commit 75795017480da0f0a1157e945043249fe625f92f
Author: Willy Tarreau <w@1wt.eu>
Date:   Tue Oct 16 16:11:56 2018 +0200

    BUG/MEDIUM: threads: fix thread_release() at the end of the rendez-vous point
    
    There is a bug in this function used to release other threads. It leaves
    the current thread marked as harmless. If after this another thread does
    a thread_isolate(), but before the first one reaches poll(), the second
    thread will believe it's alone while it's not.
    
    This must be backported to 1.8 since the rendez-vous point was merged
    into 1.8.14.
    
    (cherry picked from commit a9c0252b2e8ff7bb728b84d977ac6e9581ea12f8)
    Signed-off-by: Willy Tarreau <w@1wt.eu>

diff --git a/src/hathreads.c b/src/hathreads.c
index 9dba4356..0a7c12f7 100644
--- a/src/hathreads.c
+++ b/src/hathreads.c
@@ -221,12 +221,8 @@ void thread_isolate()
  */
 void thread_release()
 {
-	while (1) {
-		HA_ATOMIC_AND(&threads_want_rdv_mask, ~tid_bit);
-		if (!(threads_want_rdv_mask & all_threads_mask))
-			break;
-		thread_harmless_till_end();
-	}
+	HA_ATOMIC_AND(&threads_want_rdv_mask, ~tid_bit);
+	thread_harmless_end();
 }
 
 __attribute__((constructor))