From patchwork Fri Nov 1 17:35:05 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 11223545 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 AC258913 for ; Fri, 1 Nov 2019 17:35:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8C4C021855 for ; Fri, 1 Nov 2019 17:35:28 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="FjspXGU2" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729707AbfKARfU (ORCPT ); Fri, 1 Nov 2019 13:35:20 -0400 Received: from us-smtp-1.mimecast.com ([207.211.31.81]:56885 "EHLO us-smtp-delivery-1.mimecast.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1729741AbfKARfS (ORCPT ); Fri, 1 Nov 2019 13:35:18 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1572629717; 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=f31ZclG/RJxENvGCAs10O3ojjOrA9kpGCTfILvXe/Gk=; b=FjspXGU2PeyaFJLGdB1SmRC3gIlTz/m5daYv6ZZLcIfCGGKqlIxVfnhh4SChMMRgA3iGUr abrT8jtk6dDOb0WDqc0KEG8mtQ42U6JpT97KjeWOROK2MDcvE0dmgucZ+uvzzqoYe/ldfm 0poOjs1JtvhnADsZVIuK8SKGxSczF44= 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-273-596x9dcRPvmD5UotO2FJKA-1; Fri, 01 Nov 2019 13:35:14 -0400 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AFCBD800686; Fri, 1 Nov 2019 17:35:10 +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 A78ED60BEC; Fri, 1 Nov 2019 17:35:06 +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 07/11] pipe: Conditionalise wakeup in pipe_read() [ver #3] 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: Fri, 01 Nov 2019 17:35:05 +0000 Message-ID: <157262970587.13142.9476858866693533437.stgit@warthog.procyon.org.uk> In-Reply-To: <157262963995.13142.5568934007158044624.stgit@warthog.procyon.org.uk> References: <157262963995.13142.5568934007158044624.stgit@warthog.procyon.org.uk> User-Agent: StGit/unknown-version MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-MC-Unique: 596x9dcRPvmD5UotO2FJKA-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 ea134f69a292..c16950e36ded 100644 --- a/fs/pipe.c +++ b/fs/pipe.c @@ -328,11 +328,13 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) spin_lock_irq(&pipe->wait.lock); tail++; pipe->tail = 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) @@ -361,11 +363,6 @@ 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);