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ipc,msg: shorten critical region in msgsnd

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do_msgsnd() is another function that does too many things with the ipc
object lock acquired.  Take it only when needed when actually updating
msq.

Signed-off-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Rik van Riel <riel@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
This commit is contained in:
Davidlohr Bueso 2013-07-08 16:01:17 -07:00 committed by Linus Torvalds
parent ac0ba20ea6
commit 3dd1f784ed
1 changed files with 24 additions and 13 deletions
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37
ipc/msg.c
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@ -698,10 +698,11 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
msg->m_type = mtype;
msg->m_ts = msgsz;
msq = msg_lock_check(ns, msqid);
rcu_read_lock();
msq = msq_obtain_object_check(ns, msqid);
if (IS_ERR(msq)) {
err = PTR_ERR(msq);
goto out_free;
goto out_unlock1;
}
for (;;) {
@ -709,11 +710,11 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
err = -EACCES;
if (ipcperms(ns, &msq->q_perm, S_IWUGO))
goto out_unlock_free;
goto out_unlock1;
err = security_msg_queue_msgsnd(msq, msg, msgflg);
if (err)
goto out_unlock_free;
goto out_unlock1;
if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
1 + msq->q_qnum <= msq->q_qbytes) {
@ -723,32 +724,41 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
/* queue full, wait: */
if (msgflg & IPC_NOWAIT) {
err = -EAGAIN;
goto out_unlock_free;
goto out_unlock1;
}
ipc_lock_object(&msq->q_perm);
ss_add(msq, &s);
if (!ipc_rcu_getref(msq)) {
err = -EIDRM;
goto out_unlock_free;
goto out_unlock0;
}
msg_unlock(msq);
ipc_unlock_object(&msq->q_perm);
rcu_read_unlock();
schedule();
ipc_lock_by_ptr(&msq->q_perm);
rcu_read_lock();
ipc_lock_object(&msq->q_perm);
ipc_rcu_putref(msq);
if (msq->q_perm.deleted) {
err = -EIDRM;
goto out_unlock_free;
goto out_unlock0;
}
ss_del(&s);
if (signal_pending(current)) {
err = -ERESTARTNOHAND;
goto out_unlock_free;
goto out_unlock0;
}
ipc_unlock_object(&msq->q_perm);
}
ipc_lock_object(&msq->q_perm);
msq->q_lspid = task_tgid_vnr(current);
msq->q_stime = get_seconds();
@ -764,9 +774,10 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
err = 0;
msg = NULL;
out_unlock_free:
msg_unlock(msq);
out_free:
out_unlock0:
ipc_unlock_object(&msq->q_perm);
out_unlock1:
rcu_read_unlock();
if (msg != NULL)
free_msg(msg);
return err;