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authorOleg Nesterov <oleg@redhat.com>2014-12-12 16:56:24 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2014-12-13 12:42:49 -0800
commitd003f371b27016354c392464819530d47a915765 (patch)
tree0615df29b862f71b0ef14d8079218ba9edb201fd /mm/oom_kill.c
parentba914f481507a0542a7c8a3fc15d89414bc2ebf3 (diff)
oom: don't assume that a coredumping thread will exit soon
oom_kill.c assumes that PF_EXITING task should exit and free the memory soon. This is wrong in many ways and one important case is the coredump. A task can sleep in exit_mm() "forever" while the coredumping sub-thread can need more memory. Change the PF_EXITING checks to take SIGNAL_GROUP_COREDUMP into account, we add the new trivial helper for that. Note: this is only the first step, this patch doesn't try to solve other problems. The SIGNAL_GROUP_COREDUMP check is obviously racy, a task can participate in coredump after it was already observed in PF_EXITING state, so TIF_MEMDIE (which also blocks oom-killer) still can be wrongly set. fatal_signal_pending() can be true because of SIGNAL_GROUP_COREDUMP so out_of_memory() and mem_cgroup_out_of_memory() shouldn't blindly trust it. And even the name/usage of the new helper is confusing, an exiting thread can only free its ->mm if it is the only/last task in thread group. [akpm@linux-foundation.org: add comment] Signed-off-by: Oleg Nesterov <oleg@redhat.com> Cc: Cong Wang <xiyou.wangcong@gmail.com> Acked-by: David Rientjes <rientjes@google.com> Acked-by: Michal Hocko <mhocko@suse.cz> Cc: "Rafael J. Wysocki" <rjw@rjwysocki.net> Cc: Tejun Heo <tj@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/oom_kill.c')
-rw-r--r--mm/oom_kill.c6
1 files changed, 3 insertions, 3 deletions
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index 864bba992735..f694ef0d9f9a 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -281,7 +281,7 @@ enum oom_scan_t oom_scan_process_thread(struct task_struct *task,
if (oom_task_origin(task))
return OOM_SCAN_SELECT;
- if (task->flags & PF_EXITING && !force_kill) {
+ if (task_will_free_mem(task) && !force_kill) {
/*
* If this task is not being ptraced on exit, then wait for it
* to finish before killing some other task unnecessarily.
@@ -443,7 +443,7 @@ void oom_kill_process(struct task_struct *p, gfp_t gfp_mask, int order,
* If the task is already exiting, don't alarm the sysadmin or kill
* its children or threads, just set TIF_MEMDIE so it can die quickly
*/
- if (p->flags & PF_EXITING) {
+ if (task_will_free_mem(p)) {
set_tsk_thread_flag(p, TIF_MEMDIE);
put_task_struct(p);
return;
@@ -649,7 +649,7 @@ void out_of_memory(struct zonelist *zonelist, gfp_t gfp_mask,
* select it. The goal is to allow it to allocate so that it may
* quickly exit and free its memory.
*/
- if (fatal_signal_pending(current) || current->flags & PF_EXITING) {
+ if (fatal_signal_pending(current) || task_will_free_mem(current)) {
set_thread_flag(TIF_MEMDIE);
return;
}