Re: [PATCH 0/7] preempt_count rework -v2

[Kevin Easton]

On Thu, Sep 12, 2013 at 04:20:40AM +0200, Peter Zijlstra wrote:
> On Wed, Sep 11, 2013 at 04:02:14PM -0700, Linus Torvalds wrote:
> > On Wed, Sep 11, 2013 at 11:59 AM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> > >
> > > OK, stripped it down further, I couldn't quite see how to collapse the
> > > unary and binary operator variants though :/
> > 
> > Ok, this looks pretty good. I assume it works too? ;)
> 
> Only compile tested that one.. the below is kvm boot tested until root
> mount -- I'll try on actual hardware when I've gotten some sleep.
> 
> I split the thing up into two macros GEN_UNARY_RMWcc and
> GEN_BINARY_RMWcc which ends up being more readable as well as smaller
> code overall.

If you wanted to collapse the unary and binary variants as you mentioned
upthread, you could do something like (for the CC_HAVE_ASM_GOTO case):

#define GEN_RMWcc(fullop, cc, ...) \
do { \
 asm volatile goto (fullop \
 "j" cc " %l[cc_label]" \
 : : __VA_ARGS__ \
 : "memory" : cc_label); \
 return 0; \
cc_label: \
 return 1; \
} while (0)

#define GEN_UNARY_RMWcc(op, var, arg0, cc) GEN_RMWcc(op " " arg0 ";", cc, "m" (var))
#define GEN_BINARY_RMWcc(op, var, val, arg0, cc) GEN_RMWcc(op " %1, " arg0 ";", cc, "m" (var), "er" (val))

    - Kevin
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