[PATCH 10/10] oom: Make find_lock_task_mm() sparse-aware

Anton Vorontsov
2012-03-24T10:32:39Z

This is needed so that callers would not get 'context imbalance'
warnings from the sparse tool.

As a side effect, this patch fixes the following sparse warnings:

CHECK mm/oom_kill.c
mm/oom_kill.c:201:28: warning: context imbalance in 'oom_badness' -
unexpected unlock
include/linux/rcupdate.h:249:30: warning: context imbalance in
'dump_tasks' - unexpected unlock
mm/oom_kill.c:453:9: warning: context imbalance in 'oom_kill_task' -
unexpected unlock
CHECK mm/memcontrol.c
...
mm/memcontrol.c:1130:17: warning: context imbalance in
'task_in_mem_cgroup' - unexpected unlock

p.s. I know Peter Zijlstra detest the __cond_lock() stuff, but untill
we have anything better in sparse, let's use it. This particular
patch helped me to detect one bug that I myself made during
task->mm fixup series. So, it is useful.

Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
Acked-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
include/linux/oom.h | 12 +++++++++++-
mm/oom_kill.c | 2 +-
2 files changed, 12 insertions(+), 2 deletions(-)

diff --git a/include/linux/oom.h b/include/linux/oom.h
index 552fba9..26cf628 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -21,6 +21,7 @@

#ifdef __KERNEL__

+#include <linux/compiler.h>
#include <linux/sched.h>
#include <linux/types.h>
#include <linux/nodemask.h>
@@ -65,7 +66,16 @@ static inline void oom_killer_enable(void)
oom_killer_disabled = false;
}

-extern struct task_struct *find_lock_task_mm(struct task_struct *p);
+extern struct task_struct *__find_lock_task_mm(struct task_struct *p);
+
+static inline struct task_struct *find_lock_task_mm(struct task_struct *p)
+{
+ struct task_struct *ret;
+
+ ret = __find_lock_task_mm(p);
+ (void)__cond_lock(&ret->alloc_lock, ret);
+ return ret;
+}

/* sysctls */
extern int sysctl_oom_dump_tasks;
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 2958fd8..0ebb383 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -136,7 +136,7 @@ static bool has_intersects_mems_allowed(struct task_struct *tsk,
* pointer. Return p, or any of its subthreads with a valid ->mm, with
* task_lock() held.
*/
-struct task_struct *find_lock_task_mm(struct task_struct *p)
+struct task_struct *__find_lock_task_mm(struct task_struct *p)
{
struct task_struct *t = p;

--
1.7.9.2