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Update.
2000-05-07 H.J. Lu <hjl@gnu.org> * csu/initfini.c: Moved to .... * sysdeps/generic/initfini.c: ...here. * csu/Makefile (initfini.c): Set vpath to $(full_config_sysdirs).
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@ -1,3 +1,10 @@
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2000-05-07 H.J. Lu <hjl@gnu.org>
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* csu/initfini.c: Moved to ....
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* sysdeps/generic/initfini.c: ...here.
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* csu/Makefile (initfini.c): Set vpath to $(full_config_sysdirs).
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2000-05-07 Ulrich Drepper <drepper@redhat.com>
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* manual/resource.texi: Document POSIX scheduling functions.
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@ -85,6 +85,8 @@ $(objpfx)crt%.o: $(objpfx)crt%.S $(objpfx)defs.h
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CFLAGS-initfini.s = -g0 -fPIC -fno-inline-functions
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vpath initfini.c $(full_config_sysdirs)
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$(objpfx)initfini.s: initfini.c
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$(compile.c) -S $(CFLAGS-initfini.s) -finhibit-size-directive \
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$(patsubst -f%,-fno-%,$(exceptions)) -o $@
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@ -1,3 +1,21 @@
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2000-05-06 Kaz Kylheku <kaz@ashi.footprints.net>
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* mutex.c (pthread_once): IN_PROGRESS state of pthread_once_t
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object state is represented with additional bits which distinguish
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whether that state was set up in the current process, or
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in an ancestor process. If that state was set in an ancestor,
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it means that a fork happened while thread was executing the init
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function. In that case, the state is reset to NEVER.
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* mutex.c (__pthread_once_fork_prepare): New function.
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(__pthread_once_fork_child): Likewise
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(__pthread_once_fork_parent): Likewise
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(__pthread_reset_pthread_once): Removed.
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* ptfork.c (__fork): Call new handlers in mutex.c.
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* internals.h: Declarations of new mutex.c functions added.
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Declaration of removed function deleted.
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* linuxthreads.texi: Updated documentation about pthread_once
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to clarify what happens under cancellation and forking.
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2000-05-06 Kaz Kylheku <kaz@ashi.footprints.net>
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* internals.h: New thread manager request type, REQ_KICK.
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@ -414,7 +414,9 @@ int __pthread_manager(void *reqfd);
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int __pthread_manager_event(void *reqfd);
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void __pthread_manager_sighandler(int sig);
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void __pthread_reset_main_thread(void);
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void __pthread_reset_pthread_once(void);
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void __pthread_once_fork_prepare(void);
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void __pthread_once_fork_parent(void);
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void __pthread_once_fork_child(void);
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void __fresetlockfiles(void);
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void __pthread_manager_adjust_prio(int thread_prio);
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void __pthread_set_own_extricate_if(pthread_descr self, pthread_extricate_if *peif);
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@ -1368,6 +1368,15 @@ record that initialization has been performed. Subsequent calls to
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@code{pthread_once} with the same @code{once_control} argument do
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nothing.
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If a thread is cancelled while executing @var{init_routine}
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the state of the @var{once_control} variable is reset so that
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a future call to @code{pthread_once} will call the routine again.
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If the process forks while one or more threads are executing
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@code{pthread_once} initialization routines, the states of their respective
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@var{once_control} variables will appear to be reset in the child process so
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that if the child calls @code{pthread_once}, the routines will be executed.
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@code{pthread_once} always returns 0.
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@end deftypefun
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@ -17,6 +17,7 @@
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#include <errno.h>
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#include <sched.h>
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#include <stddef.h>
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#include <limits.h>
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#include "pthread.h"
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#include "internals.h"
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#include "spinlock.h"
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@ -170,6 +171,7 @@ weak_alias (__pthread_mutexattr_getkind_np, pthread_mutexattr_getkind_np)
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static pthread_mutex_t once_masterlock = PTHREAD_MUTEX_INITIALIZER;
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static pthread_cond_t once_finished = PTHREAD_COND_INITIALIZER;
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static int fork_generation = 0; /* Child process increments this after fork. */
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enum { NEVER = 0, IN_PROGRESS = 1, DONE = 2 };
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@ -199,14 +201,20 @@ int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
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state_changed = 0;
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pthread_mutex_lock(&once_masterlock);
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/* If this object was left in an IN_PROGRESS state in a parent
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process (indicated by stale generation field), reset it to NEVER. */
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if ((*once_control & 3) == IN_PROGRESS && (*once_control & ~3) != fork_generation)
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*once_control = NEVER;
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/* If init_routine is being called from another routine, wait until
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it completes. */
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while (*once_control == IN_PROGRESS) {
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while ((*once_control & 3) == IN_PROGRESS) {
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pthread_cond_wait(&once_finished, &once_masterlock);
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}
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/* Here *once_control is stable and either NEVER or DONE. */
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if (*once_control == NEVER) {
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*once_control = IN_PROGRESS;
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*once_control = IN_PROGRESS | fork_generation;
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pthread_mutex_unlock(&once_masterlock);
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pthread_cleanup_push(pthread_once_cancelhandler, once_control);
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init_routine();
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@ -225,13 +233,31 @@ int __pthread_once(pthread_once_t * once_control, void (*init_routine)(void))
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strong_alias (__pthread_once, pthread_once)
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/*
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* This is called in the child process after a fork to make
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* sure that the global mutex pthread_once is not held,
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* and that the condition variable is reset to an initial state.
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* Handle the state of the pthread_once mechanism across forks. The
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* once_masterlock is acquired in the parent process prior to a fork to ensure
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* that no thread is in the critical region protected by the lock. After the
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* fork, the lock is released. In the child, the lock and the condition
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* variable are simply reset. The child also increments its generation
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* counter which lets pthread_once calls detect stale IN_PROGRESS states
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* and reset them back to NEVER.
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*/
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void __pthread_reset_pthread_once(void)
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void __pthread_once_fork_prepare(void)
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{
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pthread_mutex_lock(&once_masterlock);
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}
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void __pthread_once_fork_parent(void)
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{
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pthread_mutex_unlock(&once_masterlock);
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}
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void __pthread_once_fork_child(void)
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{
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pthread_mutex_init(&once_masterlock, NULL);
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pthread_cond_init(&once_finished, NULL);
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if (fork_generation <= INT_MAX - 4)
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fork_generation += 4; /* leave least significant two bits zero */
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else
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fork_generation = 0;
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}
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@ -86,14 +86,16 @@ pid_t __fork(void)
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parent = pthread_atfork_parent;
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pthread_mutex_unlock(&pthread_atfork_lock);
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pthread_call_handlers(prepare);
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__pthread_once_fork_prepare();
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pid = __libc_fork();
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if (pid == 0) {
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__pthread_reset_main_thread();
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__pthread_reset_pthread_once();
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__fresetlockfiles();
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pthread_call_handlers(child);
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__pthread_once_fork_child();
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} else {
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pthread_call_handlers(parent);
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__pthread_once_fork_parent();
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}
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return pid;
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}
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