Message-ID: <42932CD2.3040204@tmr.com>
Date: Tue, 24 May 2005 09:32:02 -0400
From: Bill Davidsen <davidsen@tmr.com>
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To: Andrew Morton <akpm@osdl.org>
CC: linux-kernel@vger.kernel.org, linux-crypto@vger.kernel.org,
       davem@davemloft.net, jmorris@redhat.com
Subject: Re: [CRYPTO]: Only reschedule if !in_atomic()
References: <200505232300.j4NN07lE012726@hera.kernel.org>	<20050523162806.0e70ae4f.akpm@osdl.org>	<20050524022106.GA29081@gondor.apana.org.au> <20050523193116.62844826.akpm@osdl.org>
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Andrew Morton wrote:
> Herbert Xu <herbert@gondor.apana.org.au> wrote:
> 
>>Perhaps we should code this into the crypto API instead? For instance,
>> we can have a tfm flag that says whether we can sleep or not.
> 
> 
> Are you sure it's actually needed? Have significant scheduling latencies
> actually been observed?
> 
> Bear in mind that anyone who cares a lot about latency will be running
> CONFIG_PREEMPT kernels, in which case the whole thing is redundant anyway. 
> I generally take the position that if we're going to put a scheduling point
> into a non-premept kernel then it'd better be for a pretty bad latency
> point - more than 10 milliseconds, say.
> 
People do run crypto on old slow machines, and also laptops configured 
to use as little power as possible. I wouldn't be surprised if latencies 
got in the >10ms range pretty regularly on some systems which are pretty 
mainstream.

Just my read on it, if a flag will prevent deadlock without relying on 
callers doing the right thing, that's probably a desirable change WRT 
future stability.
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