From patchwork Wed Oct 23 20:18:10 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 11207631 Return-Path: Received: from mail.kernel.org (pdx-korg-mail-1.web.codeaurora.org [172.30.200.123]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id 0C40D1747 for ; Wed, 23 Oct 2019 20:18:25 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id DCFF621872 for ; Wed, 23 Oct 2019 20:18:24 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="DzY/CDPu" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2407436AbfJWUSV (ORCPT ); Wed, 23 Oct 2019 16:18:21 -0400 Received: from us-smtp-delivery-1.mimecast.com ([205.139.110.120]:36541 "EHLO us-smtp-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S2407429AbfJWUSU (ORCPT ); Wed, 23 Oct 2019 16:18:20 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1571861899; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=TsICzw/12FA1ze+4AGSV0OSb28CD+mZ6S94YG04i4d8=; b=DzY/CDPuESKUdWEZda60BL/+fMCerqej3Xw0sB2sWAB2GYKNnE6Lm86N/apJXHuHpAS1v0 LqoVGz75iPxb06rn3e++we18gXgVThojNXg7bUu7FnBEnWjb9umuMntO/g/RPu1kVoNfEW O/JQXeg+gyj2QP5lY3YYGep3eLO3MHg= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-158-GYEDDBkSPA-9sgTXCU1ilg-1; Wed, 23 Oct 2019 16:18:16 -0400 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 340FE107AD31; Wed, 23 Oct 2019 20:18:14 +0000 (UTC) Received: from warthog.procyon.org.uk (ovpn-121-40.rdu2.redhat.com [10.10.121.40]) by smtp.corp.redhat.com (Postfix) with ESMTP id 637C7600CC; Wed, 23 Oct 2019 20:18:11 +0000 (UTC) Organization: Red Hat UK Ltd. Registered Address: Red Hat UK Ltd, Amberley Place, 107-111 Peascod Street, Windsor, Berkshire, SI4 1TE, United Kingdom. Registered in England and Wales under Company Registration No. 3798903 Subject: [RFC PATCH 07/10] pipe: Conditionalise wakeup in pipe_read() [ver #2] From: David Howells To: torvalds@linux-foundation.org Cc: dhowells@redhat.com, Rasmus Villemoes , Greg Kroah-Hartman , Peter Zijlstra , nicolas.dichtel@6wind.com, raven@themaw.net, Christian Brauner , dhowells@redhat.com, keyrings@vger.kernel.org, linux-usb@vger.kernel.org, linux-block@vger.kernel.org, linux-security-module@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org, linux-security-module@vger.kernel.org, linux-kernel@vger.kernel.org Date: Wed, 23 Oct 2019 21:18:10 +0100 Message-ID: <157186189069.3995.10292601951655075484.stgit@warthog.procyon.org.uk> In-Reply-To: <157186182463.3995.13922458878706311997.stgit@warthog.procyon.org.uk> References: <157186182463.3995.13922458878706311997.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 X-MC-Unique: GYEDDBkSPA-9sgTXCU1ilg-1 X-Mimecast-Spam-Score: 0 Sender: linux-usb-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-usb@vger.kernel.org Only do a wakeup in pipe_read() if we made space in a completely full buffer. The producer shouldn't be waiting on pipe->wait otherwise. Signed-off-by: David Howells --- fs/pipe.c | 15 ++++++--------- 1 file changed, 6 insertions(+), 9 deletions(-) diff --git a/fs/pipe.c b/fs/pipe.c index 1274305772fb..e3a8f10750c9 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -327,11 +327,13 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) spin_lock_irq(&pipe->wait.lock); tail++; pipe_commit_read(pipe, tail); - do_wakeup = 0; - wake_up_interruptible_sync_poll_locked( - &pipe->wait, EPOLLOUT | EPOLLWRNORM); + do_wakeup = 1; + if (head - (tail - 1) == pipe->max_usage) + wake_up_interruptible_sync_poll_locked( + &pipe->wait, EPOLLOUT | EPOLLWRNORM); spin_unlock_irq(&pipe->wait.lock); - kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); + if (head - (tail - 1) == pipe->max_usage) + kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); } total_len -= chars; if (!total_len) @@ -360,11 +362,6 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) ret = -ERESTARTSYS; break; } - if (do_wakeup) { - wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNORM); - kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); - do_wakeup = 0; - } pipe_wait(pipe); } __pipe_unlock(pipe);