Commit de713b57 authored by chas williams - CONTRACTOR's avatar chas williams - CONTRACTOR Committed by David S. Miller
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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: default avatarChas Williams <chas@cmf.n4rl.navy.mil>
Acked-by: default avatarPeter Zijlstra <peterz@infradead.org>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 10545937

net/atm/svc.c

+32 −28
Original line number Diff line number Diff line
@@ -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);

		sigd_enq(new_vcc, as_accept, old_vcc, NULL, NULL);

		for (;;) {

			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) {

			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) {

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