Re: down_trylock doesn't preserve irqstate

From: Alan Cox (alan@lxorguk.ukuu.org.uk)
Date: Fri Feb 25 2000 - 21:05:30 EST


> is "locked" out trying to acquire the semaphore. This can't
> happen since interrupts are disabled. But this line of
> thought is probably not what you had in mind, since no
> matter what code has the semaphore (interrupts disabled or
> not), an interrupt should not be locked out trying to
> acquire a semaphore unconditionally.

Doing a down() for a semaphore in an interrupt is definitely not right.
A down_trylock() is quite legitimate so the code shouldnt corrupt the
irq state for that one - I agree. That assumes down_trylock is irq safe
[ie semops are irq safe] which is another matter altogether.

Calling down in an IRQ is clearly a no-no

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