tree 79989a77344aa2c2a57004d74dab79fda2c06f77
parent ba53d9deccbac6e0670bd9b1849663ecda54d648
author Thomas Gleixner <tglx@linutronix.de> 1596012808 +0200
committer Greg Kroah-Hartman <gregkh@linuxfoundation.org> 1596614813 +0200

x86/i8259: Use printk_deferred() to prevent deadlock

commit bdd65589593edd79b6a12ce86b3b7a7c6dae5208 upstream.

0day reported a possible circular locking dependency:

Chain exists of:
  &irq_desc_lock_class --> console_owner --> &port_lock_key

 Possible unsafe locking scenario:

       CPU0                    CPU1
       ----                    ----
  lock(&port_lock_key);
                               lock(console_owner);
                               lock(&port_lock_key);
  lock(&irq_desc_lock_class);

The reason for this is a printk() in the i8259 interrupt chip driver
which is invoked with the irq descriptor lock held, which reverses the
lock operations vs. printk() from arbitrary contexts.

Switch the printk() to printk_deferred() to avoid that.

Reported-by: kernel test robot <lkp@intel.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Cc: stable@vger.kernel.org
Link: https://lore.kernel.org/r/87365abt2v.fsf@nanos.tec.linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>