The patch titled
Subject: percpu: update local_ops.txt to reflect this_cpu operations
has been added to the -mm tree. Its filename is
update-local_opstxt-to-reflect-this_cpu-operations.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/update-local_opstxt-to-reflect-this_cpu-operations.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/update-local_opstxt-to-reflect-this_cpu-operations.patch
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------------------------------------------------------
From: Christoph Lameter <cl@xxxxxxxxx>
Subject: percpu: update local_ops.txt to reflect this_cpu operations
Update the documentation to reflect changes due to the availability of
this_cpu operations.
Signed-off-by: Christoph Lameter <cl@xxxxxxxxx>
Cc: Tejun Heo <tj@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/local_ops.txt | 13 +++++++++----
1 file changed, 9 insertions(+), 4 deletions(-)
diff -puN Documentation/local_ops.txt~update-local_opstxt-to-reflect-this_cpu-operations Documentation/local_ops.txt
--- a/Documentation/local_ops.txt~update-local_opstxt-to-reflect-this_cpu-operations
+++ a/Documentation/local_ops.txt
@@ -8,6 +8,11 @@ to implement them for any given architec
properly. It also stresses on the precautions that must be taken when reading
those local variables across CPUs when the order of memory writes matters.
+Note that local_t based operations are not recommended for general kernel use.
+Please use the this_cpu operations instead unless there is really a special purpose.
+Most uses of local_t in the kernel have been replaced by this_cpu operations.
+this_cpu operations combine the relocation with the local_t like semantics in
+a single instruction and yield more compact and faster executing code.
* Purpose of local atomic operations
@@ -87,10 +92,10 @@ the per cpu variable. For instance :
local_inc(&get_cpu_var(counters));
put_cpu_var(counters);
-If you are already in a preemption-safe context, you can directly use
-__get_cpu_var() instead.
+If you are already in a preemption-safe context, you can use
+this_cpu_ptr() instead.
- local_inc(&__get_cpu_var(counters));
+ local_inc(this_cpu_ptr(&counters));
@@ -134,7 +139,7 @@ static void test_each(void *info)
{
/* Increment the counter from a non preemptible context */
printk("Increment on cpu %d\n", smp_processor_id());
- local_inc(&__get_cpu_var(counters));
+ local_inc(this_cpu_ptr(&counters));
/* This is what incrementing the variable would look like within a
* preemptible context (it disables preemption) :
_
Patches currently in -mm which might be from cl@xxxxxxxxx are
origin.patch
mm-slab-slub-coding-style-whitespaces-and-tabs-mixture.patch
slab-print-slabinfo-header-in-seq-show.patch
mm-slab-reverse-iteration-on-find_mergeable.patch
mm-slub-fix-format-mismatches-in-slab_err-callers.patch
slab-improve-checking-for-invalid-gfp_flags.patch
slab-replace-smp_read_barrier_depends-with-lockless_dereference.patch
mm-compaction-pass-classzone_idx-and-alloc_flags-to-watermark-checking.patch
mm-compaction-pass-classzone_idx-and-alloc_flags-to-watermark-checking-fix.patch
mm-compaction-simplify-deferred-compaction.patch
mm-compaction-defer-only-on-compact_complete.patch
mm-compaction-always-update-cached-scanner-positions.patch
mm-compaction-always-update-cached-scanner-positions-fix.patch
mm-compaction-more-focused-lru-and-pcplists-draining.patch
mm-compaction-more-focused-lru-and-pcplists-draining-fix.patch
memcg-use-generic-slab-iterators-for-showing-slabinfo.patch
linux-next.patch
slab-fix-cpuset-check-in-fallback_alloc.patch
slub-fix-cpuset-check-in-get_any_partial.patch
remove-__get_cpu_var-and-__raw_get_cpu_var-macros.patch
update-local_opstxt-to-reflect-this_cpu-operations.patch
ia64-update-comment-that-references-__get_cpu_var.patch
parisc-update-comments-refereing-to-__get_cpu_var.patch
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