From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 7052E191F7A for ; Mon, 25 Nov 2024 10:14:33 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732529675; cv=none; b=fGW527yXcPcbyY5LCl26iNAM0cy2ELhrepw/+QzIS/we6o5IYjpGZ6Fk+N4xb7AW2f7auUat1Q4SSn0K9sSpzUuYwDBcT1OclHgd58XAIsJAypY5ZQvI3Z5tQNL3QZTarxbMnRFQhJxwlKevz0Zl2lf7Id3b3cGWw7Hq0muPE2U= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1732529675; c=relaxed/simple; bh=Y4/XLbsaScdiBxglFuyvK84aAmSs6kUP33eKszZbNag=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=LftnLA5/bexNlDBuYy9598gEb0V3AuMu4TpRfwkS4WihDI7QkzWS0CN5hHgiES+4IDn7Ry2PEAxNeNmjMCfxkt5TywGTvKVDruk+gGsHRXgIhLl4er/ZiOmqw5FM5MXnLdMw6ZlIvI8fBxKXDCdxpwhp9N+r0A34GXmfK31h8yA= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id D49BB1692; Mon, 25 Nov 2024 02:15:02 -0800 (PST) Received: from [10.1.31.25] (e127648.arm.com [10.1.31.25]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id F34343F5A1; Mon, 25 Nov 2024 02:14:29 -0800 (PST) Message-ID: <40c9de6d-4a51-4623-bb8f-86d8faedca32@arm.com> Date: Mon, 25 Nov 2024 10:14:28 +0000 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 1/2] sched/fair: Fix panic if NEXT_BUDDY enabled To: Adam Li , peterz@infradead.org, mingo@redhat.com, juri.lelli@redhat.com, vincent.guittot@linaro.org Cc: 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 References: <20241125021222.356881-1-adamli@os.amperecomputing.com> <20241125021222.356881-2-adamli@os.amperecomputing.com> Content-Language: en-US From: Christian Loehle In-Reply-To: <20241125021222.356881-2-adamli@os.amperecomputing.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/25/24 02:12, Adam Li wrote: > Enabling NEXT_BUDDY may trigger warning and kernel panic: > > [ 124.977300] cfs_rq->next->sched_delayed > [ 124.977310] WARNING: CPU: 51 PID: 2150 at kernel/sched/fair.c:5621 pick_task_fair+0x130/0x150 > > [ 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 > [ 297.619782] __schedule+0x3d0/0x628 > [ 297.623259] do_task_dead+0x50/0x60 > [ 297.626736] do_exit+0x28c/0x410 > [ 297.629955] do_group_exit+0x3c/0xa0 > [ 297.633518] get_signal+0x8c4/0x8d0 > [ 297.636996] do_signal+0x9c/0x270 > [ 297.640299] do_notify_resume+0xe0/0x198 > [ 297.644212] el0_svc+0xf4/0x170 > [ 297.647342] el0t_64_sync_handler+0x10c/0x138 > [ 297.651687] el0t_64_sync+0x1ac/0x1b0 > [ 297.655339] Code: d503201f 1400002a aa1403e0 97ffda0b (39414401) > [ 297.661439] ---[ end trace 0000000000000000 ]--- > [ 297.726593] Kernel panic - not syncing: Oops: Fatal exception > > Do not set next buddy if sched_delayed is set. > > Signed-off-by: Adam Li Should have a Fixes: 152e11f6df29 ("sched/fair: Implement delayed dequeue") I assume. > --- > kernel/sched/fair.c | 2 ++ > 1 file changed, 2 insertions(+) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index fbdca89c677f..cd1188b7f3df 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -8748,6 +8748,8 @@ static void set_next_buddy(struct sched_entity *se) > return; > if (se_is_idle(se)) > return; > + if (se->sched_delayed) > + return; > cfs_rq_of(se)->next = se; > } > }