[PATCH] atm/svc: Fix blocking in wait loop
From: chas williams - CONTRACTOR <hidden>
Date: 2014-08-12 12:16:33
Also in:
lkml, oe-lkp
Subsystem:
atm, networking [general], the rest · Maintainers:
Chas Williams, "David S. Miller", Eric Dumazet, Jakub Kicinski, Paolo Abeni, Linus Torvalds
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 <redacted> Acked-by: Peter Zijlstra <peterz@infradead.org> --- 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