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From: Greg Kroah-Hartman <>
Cc: Greg Kroah-Hartman <>,,
	Daniel Jordan <>,
	Eric Biggers <>,
	Herbert Xu <>,
	Steffen Klassert <>,
Subject: [PATCH 4.19 85/87] padata: always acquire cpu_hotplug_lock before pinst->lock
Date: Tue,  3 Mar 2020 18:44:16 +0100	[thread overview]
Message-ID: <> (raw)
In-Reply-To: <>

From: Daniel Jordan <>

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 <>
Cc: Eric Biggers <>
Cc: Herbert Xu <>
Cc: Steffen Klassert <>
Signed-off-by: Herbert Xu <>
Signed-off-by: Greg Kroah-Hartman <>

 kernel/padata.c |    4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

--- a/kernel/padata.c
+++ b/kernel/padata.c
@@ -671,8 +671,8 @@ int padata_set_cpumask(struct padata_ins
 	struct cpumask *serial_mask, *parallel_mask;
 	int err = -EINVAL;
-	mutex_lock(&pinst->lock);
+	mutex_lock(&pinst->lock);
 	switch (cpumask_type) {
@@ -690,8 +690,8 @@ int padata_set_cpumask(struct padata_ins
 	err =  __padata_set_cpumasks(pinst, parallel_mask, serial_mask);
-	put_online_cpus();
+	put_online_cpus();
 	return err;

           reply	other threads:[~2020-03-03 18:02 UTC|newest]

Thread overview: expand[flat|nested]  mbox.gz  Atom feed
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