Re: aio stress panic on 2.6.11-mm1

From: Andi Kleen
Date: Wed Mar 09 2005 - 06:22:11 EST

Arjan van de Ven <arjan@xxxxxxxxxxxxx> writes:

> On Wed, 2005-03-09 at 16:34 +0530, Suparna Bhattacharya wrote:
>> Any sense of how costly it is to use spin_lock_irq's vs spin_lock
>> (across different architectures)
> on x86 it makes a difference of maybe a few cycles. At most.
> However please consider using spin_lock_irqsave(); the _irq() variant,
> while it can be used correctly, is a major source of bugs since it
> unconditionally enables interrupts on unlock.

irqsave is much worse than _irq on P4.

However the spinlock already synchronizes the CPU, so some of the
cost should be mitigated.

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