diff --git a/include/haproxy/fd.h b/include/haproxy/fd.h
index fa24240..29765d8 100644
--- a/include/haproxy/fd.h
+++ b/include/haproxy/fd.h
@@ -370,11 +370,15 @@
 	return evts[fd / (8*sizeof(*evts))] & (1U << (fd & (8*sizeof(*evts) - 1)));
 }
 
+/* send a wake-up event to this thread, only if it's asleep and not notified yet */
 static inline void wake_thread(int thr)
 {
-	if (sleeping_thread_mask & (1UL << thr)) {
+	struct thread_ctx *ctx = &ha_thread_ctx[thr];
+
+	if (sleeping_thread_mask & (1UL << thr) &&
+	    (_HA_ATOMIC_LOAD(&ctx->flags) & TH_FL_NOTIFIED) == 0) {
 		char c = 'c';
-		_HA_ATOMIC_AND(&sleeping_thread_mask, ~(1UL << thr));
+		_HA_ATOMIC_OR(&ctx->flags, TH_FL_NOTIFIED);
 		DISGUISE(write(poller_wr_pipe[thr], &c, 1));
 	}
 }
diff --git a/include/haproxy/tinfo-t.h b/include/haproxy/tinfo-t.h
index 81a246c..51a0e27 100644
--- a/include/haproxy/tinfo-t.h
+++ b/include/haproxy/tinfo-t.h
@@ -42,6 +42,8 @@
  */
 #define TH_FL_STUCK             0x00000001
 #define TH_FL_TASK_PROFILING    0x00000002
+#define TH_FL_NOTIFIED          0x00000004  /* task was notified about the need to wake up */
+
 
 /* Thread group information. This defines a base and a count of global thread
  * IDs which belong to it, and which can be looked up into thread_info/ctx. It
diff --git a/src/haproxy.c b/src/haproxy.c
index 892d821..a1addfe 100644
--- a/src/haproxy.c
+++ b/src/haproxy.c
@@ -2805,6 +2805,7 @@
 			activity[tid].wake_tasks++;
 		else {
 			_HA_ATOMIC_OR(&sleeping_thread_mask, tid_bit);
+			_HA_ATOMIC_AND(&th_ctx->flags, ~TH_FL_NOTIFIED);
 			__ha_barrier_atomic_store();
 			if (thread_has_tasks()) {
 				activity[tid].wake_tasks++;