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authorFrancois Romieu <romieu@fr.zoreil.com>2017-03-11 19:41:36 -0500
committerDavid S. Miller <davem@davemloft.net>2017-03-13 15:37:29 -0700
commitc55fa3cccbc2c672e7f118be8f7484e53a8e9e77 (patch)
tree06147d1603162f9c84a5f2970db5884c2090aba8 /net/atm
parentbe086e7c53f1fac51eed14523b28f2214b548dd2 (diff)
downloadlinux-c55fa3cccbc2c672e7f118be8f7484e53a8e9e77.tar.bz2
atm: remove an unnecessary loop
Andrey reported this kernel warning: WARNING: CPU: 0 PID: 4114 at kernel/sched/core.c:7737 __might_sleep+0x149/0x1a0 do not call blocking ops when !TASK_RUNNING; state=1 set at [<ffffffff813fcb22>] prepare_to_wait+0x182/0x530 The deeply nested alloc_skb is a problem. Diagnosis: nesting is wrong. It makes zero sense. Fix it and the implicit task state change problem automagically goes away. alloc_skb() does not need to be in the "while" loop. alloc_skb() does not need to be in the {prepare_to_wait/add_wait_queue ... finish_wait/remove_wait_queue} block. I claim that: - alloc_tx() should only perform the "wait_for_decent_tx_drain" part - alloc_skb() ought to be done directly in vcc_sendmsg - alloc_skb() failure can be handled gracefully in vcc_sendmsg - alloc_skb() may use a (m->msg_flags & MSG_DONTWAIT) dependent GFP_{KERNEL / ATOMIC} flag Reported-by: Andrey Konovalov <andreyknvl@google.com> Reviewed-and-Tested-by: Chas Williams <3chas3@gmail.com> Signed-off-by: Chas Williams <3chas3@gmail.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/atm')
-rw-r--r--net/atm/common.c22
1 files changed, 13 insertions, 9 deletions
diff --git a/net/atm/common.c b/net/atm/common.c
index 9613381f5db0..f06422f4108d 100644
--- a/net/atm/common.c
+++ b/net/atm/common.c
@@ -62,21 +62,16 @@ static void vcc_remove_socket(struct sock *sk)
write_unlock_irq(&vcc_sklist_lock);
}
-static struct sk_buff *alloc_tx(struct atm_vcc *vcc, unsigned int size)
+static bool vcc_tx_ready(struct atm_vcc *vcc, unsigned int size)
{
- struct sk_buff *skb;
struct sock *sk = sk_atm(vcc);
if (sk_wmem_alloc_get(sk) && !atm_may_send(vcc, size)) {
pr_debug("Sorry: wmem_alloc = %d, size = %d, sndbuf = %d\n",
sk_wmem_alloc_get(sk), size, sk->sk_sndbuf);
- return NULL;
+ return false;
}
- while (!(skb = alloc_skb(size, GFP_KERNEL)))
- schedule();
- pr_debug("%d += %d\n", sk_wmem_alloc_get(sk), skb->truesize);
- atomic_add(skb->truesize, &sk->sk_wmem_alloc);
- return skb;
+ return true;
}
static void vcc_sock_destruct(struct sock *sk)
@@ -606,7 +601,7 @@ int vcc_sendmsg(struct socket *sock, struct msghdr *m, size_t size)
eff = (size+3) & ~3; /* align to word boundary */
prepare_to_wait(sk_sleep(sk), &wait, TASK_INTERRUPTIBLE);
error = 0;
- while (!(skb = alloc_tx(vcc, eff))) {
+ while (!vcc_tx_ready(vcc, eff)) {
if (m->msg_flags & MSG_DONTWAIT) {
error = -EAGAIN;
break;
@@ -628,6 +623,15 @@ int vcc_sendmsg(struct socket *sock, struct msghdr *m, size_t size)
finish_wait(sk_sleep(sk), &wait);
if (error)
goto out;
+
+ skb = alloc_skb(eff, GFP_KERNEL);
+ if (!skb) {
+ error = -ENOMEM;
+ goto out;
+ }
+ pr_debug("%d += %d\n", sk_wmem_alloc_get(sk), skb->truesize);
+ atomic_add(skb->truesize, &sk->sk_wmem_alloc);
+
skb->dev = NULL; /* for paths shared with net_device interfaces */
ATM_SKB(skb)->atm_options = vcc->atm_options;
if (!copy_from_iter_full(skb_put(skb, size), size, &m->msg_iter)) {