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 6FD14158DCD for ; Wed, 28 Aug 2024 10:23:37 +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=1724840619; cv=none; b=chiGjpHHwJKlRAMo/8ZOd8WEcNafnRxFqMuTopC9lxOLOgZYtAiklNgbDoqjxGdlkgD7aPVHyHPVpvdO56MUV3qsXSTZo+YTgqLTjhIh3yO3Phu2ieugYXhH/KSajKSiWpkuF5I6nSwnQleS0wStRu3yUbBUguuY3KuOMUQsmnU= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1724840619; c=relaxed/simple; bh=kPzJM2c0Obm6HprXy0/mVlTdPadhsamBGsBFswu7MYo=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=hu6CYy+oSw5u6fs81JXc+D6YUKDjwGDux61N0CGZEQv/fO5NWKRtJt8iOatkC9KcosdMTp8nXtn3aLx2KdQlCwmbpxe+Nr8btgAifvA+IjmkNDgYcONHnyzLGSBnvcj3zdBmsV6ES0eFaXluX5xo1KjhtTQqiCsAj+n+qAhRFj4= 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 E8750DA7; Wed, 28 Aug 2024 03:24:02 -0700 (PDT) Received: from [10.57.48.229] (unknown [10.57.48.229]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id ECCC23F73B; Wed, 28 Aug 2024 03:23:34 -0700 (PDT) Message-ID: <770da6f7-89f6-49b7-b8db-a7318abbd828@arm.com> Date: Wed, 28 Aug 2024 11:23:33 +0100 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 v2] sched/deadline: fix the hang in dl_task_of To: Huang Shijie , mingo@redhat.com Cc: patches@amperecomputing.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, vineeth@bitbyteword.org, bristot@kernel.org, linux-kernel@vger.kernel.org References: <20240828091141.12043-1-shijie@os.amperecomputing.com> Content-Language: en-US From: Hongyan Xia In-Reply-To: <20240828091141.12043-1-shijie@os.amperecomputing.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 28/08/2024 10:11, Huang Shijie wrote: > When we enable the schedstats, we will meet an OS hang like this: > -------------------------------------------------------- > [ 134.104253] kernel BUG at kernel/sched/deadline.c:63! > [ 134.132013] ------------[ cut here ]------------ > [ 134.133441] x27: 0000000000000001 > [ 134.138048] kernel BUG at kernel/sched/deadline.c:63! > [ 134.146478] x26: 0000000000000001 x25: 0000000000000000 x24: 0000000000000001 > [ 134.153607] x23: 0000000000000001 x22: 0000000000000000 x21: 0000000000000001 > [ 134.160734] x20: ffff007dbf1b6d00 x19: ffff007dbf1b7610 x18: 0000000000000014 > [ 134.162027] ------------[ cut here ]------------ > [ 134.167861] x17: 000000009deab6cd x16: 00000000527c9a1c x15: 00000000000000dc > [ 134.172473] kernel BUG at kernel/sched/deadline.c:63! > [ 134.179595] x14: 0000000001200011 x13: 0000000040001000 x12: 0000ffffb6df05bc > [ 134.191760] x11: ffff007dbf1b6d00 x10: ffff0001062dd2e8 x9 : ffff8000801215ac > [ 134.192036] ------------[ cut here ]------------ > [ 134.198888] x8 : 0000000000000000 x7 : 0000000000000021 x6 : ffff0001764ed280 > [ 134.203498] kernel BUG at kernel/sched/deadline.c:63! > [ 134.210622] x5 : 0000000000000000 x4 : 0000000000000001 x3 : ffff807d3dd24000 > [ 134.222787] x2 : 000000028b77a140 x1 : 0000003400000000 x0 : ffff007dbf1b6c80 > [ 134.229915] Call trace: > [ 134.232353] dl_task_of.part.0+0x0/0x10 > [ 134.236182] dl_server_start+0x54/0x158 > [ 134.240013] enqueue_task_fair+0x138/0x420 > [ 134.244100] enqueue_task+0x44/0xb0 > [ 134.247584] wake_up_new_task+0x1c0/0x3a0 > [ 134.251584] kernel_clone+0xe8/0x3e8 > [ 134.252022] ------------[ cut here ]------------ > [ 134.255156] __do_sys_clone+0x70/0xa8 > [ 134.259764] kernel BUG at kernel/sched/deadline.c:63! > [ 134.263412] __arm64_sys_clone+0x28/0x40 > [ 134.272360] invoke_syscall+0x50/0x120 > [ 134.276101] el0_svc_common+0x44/0xf8 > [ 134.279753] do_el0_svc+0x28/0x40 > [ 134.283058] el0_svc+0x40/0x150 > [ 134.286195] el0t_64_sync_handler+0x100/0x130 > [ 134.290546] el0t_64_sync+0x1a4/0x1a8 > [ 134.294200] Code: 35ffffa2 17ffffe3 d4210000 17ffffb4 (d4210000) > [ 134.300283] ---[ end trace 0000000000000000 ]--- > [ 134.304890] Kernel panic - not syncing: Oops - BUG: Fatal exception > [ 134.311147] SMP: stopping secondary CPUs > [ 135.365096] SMP: failed to stop secondary CPUs 8-9,16,30,43,86,88,121,149 > [ 135.371884] Kernel Offset: disabled > [ 135.375361] CPU features: 0x00,00100003,80153d29,d75ffea7 > [ 135.380749] Memory Limit: none > [ 135.383793] ---[ end Kernel panic - not syncing: Oops - BUG: Fatal exception ] > -------------------------------------------------------- > > In dl_server_start(), we set the dl_se->dl_server with 1. When schedstats > is enabled, in the following: > dl_server_start() --> enqueue_dl_entity() --> update_stats_enqueue_dl() > __schedstats_from_dl_se() -->dl_task_of() > > we will meet the BUG_ON. > > Since the fair task has already had its own schedstats, there is no need > to track anything for the associated dl_server. > > So add check in enqueue_dl_entity(), skip the update_stats_enqueue_dl() > for a dl_server dl_se. > > Tested this patch with memcached in Altra. > > Fixes: 5f6bd380c7bd ("sched/rt: Remove default bandwidth control") > Signed-off-by: Huang Shijie > --- > v1 --> v2: > Skip the update_stats_enqueue_dl() for a dl_server dl_se > in enqueue_dl_entity(). > > Btw, the update_stats_{wait_start,wait_end}_dl has already had > the dl_server() check. > > The v1 link: https://lore.kernel.org/lkml/20240826021115.9284-1-shijie@os.amperecomputing.com/T/ > --- > kernel/sched/deadline.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/kernel/sched/deadline.c b/kernel/sched/deadline.c > index 0f2df67f710b..cb9bd3a480dd 100644 > --- a/kernel/sched/deadline.c > +++ b/kernel/sched/deadline.c > @@ -2002,7 +2002,8 @@ enqueue_dl_entity(struct sched_dl_entity *dl_se, int flags) > { > WARN_ON_ONCE(on_dl_rq(dl_se)); > > - update_stats_enqueue_dl(dl_rq_of_se(dl_se), dl_se, flags); > + if (!dl_server(dl_se)) > + update_stats_enqueue_dl(dl_rq_of_se(dl_se), dl_se, flags); > > /* > * Check if a constrained deadline task was activated Thanks for the patch. I'm seeing the same crash and your fix looks good to me. Now it boots on my Juno board with CONFIG_SCHEDSTATS. Reviewed- and Tested-by: Hongyan Xia