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authorjasone <jasone@FreeBSD.org>2001-06-27 11:41:15 +0000
committerjasone <jasone@FreeBSD.org>2001-06-27 11:41:15 +0000
commit22f14eaadfe2f54e3d94f9a549dbb55a301222e1 (patch)
tree463b1f41916ef7a7abac0e3d8230ce498dcde63c /lib
parent97220dbd1ea90cd0e4fbc824e176960ac2efe949 (diff)
downloadFreeBSD-src-22f14eaadfe2f54e3d94f9a549dbb55a301222e1.zip
FreeBSD-src-22f14eaadfe2f54e3d94f9a549dbb55a301222e1.tar.gz
Fix a race condition in pthread_join(). All of the following must occur
atomically: 1) Search _thread_list for the thread to join. 2) Search _dead_list for the thread to join. 3) Set the running thread as the joiner. While we're at it, fix a race in the case where multiple threads try to join on the same thread. POSIX says that the behavior of multiple joiners is undefined, but the fix is cheap as a result of the other fix.
Diffstat (limited to 'lib')
-rw-r--r--lib/libc_r/uthread/pthread_private.h1
-rw-r--r--lib/libc_r/uthread/uthread_find_thread.c32
-rw-r--r--lib/libc_r/uthread/uthread_join.c68
-rw-r--r--lib/libkse/thread/thr_find_thread.c32
-rw-r--r--lib/libkse/thread/thr_join.c68
-rw-r--r--lib/libkse/thread/thr_private.h1
-rw-r--r--lib/libpthread/thread/thr_find_thread.c32
-rw-r--r--lib/libpthread/thread/thr_join.c68
-rw-r--r--lib/libpthread/thread/thr_private.h1
9 files changed, 159 insertions, 144 deletions
diff --git a/lib/libc_r/uthread/pthread_private.h b/lib/libc_r/uthread/pthread_private.h
index 3bfb7c0..6528c13 100644
--- a/lib/libc_r/uthread/pthread_private.h
+++ b/lib/libc_r/uthread/pthread_private.h
@@ -1207,7 +1207,6 @@ char *__ttyname_r_basic(int, char *, size_t);
char *ttyname_r(int, char *, size_t);
void _cond_wait_backout(pthread_t);
void _fd_lock_backout(pthread_t);
-int _find_dead_thread(pthread_t);
int _find_thread(pthread_t);
struct pthread *_get_curthread(void);
void _set_curthread(struct pthread *);
diff --git a/lib/libc_r/uthread/uthread_find_thread.c b/lib/libc_r/uthread/uthread_find_thread.c
index 861c4cb..e6e9294 100644
--- a/lib/libc_r/uthread/uthread_find_thread.c
+++ b/lib/libc_r/uthread/uthread_find_thread.c
@@ -64,35 +64,3 @@ _find_thread(pthread_t pthread)
/* Return zero if the thread exists: */
return ((pthread1 != NULL) ? 0:ESRCH);
}
-
-/* Find a thread in the linked list of dead threads: */
-int
-_find_dead_thread(pthread_t pthread)
-{
- pthread_t pthread1;
-
- /* Check if the caller has specified an invalid thread: */
- if (pthread == NULL || pthread->magic != PTHREAD_MAGIC)
- /* Invalid thread: */
- return(EINVAL);
-
- /*
- * Lock the garbage collector mutex to ensure that the garbage
- * collector is not using the dead thread list.
- */
- if (pthread_mutex_lock(&_gc_mutex) != 0)
- PANIC("Cannot lock gc mutex");
-
- /* Search for the specified thread: */
- TAILQ_FOREACH(pthread1, &_dead_list, dle) {
- if (pthread1 == pthread)
- break;
- }
-
- /* Unlock the garbage collector mutex: */
- if (pthread_mutex_unlock(&_gc_mutex) != 0)
- PANIC("Cannot lock gc mutex");
-
- /* Return zero if the thread exists: */
- return ((pthread1 != NULL) ? 0:ESRCH);
-}
diff --git a/lib/libc_r/uthread/uthread_join.c b/lib/libc_r/uthread/uthread_join.c
index e1a1f3d..968c24c 100644
--- a/lib/libc_r/uthread/uthread_join.c
+++ b/lib/libc_r/uthread/uthread_join.c
@@ -42,6 +42,7 @@ _pthread_join(pthread_t pthread, void **thread_return)
{
struct pthread *curthread = _get_curthread();
int ret = 0;
+ pthread_t thread;
_thread_enter_cancellation_point();
@@ -60,24 +61,63 @@ _pthread_join(pthread_t pthread, void **thread_return)
}
/*
- * Find the thread in the list of active threads or in the
- * list of dead threads:
+ * Lock the garbage collector mutex to ensure that the garbage
+ * collector is not using the dead thread list.
*/
- if ((_find_thread(pthread) != 0) && (_find_dead_thread(pthread) != 0))
- /* Return an error: */
- ret = ESRCH;
+ if (pthread_mutex_lock(&_gc_mutex) != 0)
+ PANIC("Cannot lock gc mutex");
+
+ /*
+ * Defer signals to protect the thread list from access
+ * by the signal handler:
+ */
+ _thread_kern_sig_defer();
+
+ /*
+ * Unlock the garbage collector mutex, now that the garbage collector
+ * can't be run:
+ */
+ if (pthread_mutex_unlock(&_gc_mutex) != 0)
+ PANIC("Cannot lock gc mutex");
+
+ /*
+ * Search for the specified thread in the list of active threads. This
+ * is done manually here rather than calling _find_thread() because
+ * the searches in _thread_list and _dead_list (as well as setting up
+ * join/detach state) have to be done atomically.
+ */
+ TAILQ_FOREACH(thread, &_thread_list, tle) {
+ if (thread == pthread)
+ break;
+ }
+ if (thread == NULL) {
+ /*
+ * Search for the specified thread in the list of dead threads:
+ */
+ TAILQ_FOREACH(thread, &_dead_list, dle) {
+ if (thread == pthread)
+ break;
+ }
+ }
+
+ /* Check if the thread was not found or has been detached: */
+ if (thread == NULL ||
+ ((pthread->attr.flags & PTHREAD_DETACHED) != 0)) {
+ /* Undefer and handle pending signals, yielding if necessary: */
+ _thread_kern_sig_undefer();
- /* Check if this thread has been detached: */
- else if ((pthread->attr.flags & PTHREAD_DETACHED) != 0)
/* Return an error: */
ret = ESRCH;
- else if (pthread->joiner != NULL)
+ } else if (pthread->joiner != NULL) {
+ /* Undefer and handle pending signals, yielding if necessary: */
+ _thread_kern_sig_undefer();
+
/* Multiple joiners are not supported. */
ret = ENOTSUP;
/* Check if the thread is not dead: */
- else if (pthread->state != PS_DEAD) {
+ } else if (pthread->state != PS_DEAD) {
/* Set the running thread to be the joiner: */
pthread->joiner = curthread;
@@ -103,13 +143,11 @@ _pthread_join(pthread_t pthread, void **thread_return)
*thread_return = pthread->ret;
}
- /*
- * Make the thread collectable by the garbage collector. There
- * is a race here with the garbage collector if multiple threads
- * try to join the thread, but the behavior of multiple joiners
- * is undefined, so don't bother protecting against the race.
- */
+ /* Make the thread collectable by the garbage collector. */
pthread->attr.flags |= PTHREAD_DETACHED;
+
+ /* Undefer and handle pending signals, yielding if necessary: */
+ _thread_kern_sig_undefer();
}
_thread_leave_cancellation_point();
diff --git a/lib/libkse/thread/thr_find_thread.c b/lib/libkse/thread/thr_find_thread.c
index 861c4cb..e6e9294 100644
--- a/lib/libkse/thread/thr_find_thread.c
+++ b/lib/libkse/thread/thr_find_thread.c
@@ -64,35 +64,3 @@ _find_thread(pthread_t pthread)
/* Return zero if the thread exists: */
return ((pthread1 != NULL) ? 0:ESRCH);
}
-
-/* Find a thread in the linked list of dead threads: */
-int
-_find_dead_thread(pthread_t pthread)
-{
- pthread_t pthread1;
-
- /* Check if the caller has specified an invalid thread: */
- if (pthread == NULL || pthread->magic != PTHREAD_MAGIC)
- /* Invalid thread: */
- return(EINVAL);
-
- /*
- * Lock the garbage collector mutex to ensure that the garbage
- * collector is not using the dead thread list.
- */
- if (pthread_mutex_lock(&_gc_mutex) != 0)
- PANIC("Cannot lock gc mutex");
-
- /* Search for the specified thread: */
- TAILQ_FOREACH(pthread1, &_dead_list, dle) {
- if (pthread1 == pthread)
- break;
- }
-
- /* Unlock the garbage collector mutex: */
- if (pthread_mutex_unlock(&_gc_mutex) != 0)
- PANIC("Cannot lock gc mutex");
-
- /* Return zero if the thread exists: */
- return ((pthread1 != NULL) ? 0:ESRCH);
-}
diff --git a/lib/libkse/thread/thr_join.c b/lib/libkse/thread/thr_join.c
index e1a1f3d..968c24c 100644
--- a/lib/libkse/thread/thr_join.c
+++ b/lib/libkse/thread/thr_join.c
@@ -42,6 +42,7 @@ _pthread_join(pthread_t pthread, void **thread_return)
{
struct pthread *curthread = _get_curthread();
int ret = 0;
+ pthread_t thread;
_thread_enter_cancellation_point();
@@ -60,24 +61,63 @@ _pthread_join(pthread_t pthread, void **thread_return)
}
/*
- * Find the thread in the list of active threads or in the
- * list of dead threads:
+ * Lock the garbage collector mutex to ensure that the garbage
+ * collector is not using the dead thread list.
*/
- if ((_find_thread(pthread) != 0) && (_find_dead_thread(pthread) != 0))
- /* Return an error: */
- ret = ESRCH;
+ if (pthread_mutex_lock(&_gc_mutex) != 0)
+ PANIC("Cannot lock gc mutex");
+
+ /*
+ * Defer signals to protect the thread list from access
+ * by the signal handler:
+ */
+ _thread_kern_sig_defer();
+
+ /*
+ * Unlock the garbage collector mutex, now that the garbage collector
+ * can't be run:
+ */
+ if (pthread_mutex_unlock(&_gc_mutex) != 0)
+ PANIC("Cannot lock gc mutex");
+
+ /*
+ * Search for the specified thread in the list of active threads. This
+ * is done manually here rather than calling _find_thread() because
+ * the searches in _thread_list and _dead_list (as well as setting up
+ * join/detach state) have to be done atomically.
+ */
+ TAILQ_FOREACH(thread, &_thread_list, tle) {
+ if (thread == pthread)
+ break;
+ }
+ if (thread == NULL) {
+ /*
+ * Search for the specified thread in the list of dead threads:
+ */
+ TAILQ_FOREACH(thread, &_dead_list, dle) {
+ if (thread == pthread)
+ break;
+ }
+ }
+
+ /* Check if the thread was not found or has been detached: */
+ if (thread == NULL ||
+ ((pthread->attr.flags & PTHREAD_DETACHED) != 0)) {
+ /* Undefer and handle pending signals, yielding if necessary: */
+ _thread_kern_sig_undefer();
- /* Check if this thread has been detached: */
- else if ((pthread->attr.flags & PTHREAD_DETACHED) != 0)
/* Return an error: */
ret = ESRCH;
- else if (pthread->joiner != NULL)
+ } else if (pthread->joiner != NULL) {
+ /* Undefer and handle pending signals, yielding if necessary: */
+ _thread_kern_sig_undefer();
+
/* Multiple joiners are not supported. */
ret = ENOTSUP;
/* Check if the thread is not dead: */
- else if (pthread->state != PS_DEAD) {
+ } else if (pthread->state != PS_DEAD) {
/* Set the running thread to be the joiner: */
pthread->joiner = curthread;
@@ -103,13 +143,11 @@ _pthread_join(pthread_t pthread, void **thread_return)
*thread_return = pthread->ret;
}
- /*
- * Make the thread collectable by the garbage collector. There
- * is a race here with the garbage collector if multiple threads
- * try to join the thread, but the behavior of multiple joiners
- * is undefined, so don't bother protecting against the race.
- */
+ /* Make the thread collectable by the garbage collector. */
pthread->attr.flags |= PTHREAD_DETACHED;
+
+ /* Undefer and handle pending signals, yielding if necessary: */
+ _thread_kern_sig_undefer();
}
_thread_leave_cancellation_point();
diff --git a/lib/libkse/thread/thr_private.h b/lib/libkse/thread/thr_private.h
index 3bfb7c0..6528c13 100644
--- a/lib/libkse/thread/thr_private.h
+++ b/lib/libkse/thread/thr_private.h
@@ -1207,7 +1207,6 @@ char *__ttyname_r_basic(int, char *, size_t);
char *ttyname_r(int, char *, size_t);
void _cond_wait_backout(pthread_t);
void _fd_lock_backout(pthread_t);
-int _find_dead_thread(pthread_t);
int _find_thread(pthread_t);
struct pthread *_get_curthread(void);
void _set_curthread(struct pthread *);
diff --git a/lib/libpthread/thread/thr_find_thread.c b/lib/libpthread/thread/thr_find_thread.c
index 861c4cb..e6e9294 100644
--- a/lib/libpthread/thread/thr_find_thread.c
+++ b/lib/libpthread/thread/thr_find_thread.c
@@ -64,35 +64,3 @@ _find_thread(pthread_t pthread)
/* Return zero if the thread exists: */
return ((pthread1 != NULL) ? 0:ESRCH);
}
-
-/* Find a thread in the linked list of dead threads: */
-int
-_find_dead_thread(pthread_t pthread)
-{
- pthread_t pthread1;
-
- /* Check if the caller has specified an invalid thread: */
- if (pthread == NULL || pthread->magic != PTHREAD_MAGIC)
- /* Invalid thread: */
- return(EINVAL);
-
- /*
- * Lock the garbage collector mutex to ensure that the garbage
- * collector is not using the dead thread list.
- */
- if (pthread_mutex_lock(&_gc_mutex) != 0)
- PANIC("Cannot lock gc mutex");
-
- /* Search for the specified thread: */
- TAILQ_FOREACH(pthread1, &_dead_list, dle) {
- if (pthread1 == pthread)
- break;
- }
-
- /* Unlock the garbage collector mutex: */
- if (pthread_mutex_unlock(&_gc_mutex) != 0)
- PANIC("Cannot lock gc mutex");
-
- /* Return zero if the thread exists: */
- return ((pthread1 != NULL) ? 0:ESRCH);
-}
diff --git a/lib/libpthread/thread/thr_join.c b/lib/libpthread/thread/thr_join.c
index e1a1f3d..968c24c 100644
--- a/lib/libpthread/thread/thr_join.c
+++ b/lib/libpthread/thread/thr_join.c
@@ -42,6 +42,7 @@ _pthread_join(pthread_t pthread, void **thread_return)
{
struct pthread *curthread = _get_curthread();
int ret = 0;
+ pthread_t thread;
_thread_enter_cancellation_point();
@@ -60,24 +61,63 @@ _pthread_join(pthread_t pthread, void **thread_return)
}
/*
- * Find the thread in the list of active threads or in the
- * list of dead threads:
+ * Lock the garbage collector mutex to ensure that the garbage
+ * collector is not using the dead thread list.
*/
- if ((_find_thread(pthread) != 0) && (_find_dead_thread(pthread) != 0))
- /* Return an error: */
- ret = ESRCH;
+ if (pthread_mutex_lock(&_gc_mutex) != 0)
+ PANIC("Cannot lock gc mutex");
+
+ /*
+ * Defer signals to protect the thread list from access
+ * by the signal handler:
+ */
+ _thread_kern_sig_defer();
+
+ /*
+ * Unlock the garbage collector mutex, now that the garbage collector
+ * can't be run:
+ */
+ if (pthread_mutex_unlock(&_gc_mutex) != 0)
+ PANIC("Cannot lock gc mutex");
+
+ /*
+ * Search for the specified thread in the list of active threads. This
+ * is done manually here rather than calling _find_thread() because
+ * the searches in _thread_list and _dead_list (as well as setting up
+ * join/detach state) have to be done atomically.
+ */
+ TAILQ_FOREACH(thread, &_thread_list, tle) {
+ if (thread == pthread)
+ break;
+ }
+ if (thread == NULL) {
+ /*
+ * Search for the specified thread in the list of dead threads:
+ */
+ TAILQ_FOREACH(thread, &_dead_list, dle) {
+ if (thread == pthread)
+ break;
+ }
+ }
+
+ /* Check if the thread was not found or has been detached: */
+ if (thread == NULL ||
+ ((pthread->attr.flags & PTHREAD_DETACHED) != 0)) {
+ /* Undefer and handle pending signals, yielding if necessary: */
+ _thread_kern_sig_undefer();
- /* Check if this thread has been detached: */
- else if ((pthread->attr.flags & PTHREAD_DETACHED) != 0)
/* Return an error: */
ret = ESRCH;
- else if (pthread->joiner != NULL)
+ } else if (pthread->joiner != NULL) {
+ /* Undefer and handle pending signals, yielding if necessary: */
+ _thread_kern_sig_undefer();
+
/* Multiple joiners are not supported. */
ret = ENOTSUP;
/* Check if the thread is not dead: */
- else if (pthread->state != PS_DEAD) {
+ } else if (pthread->state != PS_DEAD) {
/* Set the running thread to be the joiner: */
pthread->joiner = curthread;
@@ -103,13 +143,11 @@ _pthread_join(pthread_t pthread, void **thread_return)
*thread_return = pthread->ret;
}
- /*
- * Make the thread collectable by the garbage collector. There
- * is a race here with the garbage collector if multiple threads
- * try to join the thread, but the behavior of multiple joiners
- * is undefined, so don't bother protecting against the race.
- */
+ /* Make the thread collectable by the garbage collector. */
pthread->attr.flags |= PTHREAD_DETACHED;
+
+ /* Undefer and handle pending signals, yielding if necessary: */
+ _thread_kern_sig_undefer();
}
_thread_leave_cancellation_point();
diff --git a/lib/libpthread/thread/thr_private.h b/lib/libpthread/thread/thr_private.h
index 3bfb7c0..6528c13 100644
--- a/lib/libpthread/thread/thr_private.h
+++ b/lib/libpthread/thread/thr_private.h
@@ -1207,7 +1207,6 @@ char *__ttyname_r_basic(int, char *, size_t);
char *ttyname_r(int, char *, size_t);
void _cond_wait_backout(pthread_t);
void _fd_lock_backout(pthread_t);
-int _find_dead_thread(pthread_t);
int _find_thread(pthread_t);
struct pthread *_get_curthread(void);
void _set_curthread(struct pthread *);
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