x86/i8259: Use printk_deferred() to prevent deadlock

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

diff --git a/arch/x86/kernel/i8259.c b/arch/x86/kernel/i8259.c
index f3c76252247d6ec158716021ba296b6700a32ac4..282b4ee1339f87ce315c6c766a84689b2af394c6 100644 (file)
--- a/arch/x86/kernel/i8259.c
+++ b/arch/x86/kernel/i8259.c
@@ -207,7 +207,7 @@ spurious_8259A_irq:
                 * lets ACK and report it. [once per IRQ]
                 */
                if (!(spurious_irq_mask & irqmask)) {
-                       printk(KERN_DEBUG
+                       printk_deferred(KERN_DEBUG
                               "spurious 8259A interrupt: IRQ%d.\n", irq);
                        spurious_irq_mask |= irqmask;
                }