From: Peter Zijlstra <peterz@infradead.org>
To: Adam Li <adamli@os.amperecomputing.com>
Cc: mingo@redhat.com, juri.lelli@redhat.com,
vincent.guittot@linaro.org, dietmar.eggemann@arm.com,
rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de,
vschneid@redhat.com, linux-kernel@vger.kernel.org,
patches@amperecomputing.com, cl@linux.com,
christian.loehle@arm.com, vineethr@linux.ibm.com
Subject: Re: [PATCH v2 2/3] sched/fair: Fix panic if pick_eevdf() returns NULL
Date: Fri, 29 Nov 2024 10:18:33 +0100 [thread overview]
Message-ID: <20241129091833.GC15382@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <20241127055610.7076-3-adamli@os.amperecomputing.com>
On Wed, Nov 27, 2024 at 05:56:09AM +0000, Adam Li wrote:
> pick_eevdf() may return NULL, which triggers NULL pointer
> dereference at pick_next_entity():
> struct sched_entity *se = pick_eevdf(cfs_rq);
> if (se->sched_delayed)
>
> [ 297.371198] Unable to handle kernel NULL pointer dereference at virtual address 0000000000000051
> [ 297.406112] CPU: 116 UID: 0 PID: 10328 Comm: Grizzly-worker( Tainted: G W E 6.12.0.adam+ #1
> [ 297.597362] Call trace:
> [ 297.599795] pick_task_fair+0x50/0x150 (P)
> [ 297.603879] pick_task_fair+0x50/0x150 (L)
> [ 297.607963] pick_next_task_fair+0x30/0x3c0
> [ 297.612134] __pick_next_task+0x4c/0x220
> [ 297.616045] pick_next_task+0x44/0x980
Well, if you look at pick_task_fair() you'll see we'll not get there
unless cfs_rq->nr_running is non-zero, at which point pick_eevdf()
really should NOT be returning NULL.
If it does, something else is broken.
next prev parent reply other threads:[~2024-11-29 9:18 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-11-27 5:56 [PATCH v2 0/3] sched/fair: Fix NEXT_BUDDY panic and warning Adam Li
2024-11-27 5:56 ` [PATCH v2 1/3] sched/fair: Fix warning if NEXT_BUDDY enabled Adam Li
2024-11-28 7:29 ` K Prateek Nayak
2024-11-29 3:21 ` Adam Li
2024-11-29 4:28 ` K Prateek Nayak
2024-11-29 7:40 ` Adam Li
2024-11-29 8:00 ` K Prateek Nayak
2024-11-29 9:55 ` Peter Zijlstra
2024-11-29 10:15 ` [PATCH] sched/fair: Untangle NEXT_BUDDY and pick_next_task() Peter Zijlstra
2024-11-29 10:18 ` Peter Zijlstra
2024-11-29 10:37 ` Adam Li
2024-11-29 11:45 ` Peter Zijlstra
2024-12-06 6:47 ` Adam Li
2024-12-09 11:00 ` [tip: sched/core] " tip-bot2 for Peter Zijlstra
2024-11-29 17:46 ` [PATCH v2 1/3] sched/fair: Fix warning if NEXT_BUDDY enabled K Prateek Nayak
2024-11-29 17:53 ` K Prateek Nayak
2024-12-03 16:05 ` Peter Zijlstra
2024-12-03 16:48 ` K Prateek Nayak
2024-12-09 11:00 ` [tip: sched/core] sched/fair: Fix NEXT_BUDDY tip-bot2 for K Prateek Nayak
2024-11-27 5:56 ` [PATCH v2 2/3] sched/fair: Fix panic if pick_eevdf() returns NULL Adam Li
2024-11-29 9:18 ` Peter Zijlstra [this message]
2024-11-27 5:56 ` [PATCH v2 3/3] sched/fair: Update comments regarding last and skip buddy Adam Li
2025-03-13 8:30 ` Madadi Vineeth Reddy
2025-03-14 2:53 ` Adam Li
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