| From: Daniel Jordan <daniel.m.jordan@oracle.com> |
| Date: Tue, 3 Dec 2019 14:31:11 -0500 |
| Subject: padata: always acquire cpu_hotplug_lock before pinst->lock |
| |
| 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 |
| @@ -639,8 +639,8 @@ 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: |
| @@ -658,8 +658,8 @@ 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; |
| } |