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From: David Howells <dhowells@redhat.com>
To: torvalds@linux-foundation.org
Cc: dhowells@redhat.com, Casey Schaufler <casey@schaufler-ca.com>,
	Stephen Smalley <sds@tycho.nsa.gov>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	nicolas.dichtel@6wind.com, raven@themaw.net,
	Christian Brauner <christian@brauner.io>,
	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
Subject: [RFC PATCH 05/21] pipe: Conditionalise wakeup in pipe_read()
Date: Tue, 15 Oct 2019 22:48:34 +0100	[thread overview]
Message-ID: <157117611484.15019.2438330064445318267.stgit@warthog.procyon.org.uk> (raw)
In-Reply-To: <157117606853.15019.15459271147790470307.stgit@warthog.procyon.org.uk>

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 <dhowells@redhat.com>
---

 fs/pipe.c |   15 ++++++---------
 1 file changed, 6 insertions(+), 9 deletions(-)

diff --git a/fs/pipe.c b/fs/pipe.c
index 08af7e7bbea2..0d25cb090a03 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;
-				prelocked_wake_up_interruptible_sync_poll(
-					&pipe->wait, EPOLLOUT | EPOLLWRNORM);
+				do_wakeup = 1;
+				if (head - (tail - 1) == pipe->max_usage)
+					prelocked_wake_up_interruptible_sync_poll(
+						&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);


  parent reply	other threads:[~2019-10-15 21:48 UTC|newest]

Thread overview: 32+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-10-15 21:47 [RFC PATCH 00/21] pipe: Keyrings, Block and USB notifications David Howells
2019-10-15 21:47 ` [RFC PATCH 01/21] pipe: Reduce #inclusion of pipe_fs_i.h David Howells
2019-10-15 21:48 ` [RFC PATCH 02/21] Add a prelocked wake-up David Howells
2019-10-15 22:14   ` Linus Torvalds
2019-10-16 17:02     ` Tim Chen
2019-10-15 22:33   ` David Howells
2019-10-16 14:26   ` David Howells
2019-10-16 15:31     ` Linus Torvalds
2019-10-15 21:48 ` [RFC PATCH 03/21] pipe: Use head and tail pointers for the ring, not cursor and length David Howells
2019-10-16  7:46   ` Rasmus Villemoes
2019-10-17 10:53   ` David Howells
2019-10-15 21:48 ` [RFC PATCH 04/21] pipe: Advance tail pointer inside of wait spinlock in pipe_read() David Howells
2019-10-15 21:48 ` David Howells [this message]
2019-10-15 21:48 ` [RFC PATCH 06/21] pipe: Rearrange sequence in pipe_write() to preallocate slot David Howells
2019-10-15 21:48 ` [RFC PATCH 07/21] pipe: Remove redundant wakeup from pipe_write() David Howells
2019-10-15 21:49 ` [RFC PATCH 08/21] pipe: Check for ring full inside of the spinlock in pipe_write() David Howells
2019-10-15 22:20   ` Linus Torvalds
2019-10-15 21:49 ` [RFC PATCH 09/21] uapi: General notification queue definitions David Howells
2019-10-15 21:49 ` [RFC PATCH 10/21] security: Add hooks to rule on setting a watch David Howells
2019-10-15 21:49 ` [RFC PATCH 11/21] security: Add a hook for the point of notification insertion David Howells
2019-10-15 21:49 ` [RFC PATCH 12/21] pipe: Add general notification queue support David Howells
2019-10-15 21:49 ` [RFC PATCH 13/21] keys: Add a notification facility David Howells
2019-10-15 21:49 ` [RFC PATCH 14/21] Add sample notification program David Howells
2019-10-15 21:50 ` [RFC PATCH 15/21] pipe: Allow buffers to be marked read-whole-or-error for notifications David Howells
2019-10-15 21:50 ` [RFC PATCH 16/21] pipe: Add notification lossage handling David Howells
2019-10-15 21:50 ` [RFC PATCH 17/21] Add a general, global device notification watch list David Howells
2019-10-15 21:50 ` [RFC PATCH 18/21] block: Add block layer notifications David Howells
2019-10-15 21:50 ` [RFC PATCH 19/21] usb: Add USB subsystem notifications David Howells
2019-10-15 21:50 ` [RFC PATCH 20/21] selinux: Implement the watch_key security hook David Howells
2019-10-15 21:50 ` [RFC PATCH 21/21] smack: Implement the watch_key and post_notification hooks David Howells
2019-10-15 22:11 ` [RFC PATCH 00/21] pipe: Keyrings, Block and USB notifications James Morris
2019-10-15 22:32 ` Linus Torvalds

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