atm/svc: Fix blocking in wait loop

One should not call blocking primitives inside a wait loop, since both
require task_struct::state to sleep, so the inner will destroy the
outer state.

sigd_enq() will possibly sleep for alloc_skb().  Move sigd_enq() before
prepare_to_wait() to avoid sleeping while waiting interruptibly.  You do
not actually need to call sigd_enq() after the initial prepare_to_wait()
because we test the termination condition before calling schedule().

Based on suggestions from Peter Zijlstra.

Signed-off-by: Chas Williams <chas@cmf.n4rl.navy.mil>
Acked-by: Peter Zijlstra <peterz@infradead.org>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/atm/svc.c b/net/atm/svc.c
index d8e5d0c..1ba23f5 100644 (file)
--- a/net/atm/svc.c
+++ b/net/atm/svc.c
@@ -50,12 +50,12 @@ static void svc_disconnect(struct atm_vcc *vcc)
 
        pr_debug("%p\n", vcc);
        if (test_bit(ATM_VF_REGIS, &vcc->flags)) {
-               prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
                sigd_enq(vcc, as_close, NULL, NULL, NULL);
-               while (!test_bit(ATM_VF_RELEASED, &vcc->flags) && sigd) {
+               for (;;) {
+                       prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
+                       if (test_bit(ATM_VF_RELEASED, &vcc->flags) || !sigd)
+                               break;
                        schedule();
-                       prepare_to_wait(sk_sleep(sk), &wait,
-                                       TASK_UNINTERRUPTIBLE);
                }
                finish_wait(sk_sleep(sk), &wait);
        }
@@ -126,11 +126,12 @@ static int svc_bind(struct socket *sock, struct sockaddr *sockaddr,
        }
        vcc->local = *addr;
        set_bit(ATM_VF_WAITING, &vcc->flags);
-       prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
        sigd_enq(vcc, as_bind, NULL, NULL, &vcc->local);
-       while (test_bit(ATM_VF_WAITING, &vcc->flags) && sigd) {
-               schedule();
+       for (;;) {
                prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
+               if (!test_bit(ATM_VF_WAITING, &vcc->flags) || !sigd)
+                       break;
+               schedule();
        }
        finish_wait(sk_sleep(sk), &wait);
        clear_bit(ATM_VF_REGIS, &vcc->flags); /* doesn't count */
@@ -202,15 +203,14 @@ static int svc_connect(struct socket *sock, struct sockaddr *sockaddr,
                }
                vcc->remote = *addr;
                set_bit(ATM_VF_WAITING, &vcc->flags);
-               prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
                sigd_enq(vcc, as_connect, NULL, NULL, &vcc->remote);
                if (flags & O_NONBLOCK) {
-                       finish_wait(sk_sleep(sk), &wait);
                        sock->state = SS_CONNECTING;
                        error = -EINPROGRESS;
                        goto out;
                }
                error = 0;
+               prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
                while (test_bit(ATM_VF_WAITING, &vcc->flags) && sigd) {
                        schedule();
                        if (!signal_pending(current)) {
@@ -297,11 +297,12 @@ static int svc_listen(struct socket *sock, int backlog)
                goto out;
        }
        set_bit(ATM_VF_WAITING, &vcc->flags);
-       prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
        sigd_enq(vcc, as_listen, NULL, NULL, &vcc->local);
-       while (test_bit(ATM_VF_WAITING, &vcc->flags) && sigd) {
-               schedule();
+       for (;;) {
                prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
+               if (!test_bit(ATM_VF_WAITING, &vcc->flags) || !sigd)
+                       break;
+               schedule();
        }
        finish_wait(sk_sleep(sk), &wait);
        if (!sigd) {
@@ -387,15 +388,15 @@ static int svc_accept(struct socket *sock, struct socket *newsock, int flags)
                }
                /* wait should be short, so we ignore the non-blocking flag */
                set_bit(ATM_VF_WAITING, &new_vcc->flags);
-               prepare_to_wait(sk_sleep(sk_atm(new_vcc)), &wait,
-                               TASK_UNINTERRUPTIBLE);
                sigd_enq(new_vcc, as_accept, old_vcc, NULL, NULL);
-               while (test_bit(ATM_VF_WAITING, &new_vcc->flags) && sigd) {
+               for (;;) {
+                       prepare_to_wait(sk_sleep(sk_atm(new_vcc)), &wait,
+                                       TASK_UNINTERRUPTIBLE);
+                       if (!test_bit(ATM_VF_WAITING, &new_vcc->flags) || !sigd)
+                               break;
                        release_sock(sk);
                        schedule();
                        lock_sock(sk);
-                       prepare_to_wait(sk_sleep(sk_atm(new_vcc)), &wait,
-                                       TASK_UNINTERRUPTIBLE);
                }
                finish_wait(sk_sleep(sk_atm(new_vcc)), &wait);
                if (!sigd) {
@@ -433,12 +434,14 @@ int svc_change_qos(struct atm_vcc *vcc, struct atm_qos *qos)
        DEFINE_WAIT(wait);
 
        set_bit(ATM_VF_WAITING, &vcc->flags);
-       prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
        sigd_enq2(vcc, as_modify, NULL, NULL, &vcc->local, qos, 0);
-       while (test_bit(ATM_VF_WAITING, &vcc->flags) &&
-              !test_bit(ATM_VF_RELEASED, &vcc->flags) && sigd) {
-               schedule();
+       for (;;) {
                prepare_to_wait(sk_sleep(sk), &wait, TASK_UNINTERRUPTIBLE);
+               if (!test_bit(ATM_VF_WAITING, &vcc->flags) ||
+                   test_bit(ATM_VF_RELEASED, &vcc->flags) || !sigd) {
+                       break;
+               }
+               schedule();
        }
        finish_wait(sk_sleep(sk), &wait);
        if (!sigd)
@@ -529,18 +532,18 @@ static int svc_addparty(struct socket *sock, struct sockaddr *sockaddr,
 
        lock_sock(sk);
        set_bit(ATM_VF_WAITING, &vcc->flags);
-       prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
        sigd_enq(vcc, as_addparty, NULL, NULL,
                 (struct sockaddr_atmsvc *) sockaddr);
        if (flags & O_NONBLOCK) {
-               finish_wait(sk_sleep(sk), &wait);
                error = -EINPROGRESS;
                goto out;
        }
        pr_debug("added wait queue\n");
-       while (test_bit(ATM_VF_WAITING, &vcc->flags) && sigd) {
-               schedule();
+       for (;;) {
                prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+               if (!test_bit(ATM_VF_WAITING, &vcc->flags) || !sigd)
+                       break;
+               schedule();
        }
        finish_wait(sk_sleep(sk), &wait);
        error = xchg(&sk->sk_err_soft, 0);
@@ -558,11 +561,12 @@ static int svc_dropparty(struct socket *sock, int ep_ref)
 
        lock_sock(sk);
        set_bit(ATM_VF_WAITING, &vcc->flags);
-       prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
        sigd_enq2(vcc, as_dropparty, NULL, NULL, NULL, NULL, ep_ref);
-       while (test_bit(ATM_VF_WAITING, &vcc->flags) && sigd) {
-               schedule();
+       for (;;) {
                prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
+               if (!test_bit(ATM_VF_WAITING, &vcc->flags) || !sigd)
+                       break;
+               schedule();
        }
        finish_wait(sk_sleep(sk), &wait);
        if (!sigd) {