linux_timerfd_settime set expirations count to zero
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Authored by ankohuu_outlook.com on Jan 19 2021, 6:48 AM.

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Reviewers

dchagin
trasz

Group Reviewers

Linux Emulation

Commits

rGbf1863de6b1f: linux: make timerfd_settime(2) set expirations count to zero
rG0cb6fa6acc93: linux: make timerfd_settime(2) set expirations count to zero
rGae71b794cbed: linux: make timerfd_settime(2) set expirations count to zero

Summary

On Linux, read(2) timerfd returns an unsigned 8-byte integer (uint64_t) containing the number of expirations that have occurred, if the timer has already expired one or more times since its settings were last modified using timerfd_settime(), or since the last successful read(2).That's to say, once do a read or timerfd_settime operation, timer fd's expiration count should be zero.
Some Linux applications create timerfd and add it to epoll with LT mode, when event comes, they do timerfd_settime instead of read to stop event source from trigger, On FreeBSD timerfd_settime don't set count to zero, so cause CPU high.
Add set count to zero On FreeBSD emulation linux_timerfd_settime.

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rG FreeBSD src repository

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Event Timeline

ankohuu_outlook.com created this revision.Jan 19 2021, 6:48 AM

Herald added subscribers: Contributor Reviews (src), imp. · View Herald TranscriptJan 19 2021, 6:48 AM

ankohuu_outlook.com requested review of this revision.Jan 19 2021, 6:48 AM

Harbormaster completed remote builds in B36332: Diff 82556.Jan 19 2021, 6:48 AM

ankohuu_outlook.com added reviewers: dchagin, trasz, Linux Emulation.Jan 19 2021, 6:50 AM

I don't have experience with that code, and neither with timerfd, but your patch makes sense. Can you tell me which apps use the behaviour you're describing?

In D28231#636326, @trasz wrote:

I don't have experience with that code, and neither with timerfd, but your patch makes sense. Can you tell me which apps use the behaviour you're describing?

Sorry, according to the git-log record, I made this modification on March 30th 2020 for some Linux desktop related programs, but I did not record which program it was.

Thanks! Can you commit it yourself, or should I?

In D28231#636869, @trasz wrote:

Thanks! Can you commit it yourself, or should I?

Could you help me? I don't have permission to commit it.
I also have another review about timerfd ready to land
https://reviews.freebsd.org/D28148.
If possible please help me to commit it also, thank you.

This revision was not accepted when it landed; it landed in state Needs Review.Feb 3 2021, 7:09 PM

Closed by commit rGae71b794cbed: linux: make timerfd_settime(2) set expirations count to zero (authored by ankohuu_outlook.com, committed by trasz). · Explain Why

This revision was automatically updated to reflect the committed changes.

trasz added a commit: rGae71b794cbed: linux: make timerfd_settime(2) set expirations count to zero.

Done. Thank you, and let me know when you have any more linuxulator fixes :-)

dchagin added a commit: rG0cb6fa6acc93: linux: make timerfd_settime(2) set expirations count to zero.Mar 19 2021, 6:43 PM

dchagin added a commit: rGbf1863de6b1f: linux: make timerfd_settime(2) set expirations count to zero.Mar 21 2021, 7:06 AM