ipc,msg: shorten critical region in msgsnd
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>
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ac0ba20ea6
Коммит
3dd1f784ed
37
ipc/msg.c
37
ipc/msg.c
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@ -698,10 +698,11 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
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msg->m_type = mtype;
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msg->m_ts = msgsz;
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msq = msg_lock_check(ns, msqid);
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rcu_read_lock();
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msq = msq_obtain_object_check(ns, msqid);
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if (IS_ERR(msq)) {
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err = PTR_ERR(msq);
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goto out_free;
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goto out_unlock1;
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}
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for (;;) {
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@ -709,11 +710,11 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
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err = -EACCES;
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if (ipcperms(ns, &msq->q_perm, S_IWUGO))
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goto out_unlock_free;
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goto out_unlock1;
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err = security_msg_queue_msgsnd(msq, msg, msgflg);
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if (err)
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goto out_unlock_free;
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goto out_unlock1;
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if (msgsz + msq->q_cbytes <= msq->q_qbytes &&
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1 + msq->q_qnum <= msq->q_qbytes) {
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@ -723,32 +724,41 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
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/* queue full, wait: */
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if (msgflg & IPC_NOWAIT) {
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err = -EAGAIN;
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goto out_unlock_free;
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goto out_unlock1;
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}
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ipc_lock_object(&msq->q_perm);
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ss_add(msq, &s);
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if (!ipc_rcu_getref(msq)) {
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err = -EIDRM;
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goto out_unlock_free;
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goto out_unlock0;
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}
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msg_unlock(msq);
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ipc_unlock_object(&msq->q_perm);
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rcu_read_unlock();
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schedule();
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ipc_lock_by_ptr(&msq->q_perm);
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rcu_read_lock();
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ipc_lock_object(&msq->q_perm);
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ipc_rcu_putref(msq);
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if (msq->q_perm.deleted) {
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err = -EIDRM;
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goto out_unlock_free;
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goto out_unlock0;
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}
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ss_del(&s);
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if (signal_pending(current)) {
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err = -ERESTARTNOHAND;
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goto out_unlock_free;
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goto out_unlock0;
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}
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ipc_unlock_object(&msq->q_perm);
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}
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ipc_lock_object(&msq->q_perm);
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msq->q_lspid = task_tgid_vnr(current);
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msq->q_stime = get_seconds();
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@ -764,9 +774,10 @@ long do_msgsnd(int msqid, long mtype, void __user *mtext,
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err = 0;
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msg = NULL;
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out_unlock_free:
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msg_unlock(msq);
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out_free:
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out_unlock0:
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ipc_unlock_object(&msq->q_perm);
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out_unlock1:
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rcu_read_unlock();
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if (msg != NULL)
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free_msg(msg);
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return err;
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