iv/linux
1
0
Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

padata: always acquire cpu_hotplug_lock before pinst->lock

Browse Source 
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: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Daniel Jordan 2019-12-03 14:31:11 -05:00 committed by Greg Kroah-Hartman
parent 13684ec1e9
commit 80c4e3a257
1 changed files with 2 additions and 2 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

4
kernel/padata.c
View File

@ -640,8 +640,8 @@ 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:
@ -659,8 +659,8 @@ 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;
}