diff options
| -rw-r--r-- | ipc/msg.c | 19 |
1 files changed, 17 insertions, 2 deletions
diff --git a/ipc/msg.c b/ipc/msg.c index 4377f4a45625..245db1140ad6 100644 --- a/ipc/msg.c +++ b/ipc/msg.c @@ -253,8 +253,14 @@ static void expunge_all(struct msg_queue *msq, int res) struct msg_receiver *msr, *t; list_for_each_entry_safe(msr, t, &msq->q_receivers, r_list) { - msr->r_msg = NULL; + msr->r_msg = NULL; /* initialize expunge ordering */ wake_up_process(msr->r_tsk); + /* + * Ensure that the wakeup is visible before setting r_msg as + * the receiving end depends on it: either spinning on a nil, + * or dealing with -EAGAIN cases. See lockless receive part 1 + * and 2 in do_msgrcv(). + */ smp_mb(); msr->r_msg = ERR_PTR(res); } @@ -638,15 +644,22 @@ static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg) list_del(&msr->r_list); if (msr->r_maxsize < msg->m_ts) { + /* initialize pipelined send ordering */ msr->r_msg = NULL; wake_up_process(msr->r_tsk); - smp_mb(); + smp_mb(); /* see barrier comment below */ msr->r_msg = ERR_PTR(-E2BIG); } else { msr->r_msg = NULL; msq->q_lrpid = task_pid_vnr(msr->r_tsk); msq->q_rtime = get_seconds(); wake_up_process(msr->r_tsk); + /* + * Ensure that the wakeup is visible before + * setting r_msg, as the receiving end depends + * on it. See lockless receive part 1 and 2 in + * do_msgrcv(). + */ smp_mb(); msr->r_msg = msg; @@ -654,6 +667,7 @@ static inline int pipelined_send(struct msg_queue *msq, struct msg_msg *msg) } } } + return 0; } @@ -716,6 +730,7 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext, goto out_unlock0; } + /* enqueue the sender and prepare to block */ ss_add(msq, &s); if (!ipc_rcu_getref(msq)) { |