From 07675d98fa2304b6c64ded1099f2b08777316241 Mon Sep 17 00:00:00 2001 From: Oleg Nesterov Date: Fri, 8 Aug 2014 14:19:17 -0700 Subject: [PATCH] vm_is_stack: use for_each_thread() rather then buggy while_each_thread() commit 4449a51a7c281602d3a385044ab928322a122a02 upstream. 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 Reported-by: Aleksei Besogonov Tested-by: Aleksei Besogonov Suggested-by: David Rientjes Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/util.c | 9 +++------ 1 file changed, 3 insertions(+), 6 deletions(-) diff --git a/mm/util.c b/mm/util.c index a24aa22..c1010cb 100644 --- a/mm/util.c +++ b/mm/util.c @@ -275,17 +275,14 @@ pid_t vm_is_stack(struct task_struct *task, 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(); } -- 2.7.4