[PATCH] atm/svc: Fix blocking in wait loop
From: chas williams - CONTRACTOR
Date: Tue Aug 12 2014 - 08:16:36 EST
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@xxxxxxxxxxxxxxxxx>
Acked-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
---
net/atm/svc.c | 60 +++++++++++++++++++++++++++++++----------------------------
1 file changed, 32 insertions(+), 28 deletions(-)
diff --git a/net/atm/svc.c b/net/atm/svc.c
index d8e5d0c2..1ba23f5 100644
--- 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) {
--
1.9.3
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