ovs_threads: Avoid running pthread destructors from main thread exit.

Windows uses pthreads-win32 library to provide the Linux pthread
functionality. It is observed that when the main thread calls
a pthread destructor after it exits, undefined behavior is seen
(e.g., junk values in data, causing pthread deadlocks).
Similar behavior has been seen by
other people as seen in the following email thread:
https://sourceware.org/ml/pthreads-win32/2003/msg00001.html

To avoid this, this commit de-registers the thread destructor
when the main thread exits (via the atexit handler).

Signed-off-by: Gurucharan Shetty <gshetty@nicira.com>
Acked-by: Ben Pfaff <blp@nicira.com>

diff --git a/lib/ovs-rcu.c b/lib/ovs-rcu.c
index 76659bb..e0634cf 100644 (file)
--- a/lib/ovs-rcu.c
+++ b/lib/ovs-rcu.c
@@ -16,6 +16,7 @@
 
 #include <config.h>
 #include "ovs-rcu.h"
+#include "fatal-signal.h"
 #include "guarded-list.h"
 #include "list.h"
 #include "ovs-thread.h"
@@ -313,6 +314,18 @@ ovsrcu_thread_exit_cb(void *perthread)
     ovsrcu_unregister__(perthread);
 }
 
+/* Cancels the callback to ovsrcu_thread_exit_cb().
+ *
+ * Cancelling the call to the destructor during the main thread exit
+ * is needed while using pthreads-win32 library in Windows. It has been
+ * observed that in pthreads-win32, a call to the destructor during
+ * main thread exit causes undefined behavior. */
+static void
+ovsrcu_cancel_thread_exit_cb(void *aux OVS_UNUSED)
+{
+    pthread_setspecific(perthread_key, NULL);
+}
+
 static void
 ovsrcu_init_module(void)
 {
@@ -320,6 +333,7 @@ ovsrcu_init_module(void)
     if (ovsthread_once_start(&once)) {
         global_seqno = seq_create();
         xpthread_key_create(&perthread_key, ovsrcu_thread_exit_cb);
+        fatal_signal_add_hook(ovsrcu_cancel_thread_exit_cb, NULL, NULL, true);
         list_init(&ovsrcu_threads);
         ovs_mutex_init(&ovsrcu_threads_mutex);
 

diff --git a/lib/ovs-thread.c b/lib/ovs-thread.c
index 4161095..b2d05a6 100644 (file)
--- a/lib/ovs-thread.c
+++ b/lib/ovs-thread.c
@@ -24,6 +24,7 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include "compiler.h"
+#include "fatal-signal.h"
 #include "hash.h"
 #include "list.h"
 #include "netdev-dpdk.h"
@@ -668,6 +669,18 @@ ovsthread_key_destruct__(void *slots_)
     free(slots);
 }
 
+/* Cancels the callback to ovsthread_key_destruct__().
+ *
+ * Cancelling the call to the destructor during the main thread exit
+ * is needed while using pthreads-win32 library in Windows. It has been
+ * observed that in pthreads-win32, a call to the destructor during
+ * main thread exit causes undefined behavior. */
+static void
+ovsthread_cancel_ovsthread_key_destruct__(void *aux OVS_UNUSED)
+{
+    pthread_setspecific(tsd_key, NULL);
+}
+
 /* Initializes '*keyp' as a thread-specific data key.  The data items are
  * initially null in all threads.
  *
@@ -684,6 +697,8 @@ ovsthread_key_create(ovsthread_key_t *keyp, void (*destructor)(void *))
 
     if (ovsthread_once_start(&once)) {
         xpthread_key_create(&tsd_key, ovsthread_key_destruct__);
+        fatal_signal_add_hook(ovsthread_cancel_ovsthread_key_destruct__,
+                              NULL, NULL, true);
         ovsthread_once_done(&once);
     }
 

diff --git a/tests/test-atomic.c b/tests/test-atomic.c
index 50b3b7a..2af6a26 100644 (file)
--- a/tests/test-atomic.c
+++ b/tests/test-atomic.c
@@ -16,6 +16,7 @@
 
 #include <config.h>
 #undef NDEBUG
+#include "fatal-signal.h"
 #include "ovs-atomic.h"
 #include "ovstest.h"
 #include "ovs-thread.h"
@@ -413,6 +414,7 @@ test_atomic_seq_cst(void)
 static void
 test_atomic_main(int argc OVS_UNUSED, char *argv[] OVS_UNUSED)
 {
+    fatal_signal_init();
     test_atomic_plain();
     test_atomic_relaxed();
     test_atomic_consume();