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Add a comment describing some limitiations of this implementation.

This commit is contained in:
ad 2008-05-26 02:06:21 +00:00
parent 5f24c2accb
commit bd2852ae8c
1 changed files with 18 additions and 2 deletions
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20
lib/libpthread/pthread_cond.c
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@ -1,4 +1,4 @@
/* $NetBSD: pthread_cond.c,v 1.46 2008/05/26 00:16:35 ad Exp $ */ /* $NetBSD: pthread_cond.c,v 1.47 2008/05/26 02:06:21 ad Exp $ */
/*- /*-
* Copyright (c) 2001, 2006, 2007, 2008 The NetBSD Foundation, Inc. * Copyright (c) 2001, 2006, 2007, 2008 The NetBSD Foundation, Inc.
@ -29,8 +29,24 @@
* POSSIBILITY OF SUCH DAMAGE. * POSSIBILITY OF SUCH DAMAGE.
*/ */
/*
* We assume that there will be no contention on pthread_cond_t::ptc_lock
* because functioning applications must call both the wait and wakeup
* functions while holding the same application provided mutex. The
* spinlock is present only to prevent libpthread causing the application
* to crash or malfunction as a result of corrupted data structures, in
* the event that the application is buggy.
*
* If there is contention on spinlock when real-time threads are in use,
* it could cause a deadlock due to priority inversion: the thread holding
* the spinlock may not get CPU time to make forward progress and release
* the spinlock to a higher priority thread that is waiting for it.
* Contention on the spinlock will only occur with buggy applications,
* so at the time of writing it's not considered a major bug in libpthread.
*/
#include <sys/cdefs.h> #include <sys/cdefs.h>
__RCSID("$NetBSD: pthread_cond.c,v 1.46 2008/05/26 00:16:35 ad Exp $"); __RCSID("$NetBSD: pthread_cond.c,v 1.47 2008/05/26 02:06:21 ad Exp $");
#include <errno.h> #include <errno.h>
#include <sys/time.h> #include <sys/time.h>