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* [PATCH AUTOSEL 4.9 054/141] padata: always acquire cpu_hotplug_lock before pinst->lock
       [not found] <>
@ 2020-02-14 16:19 ` Sasha Levin
  0 siblings, 0 replies; only message in thread
From: Sasha Levin @ 2020-02-14 16:19 UTC (permalink / raw)
  To: linux-kernel, stable
  Cc: Daniel Jordan, Eric Biggers, Herbert Xu, Steffen Klassert,
	linux-crypto, Sasha Levin

From: Daniel Jordan <>

[ 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.

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 <>
Cc: Eric Biggers <>
Cc: Herbert Xu <>
Cc: Steffen Klassert <>
Signed-off-by: Herbert Xu <>
Signed-off-by: Sasha Levin <>
 kernel/padata.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/padata.c b/kernel/padata.c
index 63449fc584daf..ee5da2394cf57 100644
--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -635,8 +635,8 @@ int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
 	struct cpumask *serial_mask, *parallel_mask;
 	int err = -EINVAL;
-	mutex_lock(&pinst->lock);
+	mutex_lock(&pinst->lock);
 	switch (cpumask_type) {
@@ -654,8 +654,8 @@ int padata_set_cpumask(struct padata_instance *pinst, int cpumask_type,
 	err =  __padata_set_cpumasks(pinst, parallel_mask, serial_mask);
-	put_online_cpus();
+	put_online_cpus();
 	return err;

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