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watchdog/hardlockup/perf: Cure UP damage 

for_each_cpu() unintuitively reports CPU0 as set independend of the actual
cpumask content on UP kernels. That leads to a NULL pointer dereference
when the cleanup function is invoked and there is no event to clean up.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
This commit is contained in:
Thomas Gleixner 2017-09-25 20:21:54 +02:00
parent ab5fe3ff38
commit 115ef3b7e6
1 changed files with 6 additions and 1 deletions
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7
kernel/watchdog_hld.c
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@ -220,8 +220,13 @@ void hardlockup_detector_perf_cleanup(void)
for_each_cpu(cpu, &dead_events_mask) { for_each_cpu(cpu, &dead_events_mask) {
struct perf_event *event = per_cpu(watchdog_ev, cpu); struct perf_event *event = per_cpu(watchdog_ev, cpu);
/*
* Required because for_each_cpu() reports unconditionally
* CPU0 as set on UP kernels. Sigh.
*/
if (event)
perf_event_release_kernel(event);
per_cpu(watchdog_ev, cpu) = NULL; per_cpu(watchdog_ev, cpu) = NULL;
perf_event_release_kernel(event);
} }
cpumask_clear(&dead_events_mask); cpumask_clear(&dead_events_mask);
} }