Re: PREEMPT_RT vs bcache

From: Uwe Kleine-König
Date: Wed Aug 07 2013 - 17:12:53 EST

On Wed, Aug 07, 2013 at 01:53:57PM -0700, Kent Overstreet wrote:
> On Wed, Aug 07, 2013 at 10:28:18PM +0200, Ben Hutchings wrote:
> > As Kent said back in 2011 (commit 84759c6d18c5), bcache needs
> > {down,up}_read_non_owner(). But these are not implemented by the -rt
> > patchset when PREEMPT_RT_FULL is enabled. Can they be added, or is
> > there a fundamental conflict here?
> You should be able to cherry pick
> 84759c6d18c5144432781ddca037d929ee9db8a5 (Revert "rw_semaphore: remove
> up/down_read_non_owner") - that went in when bcache was merged.
That doesn't help with PREEMPT_RT_FULL because include/linux/rwsem.h
looks like:

[ ... some includes ... ]
#include <linux/rwsem_rt.h>
#else /* PREEMPT_RT_FULL */
[ ... vanilla content including definitions of {down,up}_read_non_owner]

So Ben's question was how (if at all) we should implement
{down,up}_read_non_owner for PREEMPT_RT_FULL.
Is it save to just use the vanilla implementation on RT?

Best regards

Pengutronix e.K. | Uwe Kleine-König |
Industrial Linux Solutions | |
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