Re: Semaphore lock up in SMP environment

From: Alan Cox (alan@lxorguk.ukuu.org.uk)
Date: Mon Mar 27 2000 - 12:58:49 EST

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In reply to: Venkatesh Ramamurthy: "Semaphore lock up in SMP environment"
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> I call up() in our ISR to release the semaphore flag . Since down() in SMP
> disable interrupts , there is no way my ISR is fired which releases the
> flag
> and so freezes the system.

Down does not disable interrupts that I can see, except momentarily when
checking the queues, and it restores them before it yields CPU time. On
exit the irqs are enabled.

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