[PATCH] oom: Make coredump interruptible

[KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>]

> Otoh, if we make do_coredump() interruptible (and we should do this
> in any case), then perhaps the TIF_MEMDIE+PF_COREDUMP is not really
> needed? Afaics we always send SIGKILL along with TIF_MEMDIE.

How is to make per-process oom flag + interruptible coredump?

this per-process oom flag can be used vmscan shortcut exiting too.
(IOW, It can help DavidR mmap_sem issue)


===========================================================
Subject: [PATCH] oom: Make coredump interruptible

If oom victim process is under core dumping, sending SIGKILL cause
no-op. Unfortunately, coredump need relatively much memory. It mean
OOM vs coredump can makes deadlock.

Then, coredump logic should check the task has received SIGKILL
from OOM.

Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
---
 fs/binfmt_elf.c       |    5 +++++
 include/linux/sched.h |    3 +++
 mm/oom_kill.c         |    1 +
 3 files changed, 9 insertions(+), 0 deletions(-)

diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
index 535e763..aa47979 100644
--- a/fs/binfmt_elf.c
+++ b/fs/binfmt_elf.c
@@ -2038,6 +2038,11 @@ static int elf_core_dump(struct coredump_params *cprm)
 				page_cache_release(page);
 			} else
 				stop = !dump_seek(cprm->file, PAGE_SIZE);
+
+			/* Now, The process received OOM. Exit soon! */
+			if (current->signal->oom_victim)
+				stop = 1;
+
 			if (stop)
 				goto end_coredump;
 		}
diff --git a/include/linux/sched.h b/include/linux/sched.h
index 8485aa2..1c4fa86 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -544,6 +544,9 @@ struct signal_struct {
 	int			notify_count;
 	struct task_struct	*group_exit_task;
 
+	/* true mean the process is OOM-killer victim. */
+	bool			oom_victim;
+
 	/* thread group stop support, overloads group_exit_code too */
 	int			group_stop_count;
 	unsigned int		flags; /* see SIGNAL_* flags below */
diff --git a/mm/oom_kill.c b/mm/oom_kill.c
index f33a1b8..39e31bf 100644
--- a/mm/oom_kill.c
+++ b/mm/oom_kill.c
@@ -400,6 +400,7 @@ static int __oom_kill_process(struct task_struct *p, struct mem_cgroup *mem,
 	 */
 	p->rt.time_slice = HZ;
 	set_tsk_thread_flag(p, TIF_MEMDIE);
+	p->signal->oom_victim = true;
 
 	force_sig(SIGKILL, p);
 
-- 
1.6.5.2



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