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sched/deadline: Fix server stopping with runnable tasks

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The deadline server can currently stop due to idle although fair tasks
are runnable. This happens essentially when:

 * the server is set to idle, a task wakes up, the server stops
 * a task wakes up, the server sets itself to idle and stops right away

Address both cases by clearing the server idle flag whenever a fair task
wakes up and accounting also for pending tasks in the definition of idle.

Fixes: f5a538c07d ("sched/deadline: Fix dl_server stop condition")
Signed-off-by: Gabriele Monaco <gmonaco@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://patch.msgid.link/20260113085159.114226-3-gmonaco@redhat.com
This commit is contained in:
Gabriele Monaco 2026-01-13 09:52:01 +01:00 committed by Peter Zijlstra
parent 1e0a2ba7af
commit ca1e8eede4
1 changed files with 9 additions and 4 deletions
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13
kernel/sched/deadline.c
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@ -1420,7 +1420,7 @@ update_stats_dequeue_dl(struct dl_rq *dl_rq, struct sched_dl_entity *dl_se, int
static void update_curr_dl_se(struct rq *rq, struct sched_dl_entity *dl_se, s64 delta_exec)
{
bool idle = rq->curr == rq->idle;
bool idle = idle_rq(rq);
s64 scaled_delta_exec;
if (unlikely(delta_exec <= 0)) {
@ -1603,8 +1603,8 @@ void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec)
* | 8 | B:zero_laxity-wait | | |
* | | | <---+ |
* | +--------------------------------+ |
* | | ^ ^ 2 |
* | | 7 | 2 +--------------------+
* | | ^ ^ 2 |
* | | 7 | 2, 1 +----------------+
* | v |
* | +-------------+ |
* +-- | C:idle-wait | -+
@ -1649,8 +1649,11 @@ void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec)
* dl_defer_idle = 0
*
*
* [1] A->B, A->D
* [1] A->B, A->D, C->B
* dl_server_start()
* dl_defer_idle = 0;
* if (dl_server_active)
* return; // [B]
* dl_server_active = 1;
* enqueue_dl_entity()
* update_dl_entity(WAKEUP)
@ -1759,6 +1762,7 @@ void dl_server_update(struct sched_dl_entity *dl_se, s64 delta_exec)
* "B:zero_laxity-wait" -> "C:idle-wait" [label="7:dl_server_update_idle"]
* "B:zero_laxity-wait" -> "D:running" [label="3:dl_server_timer"]
* "C:idle-wait" -> "A:init" [label="8:dl_server_timer"]
* "C:idle-wait" -> "B:zero_laxity-wait" [label="1:dl_server_start"]
* "C:idle-wait" -> "B:zero_laxity-wait" [label="2:dl_server_update"]
* "C:idle-wait" -> "C:idle-wait" [label="7:dl_server_update_idle"]
* "D:running" -> "A:init" [label="4:pick_task_dl"]
@ -1784,6 +1788,7 @@ void dl_server_start(struct sched_dl_entity *dl_se)
{
struct rq *rq = dl_se->rq;
dl_se->dl_defer_idle = 0;
if (!dl_server(dl_se) || dl_se->dl_server_active)
return;