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authorWill Deacon <will.deacon@arm.com>2016-08-24 10:07:14 +0100
committerAlex Shi <alex.shi@linaro.org>2017-03-23 15:52:39 +0800
commit8fcc92c874d4a62a7a37355bdec8261d7d618bd1 (patch)
tree8fb23485e7c6af2722d4c14ed651b79bdd997ddd
parentdf7d71423756ca6fc34ce3d756445250b7dfd425 (diff)
downloadlinux-linaro-stable-v4.4/topic/perf-opencsd-4.4-github.tar.gz
perf/core: Use this_cpu_ptr() when stopping AUX eventsv4.4/topic/perf-opencsd-4.4-github
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> (cherry picked from commit 8b6a3fe8fab97716990a3abde1a01fb5a34552a3) Signed-off-by: Alex Shi <alex.shi@linaro.org>
-rw-r--r--kernel/events/core.c2
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/events/core.c b/kernel/events/core.c
index 59552da6d6aa..438f5fe3074a 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -5806,7 +5806,7 @@ 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,
};