svn commit: r232209 - in head: lib/libthr/thread sys/kern

[Pawel Jakub Dawidek]

On Mon, Feb 27, 2012 at 01:38:52PM +0000, David Xu wrote:
> Author: davidxu
> Date: Mon Feb 27 13:38:52 2012
> New Revision: 232209
> URL: http://svn.freebsd.org/changeset/base/232209
> 
> Log:
>   Follow changes made in revision 232144, pass absolute timeout to kernel,
>   this eliminates a clock_gettime() syscall.

This or some other change has broken CLOCK_MONOTONIC usage with
condition variables.

You should be able to reproduce this by something like this:

	pthread_cond_t cv;
	pthread_condattr_t attr;
	pthread_mutex_t lock;
	struct timespec ts;
        int error;

	(void)pthread_mutex_init(&lock, NULL);

	(void)pthread_condattr_init(&attr);
	(void)pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);

	(void)pthread_cond_init(&cv, &attr);
	(void)pthread_condattr_destroy(&attr);

	(void)clock_gettime(CLOCK_MONOTONIC, &ts);
	ts.tv_sec += 10;
	(void)pthread_mutex_lock(&lock);
	(void)pthread_cond_timedwait(&cv, &lock, &ts);
	(void)pthread_mutex_unlock(&lock);

This should timeout after 10 seconds, but pthread_cond_timedwait(3)
returns immediately with ETIMEDOUT. CLOCK_REALTIME works properly.
Bascially pthread_condattr_setclock(&attr, CLOCK_MONOTONIC) is no-op.
If you change CLOCK_MONOTONIC to CLOCK_REALTIME in clock_gettime(2)
call, it will timeout after 10 seconds.

-- 
Pawel Jakub Dawidek                       http://www.wheelsystems.com
FreeBSD committer                         http://www.FreeBSD.org
Am I Evil? Yes, I Am!                     http://tupytaj.pl
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