summaryrefslogtreecommitdiffstats
path: root/unix
diff options
context:
space:
mode:
authorJoe Mistachkin <joe@mistachkin.com>2015-05-17 18:03:15 (GMT)
committerJoe Mistachkin <joe@mistachkin.com>2015-05-17 18:03:15 (GMT)
commitec8ad17e258e9758c10c5266ed7d4c4291b3a43b (patch)
tree3604f9fd49bb4908708f3547e2bebf85ff8fd645 /unix
parentb96efa9cbb68cfff7b6df11f8905b5719eaf7570 (diff)
downloadtcl-ec8ad17e258e9758c10c5266ed7d4c4291b3a43b.zip
tcl-ec8ad17e258e9758c10c5266ed7d4c4291b3a43b.tar.gz
tcl-ec8ad17e258e9758c10c5266ed7d4c4291b3a43b.tar.bz2
Draft fix for a potential race condition in the new Tcl_MutexUnlockAndFinalize API. Not yet tested.
Diffstat (limited to 'unix')
-rw-r--r--unix/tclUnixThrd.c67
1 files changed, 67 insertions, 0 deletions
diff --git a/unix/tclUnixThrd.c b/unix/tclUnixThrd.c
index d34bc88..42b6bda 100644
--- a/unix/tclUnixThrd.c
+++ b/unix/tclUnixThrd.c
@@ -45,6 +45,13 @@ static pthread_mutex_t allocLock = PTHREAD_MUTEX_INITIALIZER;
static pthread_mutex_t *allocLockPtr = &allocLock;
/*
+ * The mutexLock serializes Tcl_MutexLock. This is necessary to prevent
+ * races when finalizing a mutex that some other thread may want to lock.
+ */
+
+static pthread_mutex_t mutexLock = PTHREAD_MUTEX_INITIALIZER;
+
+/*
* These are for the critical sections inside this file.
*/
@@ -365,6 +372,58 @@ TclpMasterUnlock(void)
/*
*----------------------------------------------------------------------
*
+ * TclpMutexLock
+ *
+ * This procedure is used to grab a lock that serializes locking
+ * another mutex.
+ *
+ * Results:
+ * None.
+ *
+ * Side effects:
+ * None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+TclpMutexLock(void)
+{
+#ifdef TCL_THREADS
+ pthread_mutex_lock(&mutexLock);
+#endif
+}
+
+
+/*
+ *----------------------------------------------------------------------
+ *
+ * TclpMutexUnlock
+ *
+ * This procedure is used to release a lock that serializes locking
+ * another mutex.
+ *
+ * Results:
+ * None.
+ *
+ * Side effects:
+ * None.
+ *
+ *----------------------------------------------------------------------
+ */
+
+void
+TclpMutexUnlock(void)
+{
+#ifdef TCL_THREADS
+ pthread_mutex_unlock(&mutexLock);
+#endif
+}
+
+
+/*
+ *----------------------------------------------------------------------
+ *
* Tcl_GetAllocMutex
*
* This procedure returns a pointer to a statically initialized mutex for
@@ -421,6 +480,8 @@ Tcl_MutexLock(
{
pthread_mutex_t *pmutexPtr;
+retry:
+
if (*mutexPtr == NULL) {
MASTER_LOCK;
if (*mutexPtr == NULL) {
@@ -435,8 +496,14 @@ Tcl_MutexLock(
}
MASTER_UNLOCK;
}
+ TclpMutexLock();
pmutexPtr = *((pthread_mutex_t **)mutexPtr);
+ if (pmutexPtr == NULL) {
+ TclpMutexUnlock();
+ goto retry;
+ }
pthread_mutex_lock(pmutexPtr);
+ TclpMutexUnlock();
}
/*