Messages in this thread | | | From | Thomas Gleixner <> | Subject | Re: [PATCH v3] irq/core: synchronize irq_thread startup | Date | Tue, 10 May 2022 13:37:51 +0200 |
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On Tue, May 10 2022 at 13:34, Thomas Gleixner wrote: > On Tue, May 10 2022 at 10:43, Thomas Pfaff wrote: >> It can be done only before the interrupt thread is stopped, and free_irq() >> itself is already taking care about synchronizing, no matter if its done by >> __synchronize_hardirq() or by synchronize_irq(), like it was before commit >> 519cc8652b3a. > > No, it does not really take care about it. It can return with > irq_desc::threads_active > 0 due to the interrupt thread being stopped > before reaching the thread function. Think about shared interrupts.
Duh. Hit send too fast.
It does matter whether the synchronization is done via __synchronize_hardirq() or via synchronize_irq(). The latter ensured that the thread reached the thread function and handled the pending wakeup _before_ kthread_stop() become true.
So the fix is required to undo the damage created by 519cc8652b3a.
The synchronize_irq() after free_irq() is a completely different problem.
Thanks,
tglx
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