async_reply_handle_thread_unsafe() can run while holding
pending_requests.lock and currently calls rte_eal_alarm_cancel().
rte_eal_alarm_cancel() may spin-wait for an executing callback, which can
deadlock if that callback is blocked on the same lock.
Remove callback-side alarm cancellation. It is safe to do so, because any
callback triggered without a pending request becomes a noop.
Fixes: daf9bfca717e ("ipc: remove thread for async requests")
Cc: [email protected]
Signed-off-by: Anatoly Burakov <[email protected]>
---
lib/eal/common/eal_common_proc.c | 21 ++++++---------------
1 file changed, 6 insertions(+), 15 deletions(-)
diff --git a/lib/eal/common/eal_common_proc.c b/lib/eal/common/eal_common_proc.c
index d1a041b707..830c11f4ac 100644
--- a/lib/eal/common/eal_common_proc.c
+++ b/lib/eal/common/eal_common_proc.c
@@ -549,19 +549,6 @@ async_reply_handle_thread_unsafe(struct pending_request
*req)
TAILQ_REMOVE(&pending_requests.requests, req, next);
- if (rte_eal_alarm_cancel(async_reply_handle,
- (void *)(uintptr_t)req->id) < 0) {
- /* if we failed to cancel the alarm because it's already in
- * progress, don't proceed because otherwise we will end up
- * handling the same message twice.
- */
- if (rte_errno == EINPROGRESS) {
- EAL_LOG(DEBUG, "Request handling is already in
progress");
- goto no_trigger;
- }
- EAL_LOG(ERR, "Failed to cancel alarm");
- }
-
if (action == ACTION_TRIGGER)
return req;
no_trigger:
@@ -910,8 +897,12 @@ mp_request_async(const char *dst, struct rte_mp_msg *req,
return -1;
}
- /* Set alarm before allocating or sending so request timeout tracking
- * is active as soon as this request ID is reserved.
+ /* Set alarm before allocating or sending. The alarm is never cancelled:
+ * rte_eal_alarm_cancel spin-waits for an executing callback to finish,
+ * which deadlocks if we hold pending_requests.lock while the callback
+ * is blocked on it. Instead, let stale alarms fire; with ID-based
+ * lookup the callback will simply not find the request and return
+ * harmlessly.
*/
id = ++next_request_id;
if (rte_eal_alarm_set(ts->tv_sec * 1000000 + ts->tv_nsec / 1000,
--
2.47.3
