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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 /include/linux/oom.h
parentba914f481507a0542a7c8a3fc15d89414bc2ebf3 (diff)
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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 'include/linux/oom.h')
-rw-r--r--include/linux/oom.h11
1 files changed, 11 insertions, 0 deletions
diff --git a/include/linux/oom.h b/include/linux/oom.h
index e8d6e1058723..853698c721f7 100644
--- a/include/linux/oom.h
+++ b/include/linux/oom.h
@@ -92,6 +92,17 @@ static inline bool oom_gfp_allowed(gfp_t gfp_mask)
extern struct task_struct *find_lock_task_mm(struct task_struct *p);
+static inline bool task_will_free_mem(struct task_struct *task)
+{
+ /*
+ * A coredumping process may sleep for an extended period in exit_mm(),
+ * so the oom killer cannot assume that the process will promptly exit
+ * and release memory.
+ */
+ return (task->flags & PF_EXITING) &&
+ !(task->signal->flags & SIGNAL_GROUP_COREDUMP);
+}
+
/* sysctls */
extern int sysctl_oom_dump_tasks;
extern int sysctl_oom_kill_allocating_task;