Re: [PATCH 0/2] enable irqs when waiting for rwlocks

From: Robin Holt
Date: Thu Oct 23 2008 - 10:12:45 EST

On Wed, Oct 22, 2008 at 10:31:53AM -0700, Rick Jones wrote:
> Petr Tesarik wrote:
>> Hello,
>> SGI has observed that on large systems, interrupts are not serviced for
>> a long period of time when waiting for a rwlock. The following patch
>> series re-enables irqs while waiting for the lock, resembling the code
>> which is already there for spinlocks.
> Perhaps I'm just out in left field, but that (and the similar behaviour
> for obtaining a spinlock?) feels like treating a symptom rather than a
> root cause where the root cause would appear to be long lock hold
> times/contention?

Sometimes lock contention on large systems will take a few seconds to
pass. This is normal behavior which simply can not be eliminated. For
those cases, we need to rely upon being able to re-enable interrupts and
allowing other operations to continue normally. Simply put, in some
cases, nothing more can be done.

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