• Daniel Jordan's avatar
    padata: always acquire cpu_hotplug_lock before pinst->lock · 38228e88
    Daniel Jordan authored
    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: 6751fb3c ("padata: Use get_online_cpus/put_online_cpus")
    Signed-off-by: default avatarDaniel 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: default avatarHerbert Xu <herbert@gondor.apana.org.au>
    38228e88
padata.c 27.5 KB