| Commit message (Collapse) | Author | Age | Files | Lines |
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When performing a consuming read, the ring buffer swaps out a
page from the ring buffer with a empty page and this page that
was swapped out becomes the new reader page. The reader page
is owned by the reader and since it was swapped out of the ring
buffer, writers do not have access to it (there's an exception
to that rule, but it's out of scope for this commit).
When reading the "trace" file, it is a non consuming read, which
means that the data in the ring buffer will not be modified.
When the trace file is opened, a ring buffer iterator is allocated
and writes to the ring buffer are disabled, such that the iterator
will not have issues iterating over the data.
Although the ring buffer disabled writes, it does not disable other
reads, or even consuming reads. If a consuming read happens, then
the iterator is reset and starts reading from the beginning again.
My tests would sometimes trigger this bug on my i386 box:
WARNING: CPU: 0 PID: 5175 at kernel/trace/trace.c:1527 __trace_find_cmdline+0x66/0xaa()
Modules linked in:
CPU: 0 PID: 5175 Comm: grep Not tainted 3.16.0-rc3-test+ #8
Hardware name: /DG965MQ, BIOS MQ96510J.86A.0372.2006.0605.1717 06/05/2006
00000000 00000000 f09c9e1c c18796b3 c1b5d74c f09c9e4c c103a0e3 c1b5154b
f09c9e78 00001437 c1b5d74c 000005f7 c10bd85a c10bd85a c1cac57c f09c9eb0
ed0e0000 f09c9e64 c103a185 00000009 f09c9e5c c1b5154b f09c9e78 f09c9e80^M
Call Trace:
[<c18796b3>] dump_stack+0x4b/0x75
[<c103a0e3>] warn_slowpath_common+0x7e/0x95
[<c10bd85a>] ? __trace_find_cmdline+0x66/0xaa
[<c10bd85a>] ? __trace_find_cmdline+0x66/0xaa
[<c103a185>] warn_slowpath_fmt+0x33/0x35
[<c10bd85a>] __trace_find_cmdline+0x66/0xaa^M
[<c10bed04>] trace_find_cmdline+0x40/0x64
[<c10c3c16>] trace_print_context+0x27/0xec
[<c10c4360>] ? trace_seq_printf+0x37/0x5b
[<c10c0b15>] print_trace_line+0x319/0x39b
[<c10ba3fb>] ? ring_buffer_read+0x47/0x50
[<c10c13b1>] s_show+0x192/0x1ab
[<c10bfd9a>] ? s_next+0x5a/0x7c
[<c112e76e>] seq_read+0x267/0x34c
[<c1115a25>] vfs_read+0x8c/0xef
[<c112e507>] ? seq_lseek+0x154/0x154
[<c1115ba2>] SyS_read+0x54/0x7f
[<c188488e>] syscall_call+0x7/0xb
---[ end trace 3f507febd6b4cc83 ]---
>>>> ##### CPU 1 buffer started ####
Which was the __trace_find_cmdline() function complaining about the pid
in the event record being negative.
After adding more test cases, this would trigger more often. Strangely
enough, it would never trigger on a single test, but instead would trigger
only when running all the tests. I believe that was the case because it
required one of the tests to be shutting down via delayed instances while
a new test started up.
After spending several days debugging this, I found that it was caused by
the iterator becoming corrupted. Debugging further, I found out why
the iterator became corrupted. It happened with the rb_iter_reset().
As consuming reads may not read the full reader page, and only part
of it, there's a "read" field to know where the last read took place.
The iterator, must also start at the read position. In the rb_iter_reset()
code, if the reader page was disconnected from the ring buffer, the iterator
would start at the head page within the ring buffer (where writes still
happen). But the mistake there was that it still used the "read" field
to start the iterator on the head page, where it should always start
at zero because readers never read from within the ring buffer where
writes occur.
I originally wrote a patch to have it set the iter->head to 0 instead
of iter->head_page->read, but then I questioned why it wasn't always
setting the iter to point to the reader page, as the reader page is
still valid. The list_empty(reader_page->list) just means that it was
successful in swapping out. But the reader_page may still have data.
There was a bug report a long time ago that was not reproducible that
had something about trace_pipe (consuming read) not matching trace
(iterator read). This may explain why that happened.
Anyway, the correct answer to this bug is to always use the reader page
an not reset the iterator to inside the writable ring buffer.
Cc: stable@vger.kernel.org # 2.6.28+
Fixes: d769041f8653 "ring_buffer: implement new locking"
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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After writting a test to try to trigger the bug that caused the
ring buffer iterator to become corrupted, I hit another bug:
WARNING: CPU: 1 PID: 5281 at kernel/trace/ring_buffer.c:3766 rb_iter_peek+0x113/0x238()
Modules linked in: ipt_MASQUERADE sunrpc [...]
CPU: 1 PID: 5281 Comm: grep Tainted: G W 3.16.0-rc3-test+ #143
Hardware name: To Be Filled By O.E.M. To Be Filled By O.E.M./To be filled by O.E.M., BIOS SDBLI944.86P 05/08/2007
0000000000000000 ffffffff81809a80 ffffffff81503fb0 0000000000000000
ffffffff81040ca1 ffff8800796d6010 ffffffff810c138d ffff8800796d6010
ffff880077438c80 ffff8800796d6010 ffff88007abbe600 0000000000000003
Call Trace:
[<ffffffff81503fb0>] ? dump_stack+0x4a/0x75
[<ffffffff81040ca1>] ? warn_slowpath_common+0x7e/0x97
[<ffffffff810c138d>] ? rb_iter_peek+0x113/0x238
[<ffffffff810c138d>] ? rb_iter_peek+0x113/0x238
[<ffffffff810c14df>] ? ring_buffer_iter_peek+0x2d/0x5c
[<ffffffff810c6f73>] ? tracing_iter_reset+0x6e/0x96
[<ffffffff810c74a3>] ? s_start+0xd7/0x17b
[<ffffffff8112b13e>] ? kmem_cache_alloc_trace+0xda/0xea
[<ffffffff8114cf94>] ? seq_read+0x148/0x361
[<ffffffff81132d98>] ? vfs_read+0x93/0xf1
[<ffffffff81132f1b>] ? SyS_read+0x60/0x8e
[<ffffffff8150bf9f>] ? tracesys+0xdd/0xe2
Debugging this bug, which triggers when the rb_iter_peek() loops too
many times (more than 2 times), I discovered there's a case that can
cause that function to legitimately loop 3 times!
rb_iter_peek() is different than rb_buffer_peek() as the rb_buffer_peek()
only deals with the reader page (it's for consuming reads). The
rb_iter_peek() is for traversing the buffer without consuming it, and as
such, it can loop for one more reason. That is, if we hit the end of
the reader page or any page, it will go to the next page and try again.
That is, we have this:
1. iter->head > iter->head_page->page->commit
(rb_inc_iter() which moves the iter to the next page)
try again
2. event = rb_iter_head_event()
event->type_len == RINGBUF_TYPE_TIME_EXTEND
rb_advance_iter()
try again
3. read the event.
But we never get to 3, because the count is greater than 2 and we
cause the WARNING and return NULL.
Up the counter to 3.
Cc: stable@vger.kernel.org # 2.6.37+
Fixes: 69d1b839f7ee "ring-buffer: Bind time extend and data events together"
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fixes from Thomas Gleixner:
"Two fixes in the timer area:
- a long-standing lock inversion due to a printk
- suspend-related hrtimer corruption in sched_clock"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
timer: Fix lock inversion between hrtimer_bases.lock and scheduler locks
sched_clock: Avoid corrupting hrtimer tree during suspend
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clockevents_increase_min_delta() calls printk() from under
hrtimer_bases.lock. That causes lock inversion on scheduler locks because
printk() can call into the scheduler. Lockdep puts it as:
======================================================
[ INFO: possible circular locking dependency detected ]
3.15.0-rc8-06195-g939f04b #2 Not tainted
-------------------------------------------------------
trinity-main/74 is trying to acquire lock:
(&port_lock_key){-.....}, at: [<811c60be>] serial8250_console_write+0x8c/0x10c
but task is already holding lock:
(hrtimer_bases.lock){-.-...}, at: [<8103caeb>] hrtimer_try_to_cancel+0x13/0x66
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #5 (hrtimer_bases.lock){-.-...}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<8103c918>] __hrtimer_start_range_ns+0x1c/0x197
[<8107ec20>] perf_swevent_start_hrtimer.part.41+0x7a/0x85
[<81080792>] task_clock_event_start+0x3a/0x3f
[<810807a4>] task_clock_event_add+0xd/0x14
[<8108259a>] event_sched_in+0xb6/0x17a
[<810826a2>] group_sched_in+0x44/0x122
[<81082885>] ctx_sched_in.isra.67+0x105/0x11f
[<810828e6>] perf_event_sched_in.isra.70+0x47/0x4b
[<81082bf6>] __perf_install_in_context+0x8b/0xa3
[<8107eb8e>] remote_function+0x12/0x2a
[<8105f5af>] smp_call_function_single+0x2d/0x53
[<8107e17d>] task_function_call+0x30/0x36
[<8107fb82>] perf_install_in_context+0x87/0xbb
[<810852c9>] SYSC_perf_event_open+0x5c6/0x701
[<810856f9>] SyS_perf_event_open+0x17/0x19
[<8142f8ee>] syscall_call+0x7/0xb
-> #4 (&ctx->lock){......}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f04c>] _raw_spin_lock+0x21/0x30
[<81081df3>] __perf_event_task_sched_out+0x1dc/0x34f
[<8142cacc>] __schedule+0x4c6/0x4cb
[<8142cae0>] schedule+0xf/0x11
[<8142f9a6>] work_resched+0x5/0x30
-> #3 (&rq->lock){-.-.-.}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f04c>] _raw_spin_lock+0x21/0x30
[<81040873>] __task_rq_lock+0x33/0x3a
[<8104184c>] wake_up_new_task+0x25/0xc2
[<8102474b>] do_fork+0x15c/0x2a0
[<810248a9>] kernel_thread+0x1a/0x1f
[<814232a2>] rest_init+0x1a/0x10e
[<817af949>] start_kernel+0x303/0x308
[<817af2ab>] i386_start_kernel+0x79/0x7d
-> #2 (&p->pi_lock){-.-...}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<810413dd>] try_to_wake_up+0x1d/0xd6
[<810414cd>] default_wake_function+0xb/0xd
[<810461f3>] __wake_up_common+0x39/0x59
[<81046346>] __wake_up+0x29/0x3b
[<811b8733>] tty_wakeup+0x49/0x51
[<811c3568>] uart_write_wakeup+0x17/0x19
[<811c5dc1>] serial8250_tx_chars+0xbc/0xfb
[<811c5f28>] serial8250_handle_irq+0x54/0x6a
[<811c5f57>] serial8250_default_handle_irq+0x19/0x1c
[<811c56d8>] serial8250_interrupt+0x38/0x9e
[<810510e7>] handle_irq_event_percpu+0x5f/0x1e2
[<81051296>] handle_irq_event+0x2c/0x43
[<81052cee>] handle_level_irq+0x57/0x80
[<81002a72>] handle_irq+0x46/0x5c
[<810027df>] do_IRQ+0x32/0x89
[<8143036e>] common_interrupt+0x2e/0x33
[<8142f23c>] _raw_spin_unlock_irqrestore+0x3f/0x49
[<811c25a4>] uart_start+0x2d/0x32
[<811c2c04>] uart_write+0xc7/0xd6
[<811bc6f6>] n_tty_write+0xb8/0x35e
[<811b9beb>] tty_write+0x163/0x1e4
[<811b9cd9>] redirected_tty_write+0x6d/0x75
[<810b6ed6>] vfs_write+0x75/0xb0
[<810b7265>] SyS_write+0x44/0x77
[<8142f8ee>] syscall_call+0x7/0xb
-> #1 (&tty->write_wait){-.....}:
[<8104a942>] lock_acquire+0x92/0x101
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<81046332>] __wake_up+0x15/0x3b
[<811b8733>] tty_wakeup+0x49/0x51
[<811c3568>] uart_write_wakeup+0x17/0x19
[<811c5dc1>] serial8250_tx_chars+0xbc/0xfb
[<811c5f28>] serial8250_handle_irq+0x54/0x6a
[<811c5f57>] serial8250_default_handle_irq+0x19/0x1c
[<811c56d8>] serial8250_interrupt+0x38/0x9e
[<810510e7>] handle_irq_event_percpu+0x5f/0x1e2
[<81051296>] handle_irq_event+0x2c/0x43
[<81052cee>] handle_level_irq+0x57/0x80
[<81002a72>] handle_irq+0x46/0x5c
[<810027df>] do_IRQ+0x32/0x89
[<8143036e>] common_interrupt+0x2e/0x33
[<8142f23c>] _raw_spin_unlock_irqrestore+0x3f/0x49
[<811c25a4>] uart_start+0x2d/0x32
[<811c2c04>] uart_write+0xc7/0xd6
[<811bc6f6>] n_tty_write+0xb8/0x35e
[<811b9beb>] tty_write+0x163/0x1e4
[<811b9cd9>] redirected_tty_write+0x6d/0x75
[<810b6ed6>] vfs_write+0x75/0xb0
[<810b7265>] SyS_write+0x44/0x77
[<8142f8ee>] syscall_call+0x7/0xb
-> #0 (&port_lock_key){-.....}:
[<8104a62d>] __lock_acquire+0x9ea/0xc6d
[<8104a942>] lock_acquire+0x92/0x101
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<811c60be>] serial8250_console_write+0x8c/0x10c
[<8104e402>] call_console_drivers.constprop.31+0x87/0x118
[<8104f5d5>] console_unlock+0x1d7/0x398
[<8104fb70>] vprintk_emit+0x3da/0x3e4
[<81425f76>] printk+0x17/0x19
[<8105bfa0>] clockevents_program_min_delta+0x104/0x116
[<8105c548>] clockevents_program_event+0xe7/0xf3
[<8105cc1c>] tick_program_event+0x1e/0x23
[<8103c43c>] hrtimer_force_reprogram+0x88/0x8f
[<8103c49e>] __remove_hrtimer+0x5b/0x79
[<8103cb21>] hrtimer_try_to_cancel+0x49/0x66
[<8103cb4b>] hrtimer_cancel+0xd/0x18
[<8107f102>] perf_swevent_cancel_hrtimer.part.60+0x2b/0x30
[<81080705>] task_clock_event_stop+0x20/0x64
[<81080756>] task_clock_event_del+0xd/0xf
[<81081350>] event_sched_out+0xab/0x11e
[<810813e0>] group_sched_out+0x1d/0x66
[<81081682>] ctx_sched_out+0xaf/0xbf
[<81081e04>] __perf_event_task_sched_out+0x1ed/0x34f
[<8142cacc>] __schedule+0x4c6/0x4cb
[<8142cae0>] schedule+0xf/0x11
[<8142f9a6>] work_resched+0x5/0x30
other info that might help us debug this:
Chain exists of:
&port_lock_key --> &ctx->lock --> hrtimer_bases.lock
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(hrtimer_bases.lock);
lock(&ctx->lock);
lock(hrtimer_bases.lock);
lock(&port_lock_key);
*** DEADLOCK ***
4 locks held by trinity-main/74:
#0: (&rq->lock){-.-.-.}, at: [<8142c6f3>] __schedule+0xed/0x4cb
#1: (&ctx->lock){......}, at: [<81081df3>] __perf_event_task_sched_out+0x1dc/0x34f
#2: (hrtimer_bases.lock){-.-...}, at: [<8103caeb>] hrtimer_try_to_cancel+0x13/0x66
#3: (console_lock){+.+...}, at: [<8104fb5d>] vprintk_emit+0x3c7/0x3e4
stack backtrace:
CPU: 0 PID: 74 Comm: trinity-main Not tainted 3.15.0-rc8-06195-g939f04b #2
00000000 81c3a310 8b995c14 81426f69 8b995c44 81425a99 8161f671 8161f570
8161f538 8161f559 8161f538 8b995c78 8b142bb0 00000004 8b142fdc 8b142bb0
8b995ca8 8104a62d 8b142fac 000016f2 81c3a310 00000001 00000001 00000003
Call Trace:
[<81426f69>] dump_stack+0x16/0x18
[<81425a99>] print_circular_bug+0x18f/0x19c
[<8104a62d>] __lock_acquire+0x9ea/0xc6d
[<8104a942>] lock_acquire+0x92/0x101
[<811c60be>] ? serial8250_console_write+0x8c/0x10c
[<811c6032>] ? wait_for_xmitr+0x76/0x76
[<8142f11d>] _raw_spin_lock_irqsave+0x2e/0x3e
[<811c60be>] ? serial8250_console_write+0x8c/0x10c
[<811c60be>] serial8250_console_write+0x8c/0x10c
[<8104af87>] ? lock_release+0x191/0x223
[<811c6032>] ? wait_for_xmitr+0x76/0x76
[<8104e402>] call_console_drivers.constprop.31+0x87/0x118
[<8104f5d5>] console_unlock+0x1d7/0x398
[<8104fb70>] vprintk_emit+0x3da/0x3e4
[<81425f76>] printk+0x17/0x19
[<8105bfa0>] clockevents_program_min_delta+0x104/0x116
[<8105cc1c>] tick_program_event+0x1e/0x23
[<8103c43c>] hrtimer_force_reprogram+0x88/0x8f
[<8103c49e>] __remove_hrtimer+0x5b/0x79
[<8103cb21>] hrtimer_try_to_cancel+0x49/0x66
[<8103cb4b>] hrtimer_cancel+0xd/0x18
[<8107f102>] perf_swevent_cancel_hrtimer.part.60+0x2b/0x30
[<81080705>] task_clock_event_stop+0x20/0x64
[<81080756>] task_clock_event_del+0xd/0xf
[<81081350>] event_sched_out+0xab/0x11e
[<810813e0>] group_sched_out+0x1d/0x66
[<81081682>] ctx_sched_out+0xaf/0xbf
[<81081e04>] __perf_event_task_sched_out+0x1ed/0x34f
[<8104416d>] ? __dequeue_entity+0x23/0x27
[<81044505>] ? pick_next_task_fair+0xb1/0x120
[<8142cacc>] __schedule+0x4c6/0x4cb
[<81047574>] ? trace_hardirqs_off_caller+0xd7/0x108
[<810475b0>] ? trace_hardirqs_off+0xb/0xd
[<81056346>] ? rcu_irq_exit+0x64/0x77
Fix the problem by using printk_deferred() which does not call into the
scheduler.
Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Jan Kara <jack@suse.cz>
Cc: stable@vger.kernel.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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During suspend we call sched_clock_poll() to update the epoch and
accumulated time and reprogram the sched_clock_timer to fire
before the next wrap-around time. Unfortunately,
sched_clock_poll() doesn't restart the timer, instead it relies
on the hrtimer layer to do that and during suspend we aren't
calling that function from the hrtimer layer. Instead, we're
reprogramming the expires time while the hrtimer is enqueued,
which can cause the hrtimer tree to be corrupted. Furthermore, we
restart the timer during suspend but we update the epoch during
resume which seems counter-intuitive.
Let's fix this by saving the accumulated state and canceling the
timer during suspend. On resume we can update the epoch and
restart the timer similar to what we would do if we were starting
the clock for the first time.
Fixes: a08ca5d1089d "sched_clock: Use an hrtimer instead of timer"
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Link: http://lkml.kernel.org/r/1406174630-23458-1-git-send-email-john.stultz@linaro.org
Cc: Ingo Molnar <mingo@kernel.org>
Cc: stable <stable@vger.kernel.org>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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free_huge_page() is undefined without CONFIG_HUGETLBFS and there's no
need to filter PageHuge() page is such a configuration either, so avoid
exporting the symbol to fix a build error:
In file included from kernel/kexec.c:14:0:
kernel/kexec.c: In function 'crash_save_vmcoreinfo_init':
kernel/kexec.c:1623:20: error: 'free_huge_page' undeclared (first use in this function)
VMCOREINFO_SYMBOL(free_huge_page);
^
Introduced by commit 8f1d26d0e59b ("kexec: export free_huge_page to
VMCOREINFO")
Reported-by: kbuild test robot <fengguang.wu@intel.com>
Acked-by: Olof Johansson <olof@lixom.net>
Cc: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Cc: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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My IBM email addresses haven't worked for years; also map some
old-but-functional forwarding addresses to my canonical address.
Update my GPG key fingerprint; I moved to 4096R a long time ago.
Update description.
Signed-off-by: Josh Triplett <josh@joshtriplett.org>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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PG_head_mask was added into VMCOREINFO to filter huge pages in b3acc56bfe1
("kexec: save PG_head_mask in VMCOREINFO"), but makedumpfile still need
another symbol to filter *hugetlbfs* pages.
If a user hope to filter user pages, makedumpfile tries to exclude them by
checking the condition whether the page is anonymous, but hugetlbfs pages
aren't anonymous while they also be user pages.
We know it's possible to detect them in the same way as PageHuge(),
so we need the start address of free_huge_page():
int PageHuge(struct page *page)
{
if (!PageCompound(page))
return 0;
page = compound_head(page);
return get_compound_page_dtor(page) == free_huge_page;
}
For that reason, this patch changes free_huge_page() into public
to export it to VMCOREINFO.
Signed-off-by: Atsushi Kumagai <kumagai-atsushi@mxc.nes.nec.co.jp>
Acked-by: Baoquan He <bhe@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Thomas Gleixner:
"A bunch of fixes for perf and kprobes:
- revert a commit that caused a perf group regression
- silence dmesg spam
- fix kprobe probing errors on ia64 and ppc64
- filter kprobe faults from userspace
- lockdep fix for perf exit path
- prevent perf #GP in KVM guest
- correct perf event and filters"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
kprobes: Fix "Failed to find blacklist" probing errors on ia64 and ppc64
kprobes/x86: Don't try to resolve kprobe faults from userspace
perf/x86/intel: Avoid spamming kernel log for BTS buffer failure
perf/x86/intel: Protect LBR and extra_regs against KVM lying
perf: Fix lockdep warning on process exit
perf/x86/intel/uncore: Fix SNB-EP/IVT Cbox filter mappings
perf/x86/intel: Use proper dTLB-load-misses event on IvyBridge
perf: Revert ("perf: Always destroy groups on exit")
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On ia64 and ppc64, function pointers do not point to the
entry address of the function, but to the address of a
function descriptor (which contains the entry address and misc
data).
Since the kprobes code passes the function pointer stored
by NOKPROBE_SYMBOL() to kallsyms_lookup_size_offset() for
initalizing its blacklist, it fails and reports many errors,
such as:
Failed to find blacklist 0001013168300000
Failed to find blacklist 0001013000f0a000
[...]
To fix this bug, use arch_deref_entry_point() to get the
function entry address for kallsyms_lookup_size_offset()
instead of the raw function pointer.
Suzuki also pointed out that blacklist entries should also
be updated as well.
Reported-by: Tony Luck <tony.luck@gmail.com>
Fixed-by: Suzuki K. Poulose <suzuki@in.ibm.com>
Tested-by: Tony Luck <tony.luck@intel.com>
Tested-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Acked-by: Michael Ellerman <mpe@ellerman.id.au> (for powerpc)
Acked-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Jeremy Fitzhardinge <jeremy@goop.org>
Cc: sparse@chrisli.org
Cc: Paul Mackerras <paulus@samba.org>
Cc: akataria@vmware.com
Cc: anil.s.keshavamurthy@intel.com
Cc: Fenghua Yu <fenghua.yu@intel.com>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Rusty Russell <rusty@rustcorp.com.au>
Cc: Chris Wright <chrisw@sous-sol.org>
Cc: yrl.pp-manager.tt@hitachi.com
Cc: Kevin Hao <haokexin@gmail.com>
Cc: Ananth N Mavinakayanahalli <ananth@in.ibm.com>
Cc: rdunlap@infradead.org
Cc: dl9pf@gmx.de
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: David S. Miller <davem@davemloft.net>
Cc: linux-ia64@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Link: http://lkml.kernel.org/r/20140717114411.13401.2632.stgit@kbuild-fedora.novalocal
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Sasha Levin reported:
> While fuzzing with trinity inside a KVM tools guest running the latest -next
> kernel I've stumbled on the following spew:
>
> ======================================================
> [ INFO: possible circular locking dependency detected ]
> 3.15.0-next-20140613-sasha-00026-g6dd125d-dirty #654 Not tainted
> -------------------------------------------------------
> trinity-c578/9725 is trying to acquire lock:
> (&(&pool->lock)->rlock){-.-...}, at: __queue_work (kernel/workqueue.c:1346)
>
> but task is already holding lock:
> (&ctx->lock){-.....}, at: perf_event_exit_task (kernel/events/core.c:7471 kernel/events/core.c:7533)
>
> which lock already depends on the new lock.
> 1 lock held by trinity-c578/9725:
> #0: (&ctx->lock){-.....}, at: perf_event_exit_task (kernel/events/core.c:7471 kernel/events/core.c:7533)
>
> Call Trace:
> dump_stack (lib/dump_stack.c:52)
> print_circular_bug (kernel/locking/lockdep.c:1216)
> __lock_acquire (kernel/locking/lockdep.c:1840 kernel/locking/lockdep.c:1945 kernel/locking/lockdep.c:2131 kernel/locking/lockdep.c:3182)
> lock_acquire (./arch/x86/include/asm/current.h:14 kernel/locking/lockdep.c:3602)
> _raw_spin_lock (include/linux/spinlock_api_smp.h:143 kernel/locking/spinlock.c:151)
> __queue_work (kernel/workqueue.c:1346)
> queue_work_on (kernel/workqueue.c:1424)
> free_object (lib/debugobjects.c:209)
> __debug_check_no_obj_freed (lib/debugobjects.c:715)
> debug_check_no_obj_freed (lib/debugobjects.c:727)
> kmem_cache_free (mm/slub.c:2683 mm/slub.c:2711)
> free_task (kernel/fork.c:221)
> __put_task_struct (kernel/fork.c:250)
> put_ctx (include/linux/sched.h:1855 kernel/events/core.c:898)
> perf_event_exit_task (kernel/events/core.c:907 kernel/events/core.c:7478 kernel/events/core.c:7533)
> do_exit (kernel/exit.c:766)
> do_group_exit (kernel/exit.c:884)
> get_signal_to_deliver (kernel/signal.c:2347)
> do_signal (arch/x86/kernel/signal.c:698)
> do_notify_resume (arch/x86/kernel/signal.c:751)
> int_signal (arch/x86/kernel/entry_64.S:600)
Urgh.. so the only way I can make that happen is through:
perf_event_exit_task_context()
raw_spin_lock(&child_ctx->lock);
unclone_ctx(child_ctx)
put_ctx(ctx->parent_ctx);
raw_spin_unlock_irqrestore(&child_ctx->lock);
And we can avoid this by doing the change below.
I can't immediately see how this changed recently, but given that you
say it's easy to reproduce, lets fix this.
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Tejun Heo <tj@kernel.org>
Cc: Dave Jones <davej@redhat.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/20140623141242.GB19860@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Vince reported that commit 15a2d4de0eab5 ("perf: Always destroy groups
on exit") causes a regression with grouped events. In particular his
read_group_attached.c test fails.
https://github.com/deater/perf_event_tests/blob/master/tests/bugs/read_group_attached.c
Because of the context switch optimization in
perf_event_context_sched_out() the 'original' event may end up in the
child process and when that exits the change in the patch in question
destroys the actual grouping.
Therefore revert that change and only destroy inherited groups.
Reported-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-zedy3uktcp753q8fw8dagx7a@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The "uptime" trace clock added in:
commit 8aacf017b065a805d27467843490c976835eb4a5
tracing: Add "uptime" trace clock that uses jiffies
has wraparound problems when the system has been up more
than 1 hour 11 minutes and 34 seconds. It converts jiffies
to nanoseconds using:
(u64)jiffies_to_usecs(jiffy) * 1000ULL
but since jiffies_to_usecs() only returns a 32-bit value, it
truncates at 2^32 microseconds. An additional problem on 32-bit
systems is that the argument is "unsigned long", so fixing the
return value only helps until 2^32 jiffies (49.7 days on a HZ=1000
system).
Avoid these problems by using jiffies_64 as our basis, and
not converting to nanoseconds (we do convert to clock_t because
user facing API must not be dependent on internal kernel
HZ values).
Link: http://lkml.kernel.org/p/99d63c5bfe9b320a3b428d773825a37095bf6a51.1405708254.git.tony.luck@intel.com
Cc: stable@vger.kernel.org # 3.10+
Fixes: 8aacf017b065 "tracing: Add "uptime" trace clock that uses jiffies"
Signed-off-by: Tony Luck <tony.luck@intel.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull locking fixes from Thomas Gleixner:
"The locking department delivers:
- A rather large and intrusive bundle of fixes to address serious
performance regressions introduced by the new rwsem / mcs
technology. Simpler solutions have been discussed, but they would
have been ugly bandaids with more risk than doing the right thing.
- Make the rwsem spin on owner technology opt-in for architectures
and enable it only on the known to work ones.
- A few fixes to the lockdep userspace library"
* 'locking-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
locking/rwsem: Add CONFIG_RWSEM_SPIN_ON_OWNER
locking/mutex: Disable optimistic spinning on some architectures
locking/rwsem: Reduce the size of struct rw_semaphore
locking/rwsem: Rename 'activity' to 'count'
locking/spinlocks/mcs: Micro-optimize osq_unlock()
locking/spinlocks/mcs: Introduce and use init macro and function for osq locks
locking/spinlocks/mcs: Convert osq lock to atomic_t to reduce overhead
locking/spinlocks/mcs: Rename optimistic_spin_queue() to optimistic_spin_node()
locking/rwsem: Allow conservative optimistic spinning when readers have lock
tools/liblockdep: Account for bitfield changes in lockdeps lock_acquire
tools/liblockdep: Remove debug print left over from development
tools/liblockdep: Fix comparison of a boolean value with a value of 2
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Just like with mutexes (CONFIG_MUTEX_SPIN_ON_OWNER),
encapsulate the dependencies for rwsem optimistic spinning.
No logical changes here as it continues to depend on both
SMP and the XADD algorithm variant.
Signed-off-by: Davidlohr Bueso <davidlohr@hp.com>
Acked-by: Jason Low <jason.low2@hp.com>
[ Also make it depend on ARCH_SUPPORTS_ATOMIC_RMW. ]
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/1405112406-13052-2-git-send-email-davidlohr@hp.com
Cc: aswin@hp.com
Cc: Chris Mason <clm@fb.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Josef Bacik <jbacik@fusionio.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Waiman Long <Waiman.Long@hp.com>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The optimistic spin code assumes regular stores and cmpxchg() play nice;
this is found to not be true for at least: parisc, sparc32, tile32,
metag-lock1, arc-!llsc and hexagon.
There is further wreckage, but this in particular seemed easy to
trigger, so blacklist this.
Opt in for known good archs.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Reported-by: Mikulas Patocka <mpatocka@redhat.com>
Cc: David Miller <davem@davemloft.net>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: James Bottomley <James.Bottomley@hansenpartnership.com>
Cc: Vineet Gupta <vgupta@synopsys.com>
Cc: Jason Low <jason.low2@hp.com>
Cc: Waiman Long <waiman.long@hp.com>
Cc: "James E.J. Bottomley" <jejb@parisc-linux.org>
Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
Cc: John David Anglin <dave.anglin@bell.net>
Cc: James Hogan <james.hogan@imgtec.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: stable@vger.kernel.org
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Russell King <linux@arm.linux.org.uk>
Cc: Will Deacon <will.deacon@arm.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-kernel@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: sparclinux@vger.kernel.org
Link: http://lkml.kernel.org/r/20140606175316.GV13930@laptop.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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There are two definitions of struct rw_semaphore, one in linux/rwsem.h
and one in linux/rwsem-spinlock.h.
For some reason they have different names for the initial field. This
makes it impossible to use C99 named initialization for
__RWSEM_INITIALIZER() -- or we have to duplicate that entire thing
along with the structure definitions.
The simpler patch is renaming the rwsem-spinlock variant to match the
regular rwsem.
This allows us to switch to C99 named initialization.
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-bmrZolsbGmautmzrerog27io@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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In the unlock function of the cancellable MCS spinlock, the first
thing we do is to retrive the current CPU's osq node. However, due to
the changes made in the previous patch, in the common case where the
lock is not contended, we wouldn't need to access the current CPU's
osq node anymore.
This patch optimizes this by only retriving this CPU's osq node
after we attempt the initial cmpxchg to unlock the osq and found
that its contended.
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Norton <scott.norton@hp.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Waiman Long <waiman.long@hp.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1405358872-3732-5-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Currently, we initialize the osq lock by directly setting the lock's values. It
would be preferable if we use an init macro to do the initialization like we do
with other locks.
This patch introduces and uses a macro and function for initializing the osq lock.
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Norton <scott.norton@hp.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Waiman Long <waiman.long@hp.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chris Mason <clm@fb.com>
Cc: Josef Bacik <jbacik@fusionio.com>
Link: http://lkml.kernel.org/r/1405358872-3732-4-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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The cancellable MCS spinlock is currently used to queue threads that are
doing optimistic spinning. It uses per-cpu nodes, where a thread obtaining
the lock would access and queue the local node corresponding to the CPU that
it's running on. Currently, the cancellable MCS lock is implemented by using
pointers to these nodes.
In this patch, instead of operating on pointers to the per-cpu nodes, we
store the CPU numbers in which the per-cpu nodes correspond to in atomic_t.
A similar concept is used with the qspinlock.
By operating on the CPU # of the nodes using atomic_t instead of pointers
to those nodes, this can reduce the overhead of the cancellable MCS spinlock
by 32 bits (on 64 bit systems).
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Norton <scott.norton@hp.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Waiman Long <waiman.long@hp.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chris Mason <clm@fb.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Josef Bacik <jbacik@fusionio.com>
Link: http://lkml.kernel.org/r/1405358872-3732-3-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Currently, the per-cpu nodes structure for the cancellable MCS spinlock is
named "optimistic_spin_queue". However, in a follow up patch in the series
we will be introducing a new structure that serves as the new "handle" for
the lock. It would make more sense if that structure is named
"optimistic_spin_queue". Additionally, since the current use of the
"optimistic_spin_queue" structure are "nodes", it might be better if we
rename them to "node" anyway.
This preparatory patch renames all current "optimistic_spin_queue"
to "optimistic_spin_node".
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Scott Norton <scott.norton@hp.com>
Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Cc: Dave Chinner <david@fromorbit.com>
Cc: Waiman Long <waiman.long@hp.com>
Cc: Davidlohr Bueso <davidlohr@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Aswin Chandramouleeswaran <aswin@hp.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Chris Mason <clm@fb.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: Josef Bacik <jbacik@fusionio.com>
Link: http://lkml.kernel.org/r/1405358872-3732-2-git-send-email-jason.low2@hp.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Commit 4fc828e24cd9 ("locking/rwsem: Support optimistic spinning")
introduced a major performance regression for workloads such as
xfs_repair which mix read and write locking of the mmap_sem across
many threads. The result was xfs_repair ran 5x slower on 3.16-rc2
than on 3.15 and using 20x more system CPU time.
Perf profiles indicate in some workloads that significant time can
be spent spinning on !owner. This is because we don't set the lock
owner when readers(s) obtain the rwsem.
In this patch, we'll modify rwsem_can_spin_on_owner() such that we'll
return false if there is no lock owner. The rationale is that if we
just entered the slowpath, yet there is no lock owner, then there is
a possibility that a reader has the lock. To be conservative, we'll
avoid spinning in these situations.
This patch reduced the total run time of the xfs_repair workload from
about 4 minutes 24 seconds down to approximately 1 minute 26 seconds,
back to close to the same performance as on 3.15.
Retesting of AIM7, which were some of the workloads used to test the
original optimistic spinning code, confirmed that we still get big
performance gains with optimistic spinning, even with this additional
regression fix. Davidlohr found that while the 'custom' workload took
a performance hit of ~-14% to throughput for >300 users with this
additional patch, the overall gain with optimistic spinning is
still ~+45%. The 'disk' workload even improved by ~+15% at >1000 users.
Tested-by: Dave Chinner <dchinner@redhat.com>
Acked-by: Davidlohr Bueso <davidlohr@hp.com>
Signed-off-by: Jason Low <jason.low2@hp.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1404532172.2572.30.camel@j-VirtualBox
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull scheduler fix from Thomas Gleixner:
"Prevent a possible divide by zero in the debugging code"
* 'sched-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
sched: Fix possible divide by zero in avg_atom() calculation
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proc_sched_show_task() does:
if (nr_switches)
do_div(avg_atom, nr_switches);
nr_switches is unsigned long and do_div truncates it to 32 bits, which
means it can test non-zero on e.g. x86-64 and be truncated to zero for
division.
Fix the problem by using div64_ul() instead.
As a side effect calculations of avg_atom for big nr_switches are now correct.
Signed-off-by: Mateusz Guzik <mguzik@redhat.com>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: stable@vger.kernel.org
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1402750809-31991-1-git-send-email-mguzik@redhat.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull timer fix from Thomas Gleixner:
"A single fix for a long standing issue in the alarm timer subsystem,
which was noticed recently when people finally started to use alarm
timers for serious work"
* 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
alarmtimer: Fix bug where relative alarm timers were treated as absolute
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Sharvil noticed with the posix timer_settime interface, using the
CLOCK_REALTIME_ALARM or CLOCK_BOOTTIME_ALARM clockid, if the users
tried to specify a relative time timer, it would incorrectly be
treated as absolute regardless of the state of the flags argument.
This patch corrects this, properly checking the absolute/relative flag,
as well as adds further error checking that no invalid flag bits are set.
Reported-by: Sharvil Nanavati <sharvil@google.com>
Signed-off-by: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Prarit Bhargava <prarit@redhat.com>
Cc: Sharvil Nanavati <sharvil@google.com>
Cc: stable <stable@vger.kernel.org> #3.0+
Link: http://lkml.kernel.org/r/1404767171-6902-1-git-send-email-john.stultz@linaro.org
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull RCU fixes from Thomas Gleixner:
"Two RCU patches:
- Address a serious performance regression on open/close caused by
commit ac1bea85781e ("Make cond_resched() report RCU quiescent
states")
- Export RCU debug functions. Not a regression, but enablement to
address a serious recursion bug in the sl*b allocators in 3.17"
* 'core-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
rcu: Reduce overhead of cond_resched() checks for RCU
rcu: Export debug_init_rcu_head() and and debug_init_rcu_head()
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git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into core/urgent
Pull RCU fixes from Paul E. McKenney:
" This series includes the following:
1. Export a pair of debug-object interfaces for RCU that will
allow the slab allocators to avoid a recursion bug located
by Sasha Levin. Strictly speaking, this is not a regression,
but it would be good to enable the fix.
2. Address a serious performance regression on an open/close
micro-benchmark located by Dave Hansen. The offending commit
is ac1bea85781e (Make cond_resched() report RCU quiescent states). "
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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Commit ac1bea85781e (Make cond_resched() report RCU quiescent states)
fixed a problem where a CPU looping in the kernel with but one runnable
task would give RCU CPU stall warnings, even if the in-kernel loop
contained cond_resched() calls. Unfortunately, in so doing, it introduced
performance regressions in Anton Blanchard's will-it-scale "open1" test.
The problem appears to be not so much the increased cond_resched() path
length as an increase in the rate at which grace periods complete, which
increased per-update grace-period overhead.
This commit takes a different approach to fixing this bug, mainly by
moving the RCU-visible quiescent state from cond_resched() to
rcu_note_context_switch(), and by further reducing the check to a
simple non-zero test of a single per-CPU variable. However, this
approach requires that the force-quiescent-state processing send
resched IPIs to the offending CPUs. These will be sent only once
the grace period has reached an age specified by the boot/sysfs
parameter rcutree.jiffies_till_sched_qs, or once the grace period
reaches an age halfway to the point at which RCU CPU stall warnings
will be emitted, whichever comes first.
Reported-by: Dave Hansen <dave.hansen@intel.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Christoph Lameter <cl@gentwo.org>
Cc: Mike Galbraith <umgwanakikbuti@gmail.com>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
[ paulmck: Made rcu_momentary_dyntick_idle() as suggested by the
ktest build robot. Also fixed smp_mb() comment as noted by
Oleg Nesterov. ]
Merge with e552592e (Reduce overhead of cond_resched() checks for RCU)
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
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Currently, call_rcu() relies on implicit allocation and initialization
for the debug-objects handling of RCU callbacks. If you hammer the
kernel hard enough with Sasha's modified version of trinity, you can end
up with the sl*b allocators recursing into themselves via this implicit
call_rcu() allocation.
This commit therefore exports the debug_init_rcu_head() and
debug_rcu_head_free() functions, which permits the allocators to allocated
and pre-initialize the debug-objects information, so that there no longer
any need for call_rcu() to do that initialization, which in turn prevents
the recursion into the memory allocators.
Reported-by: Sasha Levin <sasha.levin@oracle.com>
Suggested-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Acked-by: Thomas Gleixner <tglx@linutronix.de>
Looks-good-to: Christoph Lameter <cl@linux.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm
Pull ACPI and power management fixes from Rafael Wysocki:
"These are a few recent regression fixes, a revert of the ACPI video
commit I promised, a system resume fix related to request_firmware(),
an ACPI video quirk for one more Win8-oriented BIOS, an ACPI device
enumeration documentation update and a few fixes for ARM cpufreq
drivers.
Specifics:
- Fix for a recently introduced NULL pointer dereference in the core
system suspend code occuring when platforms without ACPI attempt to
use the "freeze" sleep state from Zhang Rui.
- Fix for a recently introduced build warning in cpufreq headers from
Brian W Hart.
- Fix for a 3.13 cpufreq regression related to sysem resume that
triggers on some systems with multiple CPU clusters from Viresh
Kumar.
- Fix for a 3.4 regression in request_firmware() resulting in
WARN_ON()s on some systems during system resume from Takashi Iwai.
- Revert of the ACPI video commit that changed the default value of
the video.brightness_switch_enabled command line argument to 0 as
it has been reported to break existing setups.
- ACPI device enumeration documentation update to take recent code
changes into account and make the documentation match the code
again from Darren Hart.
- Fixes for the sa1110, imx6q, kirkwood, and cpu0 cpufreq drivers
from Linus Walleij, Nicolas Del Piano, Quentin Armitage, Viresh
Kumar.
- New ACPI video blacklist entry for HP ProBook 4540s from Hans de
Goede"
* tag 'pm+acpi-3.16-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/rafael/linux-pm:
cpufreq: make table sentinel macros unsigned to match use
cpufreq: move policy kobj to policy->cpu at resume
cpufreq: cpu0: OPPs can be populated at runtime
cpufreq: kirkwood: Reinstate cpufreq driver for ARCH_KIRKWOOD
cpufreq: imx6q: Select PM_OPP
cpufreq: sa1110: set memory type for h3600
ACPI / video: Add use_native_backlight quirk for HP ProBook 4540s
PM / sleep: fix freeze_ops NULL pointer dereferences
PM / sleep: Fix request_firmware() error at resume
Revert "ACPI / video: change acpi-video brightness_switch_enabled default to 0"
ACPI / documentation: Remove reference to acpi_platform_device_ids from enumeration.txt
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This patch fixes a NULL pointer dereference issue introduced by
commit 1f0b63866fc1 (ACPI / PM: Hold ACPI scan lock over the "freeze"
sleep state).
Fixes: 1f0b63866fc1 (ACPI / PM: Hold ACPI scan lock over the "freeze" sleep state)
Link: http://marc.info/?l=linux-pm&m=140541182017443&w=2
Reported-and-tested-by: Alexander Stein <alexander.stein@systec-electronic.com>
Signed-off-by: Zhang Rui <rui.zhang@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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The commit [247bc037: PM / Sleep: Mitigate race between the freezer
and request_firmware()] introduced the finer state control, but it
also leads to a new bug; for example, a bug report regarding the
firmware loading of intel BT device at suspend/resume:
https://bugzilla.novell.com/show_bug.cgi?id=873790
The root cause seems to be a small window between the process resume
and the clear of usermodehelper lock. The request_firmware() function
checks the UMH lock and gives up when it's in UMH_DISABLE state. This
is for avoiding the invalid f/w loading during suspend/resume phase.
The problem is, however, that usermodehelper_enable() is called at the
end of thaw_processes(). Thus, a thawed process in between can kick
off the f/w loader code path (in this case, via btusb_setup_intel())
even before the call of usermodehelper_enable(). Then
usermodehelper_read_trylock() returns an error and request_firmware()
spews WARN_ON() in the end.
This oneliner patch fixes the issue just by setting to UMH_FREEZING
state again before restarting tasks, so that the call of
request_firmware() will be blocked until the end of this function
instead of returning an error.
Fixes: 247bc0374254 (PM / Sleep: Mitigate race between the freezer and request_firmware())
Link: https://bugzilla.novell.com/show_bug.cgi?id=873790
Cc: 3.4+ <stable@vger.kernel.org> # 3.4+
Signed-off-by: Takashi Iwai <tiwai@suse.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
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git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace
Pull tracing fixes from Steven Rostedt:
"A few more fixes for ftrace infrastructure.
I was cleaning out my INBOX and found two fixes from zhangwei from a
year ago that were lost in my mail. These fix an inconsistency
between trace_puts() and the way trace_printk() works. The reason
this is important to fix is because when trace_printk() doesn't have
any arguments, it turns into a trace_puts(). Not being able to enable
a stack trace against trace_printk() because it does not have any
arguments is quite confusing. Also, the fix is rather trivial and low
risk.
While porting some changes to PowerPC I discovered that it still has
the function graph tracer filter bug that if you also enable stack
tracing the function graph tracer filter is ignored. I fixed that up.
Finally, Martin Lau, fixed a bug that would cause readers of the
ftrace ring buffer to block forever even though it was suppose to be
NONBLOCK"
This also includes the fix from an earlier pull request:
"Oleg Nesterov fixed a memory leak that happens if a user creates a
tracing instance, sets up a filter in an event, and then removes that
instance. The filter allocates memory that is never freed when the
instance is destroyed"
* tag 'trace-fixes-v3.16-rc5-v2' of git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-trace:
ring-buffer: Fix polling on trace_pipe
tracing: Add TRACE_ITER_PRINTK flag check in __trace_puts/__trace_bputs
tracing: Fix graph tracer with stack tracer on other archs
tracing: Add ftrace_trace_stack into __trace_puts/__trace_bputs
tracing: instance_rmdir() leaks ftrace_event_file->filter
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ring_buffer_poll_wait() should always put the poll_table to its wait_queue
even there is immediate data available. Otherwise, the following epoll and
read sequence will eventually hang forever:
1. Put some data to make the trace_pipe ring_buffer read ready first
2. epoll_ctl(efd, EPOLL_CTL_ADD, trace_pipe_fd, ee)
3. epoll_wait()
4. read(trace_pipe_fd) till EAGAIN
5. Add some more data to the trace_pipe ring_buffer
6. epoll_wait() -> this epoll_wait() will block forever
~ During the epoll_ctl(efd, EPOLL_CTL_ADD,...) call in step 2,
ring_buffer_poll_wait() returns immediately without adding poll_table,
which has poll_table->_qproc pointing to ep_poll_callback(), to its
wait_queue.
~ During the epoll_wait() call in step 3 and step 6,
ring_buffer_poll_wait() cannot add ep_poll_callback() to its wait_queue
because the poll_table->_qproc is NULL and it is how epoll works.
~ When there is new data available in step 6, ring_buffer does not know
it has to call ep_poll_callback() because it is not in its wait queue.
Hence, block forever.
Other poll implementation seems to call poll_wait() unconditionally as the very
first thing to do. For example, tcp_poll() in tcp.c.
Link: http://lkml.kernel.org/p/20140610060637.GA14045@devbig242.prn2.facebook.com
Cc: stable@vger.kernel.org # 2.6.27
Fixes: 2a2cc8f7c4d0 "ftrace: allow the event pipe to be polled"
Reviewed-by: Chris Mason <clm@fb.com>
Signed-off-by: Martin Lau <kafai@fb.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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The TRACE_ITER_PRINTK check in __trace_puts/__trace_bputs is missing,
so add it, to be consistent with __trace_printk/__trace_bprintk.
Those functions are all called by the same function: trace_printk().
Link: http://lkml.kernel.org/p/51E7A7D6.8090900@huawei.com
Cc: stable@vger.kernel.org # 3.11+
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Running my ftrace tests on PowerPC, it failed the test that checks
if function_graph tracer is affected by the stack tracer. It was.
Looking into this, I found that the update_function_graph_func()
must be called even if the trampoline function is not changed.
This is because archs like PowerPC do not support ftrace_ops being
passed by assembly and instead uses a helper function (what the
trampoline function points to). Since this function is not changed
even when multiple ftrace_ops are added to the code, the test that
falls out before calling update_function_graph_func() will miss that
the update must still be done.
Call update_function_graph_function() for all calls to
update_ftrace_function()
Cc: stable@vger.kernel.org # 3.3+
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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Currently trace option stacktrace is not applicable for
trace_printk with constant string argument, the reason is
in __trace_puts/__trace_bputs ftrace_trace_stack is missing.
In contrast, when using trace_printk with non constant string
argument(will call into __trace_printk/__trace_bprintk), then
trace option stacktrace is workable, this inconstant result
will confuses users a lot.
Link: http://lkml.kernel.org/p/51E7A7C9.9040401@huawei.com
Cc: stable@vger.kernel.org # 3.10+
Signed-off-by: zhangwei(Jovi) <jovi.zhangwei@huawei.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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instance_rmdir() path destroys the event files but forgets to free
file->filter. Change remove_event_file_dir() to free_event_filter().
Link: http://lkml.kernel.org/p/20140711190638.GA19517@redhat.com
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Tom Zanussi <tom.zanussi@linux.intel.com>
Cc: "zhangwei(Jovi)" <jovi.zhangwei@huawei.com>
Cc: stable@vger.kernel.org # 3.11+
Fixes: f6a84bdc75b5 "tracing: Introduce remove_event_file_dir()"
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip
Pull perf fixes from Ingo Molnar:
"Tooling fixes and an Intel PMU driver fixlet"
* 'perf-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
perf: Do not allow optimized switch for non-cloned events
perf/x86/intel: ignore CondChgd bit to avoid false NMI handling
perf symbols: Get kernel start address by symbol name
perf tools: Fix segfault in cumulative.callchain report
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The context check in perf_event_context_sched_out allows
non-cloned context to be part of the optimized schedule
out switch.
This could move non-cloned context into another workload
child. Once this child exits, the context is closed and
leaves all original (parent) events in closed state.
Any other new cloned event will have closed state and not
measure anything. And probably causing other odd bugs.
Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: <stable@vger.kernel.org>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: David Ahern <dsahern@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Link: http://lkml.kernel.org/r/1403598026-2310-2-git-send-email-jolsa@kernel.org
Signed-off-by: Ingo Molnar <mingo@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup
Pull cgroup fixes from Tejun Heo:
"Mostly fixes for the fallouts from the recent cgroup core changes.
The decoupled nature of cgroup dynamic hierarchy management
(hierarchies are created dynamically on mount but may or may not be
reused once unmounted depending on remaining usages) led to more
ugliness being added to kernfs.
Hopefully, this is the last of it"
* 'for-3.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup:
cpuset: break kernfs active protection in cpuset_write_resmask()
cgroup: fix a race between cgroup_mount() and cgroup_kill_sb()
kernfs: introduce kernfs_pin_sb()
cgroup: fix mount failure in a corner case
cpuset,mempolicy: fix sleeping function called from invalid context
cgroup: fix broken css_has_online_children()
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Writing to either "cpuset.cpus" or "cpuset.mems" file flushes
cpuset_hotplug_work so that cpu or memory hotunplug doesn't end up
migrating tasks off a cpuset after new resources are added to it.
As cpuset_hotplug_work calls into cgroup core via
cgroup_transfer_tasks(), this flushing adds the dependency to cgroup
core locking from cpuset_write_resmak(). This used to be okay because
cgroup interface files were protected by a different mutex; however,
8353da1f91f1 ("cgroup: remove cgroup_tree_mutex") simplified the
cgroup core locking and this dependency became a deadlock hazard -
cgroup file removal performed under cgroup core lock tries to drain
on-going file operation which is trying to flush cpuset_hotplug_work
blocked on the same cgroup core lock.
The locking simplification was done because kernfs added an a lot
easier way to deal with circular dependencies involving kernfs active
protection. Let's use the same strategy in cpuset and break active
protection in cpuset_write_resmask(). While it isn't the prettiest,
this is a very rare, likely unique, situation which also goes away on
the unified hierarchy.
The commands to trigger the deadlock warning without the patch and the
lockdep output follow.
localhost:/ # mount -t cgroup -o cpuset xxx /cpuset
localhost:/ # mkdir /cpuset/tmp
localhost:/ # echo 1 > /cpuset/tmp/cpuset.cpus
localhost:/ # echo 0 > cpuset/tmp/cpuset.mems
localhost:/ # echo $$ > /cpuset/tmp/tasks
localhost:/ # echo 0 > /sys/devices/system/cpu/cpu1/online
======================================================
[ INFO: possible circular locking dependency detected ]
3.16.0-rc1-0.1-default+ #7 Not tainted
-------------------------------------------------------
kworker/1:0/32649 is trying to acquire lock:
(cgroup_mutex){+.+.+.}, at: [<ffffffff8110e3d7>] cgroup_transfer_tasks+0x37/0x150
but task is already holding lock:
(cpuset_hotplug_work){+.+...}, at: [<ffffffff81085412>] process_one_work+0x192/0x520
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #2 (cpuset_hotplug_work){+.+...}:
...
-> #1 (s_active#175){++++.+}:
...
-> #0 (cgroup_mutex){+.+.+.}:
...
other info that might help us debug this:
Chain exists of:
cgroup_mutex --> s_active#175 --> cpuset_hotplug_work
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(cpuset_hotplug_work);
lock(s_active#175);
lock(cpuset_hotplug_work);
lock(cgroup_mutex);
*** DEADLOCK ***
2 locks held by kworker/1:0/32649:
#0: ("events"){.+.+.+}, at: [<ffffffff81085412>] process_one_work+0x192/0x520
#1: (cpuset_hotplug_work){+.+...}, at: [<ffffffff81085412>] process_one_work+0x192/0x520
stack backtrace:
CPU: 1 PID: 32649 Comm: kworker/1:0 Not tainted 3.16.0-rc1-0.1-default+ #7
...
Call Trace:
[<ffffffff815a5f78>] dump_stack+0x72/0x8a
[<ffffffff810c263f>] print_circular_bug+0x10f/0x120
[<ffffffff810c481e>] check_prev_add+0x43e/0x4b0
[<ffffffff810c4ee6>] validate_chain+0x656/0x7c0
[<ffffffff810c53d2>] __lock_acquire+0x382/0x660
[<ffffffff810c57a9>] lock_acquire+0xf9/0x170
[<ffffffff815aa13f>] mutex_lock_nested+0x6f/0x380
[<ffffffff8110e3d7>] cgroup_transfer_tasks+0x37/0x150
[<ffffffff811129c0>] hotplug_update_tasks_insane+0x110/0x1d0
[<ffffffff81112bbd>] cpuset_hotplug_update_tasks+0x13d/0x180
[<ffffffff811148ec>] cpuset_hotplug_workfn+0x18c/0x630
[<ffffffff810854d4>] process_one_work+0x254/0x520
[<ffffffff810875dd>] worker_thread+0x13d/0x3d0
[<ffffffff8108e0c8>] kthread+0xf8/0x100
[<ffffffff815acaec>] ret_from_fork+0x7c/0xb0
Signed-off-by: Tejun Heo <tj@kernel.org>
Reported-by: Li Zefan <lizefan@huawei.com>
Tested-by: Li Zefan <lizefan@huawei.com>
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We've converted cgroup to kernfs so cgroup won't be intertwined with
vfs objects and locking, but there are dark areas.
Run two instances of this script concurrently:
for ((; ;))
{
mount -t cgroup -o cpuacct xxx /cgroup
umount /cgroup
}
After a while, I saw two mount processes were stuck at retrying, because
they were waiting for a subsystem to become free, but the root associated
with this subsystem never got freed.
This can happen, if thread A is in the process of killing superblock but
hasn't called percpu_ref_kill(), and at this time thread B is mounting
the same cgroup root and finds the root in the root list and performs
percpu_ref_try_get().
To fix this, we try to increase both the refcnt of the superblock and the
percpu refcnt of cgroup root.
v2:
- we should try to get both the superblock refcnt and cgroup_root refcnt,
because cgroup_root may have no superblock assosiated with it.
- adjust/add comments.
tj: Updated comments. Renamed @sb to @pinned_sb.
Cc: <stable@vger.kernel.org> # 3.15
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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# cat test.sh
#! /bin/bash
mount -t cgroup -o cpu xxx /cgroup
umount /cgroup
mount -t cgroup -o cpu,cpuacct xxx /cgroup
umount /cgroup
# ./test.sh
mount: xxx already mounted or /cgroup busy
mount: according to mtab, xxx is already mounted on /cgroup
It's because the cgroupfs_root of the first mount was under destruction
asynchronously.
Fix this by delaying and then retrying mount for this case.
v3:
- put the refcnt immediately after getting it. (Tejun)
v2:
- use percpu_ref_tryget_live() rather that introducing
percpu_ref_alive(). (Tejun)
- adjust comment.
tj: Updated the comment a bit.
Cc: <stable@vger.kernel.org> # 3.15
Signed-off-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
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When runing with the kernel(3.15-rc7+), the follow bug occurs:
[ 9969.258987] BUG: sleeping function called from invalid context at kernel/locking/mutex.c:586
[ 9969.359906] in_atomic(): 1, irqs_disabled(): 0, pid: 160655, name: python
[ 9969.441175] INFO: lockdep is turned off.
[ 9969.488184] CPU: 26 PID: 160655 Comm: python Tainted: G A 3.15.0-rc7+ #85
[ 9969.581032] Hardware name: FUJITSU-SV PRIMEQUEST 1800E/SB, BIOS PRIMEQUEST 1000 Series BIOS Version 1.39 11/16/2012
[ 9969.706052] ffffffff81a20e60 ffff8803e941fbd0 ffffffff8162f523 ffff8803e941fd18
[ 9969.795323] ffff8803e941fbe0 ffffffff8109995a ffff8803e941fc58 ffffffff81633e6c
[ 9969.884710] ffffffff811ba5dc ffff880405c6b480 ffff88041fdd90a0 0000000000002000
[ 9969.974071] Call Trace:
[ 9970.003403] [<ffffffff8162f523>] dump_stack+0x4d/0x66
[ 9970.065074] [<ffffffff8109995a>] __might_sleep+0xfa/0x130
[ 9970.130743] [<ffffffff81633e6c>] mutex_lock_nested+0x3c/0x4f0
[ 9970.200638] [<ffffffff811ba5dc>] ? kmem_cache_alloc+0x1bc/0x210
[ 9970.272610] [<ffffffff81105807>] cpuset_mems_allowed+0x27/0x140
[ 9970.344584] [<ffffffff811b1303>] ? __mpol_dup+0x63/0x150
[ 9970.409282] [<ffffffff811b1385>] __mpol_dup+0xe5/0x150
[ 9970.471897] [<ffffffff811b1303>] ? __mpol_dup+0x63/0x150
[ 9970.536585] [<ffffffff81068c86>] ? copy_process.part.23+0x606/0x1d40
[ 9970.613763] [<ffffffff810bf28d>] ? trace_hardirqs_on+0xd/0x10
[ 9970.683660] [<ffffffff810ddddf>] ? monotonic_to_bootbased+0x2f/0x50
[ 9970.759795] [<ffffffff81068cf0>] copy_process.part.23+0x670/0x1d40
[ 9970.834885] [<ffffffff8106a598>] do_fork+0xd8/0x380
[ 9970.894375] [<ffffffff81110e4c>] ? __audit_syscall_entry+0x9c/0xf0
[ 9970.969470] [<ffffffff8106a8c6>] SyS_clone+0x16/0x20
[ 9971.030011] [<ffffffff81642009>] stub_clone+0x69/0x90
[ 9971.091573] [<ffffffff81641c29>] ? system_call_fastpath+0x16/0x1b
The cause is that cpuset_mems_allowed() try to take
mutex_lock(&callback_mutex) under the rcu_read_lock(which was hold in
__mpol_dup()). And in cpuset_mems_allowed(), the access to cpuset is
under rcu_read_lock, so in __mpol_dup, we can reduce the rcu_read_lock
protection region to protect the access to cpuset only in
current_cpuset_is_being_rebound(). So that we can avoid this bug.
This patch is a temporary solution that just addresses the bug
mentioned above, can not fix the long-standing issue about cpuset.mems
rebinding on fork():
"When the forker's task_struct is duplicated (which includes
->mems_allowed) and it races with an update to cpuset_being_rebound
in update_tasks_nodemask() then the task's mems_allowed doesn't get
updated. And the child task's mems_allowed can be wrong if the
cpuset's nodemask changes before the child has been added to the
cgroup's tasklist."
Signed-off-by: Gu Zheng <guz.fnst@cn.fujitsu.com>
Acked-by: Li Zefan <lizefan@huawei.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable <stable@vger.kernel.org>
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After running:
# mount -t cgroup cpu xxx /cgroup && mkdir /cgroup/sub && \
rmdir /cgroup/sub && umount /cgroup
I found the cgroup root still existed:
# cat /proc/cgroups
#subsys_name hierarchy num_cgroups enabled
cpuset 0 1 1
cpu 1 1 1
...
It turned out css_has_online_children() is broken.
Signed-off-by: Li Zefan <lizefan@huawei.com>
Sigend-off-by: Tejun Heo <tj@kernel.org>
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git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq
Pull workqueue fixes from Tejun Heo:
"Two workqueue fixes. Both are one liners. One fixes missing uevent
for workqueue files on sysfs. The other one fixes missing zeroing of
NUMA cpu masks which can lead to oopses among other things"
* 'for-3.16-fixes' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/wq:
workqueue: zero cpumask of wq_numa_possible_cpumask on init
workqueue: fix dev_set_uevent_suppress() imbalance
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When hot-adding and onlining CPU, kernel panic occurs, showing following
call trace.
BUG: unable to handle kernel paging request at 0000000000001d08
IP: [<ffffffff8114acfd>] __alloc_pages_nodemask+0x9d/0xb10
PGD 0
Oops: 0000 [#1] SMP
...
Call Trace:
[<ffffffff812b8745>] ? cpumask_next_and+0x35/0x50
[<ffffffff810a3283>] ? find_busiest_group+0x113/0x8f0
[<ffffffff81193bc9>] ? deactivate_slab+0x349/0x3c0
[<ffffffff811926f1>] new_slab+0x91/0x300
[<ffffffff815de95a>] __slab_alloc+0x2bb/0x482
[<ffffffff8105bc1c>] ? copy_process.part.25+0xfc/0x14c0
[<ffffffff810a3c78>] ? load_balance+0x218/0x890
[<ffffffff8101a679>] ? sched_clock+0x9/0x10
[<ffffffff81105ba9>] ? trace_clock_local+0x9/0x10
[<ffffffff81193d1c>] kmem_cache_alloc_node+0x8c/0x200
[<ffffffff8105bc1c>] copy_process.part.25+0xfc/0x14c0
[<ffffffff81114d0d>] ? trace_buffer_unlock_commit+0x4d/0x60
[<ffffffff81085a80>] ? kthread_create_on_node+0x140/0x140
[<ffffffff8105d0ec>] do_fork+0xbc/0x360
[<ffffffff8105d3b6>] kernel_thread+0x26/0x30
[<ffffffff81086652>] kthreadd+0x2c2/0x300
[<ffffffff81086390>] ? kthread_create_on_cpu+0x60/0x60
[<ffffffff815f20ec>] ret_from_fork+0x7c/0xb0
[<ffffffff81086390>] ? kthread_create_on_cpu+0x60/0x60
In my investigation, I found the root cause is wq_numa_possible_cpumask.
All entries of wq_numa_possible_cpumask is allocated by
alloc_cpumask_var_node(). And these entries are used without initializing.
So these entries have wrong value.
When hot-adding and onlining CPU, wq_update_unbound_numa() is called.
wq_update_unbound_numa() calls alloc_unbound_pwq(). And alloc_unbound_pwq()
calls get_unbound_pool(). In get_unbound_pool(), worker_pool->node is set
as follow:
3592 /* if cpumask is contained inside a NUMA node, we belong to that node */
3593 if (wq_numa_enabled) {
3594 for_each_node(node) {
3595 if (cpumask_subset(pool->attrs->cpumask,
3596 wq_numa_possible_cpumask[node])) {
3597 pool->node = node;
3598 break;
3599 }
3600 }
3601 }
But wq_numa_possible_cpumask[node] does not have correct cpumask. So, wrong
node is selected. As a result, kernel panic occurs.
By this patch, all entries of wq_numa_possible_cpumask are allocated by
zalloc_cpumask_var_node to initialize them. And the panic disappeared.
Signed-off-by: Yasuaki Ishimatsu <isimatu.yasuaki@jp.fujitsu.com>
Reviewed-by: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
Fixes: bce903809ab3 ("workqueue: add wq_numa_tbl_len and wq_numa_possible_cpumask[]")
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Uevents are suppressed during attributes registration, but never
restored, so kobject_uevent() does nothing.
Signed-off-by: Maxime Bizon <mbizon@freebox.fr>
Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: stable@vger.kernel.org
Fixes: 226223ab3c4118ddd10688cc2c131135848371ab
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