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Date: Tue, 3 Dec 2019 14:31:11 -0500 From: Daniel Jordan <daniel.m.jordan@...cle.com> To: Herbert Xu <herbert@...dor.apana.org.au>, Steffen Klassert <steffen.klassert@...unet.com> Cc: Eric Biggers <ebiggers@...nel.org>, Jonathan Corbet <corbet@....net>, linux-crypto@...r.kernel.org, linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org, Daniel Jordan <daniel.m.jordan@...cle.com> Subject: [PATCH v2 2/5] padata: always acquire cpu_hotplug_lock before pinst->lock 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. padata doesn't take cpu_hotplug_lock and pinst->lock in a consistent order. Which should be first? CPU hotplug calls into padata with cpu_hotplug_lock already held, so it should have priority. Fixes: 6751fb3c0e0c ("padata: Use get_online_cpus/put_online_cpus") Signed-off-by: Daniel Jordan <daniel.m.jordan@...cle.com> Cc: Eric Biggers <ebiggers@...nel.org> Cc: Herbert Xu <herbert@...dor.apana.org.au> Cc: Steffen Klassert <steffen.klassert@...unet.com> Cc: linux-crypto@...r.kernel.org Cc: linux-kernel@...r.kernel.org --- kernel/padata.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/kernel/padata.c b/kernel/padata.c index a2fa6223e1a0..2f8db63aefc4 100644 --- a/kernel/padata.c +++ b/kernel/padata.c @@ -643,8 +643,8 @@ int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type, struct cpumask *serial_mask, *parallel_mask; int err = -EINVAL; - mutex_lock(&pinst->lock); get_online_cpus(); + mutex_lock(&pinst->lock); switch (cpumask_type) { case PADATA_CPU_PARALLEL: @@ -662,8 +662,8 @@ int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type, err = __padata_set_cpumasks(pinst, parallel_mask, serial_mask); out: - put_online_cpus(); mutex_unlock(&pinst->lock); + put_online_cpus(); return err; } -- 2.24.0
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