[PATCH 6.1.y] sched/deadline: Fix warning in migrate_enable for boosted tasks

[PATCH 6.1.y] sched/deadline: Fix warning in migrate_enable for boosted tasks

[bin.lan.cn]

From: Wander Lairson Costa <wander@redhat.com>

[ Upstream commit 0664e2c311b9fa43b33e3e81429cd0c2d7f9c638 ]

When running the following command:

while true; do
    stress-ng --cyclic 30 --timeout 30s --minimize --quiet
done

a warning is eventually triggered:

WARNING: CPU: 43 PID: 2848 at kernel/sched/deadline.c:794
setup_new_dl_entity+0x13e/0x180
...
Call Trace:
 <TASK>
 ? show_trace_log_lvl+0x1c4/0x2df
 ? enqueue_dl_entity+0x631/0x6e0
 ? setup_new_dl_entity+0x13e/0x180
 ? __warn+0x7e/0xd0
 ? report_bug+0x11a/0x1a0
 ? handle_bug+0x3c/0x70
 ? exc_invalid_op+0x14/0x70
 ? asm_exc_invalid_op+0x16/0x20
 enqueue_dl_entity+0x631/0x6e0
 enqueue_task_dl+0x7d/0x120
 __do_set_cpus_allowed+0xe3/0x280
 __set_cpus_allowed_ptr_locked+0x140/0x1d0
 __set_cpus_allowed_ptr+0x54/0xa0
 migrate_enable+0x7e/0x150
 rt_spin_unlock+0x1c/0x90
 group_send_sig_info+0xf7/0x1a0
 ? kill_pid_info+0x1f/0x1d0
 kill_pid_info+0x78/0x1d0
 kill_proc_info+0x5b/0x110
 __x64_sys_kill+0x93/0xc0
 do_syscall_64+0x5c/0xf0
 entry_SYSCALL_64_after_hwframe+0x6e/0x76
 RIP: 0033:0x7f0dab31f92b

This warning occurs because set_cpus_allowed dequeues and enqueues tasks
with the ENQUEUE_RESTORE flag set. If the task is boosted, the warning
is triggered. A boosted task already had its parameters set by
rt_mutex_setprio, and a new call to setup_new_dl_entity is unnecessary,
hence the WARN_ON call.

Check if we are requeueing a boosted task and avoid calling
setup_new_dl_entity if that's the case.

Fixes: 295d6d5e3736 ("sched/deadline: Fix switching to -deadline")
Signed-off-by: Wander Lairson Costa <wander@redhat.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Juri Lelli <juri.lelli@redhat.com>
Link: https://lore.kernel.org/r/20240724142253.27145-2-wander@redhat.com
[Minor context change fixed.]
Signed-off-by: Bin Lan <bin.lan.cn@windriver.com>
Signed-off-by: He Zhe <zhe.he@windriver.com>
---
Build test passed.
---
 kernel/sched/deadline.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c
index 7f378fa0b6ed..e1371227a3bf 100644
--- a/kernel/sched/deadline.c
+++ b/kernel/sched/deadline.c
@@ -1656,6 +1656,7 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags)
 	} else if (flags & ENQUEUE_REPLENISH) {
 		replenish_dl_entity(dl_se);
 	} else if ((flags & ENQUEUE_RESTORE) &&
+		  !is_dl_boosted(dl_se) &&
 		  dl_time_before(dl_se->deadline,
 				 rq_clock(rq_of_dl_rq(dl_rq_of_se(dl_se))))) {
 		setup_new_dl_entity(dl_se);
-- 
2.34.1

Re: [PATCH 6.1.y] sched/deadline: Fix warning in migrate_enable for boosted tasks

[Sasha Levin]

[ Sasha's backport helper bot ]

Hi,

✅ All tests passed successfully. No issues detected.
No action required from the submitter.

The upstream commit SHA1 provided is correct: 0664e2c311b9fa43b33e3e81429cd0c2d7f9c638

WARNING: Author mismatch between patch and upstream commit:
Backport author: bin.lan.cn@windriver.com
Commit author: Wander Lairson Costa<wander@redhat.com>

Status in newer kernel trees:
6.14.y | Present (exact SHA1)
6.12.y | Present (different SHA1: e41074904d9e)
6.6.y | Present (different SHA1: b600d3040285)

Note: The patch differs from the upstream commit:
---
1:  0664e2c311b9f < -:  ------------- sched/deadline: Fix warning in migrate_enable for boosted tasks
-:  ------------- > 1:  183a577efa2e0 sched/deadline: Fix warning in migrate_enable for boosted tasks
---

Results of testing on various branches:

| Branch                    | Patch Apply | Build Test |
|---------------------------|-------------|------------|
| stable/linux-6.1.y        |  Success    |  Success   |