On 10/03/13 01:04, Mathieu Desnoyers wrote: > ----- Original Message ----- >> From: "Andreas Schwab" <schwab@xxxxxxx> >> To: "Mathieu Desnoyers" <mathieu.desnoyers@xxxxxxxxxxxx> >> Cc: "David Miller" <davem@xxxxxxxxxxxxx>, libc-alpha@xxxxxxxxxxxxxx, "Paul E. McKenney" <paulmck@xxxxxxxxxxxxxxxxxx> >> Sent: Wednesday, October 2, 2013 4:11:23 AM >> Subject: Re: Race and segmentation fault in pthread_kill() vs thread teardown >> >> The POSIX spec is pretty clear: >> >> If an application attempts to use a thread ID whose lifetime has ended, >> the behavior is undefined. >> >> I'd suggest to file a bug report with the Austin group wrt to the >> wording in pthread_kill. > > CCing man pages maintainers, > > Interestingly enough, the specification has been updated: > > http://pubs.opengroup.org/onlinepubs/9699919799/functions/pthread_kill.html > > to remove the ESRCH return value in > > Issue 7 > Austin Group Interpretation 1003.1-2001 #142 is applied, removing the [ESRCH] error condition. > > It looks like a discrepancy between the spec and the man page that causes this confusion. We might want to update pthread_kill(3), keeping ESRCH documented, but clearly marked as deprecated, and clarify that calling pthread_kill() on a non-existing thread is undefined. > > We should probably remove this part entirely: > > " but error checking is still per‐ > formed; this can be used to check for the existence of a thread ID." > > Thoughts ? Mathieu, et al. I applied the patch below. Look okay to you? Cheers, Michael diff --git a/man3/pthread_kill.3 b/man3/pthread_kill.3 index 674168f..bbf5573 100644 --- a/man3/pthread_kill.3 +++ b/man3/pthread_kill.3 @@ -47,8 +47,7 @@ The signal is asynchronously directed to If .I sig -is 0, then no signal is sent, but error checking is still performed; -this can be used to check for the existence of a thread ID. +is 0, then no signal is sent, but error checking is still performed. .SH RETURN VALUE On success, .BR pthread_kill () @@ -58,13 +57,8 @@ on error, it returns an error number, and no signal is sent. .TP .B EINVAL An invalid signal was specified. -.TP -.B ESRCH -No thread with the ID -.I thread -could be found. .SH CONFORMING TO -POSIX.1-2001. +POSIX.1-2008. .SH NOTES Signal dispositions are process-wide: if a signal handler is installed, @@ -72,6 +66,19 @@ the handler will be invoked in the thread .IR thread , but if the disposition of the signal is "stop", "continue", or "terminate", this action will affect the whole process. + +POSIX.1-2008 recommends that if an implementation detects the use +of a thread ID after the end of its lifetime, +.BR pthread_kill () +should return the error +.BR ESRCH . +The glibc implementation returns this error in the cases where +an invalid thread ID can be detected. +But note also that POSIX says that an attempt to use a thread ID whose +lifetime has ended produces undefined behavior, +and an attempt to use an invalid thread ID in a call to +.BR pthread_kill () +can, for example, cause a segmentation fault. .SH SEE ALSO .BR kill (2), .BR sigaction (2), -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
