Date: Fri, 19 Apr 2013 10:16:00 +0000 (UTC) From: Jilles Tjoelker <jilles@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: svn commit: r249644 - head/sys/kern Message-ID: <201304191016.r3JAG0wI097651@svn.freebsd.org>
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Author: jilles Date: Fri Apr 19 10:16:00 2013 New Revision: 249644 URL: http://svnweb.freebsd.org/changeset/base/249644 Log: sem: Restart the POSIX sem_* calls after signals with SA_RESTART set. Programs often do not expect an [EINTR] return from sem_wait() and POSIX only allows it if the signal was installed without SA_RESTART. The timeout in sem_timedwait() is absolute so it can be restarted normally. The umtx call can be invoked with a relative timeout and in that case [ERESTART] must be changed to [EINTR]. However, libc does not do this. The old POSIX semaphore implementation did this correctly (before r249566), unlike the new umtx one. It may be desirable to avoid [EINTR] completely, which matches the pthread functions and is explicitly permitted by POSIX. However, the kernel must return [EINTR] at least for signals with SA_RESTART clear, otherwise pthread cancellation will not abort a semaphore wait. In this commit, only restore the 8.x behaviour which is also permitted by POSIX. Discussed with: jhb MFC after: 1 week Modified: head/sys/kern/kern_umtx.c head/sys/kern/uipc_sem.c Modified: head/sys/kern/kern_umtx.c ============================================================================== --- head/sys/kern/kern_umtx.c Fri Apr 19 09:19:10 2013 (r249643) +++ head/sys/kern/kern_umtx.c Fri Apr 19 10:16:00 2013 (r249644) @@ -2980,7 +2980,9 @@ do_sem_wait(struct thread *td, struct _u error = 0; else { umtxq_remove(uq); - if (error == ERESTART) + /* A relative timeout cannot be restarted. */ + if (error == ERESTART && timeout != NULL && + (timeout->_flags & UMTX_ABSTIME) == 0) error = EINTR; } umtxq_unlock(&uq->uq_key); Modified: head/sys/kern/uipc_sem.c ============================================================================== --- head/sys/kern/uipc_sem.c Fri Apr 19 09:19:10 2013 (r249643) +++ head/sys/kern/uipc_sem.c Fri Apr 19 10:16:00 2013 (r249644) @@ -846,8 +846,6 @@ kern_sem_wait(struct thread *td, semid_t err: mtx_unlock(&sem_lock); fdrop(fp, td); - if (error == ERESTART) - error = EINTR; DP(("<<< kern_sem_wait leaving, pid=%d, error = %d\n", (int)td->td_proc->p_pid, error)); return (error);
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