From 5407a56257b6ade44fd9bcac972c99845b7413cd Mon Sep 17 00:00:00 2001 From: Phil Carmody Date: Wed, 26 May 2010 14:42:42 -0700 Subject: [PATCH] mm: remove unnecessary use of atomic 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 Acked-by: Kirill A. Shutemov Cc: Balbir Singh Cc: Daisuke Nishimura Acked-by: KAMEZAWA Hiroyuki Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/memcontrol.c | 14 +++++++------- 1 file changed, 7 insertions(+), 7 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index be5f478..93b0239 100644 --- a/mm/memcontrol.c +++ b/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 */ @@ -3412,7 +3412,7 @@ static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap) * 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 @@ -3436,7 +3436,7 @@ static void __mem_cgroup_threshold(struct mem_cgroup *memcg, bool swap) 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(); } @@ -3528,7 +3528,7 @@ static int mem_cgroup_usage_register_event(struct cgroup *cgrp, 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) { /* @@ -3536,7 +3536,7 @@ static int mem_cgroup_usage_register_event(struct cgroup *cgrp, * until rcu_assign_pointer(), so it's safe to increment * it here. */ - atomic_inc(&thresholds_new->current_threshold); + ++thresholds_new->current_threshold; } } @@ -3607,7 +3607,7 @@ static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp, 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; @@ -3619,7 +3619,7 @@ static int mem_cgroup_usage_unregister_event(struct cgroup *cgrp, * until rcu_assign_pointer(), so it's safe to increment * it here. */ - atomic_inc(&thresholds_new->current_threshold); + ++thresholds_new->current_threshold; } j++; } -- 2.7.4