Fix bug in msgsnd

Hello linus & Alan,

This patch fixes a bug in msgsnd. If a message is sent via pipelined_send(), the q_lrpid field of the associated message queue (last pid receive) is not updated correctly. The existing code (apparently by mistake) updates the lspid field instead. The second problem is that, for the pipelinesend case, q_lstime(last msgsnd time) is set AFTER q_lrtime(last msgrcv time), yielding a negative time delta.

This patch is against kernel 2.4.9 and has been tested. Please apply.

Please CC your feedback to me also, thanks.

--
Mingming Cao
IBM Linux Technology Center

diff -urN -X dontdiff linux/ipc/msg.c linux-tk/ipc/msg.c

ipc/msg.c Tue Sep 11 16:21:31 2001 renamed from ipc/msg.c Tue Sep 11 16:21:42 2001 +4 -4

@@ -613,7 +613,7 @@
                                wake_up_process(msr->r_tsk);
                        } else {
                                msr->r_msg = msg;
-                               msq->q_lspid = msr->r_tsk->pid;
+                               msq->q_lrpid = msr->r_tsk->pid;
                                msq->q_rtime = CURRENT_TIME;
                                wake_up_process(msr->r_tsk);
                                return 1;

@@ -683,6 +683,9 @@
                goto retry;
        }
 
+       msq->q_lspid = current->pid;
+       msq->q_stime = CURRENT_TIME;
+
        if(!pipelined_send(msq,msg)) {
                /* noone is waiting for this message, enqueue it */
                list_add_tail(&msg->m_list,&msq->q_messages);

@@ -694,8 +697,6 @@
 
        err = 0;
        msg = NULL;
-       msq->q_lspid = current->pid;
-       msq->q_stime = CURRENT_TIME;
 
 out_unlock_free:
        msg_unlock(msqid);
-

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