From: Willy Tarreau <w@1wt.eu>
Date: Tue, 30 Jun 2020 09:48:48 +0000 (+0200)
Subject: MEDIUM: sched: create a new TASK_KILLED task flag
X-Git-Tag: v2.2-dev12~30
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=8a6049c2680fe1bdacf53a90e4c3ff97bc791ec9;p=thirdparty%2Fhaproxy.git

MEDIUM: sched: create a new TASK_KILLED task flag

This flag, when set, will be used to indicate that the task must die.
At the moment this may only be placed by the task itself or by the
scheduler when placing it into the TL_NORMAL queue.
---

diff --git a/include/haproxy/task-t.h b/include/haproxy/task-t.h
index 88f2bdd945..cf86c0a3ee 100644
--- a/include/haproxy/task-t.h
+++ b/include/haproxy/task-t.h
@@ -38,6 +38,7 @@
 #define TASK_SHARED_WQ    0x0008  /* The task's expiration may be updated by other
                                    * threads, must be set before first queue/wakeup */
 #define TASK_SELF_WAKING  0x0010  /* task/tasklet found waking itself */
+#define TASK_KILLED       0x0020  /* task/tasklet killed, may now be freed */
 
 #define TASK_WOKEN_INIT   0x0100  /* woken up for initialisation purposes */
 #define TASK_WOKEN_TIMER  0x0200  /* woken up because of expired timer */
diff --git a/src/task.c b/src/task.c
index b65000b8f3..7626e6037e 100644
--- a/src/task.c
+++ b/src/task.c
@@ -379,7 +379,7 @@ unsigned int run_tasks_from_lists(unsigned int budgets[])
 
 		budgets[queue]--;
 		t = (struct task *)LIST_ELEM(tl_queues[queue].n, struct tasklet *, list);
-		state = (t->state & (TASK_SHARED_WQ|TASK_SELF_WAKING));
+		state = t->state & (TASK_SHARED_WQ|TASK_SELF_WAKING|TASK_KILLED);
 
 		ti->flags &= ~TI_FL_STUCK; // this thread is still running
 		activity[tid].ctxsw++;
@@ -414,11 +414,18 @@ unsigned int run_tasks_from_lists(unsigned int budgets[])
 		}
 
 		__ha_barrier_store();
-		if (likely(process == process_stream))
+
+		/* Note for below: if TASK_KILLED arrived before we've read the state, we
+		 * directly free the task. Otherwise it will be seen after processing and
+		 * it's freed on the exit path.
+		 */
+		if (likely(!(state & TASK_KILLED) && process == process_stream))
 			t = process_stream(t, ctx, state);
-		else if (process != NULL)
+		else if (!(state & TASK_KILLED) && process != NULL)
 			t = process(t, ctx, state);
 		else {
+			if (task_in_wq(t))
+				__task_unlink_wq(t);
 			__task_free(t);
 			sched->current = NULL;
 			__ha_barrier_store();
@@ -440,7 +447,12 @@ unsigned int run_tasks_from_lists(unsigned int budgets[])
 			}
 
 			state = _HA_ATOMIC_AND(&t->state, ~TASK_RUNNING);
-			if (state & TASK_WOKEN_ANY)
+			if (unlikely(state & TASK_KILLED)) {
+				if (task_in_wq(t))
+					__task_unlink_wq(t);
+				__task_free(t);
+			}
+			else if (state & TASK_WOKEN_ANY)
 				task_wakeup(t, 0);
 			else
 				task_queue(t);