Commit 7a2c1b27 authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'printk-for-6.19-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux 

Pull printk fix from Petr Mladek:

 - Prevent softlockup by restoring IRQs in atomic flush after each
   record

* tag 'printk-for-6.19-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/printk/linux:
  printk/nbcon: Restore IRQ in atomic flush after each emitted record
parents 353c6f43 9bd18e12

kernel/printk/nbcon.c

+18 −20
Original line number Diff line number Diff line
@@ -1557,18 +1557,27 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq) 
	ctxt->allow_unsafe_takeover	= nbcon_allow_unsafe_takeover();



	while (nbcon_seq_read(con) < stop_seq) {

		/*

		 * Atomic flushing does not use console driver synchronization

		 * (i.e. it does not hold the port lock for uart consoles).

		 * Therefore IRQs must be disabled to avoid being interrupted

		 * and then calling into a driver that will deadlock trying

		 * to acquire console ownership.

		 */

		scoped_guard(irqsave) {

			if (!nbcon_context_try_acquire(ctxt, false))

				return -EPERM;



			/*

		 * nbcon_emit_next_record() returns false when the console was

		 * handed over or taken over. In both cases the context is no

		 * longer valid.

			 * nbcon_emit_next_record() returns false when

			 * the console was handed over or taken over.

			 * In both cases the context is no longer valid.

			 */

			if (!nbcon_emit_next_record(&wctxt, true))

				return -EAGAIN;



			nbcon_context_release(ctxt);

		}



		if (!ctxt->backlog) {

			/* Are there reserved but not yet finalized records? */
@@ -1595,22 +1604,11 @@ static int __nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq) 
static void nbcon_atomic_flush_pending_con(struct console *con, u64 stop_seq)

{

	struct console_flush_type ft;

	unsigned long flags;

	int err;



again:

	/*

	 * Atomic flushing does not use console driver synchronization (i.e.

	 * it does not hold the port lock for uart consoles). Therefore IRQs

	 * must be disabled to avoid being interrupted and then calling into

	 * a driver that will deadlock trying to acquire console ownership.

	 */

	local_irq_save(flags);



	err = __nbcon_atomic_flush_pending_con(con, stop_seq);



	local_irq_restore(flags);



	/*

	 * If there was a new owner (-EPERM, -EAGAIN), that context is

	 * responsible for completing.