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| author | Rabin Vincent <rabinv@axis.com> | 2017-04-05 15:14:08 +0200 |
|---|---|---|
| committer | Ralf Baechle <ralf@linux-mips.org> | 2017-04-10 12:25:07 +0200 |
| commit | f2b42866b1bb30c1f62a84f6d829b8789495da95 (patch) | |
| tree | 741b9f42bcdba9b7453e693eded39d9afe774468 /arch | |
| parent | 9eec1c01a073fe1fdba4e50e53bd953d1c59ad00 (diff) | |
| download | linux-0-day-f2b42866b1bb30c1f62a84f6d829b8789495da95.tar.gz linux-0-day-f2b42866b1bb30c1f62a84f6d829b8789495da95.tar.xz | |
MIPS: perf: fix deadlock
mipsxx_pmu_handle_shared_irq() calls irq_work_run() while holding the
pmuint_rwlock for read. irq_work_run() can, via perf_pending_event(),
call try_to_wake_up() which can try to take rq->lock.
However, perf can also call perf_pmu_enable() (and thus take the
pmuint_rwlock for write) while holding the rq->lock, from
finish_task_switch() via perf_event_context_sched_in().
This leads to an ABBA deadlock:
PID: 3855 TASK: 8f7ce288 CPU: 2 COMMAND: "process"
#0 [89c39ac8] __delay at 803b5be4
#1 [89c39ac8] do_raw_spin_lock at 8008fdcc
#2 [89c39af8] try_to_wake_up at 8006e47c
#3 [89c39b38] pollwake at 8018eab0
#4 [89c39b68] __wake_up_common at 800879f4
#5 [89c39b98] __wake_up at 800880e4
#6 [89c39bc8] perf_event_wakeup at 8012109c
#7 [89c39be8] perf_pending_event at 80121184
#8 [89c39c08] irq_work_run_list at 801151f0
#9 [89c39c38] irq_work_run at 80115274
#10 [89c39c50] mipsxx_pmu_handle_shared_irq at 8002cc7c
PID: 1481 TASK: 8eaac6a8 CPU: 3 COMMAND: "process"
#0 [8de7f900] do_raw_write_lock at 800900e0
#1 [8de7f918] perf_event_context_sched_in at 80122310
#2 [8de7f938] __perf_event_task_sched_in at 80122608
#3 [8de7f958] finish_task_switch at 8006b8a4
#4 [8de7f998] __schedule at 805e4dc4
#5 [8de7f9f8] schedule at 805e5558
#6 [8de7fa10] schedule_hrtimeout_range_clock at 805e9984
#7 [8de7fa70] poll_schedule_timeout at 8018e8f8
#8 [8de7fa88] do_select at 8018f338
#9 [8de7fd88] core_sys_select at 8018f5cc
#10 [8de7fee0] sys_select at 8018f854
#11 [8de7ff28] syscall_common at 80028fc8
The lock seems to be there to protect the hardware counters so there is
no need to hold it across irq_work_run().
Signed-off-by: Rabin Vincent <rabinv@axis.com>
Signed-off-by: Ralf Baechle <ralf@linux-mips.org>
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/mips/kernel/perf_event_mipsxx.c | 9 |
1 files changed, 5 insertions, 4 deletions
diff --git a/arch/mips/kernel/perf_event_mipsxx.c b/arch/mips/kernel/perf_event_mipsxx.c index 8c35b3152e1eb..9452b02ce0797 100644 --- a/arch/mips/kernel/perf_event_mipsxx.c +++ b/arch/mips/kernel/perf_event_mipsxx.c @@ -1446,6 +1446,11 @@ static int mipsxx_pmu_handle_shared_irq(void) HANDLE_COUNTER(0) } +#ifdef CONFIG_MIPS_PERF_SHARED_TC_COUNTERS + read_unlock(&pmuint_rwlock); +#endif + resume_local_counters(); + /* * Do all the work for the pending perf events. We can do this * in here because the performance counter interrupt is a regular @@ -1454,10 +1459,6 @@ static int mipsxx_pmu_handle_shared_irq(void) if (handled == IRQ_HANDLED) irq_work_run(); -#ifdef CONFIG_MIPS_PERF_SHARED_TC_COUNTERS - read_unlock(&pmuint_rwlock); -#endif - resume_local_counters(); return handled; } |