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Date: Mon, 29 Jun 2015 15:36:05 +0200 From: Eric Dumazet <eric.dumazet@...il.com> To: "Jason A. Donenfeld" <Jason@...c4.com> Cc: "David S. Miller" <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>, netdev@...r.kernel.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH] sock: honor GFP_ATOMIC when allocating send skbs On Mon, 2015-06-29 at 15:06 +0200, Jason A. Donenfeld wrote: > Some sockets set sock->sk->sk_allocation = GFP_ATOMIC. In spite of this, > functions that call sock_alloc_send_skb will then call > sock_alloc_send_pskb, which very often results in sleeping. Since the > intention of callers setting sk_allocation = GFP_ATOMIC might be to be > able to send from atomic context, we need to honor this and not sleep. What exact problem have you noticed ? We need details please. GFP_ATOMIC in these path does not mean 'do not wait' but instead 'allocate from emergency pools'. We already have many ways to state ' do not wait', maybe you should use them. > > Signed-off-by: Jason A. Donenfeld <Jason@...c4.com> > --- > net/core/sock.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/net/core/sock.c b/net/core/sock.c > index 1e1fe9a..f00e691 100644 > --- a/net/core/sock.c > +++ b/net/core/sock.c > @@ -1804,34 +1804,37 @@ struct sk_buff *sock_alloc_send_pskb(struct sock *sk, unsigned long header_len, > unsigned long data_len, int noblock, > int *errcode, int max_page_order) > { > struct sk_buff *skb; > long timeo; > int err; > > timeo = sock_sndtimeo(sk, noblock); > for (;;) { > err = sock_error(sk); > if (err != 0) > goto failure; > > err = -EPIPE; > if (sk->sk_shutdown & SEND_SHUTDOWN) > goto failure; > > + if (sk->sk_allocation & GFP_ATOMIC) > + break; > + This is the wrong place to put this test, as following one is probably the one that is hit most of the times (fast path) > if (sk_wmem_alloc_get(sk) < sk->sk_sndbuf) > break; Anyway, testing for GFP_ATOMIC 'flag' is wrong. You probably meant to test __GFP_WAIT instead, but you need to give more details. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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