realtimer_expire: avoid proc lock recursion when called from itimer_proc_continue()
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Authored by kib on Apr 13 2021, 1:52 PM.

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rG75c5cf7a720f: filt_timerexpire: avoid process lock recursion
rG5cc1d199412e: realtimer_expire: avoid proc lock recursion when called from…

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It is fine to drop the process lock there, process cannot exit until its timers are cleared.

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rG FreeBSD src repository

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kib requested review of this revision.Apr 13 2021, 1:52 PM

kib created this revision.

Upload the correct version of the patch.
PHOLD() there is not needed and is even wrong.

I believe there is a similar recursion with kqueue timers: kqtimer_proc_continue() holds the proc lock, and filt_timerexpire() may attempt to acquire it.

Handle recursion in filter_timerexpire()

markj accepted this revision.Apr 13 2021, 8:41 PM

This revision is now accepted and ready to land.Apr 13 2021, 8:41 PM

Closed by commit rG5cc1d199412e: realtimer_expire: avoid proc lock recursion when called from… (authored by kib). · Explain WhyApr 14 2021, 7:59 AM

This revision was automatically updated to reflect the committed changes.

kib added a commit: rG5cc1d199412e: realtimer_expire: avoid proc lock recursion when called from….

kib added a commit: rG75c5cf7a720f: filt_timerexpire: avoid process lock recursion.

aly_aaronly.me mentioned this in D49576: Remove extra PROC_UNLOCK() from itimer_fire().Mar 30 2025, 12:36 AM

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sys/

kern/

kern_event.c

22 lines

kern_time.c

24 lines

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sys/kern/kern_event.c