alarm: make cancellation thread-safe

It eliminates a race between threads using rte_alarm_cancel() and
rte_alarm_set().

Signed-off-by: Pawel Wodkowski <pawelx.wodkowski@intel.com>
Acked-by: Konstantin Ananyev <konstantin.ananyev@intel.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>

diff --git a/lib/librte_eal/common/include/rte_alarm.h b/lib/librte_eal/common/include/rte_alarm.h
index d451522..4012cd6 100644 (file)
--- a/lib/librte_eal/common/include/rte_alarm.h
+++ b/lib/librte_eal/common/include/rte_alarm.h
@@ -76,7 +76,8 @@ typedef void (*rte_eal_alarm_callback)(void *arg);
 int rte_eal_alarm_set(uint64_t us, rte_eal_alarm_callback cb, void *cb_arg);
 
 /**
- * Function to cancel an alarm callback which has been registered before.
+ * Function to cancel an alarm callback which has been registered before. If
+ * used outside alarm callback it wait for all callbacks to finish execution.
  *
  * @param cb_fn
  *  alarm callback
@@ -86,7 +87,14 @@ int rte_eal_alarm_set(uint64_t us, rte_eal_alarm_callback cb, void *cb_arg);
  *  can be used here.
  *
  * @return
- *  - The number of callbacks removed
+ *    - value greater than 0 and rte_errno not changed - returned value is
+ *      the number of canceled alarm callback functions
+ *    - value greater or equal 0 and rte_errno set to EINPROGRESS, at least one
+ *      alarm could not be canceled because cancellation was requested from alarm
+ *      callback context. Returned value is the number of succesfuly canceled
+ *      alarm callbacks
+ *    -  0 and rte_errno set to ENOENT - no alarm found
+ *    - -1 and rte_errno set to EINVAL - invalid parameter (NULL callback)
  */
 int rte_eal_alarm_cancel(rte_eal_alarm_callback cb_fn, void *cb_arg);
 

diff --git a/lib/librte_eal/linuxapp/eal/eal_alarm.c b/lib/librte_eal/linuxapp/eal/eal_alarm.c
index 480f0cb..e8da32f 100644 (file)
--- a/lib/librte_eal/linuxapp/eal/eal_alarm.c
+++ b/lib/librte_eal/linuxapp/eal/eal_alarm.c
@@ -69,7 +69,8 @@ struct alarm_entry {
        struct timeval time;
        rte_eal_alarm_callback cb_fn;
        void *cb_arg;
-       volatile int executing;
+       volatile uint8_t executing;
+       volatile pthread_t executing_id;
 };
 
 static LIST_HEAD(alarm_list, alarm_entry) alarm_list = LIST_HEAD_INITIALIZER();
@@ -108,11 +109,13 @@ eal_alarm_callback(struct rte_intr_handle *hdl __rte_unused,
                        (ap->time.tv_sec < now.tv_sec || (ap->time.tv_sec == now.tv_sec &&
                                                ap->time.tv_usec <= now.tv_usec))){
                ap->executing = 1;
+               ap->executing_id = pthread_self();
                rte_spinlock_unlock(&alarm_list_lk);
 
                ap->cb_fn(ap->cb_arg);
 
                rte_spinlock_lock(&alarm_list_lk);
+
                LIST_REMOVE(ap, next);
                rte_free(ap);
        }
@@ -145,7 +148,7 @@ rte_eal_alarm_set(uint64_t us, rte_eal_alarm_callback cb_fn, void *cb_arg)
        if (us < 1 || us > (UINT64_MAX - US_PER_S) || cb_fn == NULL)
                return -EINVAL;
 
-       new_alarm = rte_malloc(NULL, sizeof(*new_alarm), 0);
+       new_alarm = rte_zmalloc(NULL, sizeof(*new_alarm), 0);
        if (new_alarm == NULL)
                return -ENOMEM;
 
@@ -156,7 +159,6 @@ rte_eal_alarm_set(uint64_t us, rte_eal_alarm_callback cb_fn, void *cb_arg)
        new_alarm->cb_arg = cb_arg;
        new_alarm->time.tv_usec = (now.tv_usec + us) % US_PER_S;
        new_alarm->time.tv_sec = now.tv_sec + ((now.tv_usec + us) / US_PER_S);
-       new_alarm->executing = 0;
 
        rte_spinlock_lock(&alarm_list_lk);
        if (!handler_registered) {
@@ -202,34 +204,65 @@ rte_eal_alarm_cancel(rte_eal_alarm_callback cb_fn, void *cb_arg)
 {
        struct alarm_entry *ap, *ap_prev;
        int count = 0;
+       int err = 0;
+       int executing;
 
-       if (!cb_fn)
+       if (!cb_fn) {
+               rte_errno = EINVAL;
                return -1;
-
-       rte_spinlock_lock(&alarm_list_lk);
-       /* remove any matches at the start of the list */
-       while ((ap = LIST_FIRST(&alarm_list)) != NULL &&
-                       cb_fn == ap->cb_fn && ap->executing == 0 &&
-                       (cb_arg == (void *)-1 || cb_arg == ap->cb_arg)) {
-               LIST_REMOVE(ap, next);
-               rte_free(ap);
-               count++;
        }
-       ap_prev = ap;
 
-       /* now go through list, removing entries not at start */
-       LIST_FOREACH(ap, &alarm_list, next) {
-               /* this won't be true first time through */
-               if (cb_fn == ap->cb_fn &&  ap->executing == 0 &&
+       do {
+               executing = 0;
+               rte_spinlock_lock(&alarm_list_lk);
+               /* remove any matches at the start of the list */
+               while ((ap = LIST_FIRST(&alarm_list)) != NULL &&
+                               cb_fn == ap->cb_fn &&
                                (cb_arg == (void *)-1 || cb_arg == ap->cb_arg)) {
-                       LIST_REMOVE(ap,next);
-                       rte_free(ap);
-                       count++;
-                       ap = ap_prev;
+
+                       if (ap->executing == 0) {
+                               LIST_REMOVE(ap, next);
+                               rte_free(ap);
+                               count++;
+                       } else {
+                               /* If calling from other context, mark that alarm is executing
+                                * so loop can spin till it finish. Otherwise we are trying to
+                                * cancel our self - mark it by EINPROGRESS */
+                               if (pthread_equal(ap->executing_id, pthread_self()) == 0)
+                                       executing++;
+                               else
+                                       err = EINPROGRESS;
+
+                               break;
+                       }
                }
                ap_prev = ap;
-       }
-       rte_spinlock_unlock(&alarm_list_lk);
+
+               /* now go through list, removing entries not at start */
+               LIST_FOREACH(ap, &alarm_list, next) {
+                       /* this won't be true first time through */
+                       if (cb_fn == ap->cb_fn &&
+                                       (cb_arg == (void *)-1 || cb_arg == ap->cb_arg)) {
+
+                               if (ap->executing == 0) {
+                                       LIST_REMOVE(ap, next);
+                                       rte_free(ap);
+                                       count++;
+                                       ap = ap_prev;
+                               } else if (pthread_equal(ap->executing_id, pthread_self()) == 0)
+                                       executing++;
+                               else
+                                       err = EINPROGRESS;
+                       }
+                       ap_prev = ap;
+               }
+               rte_spinlock_unlock(&alarm_list_lk);
+       } while (executing != 0);
+
+       if (count == 0 && err == 0)
+               rte_errno = ENOENT;
+       else if (err)
+               rte_errno = err;
+
        return count;
 }
-