKenney2016-03-311-2/+3
| | | | | | | | | | | | | | | | | | | | | | The current mutex-based funnel-locking approach used by expedited grace periods is subject to severe unfairness. The problem arises when a few tasks, making a path from leaves to root, all wake up before other tasks do. A new task can then follow this path all the way to the root, which needlessly delays tasks whose grace period is done, but who do not happen to acquire the lock quickly enough. This commit avoids this problem by maintaining per-rcu_node wait queues, along with a per-rcu_node counter that tracks the latest grace period sought by an earlier task to visit this node. If that grace period would satisfy the current task, instead of proceeding up the tree, it waits on the current rcu_node structure using a pair of wait queues provided for that purpose. This decouples awakening of old tasks from the arrival of new tasks. If the wakeups prove to be a bottleneck, additional kthreads can be brought to bear for that purpose. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Add event tracing definitions for expedited grace periodsPaul E. McKenney2016-03-311-2/+76
| | | | Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
* rcu: Apply rcu_seq operations to _rcu_barrier()Paul E. McKenney2015-07-171-1/+0
| | | | | | | The rcu_seq operations were open-coded in _rcu_barrier(), so this commit replaces the open-coding with the shiny new rcu_seq operations. Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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