The patch titled
mm: remove unnecessary use of atomic
has been added to the -mm tree. Its filename is
mm-remove-unnecessary-use-of-atomic.patch
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------------------------------------------------------
Subject: mm: remove unnecessary use of atomic
From: Phil Carmody <ext-phil.2.carmody@xxxxxxxxx>
The bottom 4 hunks are atomically changing memory to which there are no
aliases as it's freshly allocated, so there's no need to use atomic
operations.
The other hunks are just atomic_read and atomic_set, and do not involve
any read-modify-write. The use of atomic_{read,set} doesn't prevent a
read/write or write/write race, so if a race were possible (I'm not saying
one is), then it would still be there even with atomic_set.
See:
http://digitalvampire.org/blog/index.php/2007/05/13/atomic-cargo-cults/
Signed-off-by: Phil Carmody <ext-phil.2.carmody@xxxxxxxxx>
Acked-by: Kirill A. Shutemov <kirill@xxxxxxxxxxxxx>
Cc: Balbir Singh <balbir@xxxxxxxxxx>
Cc: Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx>
Acked-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/memcontrol.c | 14 +++++++-------
1 file changed, 7 insertions(+), 7 deletions(-)
diff -puN mm/memcontrol.c~mm-remove-unnecessary-use-of-atomic mm/memcontrol.c
--- a/mm/memcontrol.c~mm-remove-unnecessary-use-of-atomic
+++ a/mm/memcontrol.c
@@ -152,7 +152,7 @@ struct mem_cgroup_threshold {
/* For threshold */
struct mem_cgroup_threshold_ary {
/* An array index points to threshold just below usage. */
- atomic_t current_threshold;
+ int current_threshold;
/* Size of entries[] */
unsigned int size;
/* Array of thresholds */
@@ -3447,7 +3447,7 @@ static void __mem_cgroup_threshold(struc
* If it's not true, a threshold was crossed after last
* call of __mem_cgroup_threshold().
*/
- i = atomic_read(&t->current_threshold);
+ i = t->current_threshold;
/*
* Iterate backward over array of thresholds starting from
@@ -3471,7 +3471,7 @@ static void __mem_cgroup_threshold(struc
eventfd_signal(t->entries[i].eventfd, 1);
/* Update current_threshold */
- atomic_set(&t->current_threshold, i - 1);
+ t->current_threshold = i - 1;
unlock:
rcu_read_unlock();
}
@@ -3563,7 +3563,7 @@ static int mem_cgroup_usage_register_eve
compare_thresholds, NULL);
/* Find current threshold */
- atomic_set(&thresholds_new->current_threshold, -1);
+ thresholds_new->current_threshold = -1;
for (i = 0; i < size; i++) {
if (thresholds_new->entries[i].threshold < usage) {
/*
@@ -3571,7 +3571,7 @@ static int mem_cgroup_usage_register_eve
* until rcu_assign_pointer(), so it's safe to increment
* it here.
*/
- atomic_inc(&thresholds_new->current_threshold);
+ ++thresholds_new->current_threshold;
}
}
@@ -3642,7 +3642,7 @@ static int mem_cgroup_usage_unregister_e
thresholds_new->size = size;
/* Copy thresholds and find current threshold */
- atomic_set(&thresholds_new->current_threshold, -1);
+ thresholds_new->current_threshold = -1;
for (i = 0, j = 0; i < thresholds->size; i++) {
if (thresholds->entries[i].eventfd == eventfd)
continue;
@@ -3654,7 +3654,7 @@ static int mem_cgroup_usage_unregister_e
* until rcu_assign_pointer(), so it's safe to increment
* it here.
*/
- atomic_inc(&thresholds_new->current_threshold);
+ ++thresholds_new->current_threshold;
}
j++;
}
_
Patches currently in -mm which might be from ext-phil.2.carmody@xxxxxxxxx are
linux-next.patch
errh-add-__must_check-to-error-pointer-handlers.patch
hvsi-messed-up-error-checking-getting-state-name.patch
mm-remove-unnecessary-use-of-atomic.patch
mm-memcontrol-uninitialised-return-value.patch
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