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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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Sender: owner-linux-security-module@vger.kernel.org Precedence: bulk List-ID: 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) =09=09=09=09spin_lock_irq(&pipe->wait.lock); =09=09=09=09tail++; =09=09=09=09pipe_commit_read(pipe, tail); -=09=09=09=09do_wakeup =3D 0; -=09=09=09=09wake_up_interruptible_sync_poll_locked( -=09=09=09=09=09&pipe->wait, EPOLLOUT | EPOLLWRNORM); +=09=09=09=09do_wakeup =3D 1; +=09=09=09=09if (head - (tail - 1) =3D=3D pipe->max_usage) +=09=09=09=09=09wake_up_interruptible_sync_poll_locked( +=09=09=09=09=09=09&pipe->wait, EPOLLOUT | EPOLLWRNORM); =09=09=09=09spin_unlock_irq(&pipe->wait.lock); -=09=09=09=09kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); +=09=09=09=09if (head - (tail - 1) =3D=3D pipe->max_usage) +=09=09=09=09=09kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); =09=09=09} =09=09=09total_len -=3D chars; =09=09=09if (!total_len) @@ -360,11 +362,6 @@ pipe_read(struct kiocb *iocb, struct iov_iter *to) =09=09=09=09ret =3D -ERESTARTSYS; =09=09=09break; =09=09} -=09=09if (do_wakeup) { -=09=09=09wake_up_interruptible_sync_poll(&pipe->wait, EPOLLOUT | EPOLLWRNO= RM); - =09=09=09kill_fasync(&pipe->fasync_writers, SIGIO, POLL_OUT); -=09=09=09do_wakeup =3D 0; -=09=09} =09=09pipe_wait(pipe); =09} =09__pipe_unlock(pipe);