6.17-stable review patch. If anyone has any objections, please let me know.
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From: Peter Zijlstra (Intel) peterz@infradead.org
[ Upstream commit ee6e44dfe6e50b4a5df853d933a96bdff5309e6e ]
IBM CI tool reported kernel warning[1] when running a CPU removal operation through drmgr[2]. i.e "drmgr -c cpu -r -q 1"
WARNING: CPU: 0 PID: 0 at kernel/sched/cpudeadline.c:219 cpudl_set+0x58/0x170 NIP [c0000000002b6ed8] cpudl_set+0x58/0x170 LR [c0000000002b7cb8] dl_server_timer+0x168/0x2a0 Call Trace: [c000000002c2f8c0] init_stack+0x78c0/0x8000 (unreliable) [c0000000002b7cb8] dl_server_timer+0x168/0x2a0 [c00000000034df84] __hrtimer_run_queues+0x1a4/0x390 [c00000000034f624] hrtimer_interrupt+0x124/0x300 [c00000000002a230] timer_interrupt+0x140/0x320
Git bisects to: commit 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck")
This happens since: - dl_server hrtimer gets enqueued close to cpu offline, when kthread_park enqueues a fair task. - CPU goes offline and drmgr removes it from cpu_present_mask. - hrtimer fires and warning is hit.
Fix it by stopping the dl_server before CPU is marked dead.
[1]: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.c... [2]: https://github.com/ibm-power-utilities/powerpc-utils/tree/next/src/drmgr
[sshegde: wrote the changelog and tested it] Fixes: 4ae8d9aa9f9d ("sched/deadline: Fix dl_server getting stuck") Closes: https://lore.kernel.org/all/8218e149-7718-4432-9312-f97297c352b9@linux.ibm.c... Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Reported-by: Venkat Rao Bagalkote venkat88@linux.ibm.com Signed-off-by: Shrikanth Hegde sshegde@linux.ibm.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Tested-by: Marek Szyprowski m.szyprowski@samsung.com Tested-by: Shrikanth Hegde sshegde@linux.ibm.com Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/sched/core.c | 2 ++ kernel/sched/deadline.c | 3 +++ 2 files changed, 5 insertions(+)
diff --git a/kernel/sched/core.c b/kernel/sched/core.c index ccba6fc3c3fed..8575d67cbf738 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -8603,10 +8603,12 @@ int sched_cpu_dying(unsigned int cpu) sched_tick_stop(cpu);
rq_lock_irqsave(rq, &rf); + update_rq_clock(rq); if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) { WARN(true, "Dying CPU not properly vacated!"); dump_rq_tasks(rq, KERN_WARNING); } + dl_server_stop(&rq->fair_server); rq_unlock_irqrestore(rq, &rf);
calc_load_migrate(rq); diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c index 615411a0a8813..7b7671060bf9e 100644 --- a/kernel/sched/deadline.c +++ b/kernel/sched/deadline.c @@ -1582,6 +1582,9 @@ void dl_server_start(struct sched_dl_entity *dl_se) if (!dl_server(dl_se) || dl_se->dl_server_active) return;
+ if (WARN_ON_ONCE(!cpu_online(cpu_of(rq)))) + return; + dl_se->dl_server_active = 1; enqueue_dl_entity(dl_se, ENQUEUE_WAKEUP); if (!dl_task(dl_se->rq->curr) || dl_entity_preempt(dl_se, &rq->curr->dl))