The patch titled
Subject: mm/oom_kill: fix the wrong task->mm == mm checks in oom_kill_process()
has been removed from the -mm tree. Its filename was
mm-oom_kill-fix-the-wrong-task-mm-==-mm-checks-in-oom_kill_process.patch
This patch was dropped because it was merged into mainline or a subsystem tree
------------------------------------------------------
From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: mm/oom_kill: fix the wrong task->mm == mm checks in oom_kill_process()
Both "child->mm == mm" and "p->mm != mm" checks in oom_kill_process() are
wrong. task->mm can be NULL if the task is the exited group leader. This
means in particular that "kill sharing same memory" loop can miss a
process with a zombie leader which uses the same ->mm.
Note: the process_has_mm(child, p->mm) check is still not 100% correct,
p->mm can be NULL too. This is minor, but probably deserves a fix or a
comment anyway.
[akpm@xxxxxxxxxxxxxxxxxxxx: document process_shares_mm() a bit]
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Acked-by: David Rientjes <rientjes@xxxxxxxxxx>
Acked-by: Michal Hocko <mhocko@xxxxxxxx>
Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx>
Cc: Kyle Walker <kwalker@xxxxxxxxxx>
Cc: Stanislav Kozina <skozina@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/oom_kill.c | 22 ++++++++++++++++++++--
1 file changed, 20 insertions(+), 2 deletions(-)
diff -puN mm/oom_kill.c~mm-oom_kill-fix-the-wrong-task-mm-==-mm-checks-in-oom_kill_process mm/oom_kill.c
--- a/mm/oom_kill.c~mm-oom_kill-fix-the-wrong-task-mm-==-mm-checks-in-oom_kill_process
+++ a/mm/oom_kill.c
@@ -474,6 +474,24 @@ void oom_killer_enable(void)
oom_killer_disabled = false;
}
+/*
+ * task->mm can be NULL if the task is the exited group leader. So to
+ * determine whether the task is using a particular mm, we examine all the
+ * task's threads: if one of those is using this mm then this task was also
+ * using it.
+ */
+static bool process_shares_mm(struct task_struct *p, struct mm_struct *mm)
+{
+ struct task_struct *t;
+
+ for_each_thread(p, t) {
+ struct mm_struct *t_mm = READ_ONCE(t->mm);
+ if (t_mm)
+ return t_mm == mm;
+ }
+ return false;
+}
+
#define K(x) ((x) << (PAGE_SHIFT-10))
/*
* Must be called while holding a reference to p, which will be released upon
@@ -521,7 +539,7 @@ void oom_kill_process(struct oom_control
list_for_each_entry(child, &t->children, sibling) {
unsigned int child_points;
- if (child->mm == p->mm)
+ if (process_shares_mm(child, p->mm))
continue;
/*
* oom_badness() returns 0 if the thread is unkillable
@@ -575,7 +593,7 @@ void oom_kill_process(struct oom_control
*/
rcu_read_lock();
for_each_process(p) {
- if (p->mm != mm)
+ if (!process_shares_mm(p, mm))
continue;
if (same_thread_group(p, victim))
continue;
_
Patches currently in -mm which might be from oleg@xxxxxxxxxx are
proc-actually-make-proc_fd_permission-thread-friendly.patch
change-current_is_single_threaded-to-use-for_each_thread.patch
signals-kill-block_all_signals-and-unblock_all_signals.patch
signal-turn-dequeue_signal_lock-into-kernel_dequeue_signal.patch
signal-turn-dequeue_signal_lock-into-kernel_dequeue_signal-fix.patch
signal-introduce-kernel_signal_stop-to-fix-jffs2_garbage_collect_thread.patch
signal-remove-jffs2_garbage_collect_thread-allow_signalsigcont.patch
coredump-ensure-all-coredumping-tasks-have-signal_group_coredump.patch
coredump-change-zap_threads-and-zap_process-to-use-for_each_thread.patch
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