From: Sasha Levin <sashal@kernel.org>
To: Daniel Jordan <daniel.m.jordan@oracle.com>
Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
linux-kernel@vger.kernel.org, stable@vger.kernel.org,
Eric Biggers <ebiggers@kernel.org>,
Herbert Xu <herbert@gondor.apana.org.au>,
Steffen Klassert <steffen.klassert@secunet.com>,
linux-crypto@vger.kernel.org
Subject: Re: [PATCH 4.19 061/191] padata: always acquire cpu_hotplug_lock before pinst->lock
Date: Sat, 22 Feb 2020 14:02:50 -0500 [thread overview]
Message-ID: <20200222190250.GD26320@sasha-vm> (raw)
In-Reply-To: <20200222000045.cl45vclfhvkjursm@ca-dmjordan1.us.oracle.com>
On Fri, Feb 21, 2020 at 07:00:45PM -0500, Daniel Jordan wrote:
>On Fri, Feb 21, 2020 at 08:40:34AM +0100, Greg Kroah-Hartman wrote:
>> From: Daniel Jordan <daniel.m.jordan@oracle.com>
>>
>> [ Upstream commit 38228e8848cd7dd86ccb90406af32de0cad24be3 ]
>>
>> lockdep complains when padata's paths to update cpumasks via CPU hotplug
>> and sysfs are both taken:
>>
>> # echo 0 > /sys/devices/system/cpu/cpu1/online
>> # echo ff > /sys/kernel/pcrypt/pencrypt/parallel_cpumask
>>
>> ======================================================
>> WARNING: possible circular locking dependency detected
>> 5.4.0-rc8-padata-cpuhp-v3+ #1 Not tainted
>> ------------------------------------------------------
>> bash/205 is trying to acquire lock:
>> ffffffff8286bcd0 (cpu_hotplug_lock.rw_sem){++++}, at: padata_set_cpumask+0x2b/0x120
>>
>> but task is already holding lock:
>> ffff8880001abfa0 (&pinst->lock){+.+.}, at: padata_set_cpumask+0x26/0x120
>>
>> which lock already depends on the new lock.
>
>I think this patch should be dropped from all stable queues (4.4, 4.9, 4.14,
>4.19, 5.4, and 5.5).
>
>The main benefit is to un-break lockdep for testing with future padata changes,
>and an actual deadlock seems unlikely.
>
>These stable versions don't fix the ordering in padata_remove_cpu() either
>(nothing calls it though).
>
>I tried the other stable padata patch in this cycle ("padata: validate cpumask
>without removed CPU during offline"), it passed my tests and should stay in.
I've dropped it, thanks.
--
Thanks,
Sasha
prev parent reply other threads:[~2020-02-22 19:02 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20200221072250.732482588@linuxfoundation.org>
2020-02-21 7:40 ` [PATCH 4.19 061/191] padata: always acquire cpu_hotplug_lock before pinst->lock Greg Kroah-Hartman
2020-02-22 0:00 ` Daniel Jordan
2020-02-22 19:02 ` Sasha Levin [this message]
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