linux-kernel - Re: [PATCH RFC -rt] Allow rcutorture to handle synchronize

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Message-Id: <1186180712.2677.16.camel@josh-work.beaverton.ibm.com>
Date:	Fri, 03 Aug 2007 15:38:32 -0700
From:	Josh Triplett <josht@...ux.vnet.ibm.com>
To:	paulmck@...ux.vnet.ibm.com
Cc:	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	mingo@...e.hu, dipankar@...ibm.com, ego@...ibm.com,
	vatsa@...ibm.com
Subject: Re: [PATCH RFC -rt] Allow rcutorture to handle synchronize_sched()

On Fri, 2007-08-03 at 11:44 -0700, Paul E. McKenney wrote:
> The rcutorture module uses a random-number generator that periodically
> calls get_random_bytes() to add entropy.  This random-number generator
> is invoked from within the RCU read-side critical section, which, in the
> case of the synchronize_sched() variant of RCU, has preeemption disabled.
> Unfortunately, get_random_bytes() ends up acquiring normal spinlocks,
> which can block in -rt, resulting in very large numbers of "scheduling
> while atomic" messages.
> 
> This patch takes a very crude approach, simply substituting the time
> of day for get_random_bytes().
> 
> Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com>

Acked-by: Josh Triplett <josh@...nel.org>


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