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SubjectRe: [PATCH] softirq: add irq off checking for __raise_softirq_irqoff
On Thu, Aug 06, 2020 at 12:07:29PM +0800, Jiafei Pan wrote:
> __raise_softirq_irqoff will update per-CPU mask of pending softirqs,
> it need to be called in irq disabled context in order to keep it atomic
> operation, otherwise it will be interrupted by hardware interrupt,
> and per-CPU softirqs pending mask will be corrupted, the result is
> there will be unexpected issue, for example hrtimer soft irq will
> be losed and soft hrtimer will never be expire and handled.
>
> Adding irqs disabled checking here to provide warning in irqs enabled
> context.
>
> Signed-off-by: Jiafei Pan <Jiafei.Pan@nxp.com>
> ---
> kernel/softirq.c | 5 +++++
> 1 file changed, 5 insertions(+)
>
> diff --git a/kernel/softirq.c b/kernel/softirq.c
> index bf88d7f62433..11f61e54a3ae 100644
> --- a/kernel/softirq.c
> +++ b/kernel/softirq.c
> @@ -481,6 +481,11 @@ void raise_softirq(unsigned int nr)
>
> void __raise_softirq_irqoff(unsigned int nr)
> {
> + /* This function can only be called in irq disabled context,
> + * otherwise or_softirq_pending will be interrupted by hardware
> + * interrupt, so that there will be unexpected issue.
> + */

Comment style is wrong, also I'm not sure the comment is really
helpfull.

> + WARN_ON_ONCE(!irqs_disabled());

lockdep_assert_irqs_disabled();

> trace_softirq_raise(nr);
> or_softirq_pending(1UL << nr);
> }

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