Re: [RFC][PATCH 2/2] add a counter for writers spinning on a rwlock

[Peter Zijlstra]

On Sun, 2009-01-25 at 12:50 -0800, Frederic Weisbecker wrote:
> This patch adds a counter for writers that enter a rwlock slow path.
> For example it can be useful for slow background tasks which perform some jobs
> on the tasklist, such as the hung_task detector (kernel/hung_task.c).
> 
> It adds a inc/dec pair on the slow path and 4 bytes for each rwlocks, so the overhead
> is not null.
> 
> Only x86 is supported for now, writers_spinning_lock() will return 0 on other archs (which
> is perhaps not a good idea).
> 
> Comments?

_why_ ?



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