coredump: kill mm->core_done

Now that we have core_state->dumper list we can use it to wake up the
sub-threads waiting for the coredump completion.

This uglifies the code and .text grows by 47 bytes, but otoh mm_struct
lessens by sizeof(struct completion).  Also, with this change we can
decouple exit_mm() from the coredumping code.

Signed-off-by: Oleg Nesterov <oleg@tv-sign.ru>
Cc: Roland McGrath <roland@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/kernel/exit.c b/kernel/exit.c
index b66f0d55c791..8a4d4d12e294 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -691,7 +691,13 @@ static void exit_mm(struct task_struct * tsk)
 		if (atomic_dec_and_test(&core_state->nr_threads))
 			complete(&core_state->startup);
 
-		wait_for_completion(&mm->core_done);
+		for (;;) {
+			set_task_state(tsk, TASK_UNINTERRUPTIBLE);
+			if (!self.task) /* see coredump_finish() */
+				break;
+			schedule();
+		}
+		__set_task_state(tsk, TASK_RUNNING);
 		down_read(&mm->mmap_sem);
 	}
 	atomic_inc(&mm->mm_count);