Makefile.am: Clean flake8-check too.

[cascardo/ovs.git] / lib / ovs-rcu.c

diff --git a/lib/ovs-rcu.c b/lib/ovs-rcu.c
index 11c67c9..b8f8bc4 100644 (file)
--- a/lib/ovs-rcu.c
+++ b/lib/ovs-rcu.c
@@ -16,13 +16,14 @@
 
 #include <config.h>
 #include "ovs-rcu.h"
+#include "fatal-signal.h"
 #include "guarded-list.h"
 #include "list.h"
 #include "ovs-thread.h"
 #include "poll-loop.h"
 #include "seq.h"
 #include "timeval.h"
-#include "vlog.h"
+#include "openvswitch/vlog.h"
 
 VLOG_DEFINE_THIS_MODULE(ovs_rcu);
 
@@ -32,13 +33,13 @@ struct ovsrcu_cb {
 };
 
 struct ovsrcu_cbset {
-    struct list list_node;
+    struct ovs_list list_node;
     struct ovsrcu_cb cbs[16];
     int n_cbs;
 };
 
 struct ovsrcu_perthread {
-    struct list list_node;      /* In global list. */
+    struct ovs_list list_node;  /* In global list. */
 
     struct ovs_mutex mutex;
     uint64_t seqno;
@@ -49,7 +50,7 @@ struct ovsrcu_perthread {
 static struct seq *global_seqno;
 
 static pthread_key_t perthread_key;
-static struct list ovsrcu_threads;
+static struct ovs_list ovsrcu_threads;
 static struct ovs_mutex ovsrcu_threads_mutex;
 
 static struct guarded_list flushed_cbsets;
@@ -211,6 +212,19 @@ ovsrcu_synchronize(void)
 /* Registers 'function' to be called, passing 'aux' as argument, after the
  * next grace period.
  *
+ * The call is guaranteed to happen after the next time all participating
+ * threads have quiesced at least once, but there is no quarantee that all
+ * registered functions are called as early as possible, or that the functions
+ * registered by different threads would be called in the order the
+ * registrations took place.  In particular, even if two threads provably
+ * register a function each in a specific order, the functions may still be
+ * called in the opposite order, depending on the timing of when the threads
+ * call ovsrcu_quiesce(), how many functions they postpone, and when the
+ * ovs-rcu thread happens to grab the functions to be called.
+ *
+ * All functions registered by a single thread are guaranteed to execute in the
+ * registering order, however.
+ *
  * This function is more conveniently called through the ovsrcu_postpone()
  * macro, which provides a type-safe way to allow 'function''s parameter to be
  * any pointer type. */
@@ -239,8 +253,8 @@ ovsrcu_postpone__(void (*function)(void *aux), void *aux)
 static bool
 ovsrcu_call_postponed(void)
 {
-    struct ovsrcu_cbset *cbset, *next_cbset;
-    struct list cbsets;
+    struct ovsrcu_cbset *cbset;
+    struct ovs_list cbsets;
 
     guarded_list_pop_all(&flushed_cbsets, &cbsets);
     if (list_is_empty(&cbsets)) {
@@ -249,13 +263,12 @@ ovsrcu_call_postponed(void)
 
     ovsrcu_synchronize();
 
-    LIST_FOR_EACH_SAFE (cbset, next_cbset, list_node, &cbsets) {
+    LIST_FOR_EACH_POP (cbset, list_node, &cbsets) {
         struct ovsrcu_cb *cb;
 
         for (cb = cbset->cbs; cb < &cbset->cbs[cbset->n_cbs]; cb++) {
             cb->function(cb->aux);
         }
-        list_remove(&cbset->list_node);
         free(cbset);
     }
 
@@ -314,6 +327,18 @@ 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)
 {
@@ -321,6 +346,7 @@ 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);