lkml.org 
[lkml]   [2014]   [Apr]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: How do I increment a per-CPU variable without warning?
On Wed, Apr 16, 2014 at 09:06:21AM -0700, Paul E. McKenney wrote:
> On Wed, Apr 16, 2014 at 10:08:03AM -0500, Christoph Lameter wrote:
> > On Tue, 15 Apr 2014, Paul E. McKenney wrote:
> >
> > > Hello, Christoph,
> > >
> > > I have a patch that currently uses __this_cpu_inc_return() to increment a
> > > per-CPU variable, but without preemption disabled. Of course, given that
> > > preemption is enabled, it might well end up picking up one CPU's counter,
> > > adding one to it, then storing the result into some other CPU's counter.
> > > But this is OK, the test can be probabilistic. And when I run this
> > > against v3.14 and earlier, it works fine.
> >
> > We introduced raw_cpu_inc_return to squish these warnings.
>
> Cool, this is a good short-term fix.

Or at least it is given the following patch. Was this the intent?

Thanx, Paul

------------------------------------------------------------------------

percpu: Fix raw_cpu_inc_return()

The definition for raw_cpu_add_return() uses the operation prefix
"raw_add_return_", but the definitions in the various percpu.h files
expect "raw_cpu_add_return_". This commit therefore appropriately
adjusts the definition of raw_cpu_add_return().

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Christoph Lameter <cl@linux.com>

diff --git a/include/linux/percpu.h b/include/linux/percpu.h
index e7a0b95ed527..495c6543a8f2 100644
--- a/include/linux/percpu.h
+++ b/include/linux/percpu.h
@@ -639,7 +639,7 @@ do { \
# define raw_cpu_add_return_8(pcp, val) raw_cpu_generic_add_return(pcp, val)
# endif
# define raw_cpu_add_return(pcp, val) \
- __pcpu_size_call_return2(raw_add_return_, pcp, val)
+ __pcpu_size_call_return2(raw_cpu_add_return_, pcp, val)
#endif

#define raw_cpu_sub_return(pcp, val) raw_cpu_add_return(pcp, -(typeof(pcp))(val))


\
 
 \ /
  Last update: 2014-04-16 20:01    [W:0.070 / U:1.108 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site