25 Jan
2006
25 Jan
'06
10:27 p.m.
On 1/25/06, Lee Revell <rlrevell(a)joe-job.com> wrote:
One Harold Chu on LKML is insisting that POSIX
requires
pthread_mutex_unlock to reschedule if other threads are waiting on the
mutex, and that even if the calling thread immediately tries to lock the
mutex again another thread must get it. I contend that both of these
assertions are wrong - first, I just don't read the standard that way,
and second, it would lead to obviously incorrect behavior - unlocking a
mutex would no longer be an RT safe operation. What would be the point
of trylock() in RT code if unlocking is going to cause a reschedule
anyway?
Can anyone back me up on this?
Lee
In "Programming with POSIX Threads" by David R. Butenhof,
pthread_mutex_unlock is said to do this:
"Unlock a mutex. The mutex becomes unowned. If any threads are
waiting for the mutex, one is awakened..."
Seems to suggest a reschedule. Butenhof worked on the POSIX
standards, so I would consider him an authority.