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| author | Will Deacon <will.deacon@arm.com> | 2016-08-24 10:07:14 +0100 |
|---|---|---|
| committer | Ingo Molnar <mingo@kernel.org> | 2016-08-24 15:03:10 +0200 |
| commit | 8b6a3fe8fab97716990a3abde1a01fb5a34552a3 (patch) | |
| tree | ce7acd4fd8743c0c4bcb7572da84fd1ee6ec3f46 /kernel/events | |
| parent | de737f33ab23b213650c624e79ee479f12e3c500 (diff) | |
| download | linux-8b6a3fe8fab97716990a3abde1a01fb5a34552a3.tar.gz linux-8b6a3fe8fab97716990a3abde1a01fb5a34552a3.tar.bz2 linux-8b6a3fe8fab97716990a3abde1a01fb5a34552a3.zip | |
perf/core: Use this_cpu_ptr() when stopping AUX events
When tearing down an AUX buf for an event via perf_mmap_close(),
__perf_event_output_stop() is called on the event's CPU to ensure that
trace generation is halted before the process of unmapping and
freeing the buffer pages begins.
The callback is performed via cpu_function_call(), which ensures that it
runs with interrupts disabled and is therefore not preemptible.
Unfortunately, the current code grabs the per-cpu context pointer using
get_cpu_ptr(), which unnecessarily disables preemption and doesn't pair
the call with put_cpu_ptr(), leading to a preempt_count() imbalance and
a BUG when freeing the AUX buffer later on:
WARNING: CPU: 1 PID: 2249 at kernel/events/ring_buffer.c:539 __rb_free_aux+0x10c/0x120
Modules linked in:
[...]
Call Trace:
[<ffffffff813379dd>] dump_stack+0x4f/0x72
[<ffffffff81059ff6>] __warn+0xc6/0xe0
[<ffffffff8105a0c8>] warn_slowpath_null+0x18/0x20
[<ffffffff8112761c>] __rb_free_aux+0x10c/0x120
[<ffffffff81128163>] rb_free_aux+0x13/0x20
[<ffffffff8112515e>] perf_mmap_close+0x29e/0x2f0
[<ffffffff8111da30>] ? perf_iterate_ctx+0xe0/0xe0
[<ffffffff8115f685>] remove_vma+0x25/0x60
[<ffffffff81161796>] exit_mmap+0x106/0x140
[<ffffffff8105725c>] mmput+0x1c/0xd0
[<ffffffff8105cac3>] do_exit+0x253/0xbf0
[<ffffffff8105e32e>] do_group_exit+0x3e/0xb0
[<ffffffff81068d49>] get_signal+0x249/0x640
[<ffffffff8101c273>] do_signal+0x23/0x640
[<ffffffff81905f42>] ? _raw_write_unlock_irq+0x12/0x30
[<ffffffff81905f69>] ? _raw_spin_unlock_irq+0x9/0x10
[<ffffffff81901896>] ? __schedule+0x2c6/0x710
[<ffffffff810022a4>] exit_to_usermode_loop+0x74/0x90
[<ffffffff81002a56>] prepare_exit_to_usermode+0x26/0x30
[<ffffffff81906d1b>] retint_user+0x8/0x10
This patch uses this_cpu_ptr() instead of get_cpu_ptr(), since preemption is
already disabled by the caller.
Signed-off-by: Will Deacon <will.deacon@arm.com>
Reviewed-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Fixes: 95ff4ca26c49 ("perf/core: Free AUX pages in unmap path")
Link: http://lkml.kernel.org/r/20160824091905.GA16944@arm.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Diffstat (limited to 'kernel/events')
| -rw-r--r-- | kernel/events/core.c | 2 |
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c index 5650f5317e0c..3cfabdf7b942 100644 --- a/kernel/events/core.c +++ b/kernel/events/core.c @@ -6166,7 +6166,7 @@ static int __perf_pmu_output_stop(void *info) { struct perf_event *event = info; struct pmu *pmu = event->pmu; - struct perf_cpu_context *cpuctx = get_cpu_ptr(pmu->pmu_cpu_context); + struct perf_cpu_context *cpuctx = this_cpu_ptr(pmu->pmu_cpu_context); struct remote_output ro = { .rb = event->rb, }; |