From: Oleg Nesterov <oleg@xxxxxxxxxx>
Subject: vm_is_stack: use for_each_thread() rather then buggy while_each_thread()
Aleksei hit the soft lockup during reading /proc/PID/smaps. David
investigated the problem and suggested the right fix.
while_each_thread() is racy and should die, this patch updates
vm_is_stack().
Signed-off-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Reported-by: Aleksei Besogonov <alex.besogonov@xxxxxxxxx>
Tested-by: Aleksei Besogonov <alex.besogonov@xxxxxxxxx>
Suggested-by: David Rientjes <rientjes@xxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/util.c | 9 +++------
1 file changed, 3 insertions(+), 6 deletions(-)
diff -puN mm/util.c~vm_is_stack-use-for_each_thread-rather-then-buggy-while_each_thread mm/util.c
--- a/mm/util.c~vm_is_stack-use-for_each_thread-rather-then-buggy-while_each_thread
+++ a/mm/util.c
@@ -183,17 +183,14 @@ pid_t vm_is_stack(struct task_struct *ta
if (in_group) {
struct task_struct *t;
- rcu_read_lock();
- if (!pid_alive(task))
- goto done;
- t = task;
- do {
+ rcu_read_lock();
+ for_each_thread(task, t) {
if (vm_is_stack_for_task(t, vma)) {
ret = t->pid;
goto done;
}
- } while_each_thread(task, t);
+ }
done:
rcu_read_unlock();
}
_
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