Re: [PATCH 6/9] pm/irq: make for_each_irq_desc() safe of irq_desc release

Rafael J. Wysocki
2022-04-20T16:24:04Z

On Wed, Apr 20, 2022 at 4:06 PM Pingfan Liu <kernelfans@gmail.com> wrote:
>
> The invloved context is no a RCU read section. Furthermore there may be
> more than one task at this point. Hence it demands a measure to prevent
> irq_desc from freeing. Use irq_lock_sparse to serve the protection
> purpose.

Can you please describe an example scenario in which the added locking
will prevent a failure from occurring?

> Signed-off-by: Pingfan Liu <kernelfans@gmail.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>
> Cc: "Rafael J. Wysocki" <rafael@kernel.org>
> To: linux-kernel@vger.kernel.org
> ---
> kernel/irq/pm.c | 3 +++
> 1 file changed, 3 insertions(+)
>
> diff --git a/kernel/irq/pm.c b/kernel/irq/pm.c
> index ca71123a6130..4b67a4c7de3c 100644
> --- a/kernel/irq/pm.c
> +++ b/kernel/irq/pm.c
> @@ -133,6 +133,7 @@ void suspend_device_irqs(void)
> struct irq_desc *desc;
> int irq;
>
> + irq_lock_sparse();
> for_each_irq_desc(irq, desc) {
> unsigned long flags;
> bool sync;
> @@ -146,6 +147,7 @@ void suspend_device_irqs(void)
> if (sync)
> synchronize_irq(irq);
> }
> + irq_unlock_sparse();
> }
> EXPORT_SYMBOL_GPL(suspend_device_irqs);
>
> @@ -186,6 +188,7 @@ static void resume_irqs(bool want_early)
> struct irq_desc *desc;
> int irq;
>
> + /* The early resume stage is free of irq_desc release */
> for_each_irq_desc(irq, desc) {
> unsigned long flags;
> bool is_early = desc->action &&
> --
> 2.31.1
>