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Subject: Re: [Lse-tech] Re: [Patch 2/7] Add sysctl for schedstats
From: Arjan van de Ven <arjan@infradead.org>
To: balbir@in.ibm.com
Cc: Ingo Molnar <mingo@elte.hu>, Shailabh Nagar <nagar@watson.ibm.com>,
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On Mon, 2006-02-27 at 16:16 +0530, Balbir Singh wrote:
> <snip>
> > why not just introduce a schedstats_lock mutex, and acquire it for both 
> > the 'if (schedstats_sysctl)' line and the schedstats_set() line. That 
> > will make the locking meaningful: two parallel sysctl ops will be atomic 
> > to each other. [right now they wont be and they can clear schedstat data 
> > in parallel -> not a big problem but it makes schedstats_lock rather 
> > meaningless]
> >
> 
> Ingo,
> 
> Can sysctl's run in parallel? sys_sysctl() is protects the call
> to do_sysctl() with BKL (lock_kernel/unlock_kernel).
> 
> Am I missing something?


your sysctl functions sleep. the BKL is useless in the light of sleeping
code...


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