Re: [PATCH] Linux Kernel Markers 0.13 for 2.6.17
From: Mathieu Desnoyers
Date: Mon Sep 25 2006 - 20:26:13 EST
* Jeremy Fitzhardinge (jeremy@xxxxxxxx) wrote:
> Mathieu Desnoyers wrote:
> >Just as a precision :
> >The following sequence (please refer to the code below for local symbols
> >1 and 2) :
> >call (*__mark_call_##name)(format, ## args);
> >is insured because :
> >1 is part of an inline assembly with rw dependency on __marker_sequencer
> >the call is surrounded by memory barriers.
> >2 is part of an inline assembly with rw dependency on __marker_sequencer
> What do you mean the call is surrounded by memory barriers? Do you mean
> a call has an implicit barrier, or something else?
Yes, preempt_disable() has a barrier(), on gcc :
__asm__ __volatile__("": : :"memory").
> Either way, this doesn't prevent some otherwise unrelated
> non-memory-using code from being scheduled in there, which would not be
> executed. The gcc manual really strongly discourages jumping between
> inline asms, because they have basically unpredictable results.
Ok, I will do the call in assembly then.
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