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[2/3] ibacm: Calculate correct tv_nsec value in event_wait()

Message ID 20171110222853.10387.81730.stgit@phlsvslse11.ph.intel.com (mailing list archive)
State Changes Requested
Headers show

Commit Message

Michael J. Ruhl Nov. 10, 2017, 10:29 p.m. UTC 
From: Michael J. Ruhl <michael.j.ruhl@intel.com>

The event_wait() function calculates a tv_nsec value based on the
given timeout.  If the tv_nsec value calculation ends ups larger
than 1 second, the pthread_cond_timedwait() will return EINVAL,
and will not wait.

This causes the retry loop to spin (busy wait) until the actual
timeout occurs.

Ensure that the tv_nsec value is less than 1 second.

Reviewed-by: Mike Marciniszyn <mike.marciniszyn@intel.com>
Reviewed-by: Dennis Dalessandro <dennis.dalessandro@intel.com>
Signed-off-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
---
 ibacm/linux/osd.h |    5 +++++
 1 files changed, 5 insertions(+), 0 deletions(-)


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Comments

Jason Gunthorpe Nov. 11, 2017, 4:26 p.m. UTC | #1 
On Fri, Nov 10, 2017 at 05:29:02PM -0500, Michael J. Ruhl wrote:
>  	gettimeofday(&curtime, NULL);

Ugh, the use of gettimeofday for this kind of stuff is also a serious bug.

This needs to use clock_gettime(CLOCK_MONOTONIC) and
pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);

Jason
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Michael J. Ruhl Nov. 13, 2017, 1:30 p.m. UTC | #2 
> -----Original Message-----
> From: Jason Gunthorpe [mailto:jgg@ziepe.ca]
> Sent: Saturday, November 11, 2017 11:26 AM
> To: Ruhl, Michael J <michael.j.ruhl@intel.com>
> Cc: linux-rdma@vger.kernel.org
> Subject: Re: [PATCH 2/3] ibacm: Calculate correct tv_nsec value in
> event_wait()
> 
> On Fri, Nov 10, 2017 at 05:29:02PM -0500, Michael J. Ruhl wrote:
> >  	gettimeofday(&curtime, NULL);
> 
> Ugh, the use of gettimeofday for this kind of stuff is also a serious bug.
> 
> This needs to use clock_gettime(CLOCK_MONOTONIC) and
> pthread_condattr_setclock(&attr, CLOCK_MONOTONIC);

Yeah, that one is a lot cleaner.  I will get a new patch out shortly.

Thanks,

Mike
 
> Jason
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diff mbox

Patch

diff --git a/ibacm/linux/osd.h b/ibacm/linux/osd.h
index 95713e6..d6cbb8f 100644
--- a/ibacm/linux/osd.h
+++ b/ibacm/linux/osd.h
@@ -92,6 +92,7 @@  static inline void event_init(event_t *e)
 	pthread_mutex_init(&e->mutex, NULL);
 }
 #define event_signal(e)	pthread_cond_signal(&(e)->cond)
+#define ONE_SEC_IN_NSEC  1000000000
 static inline int event_wait(event_t *e, int timeout)
 {
 	struct timeval curtime;
@@ -101,6 +102,10 @@  static inline int event_wait(event_t *e, int timeout)
 	gettimeofday(&curtime, NULL);
 	wait.tv_sec = curtime.tv_sec + ((unsigned) timeout) / 1000;
 	wait.tv_nsec = (curtime.tv_usec + (((unsigned) timeout) % 1000) * 1000) * 1000;
+	if (wait.tv_nsec > ONE_SEC_IN_NSEC) {
+		wait.tv_sec++;
+		wait.tv_nsec -= ONE_SEC_IN_NSEC;
+	}
 	pthread_mutex_lock(&e->mutex);
 	ret = pthread_cond_timedwait(&e->cond, &e->mutex, &wait);
 	pthread_mutex_unlock(&e->mutex);