Re: [PATCH net-next v2] tcp: ensure epoll edge trigger wakeup when write queue is empty
From: Jason Baron jba...@akamai.com Date: Wed, 20 May 2015 15:52:53 + (GMT) From: Jason Baron jba...@akamai.com We currently rely on the setting of SOCK_NOSPACE in the write() path to ensure that we wake up any epoll edge trigger waiters when acks return to free space in the write queue. However, if we fail to allocate even a single skb in the write queue, we could end up waiting indefinitely. Fix this by explicitly issuing a wakeup when we detect the condition of an empty write queue and a return value of -EAGAIN. This allows userspace to re-try as we expect this to be a temporary failure. I've tested this approach by artificially making sk_stream_alloc_skb() return NULL periodically. In that case, epoll edge trigger waiters will hang indefinitely in epoll_wait() without this patch. Signed-off-by: Jason Baron jba...@akamai.com --- v2: - ensure it compiles :) Applied, thanks Jason :) -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
Re: [PATCH net-next v2] tcp: ensure epoll edge trigger wakeup when write queue is empty
On Wed, 2015-05-20 at 15:52 +, Jason Baron wrote: From: Jason Baron jba...@akamai.com We currently rely on the setting of SOCK_NOSPACE in the write() path to ensure that we wake up any epoll edge trigger waiters when acks return to free space in the write queue. However, if we fail to allocate even a single skb in the write queue, we could end up waiting indefinitely. Fix this by explicitly issuing a wakeup when we detect the condition of an empty write queue and a return value of -EAGAIN. This allows userspace to re-try as we expect this to be a temporary failure. I've tested this approach by artificially making sk_stream_alloc_skb() return NULL periodically. In that case, epoll edge trigger waiters will hang indefinitely in epoll_wait() without this patch. Signed-off-by: Jason Baron jba...@akamai.com --- Acked-by: Eric Dumazet eduma...@google.com -- To unsubscribe from this list: send the line unsubscribe netdev in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
