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, 22 insertions, 3 deletions

diff --git a/fs/exec.c b/fs/exec.c
index fe2873b8037f..bff43aeb235e 100644
--- a/fs/exec.c
+++ b/fs/exec.c
@@ -1602,7 +1602,6 @@ static int coredump_wait(int exit_code, struct core_state *core_state)
 	struct completion *vfork_done;
 	int core_waiters;
 
-	init_completion(&mm->core_done);
 	init_completion(&core_state->startup);
 	core_state->dumper.task = tsk;
 	core_state->dumper.next = NULL;
@@ -1628,6 +1627,27 @@ fail:
 	return core_waiters;
 }
 
+static void coredump_finish(struct mm_struct *mm)
+{
+	struct core_thread *curr, *next;
+	struct task_struct *task;
+
+	next = mm->core_state->dumper.next;
+	while ((curr = next) != NULL) {
+		next = curr->next;
+		task = curr->task;
+		/*
+		 * see exit_mm(), curr->task must not see
+		 * ->task == NULL before we read ->next.
+		 */
+		smp_mb();
+		curr->task = NULL;
+		wake_up_process(task);
+	}
+
+	mm->core_state = NULL;
+}
+
 /*
  * set_dumpable converts traditional three-value dumpable to two flags and
  * stores them into mm->flags.  It modifies lower two bits of mm->flags, but
@@ -1812,8 +1832,7 @@ fail_unlock:
 		argv_free(helper_argv);
 
 	current->fsuid = fsuid;
-	complete_all(&mm->core_done);
-	mm->core_state = NULL;
+	coredump_finish(mm);
 fail:
 	return retval;
 }