On Fri, 27 May 2016 13:07:10 +1000 Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx> wrote:
> Hi Andrew,
>
> After merging the akpm-current tree, today's linux-next build (arm
> multi_v7_defconfig) produced this warning:
>
> mm/oom_kill.c: In function '__oom_reap_task':
> mm/oom_kill.c:537:2: warning: 'mm' may be used uninitialized in this function [-Wmaybe-uninitialized]
> mmput_async(mm);
> ^
>
> Introduced by commit
>
> df1e2f56632d ("oom_reaper: close race with exiting task")
>
> This is real - the first "goto unlock_oom" is before "mm" has been
> assigned.
Yup, thanks.
From: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Subject: oom_reaper-close-race-with-exiting-task-fix
fix use of unused `mm', Per Stephen
Reported-by: Stephen Rothwell <sfr@xxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 5 +++--
1 file changed, 3 insertions(+), 2 deletions(-)
diff -puN mm/oom_kill.c~oom_reaper-close-race-with-exiting-task-fix mm/oom_kill.c
--- a/mm/oom_kill.c~oom_reaper-close-race-with-exiting-task-fix
+++ a/mm/oom_kill.c
@@ -443,7 +443,7 @@ static bool __oom_reap_task(struct task_
{
struct mmu_gather tlb;
struct vm_area_struct *vma;
- struct mm_struct *mm;
+ struct mm_struct *mm = NULL;
struct task_struct *p;
struct zap_details details = {.check_swap_entries = true,
.ignore_dirty = true};
@@ -534,7 +534,8 @@ unlock_oom:
* different context because we shouldn't risk we get stuck there and
* put the oom_reaper out of the way.
*/
- mmput_async(mm);
+ if (mm)
+ mmput_async(mm);
return ret;
}
_
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