From: Willy Tarreau <w@1wt.eu>
Date: Tue, 6 Sep 2022 14:31:30 +0000 (+0200)
Subject: BUG/MINOR: task: make task_instant_wakeup() work on a task not a tasklet
X-Git-Tag: v2.7-dev6~90
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=0fae3a0360314285a17153cac76413184143ee74;p=thirdparty%2Fhaproxy.git

BUG/MINOR: task: make task_instant_wakeup() work on a task not a tasklet

There's a subtle (harmless) bug in task_instant_wakeup(). As it uses
some tasklet code instead of some task code, the debug part also acts
on the tasklet equivalent, and the call_date is only set when DEBUG_TASK
is set instead of inconditionally like with tasks. As such, without this
debugging macro, call dates are not updated for tasks woken this way.

There isn't any impact yet because this function was introduced in 2.6 to
solve certain classes of issues and is not used yet, and in the worst case
it would only affect the reported latency time.

This may be backported to 2.6 in case a future fix would depend on it but
currently will not fix existing code.
---

diff --git a/include/haproxy/task.h b/include/haproxy/task.h
index f2ff7e7cbe..7a58e3ed9c 100644
--- a/include/haproxy/task.h
+++ b/include/haproxy/task.h
@@ -384,7 +384,6 @@ static inline void _tasklet_wakeup_on(struct tasklet *tl, int thr, const char *f
 #define task_instant_wakeup(t, f) _task_instant_wakeup(t, f, __FILE__, __LINE__)
 static inline void _task_instant_wakeup(struct task *t, unsigned int f, const char *file, int line)
 {
-	struct tasklet *tl = (struct tasklet *)t;
 	int thr = t->tid;
 	unsigned int state;
 
@@ -392,7 +391,7 @@ static inline void _task_instant_wakeup(struct task *t, unsigned int f, const ch
 		thr = tid;
 
 	/* first, let's update the task's state with the wakeup condition */
-	state = _HA_ATOMIC_OR_FETCH(&tl->state, f);
+	state = _HA_ATOMIC_OR_FETCH(&t->state, f);
 
 	/* next we need to make sure the task was not/will not be added to the
 	 * run queue because the tasklet list's mt_list uses the same storage
@@ -402,21 +401,21 @@ static inline void _task_instant_wakeup(struct task *t, unsigned int f, const ch
 		/* do nothing if someone else already added it */
 		if (state & (TASK_QUEUED|TASK_RUNNING))
 			return;
-	} while (!_HA_ATOMIC_CAS(&tl->state, &state, state | TASK_QUEUED));
+	} while (!_HA_ATOMIC_CAS(&t->state, &state, state | TASK_QUEUED));
 
 	BUG_ON_HOT(task_in_rq(t));
 
 	/* at this point we're the first ones to add this task to the list */
 #ifdef DEBUG_TASK
-	if ((unsigned int)tl->debug.caller_idx > 1)
+	if ((unsigned int)t->debug.caller_idx > 1)
 		ABORT_NOW();
-	tl->debug.caller_idx = !tl->debug.caller_idx;
-	tl->debug.caller_file[tl->debug.caller_idx] = file;
-	tl->debug.caller_line[tl->debug.caller_idx] = line;
-	if (_HA_ATOMIC_LOAD(&th_ctx->flags) & TH_FL_TASK_PROFILING)
-		tl->call_date = now_mono_time();
+	t->debug.caller_idx = !t->debug.caller_idx;
+	t->debug.caller_file[t->debug.caller_idx] = file;
+	t->debug.caller_line[t->debug.caller_idx] = line;
 #endif
-	__tasklet_wakeup_on(tl, thr);
+	if (_HA_ATOMIC_LOAD(&th_ctx->flags) & TH_FL_TASK_PROFILING)
+		t->call_date = now_mono_time();
+	__tasklet_wakeup_on((struct tasklet *)t, thr);
 }
 
 /* schedules tasklet <tl> to run immediately after the current one is done