From ed247b7ca0d20b4528eec362f8435594818d7601 Mon Sep 17 00:00:00 2001
From: Manfred Spraul
Date: Fri, 6 Jun 2014 14:37:49 -0700
Subject: ipc/sem.c: store which operation blocks in perform_atomic_semop()

Preparation for the next patch:

In the slow-path of perform_atomic_semop(), store a pointer to the
operation that caused the operation to block.

Signed-off-by: Manfred Spraul <manfred@colorfullife.com>
Cc: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Michael Kerrisk <mtk.manpages@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
 ipc/sem.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/ipc/sem.c b/ipc/sem.c
index b93b561842cd..d61362b31f1e 100644
--- a/ipc/sem.c
+++ b/ipc/sem.c
@@ -109,6 +109,7 @@ struct sem_queue {
 	int			pid;	 /* process id of requesting process */
 	int			status;	 /* completion status of operation */
 	struct sembuf		*sops;	 /* array of pending operations */
+	struct sembuf		*blocking; /* the operation that blocked */
 	int			nsops;	 /* number of operations */
 	int			alter;	 /* does *sops alter the array? */
 };
@@ -642,6 +643,8 @@ out_of_range:
 	goto undo;
 
 would_block:
+	q->blocking = sop;
+
 	if (sop->sem_flg & IPC_NOWAIT)
 		result = -EAGAIN;
 	else
-- 
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