Messages in this thread | | | Date | Fri, 31 Mar 2023 12:42:09 +0900 | From | Sergey Senozhatsky <> | Subject | Re: [PATCH 4/7] sempahore: add a helper for a concurrency limiter |
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On (23/03/30 09:23), Linus Torvalds wrote: > Although we also do have some other issues - I think down_trylock() is > ok in irq contexts, but mutex_trylock() is not. Maybe that's why > printk uses semaphores? I forget.
Yes, correct. IIRC we also cannot safely call mutex_unlock() from IRQ context because it takes some internal mutex spin_lock in a non-IRQ-safe manner. Semaphore is OK in this regard, both semaphore try_lock() and unlock() can be called from IRQ.
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