From: Ben Hutchings <ben@decadent.org.uk>
To: linux-kernel@vger.kernel.org, stable@vger.kernel.org
Cc: akpm@linux-foundation.org, Denis Kirjanov <kda@linux-powerpc.org>,
"Steffen Klassert" <steffen.klassert@secunet.com>,
"Eric Biggers" <ebiggers@kernel.org>,
linux-crypto@vger.kernel.org,
"Herbert Xu" <herbert@gondor.apana.org.au>,
"Daniel Jordan" <daniel.m.jordan@oracle.com>
Subject: [PATCH 3.16 15/99] padata: always acquire cpu_hotplug_lock before pinst->lock
Date: Wed, 20 May 2020 15:13:43 +0100 [thread overview]
Message-ID: <lsq.1589984008.683956171@decadent.org.uk> (raw)
In-Reply-To: <lsq.1589984008.673931885@decadent.org.uk>
3.16.84-rc1 review patch. If anyone has any objections, please let me know.
------------------
From: Daniel Jordan <daniel.m.jordan@oracle.com>
commit 38228e8848cd7dd86ccb90406af32de0cad24be3 upstream.
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@oracle.com>
Cc: Eric Biggers <ebiggers@kernel.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Steffen Klassert <steffen.klassert@secunet.com>
Cc: linux-crypto@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
kernel/padata.c | 4 ++--
1 file changed, 2 insertions(+), 2 deletions(-)
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -614,8 +614,8 @@ int padata_set_cpumask(struct padata_ins
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:
@@ -633,8 +633,8 @@ int padata_set_cpumask(struct padata_ins
err = __padata_set_cpumasks(pinst, parallel_mask, serial_mask);
out:
- put_online_cpus();
mutex_unlock(&pinst->lock);
+ put_online_cpus();
return err;
}
prev parent reply other threads:[~2020-05-20 14:28 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <lsq.1589984008.673931885@decadent.org.uk>
2020-05-20 14:13 ` [PATCH 3.16 10/99] padata: initialize pd->cpu with effective cpumask Ben Hutchings
2020-05-20 14:13 ` [PATCH 3.16 12/99] padata: purge get_cpu and reorder_via_wq from padata_do_serial Ben Hutchings
2020-05-20 14:13 ` Ben Hutchings [this message]
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