The patch titled
oom: fix locking for oom_adj and oom_score_adj
has been added to the -mm tree. Its filename is
oom-fix-locking-for-oom_adj-and-oom_score_adj.patch
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See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find
out what to do about this
The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/
------------------------------------------------------
Subject: oom: fix locking for oom_adj and oom_score_adj
From: David Rientjes <rientjes@xxxxxxxxxx>
The locking order in oom_adjust_write() and oom_score_adj_write() for
task->alloc_lock and task->sighand->siglock is reversed, and lockdep
notices that irqs could encounter an ABBA scenario.
This fixes the locking order so that we always take task_lock(task) prior
to lock_task_sighand(task).
Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
Reported-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx>
Cc: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Cc: Rik van Riel <riel@xxxxxxxxxx>
Cc: Ying Han <yinghan@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
fs/proc/base.c | 40 +++++++++++++++++++++-------------------
1 file changed, 21 insertions(+), 19 deletions(-)
diff -puN fs/proc/base.c~oom-fix-locking-for-oom_adj-and-oom_score_adj fs/proc/base.c
--- a/fs/proc/base.c~oom-fix-locking-for-oom_adj-and-oom_score_adj
+++ a/fs/proc/base.c
@@ -1044,9 +1044,16 @@ static ssize_t oom_adjust_write(struct f
err = -ESRCH;
goto out;
}
+
+ task_lock(task);
+ if (!task->mm) {
+ err = -EINVAL;
+ goto err_task_lock;
+ }
+
if (!lock_task_sighand(task, &flags)) {
err = -ESRCH;
- goto err_task_struct;
+ goto err_task_lock;
}
if (oom_adjust < task->signal->oom_adj && !capable(CAP_SYS_RESOURCE)) {
@@ -1054,12 +1061,6 @@ static ssize_t oom_adjust_write(struct f
goto err_sighand;
}
- task_lock(task);
- if (!task->mm) {
- err = -EINVAL;
- goto err_task_lock;
- }
-
if (oom_adjust != task->signal->oom_adj) {
if (oom_adjust == OOM_DISABLE)
atomic_inc(&task->mm->oom_disable_count);
@@ -1085,11 +1086,10 @@ static ssize_t oom_adjust_write(struct f
else
task->signal->oom_score_adj = (oom_adjust * OOM_SCORE_ADJ_MAX) /
-OOM_DISABLE;
-err_task_lock:
- task_unlock(task);
err_sighand:
unlock_task_sighand(task, &flags);
-err_task_struct:
+err_task_lock:
+ task_unlock(task);
put_task_struct(task);
out:
return err < 0 ? err : count;
@@ -1152,21 +1152,24 @@ static ssize_t oom_score_adj_write(struc
err = -ESRCH;
goto out;
}
+
+ task_lock(task);
+ if (!task->mm) {
+ err = -EINVAL;
+ goto err_task_lock;
+ }
+
if (!lock_task_sighand(task, &flags)) {
err = -ESRCH;
- goto err_task_struct;
+ goto err_task_lock;
}
+
if (oom_score_adj < task->signal->oom_score_adj &&
!capable(CAP_SYS_RESOURCE)) {
err = -EACCES;
goto err_sighand;
}
- task_lock(task);
- if (!task->mm) {
- err = -EINVAL;
- goto err_task_lock;
- }
if (oom_score_adj != task->signal->oom_score_adj) {
if (oom_score_adj == OOM_SCORE_ADJ_MIN)
atomic_inc(&task->mm->oom_disable_count);
@@ -1183,11 +1186,10 @@ static ssize_t oom_score_adj_write(struc
else
task->signal->oom_adj = (oom_score_adj * OOM_ADJUST_MAX) /
OOM_SCORE_ADJ_MAX;
-err_task_lock:
- task_unlock(task);
err_sighand:
unlock_task_sighand(task, &flags);
-err_task_struct:
+err_task_lock:
+ task_unlock(task);
put_task_struct(task);
out:
return err < 0 ? err : count;
_
Patches currently in -mm which might be from rientjes@xxxxxxxxxx are
linux-next.patch
oom-add-per-mm-oom-disable-count.patch
oom-avoid-killing-a-task-if-a-thread-sharing-its-mm-cannot-be-killed.patch
oom-kill-all-threads-sharing-oom-killed-tasks-mm.patch
oom-kill-all-threads-sharing-oom-killed-tasks-mm-fix.patch
oom-kill-all-threads-sharing-oom-killed-tasks-mm-fix-fix.patch
oom-rewrite-error-handling-for-oom_adj-and-oom_score_adj-tunables.patch
oom-fix-locking-for-oom_adj-and-oom_score_adj.patch
jbd-remove-dependency-on-__gfp_nofail.patch
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