Red Hat Bugzilla – Bug 50036
pthread_once shouldn't return immediately if call in progress
Last modified: 2007-04-18 12:35:10 EDT
From the net:
The pthread_once() implementation seems have different semantics with the
one in POSIX standard pthread.
(The reference is in page 118 in O'Reilly's book"Pthreads programming" 1st
ed. I assume that the book is correct on this.)
This is the text describing pthread_once() semantics on the book: "No
will exit from pthread_once mechanism until the routine's first caller has
which is true. The poster suggested:
In a word, I think there should be a pair of mutex lock/unlocks around the
invocation of the function pointer passed by user in pthread_once() in
compat/posix/current/src/pthread.cxx to guarantee the correct semantics.
My reply includes:
That wouldn't be ideal as _all_ pthread_once's would be serialized. This
would be fatal if the called routine itself called pthread_once. Also we
have to worry about the thread being cancelled in the called routine.
Instead, at a guess, the thing to do is to use the pthread_once_t to record
whether the routine is currently still being processed, and then broadcast
a condition variable to cause it to be checked by any waiting routines that
have called it.
This bug has moved to http://bugs.ecos.sourceware.org/show_bug.cgi?id=50036