From c46c965540386d47c26eb7fc5218b72ddf19b8e0 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Wed, 4 Mar 2015 23:26:01 +0100 Subject: [PATCH] BUG/MEDIUM: task: fix recently introduced scheduler skew Commit 501260b ("MEDIUM: task: always ensure that the run queue is consistent") introduced a skew in the scheduler : if a negatively niced task is woken up, it can be inserted prior to the current index and will be skipped as long as there is some activity with less prioritary tasks. The immediate effect is that it's not possible to get access to the stats under full load until the load goes down. This is because the rq_next constantly evolves within more recent positions. The fix is simple, __task_wakeup() must empty rq_next. The sad thing is that this issue was fixed during development and missed during the commit. No backport is needed, this is purely 1.6 stuff. --- src/task.c | 1 + 1 file changed, 1 insertion(+) diff --git a/src/task.c b/src/task.c index 4985aa22a..d475322c4 100644 --- a/src/task.c +++ b/src/task.c @@ -65,6 +65,7 @@ struct task *__task_wakeup(struct task *t) t->state &= ~TASK_WOKEN_ANY; eb32_insert(&rqueue, &t->rq); + rq_next = NULL; return t; }