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git://git.kernel.org/pub/scm/linux/kernel/git/xiang/erofs.git
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Dapeng Mi
eb3182ef04
cpu-clock usage by the async-profiler tool can trigger a system hang, which got bisected back to the following commit by Octavia Togami:18dbcbfabf("perf: Fix the POLL_HUP delivery breakage") causes this issue The root cause of the hang is that cpu-clock is a special type of SW event which relies on hrtimers. The __perf_event_overflow() callback is invoked from the hrtimer handler for cpu-clock events, and __perf_event_overflow() tries to call cpu_clock_event_stop() to stop the event, which calls htimer_cancel() to cancel the hrtimer. But that's a recursion into the hrtimer code from a hrtimer handler, which (unsurprisingly) deadlocks. To fix this bug, use hrtimer_try_to_cancel() instead, and set the PERF_HES_STOPPED flag, which causes perf_swevent_hrtimer() to stop the event once it sees the PERF_HES_STOPPED flag. [ mingo: Fixed the comments and improved the changelog. ] Closes: https://lore.kernel.org/all/CAHPNGSQpXEopYreir+uDDEbtXTBvBvi8c6fYXJvceqtgTPao3Q@mail.gmail.com/ Fixes:18dbcbfabf("perf: Fix the POLL_HUP delivery breakage") Reported-by: Octavia Togami <[email protected]> Suggested-by: Peter Zijlstra <[email protected]> Signed-off-by: Dapeng Mi <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Signed-off-by: Ingo Molnar <[email protected]> Tested-by: Octavia Togami <[email protected]> Cc: [email protected] Link: https://github.com/lucko/spark/issues/530 Link: https://patch.msgid.link/[email protected]