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* [Bug nptl/26801] New: pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI futexs @ 2020-10-28 13:54 yeatesrichardr at johndeere dot com 2020-10-28 13:59 ` [Bug nptl/26801] " yeatesrichardr at johndeere dot com ` (4 more replies) 0 siblings, 5 replies; 6+ messages in thread From: yeatesrichardr at johndeere dot com @ 2020-10-28 13:54 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=26801 Bug ID: 26801 Summary: pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI futexs Product: glibc Version: 2.30 Status: UNCONFIRMED Severity: normal Priority: P2 Component: nptl Assignee: unassigned at sourceware dot org Reporter: yeatesrichardr at johndeere dot com CC: drepper.fsp at gmail dot com Target Milestone: --- Created attachment 12925 --> https://sourceware.org/bugzilla/attachment.cgi?id=12925&action=edit Test program showing early return from pthread_mutex_clocklock() When a pthread mutex is ROBUST_NP, ERRORCHECK, and PRIO_INHERIT (other combination may fall into this same category) and pthread_mutex_clocklock() is used with CLOCK_MONOTONIC, the call will return immediately with ETIMEDOUT if the mutex is already taken at the time of the call. This was tested with glibc 2.30, but still appears to be present in the latest source code. The root cause is at line 381 of pthread_mutex_timedlock.c: int e = futex_lock_pi64 (&mutex->__data.__lock, abstime, private); Here, the CLOCK_MONOTONIC abstime is being passed to futex_lock_pi64 which requires a CLOCK_REALTIME abstime. Of course, a CLOCK_MONOTONIC looks a lot "earlier" than a CLOCK_REALTIME, so it times out immediately. It's not sufficient to convert from CLOCK_MONOTONIC to CLOCK_REALTIME since that would violate the assumption one is using, that changes to the wall clock time won't interfere with CLOCK_MONOTONIC timed waits. This was tested with kernel 5.4.47. Example program is attached. -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug nptl/26801] pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI futexs 2020-10-28 13:54 [Bug nptl/26801] New: pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI futexs yeatesrichardr at johndeere dot com @ 2020-10-28 13:59 ` yeatesrichardr at johndeere dot com 2020-10-28 14:01 ` [Bug nptl/26801] pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI mutexes yeatesrichardr at johndeere dot com ` (3 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: yeatesrichardr at johndeere dot com @ 2020-10-28 13:59 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=26801 --- Comment #1 from Ric Yeates <yeatesrichardr at johndeere dot com> --- Forgot to include example output. $ futex_bug FAILURE: ETIMEDOUT should have been returned after 10 or more seconds, returned after 0 seconds. $ uname -a Linux PCMA4MA000002.local.domain 5.4.47-2.2.0 #1 SMP PREEMPT Mon Oct 26 23:52:12 UTC 2020 aarch64 GNU/Linux -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug nptl/26801] pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI mutexes 2020-10-28 13:54 [Bug nptl/26801] New: pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI futexs yeatesrichardr at johndeere dot com 2020-10-28 13:59 ` [Bug nptl/26801] " yeatesrichardr at johndeere dot com @ 2020-10-28 14:01 ` yeatesrichardr at johndeere dot com 2020-10-28 17:33 ` yeatesrichardr at johndeere dot com ` (2 subsequent siblings) 4 siblings, 0 replies; 6+ messages in thread From: yeatesrichardr at johndeere dot com @ 2020-10-28 14:01 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=26801 Ric Yeates <yeatesrichardr at johndeere dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- Summary|pthread_mutex_clocklock |pthread_mutex_clocklock |with CLOCK_MONOTONIC can |with CLOCK_MONOTONIC can |fail on PI futexs |fail on PI mutexes -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug nptl/26801] pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI mutexes 2020-10-28 13:54 [Bug nptl/26801] New: pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI futexs yeatesrichardr at johndeere dot com 2020-10-28 13:59 ` [Bug nptl/26801] " yeatesrichardr at johndeere dot com 2020-10-28 14:01 ` [Bug nptl/26801] pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI mutexes yeatesrichardr at johndeere dot com @ 2020-10-28 17:33 ` yeatesrichardr at johndeere dot com 2020-10-28 20:02 ` adhemerval.zanella at linaro dot org 2020-11-25 15:31 ` adhemerval.zanella at linaro dot org 4 siblings, 0 replies; 6+ messages in thread From: yeatesrichardr at johndeere dot com @ 2020-10-28 17:33 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=26801 Ric Yeates <yeatesrichardr at johndeere dot com> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |yeatesrichardr at johndeere dot co | |m -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug nptl/26801] pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI mutexes 2020-10-28 13:54 [Bug nptl/26801] New: pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI futexs yeatesrichardr at johndeere dot com ` (2 preceding siblings ...) 2020-10-28 17:33 ` yeatesrichardr at johndeere dot com @ 2020-10-28 20:02 ` adhemerval.zanella at linaro dot org 2020-11-25 15:31 ` adhemerval.zanella at linaro dot org 4 siblings, 0 replies; 6+ messages in thread From: adhemerval.zanella at linaro dot org @ 2020-10-28 20:02 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=26801 Adhemerval Zanella <adhemerval.zanella at linaro dot org> changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |adhemerval.zanella at linaro dot o | |rg --- Comment #2 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> --- We need kernel support for FUTEX_LOCK_PI with CLOCK_REALTIME due possible non continuous clock, but currently Linux does not supporting set the clock for the PI operations (it always assumes CLOCK_REALTIME). I think it would be better to just return EINVAL is a clock different than CLOCK_REALTIME is used with pthread_mutex_clocklock and PTHREAD_PRIO_INHERIT. -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
* [Bug nptl/26801] pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI mutexes 2020-10-28 13:54 [Bug nptl/26801] New: pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI futexs yeatesrichardr at johndeere dot com ` (3 preceding siblings ...) 2020-10-28 20:02 ` adhemerval.zanella at linaro dot org @ 2020-11-25 15:31 ` adhemerval.zanella at linaro dot org 4 siblings, 0 replies; 6+ messages in thread From: adhemerval.zanella at linaro dot org @ 2020-11-25 15:31 UTC (permalink / raw) To: glibc-bugs https://sourceware.org/bugzilla/show_bug.cgi?id=26801 Adhemerval Zanella <adhemerval.zanella at linaro dot org> changed: What |Removed |Added ---------------------------------------------------------------------------- Resolution|--- |FIXED Assignee|unassigned at sourceware dot org |adhemerval.zanella at linaro dot o | |rg Target Milestone|--- |2.33 Status|UNCONFIRMED |RESOLVED --- Comment #3 from Adhemerval Zanella <adhemerval.zanella at linaro dot org> --- Fixed on 2.33. -- You are receiving this mail because: You are on the CC list for the bug. ^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2020-11-25 15:31 UTC | newest] Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed) -- links below jump to the message on this page -- 2020-10-28 13:54 [Bug nptl/26801] New: pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI futexs yeatesrichardr at johndeere dot com 2020-10-28 13:59 ` [Bug nptl/26801] " yeatesrichardr at johndeere dot com 2020-10-28 14:01 ` [Bug nptl/26801] pthread_mutex_clocklock with CLOCK_MONOTONIC can fail on PI mutexes yeatesrichardr at johndeere dot com 2020-10-28 17:33 ` yeatesrichardr at johndeere dot com 2020-10-28 20:02 ` adhemerval.zanella at linaro dot org 2020-11-25 15:31 ` adhemerval.zanella at linaro dot org
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