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>

1 files changed, 3 insertions, 0 deletions

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