Messages in this thread | | | Date | Sun, 24 Jun 2018 11:47:31 +0200 (CEST) | From | Thomas Gleixner <> | Subject | Re: [PATCH v2 1/2] genirq: Update code comments wrt recycled thread_mask |
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Lukas,
On Sun, 24 Jun 2018, Lukas Wunner wrote:
> Previously a race existed between __free_irq() and __setup_irq() wherein > the thread_mask of a just removed action could be handed out to a newly > added action and the freed irq thread would then tread on the oneshot > mask bit of the newly added irq thread in irq_finalize_oneshot(): > > time > | __free_irq() > | raw_spin_lock_irqsave(&desc->lock, flags); > | <remove action from linked list> > | raw_spin_unlock_irqrestore(&desc->lock, flags); > | > | __setup_irq() > | raw_spin_lock_irqsave(&desc->lock, flags); > | <traverse linked list to determine oneshot mask bit> > | raw_spin_unlock_irqrestore(&desc->lock, flags); > | > | irq_thread() of freed irq (__free_irq() waits in synchronize_irq()) > | irq_thread_fn() > | irq_finalize_oneshot() > | raw_spin_lock_irq(&desc->lock); > | desc->threads_oneshot &= ~action->thread_mask; > | raw_spin_unlock_irq(&desc->lock); > v > > The race was known at least since 2012 when it was documented in a code > comment by commit e04268b0effc ("genirq: Remove paranoid warnons and > bogus fixups").
The race was known, but it was also harmless as nothing would touch stuff after synchronize_irq().
> But it wasn't until 2017 that it was fixed by commit 9114014cf4e6 > ("genirq: Add mutex to irq desc to serialize request/free_irq()"), > apparently inadvertantly so because the race is neither mentioned in the > commit message nor was the code comment updated. Make up for that.
Thanks for following up. This update is very well done.
tglx
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