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From: Christoph Hellwig <hch@lst.de>
To: viro@zeniv.linux.org.uk
Cc: Avi Kivity <avi@scylladb.com>,
	linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
	netdev@vger.kernel.org, linux-api@vger.kernel.org,
	linux-kernel@vger.kernel.org
Subject: [PATCH 09/31] aio: try to complete poll iocbs without context switch
Date: Tue, 22 May 2018 13:30:46 +0200	[thread overview]
Message-ID: <20180522113108.25713-10-hch@lst.de> (raw)
In-Reply-To: <20180522113108.25713-1-hch@lst.de>

If we can acquire ctx_lock without spinning we can just remove our
iocb from the active_reqs list, and thus complete the iocbs from the
wakeup context.

Signed-off-by: Christoph Hellwig <hch@lst.de>
---
 fs/aio.c | 20 +++++++++++++++++---
 1 file changed, 17 insertions(+), 3 deletions(-)

diff --git a/fs/aio.c b/fs/aio.c
index 4d1eabce6659..85d9102431db 100644
--- a/fs/aio.c
+++ b/fs/aio.c
@@ -1632,6 +1632,7 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
 		void *key)
 {
 	struct poll_iocb *req = container_of(wait, struct poll_iocb, wait);
+	struct aio_kiocb *iocb = container_of(req, struct aio_kiocb, poll);
 	struct file *file = req->file;
 	__poll_t mask = key_to_poll(key);
 
@@ -1647,9 +1648,22 @@ static int aio_poll_wake(struct wait_queue_entry *wait, unsigned mode, int sync,
 
 	__aio_poll_remove(req);
 
-	req->events = mask;
-	INIT_WORK(&req->work, aio_poll_work);
-	schedule_work(&req->work);
+	/*
+	 * Try completing without a context switch if we can acquire ctx_lock
+	 * without spinning.  Otherwise we need to defer to a workqueue to
+	 * avoid a deadlock due to the lock order.
+	 */
+	if (spin_trylock(&iocb->ki_ctx->ctx_lock)) {
+		list_del_init(&iocb->ki_list);
+		spin_unlock(&iocb->ki_ctx->ctx_lock);
+
+		__aio_poll_complete(req, mask);
+	} else {
+		req->events = mask;
+		INIT_WORK(&req->work, aio_poll_work);
+		schedule_work(&req->work);
+	}
+
 	return 1;
 }
 
-- 
2.17.0

  parent reply	other threads:[~2018-05-22 11:31 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-22 11:30 aio poll and a new in-kernel poll API V12 Christoph Hellwig
2018-05-22 11:30 ` [PATCH 01/31] fs: unexport poll_schedule_timeout Christoph Hellwig
2018-05-22 11:30 ` [PATCH 02/31] fs: cleanup do_pollfd Christoph Hellwig
2018-05-22 11:30 ` [PATCH 03/31] fs: update documentation to mention __poll_t and match the code Christoph Hellwig
2018-05-22 11:30 ` [PATCH 04/31] fs: add new vfs_poll and file_can_poll helpers Christoph Hellwig
2018-05-22 11:30 ` [PATCH 05/31] fs: introduce new ->get_poll_head and ->poll_mask methods Christoph Hellwig
2018-05-22 11:30 ` [PATCH 06/31] aio: simplify KIOCB_KEY handling Christoph Hellwig
2018-05-22 11:30 ` [PATCH 07/31] aio: simplify cancellation Christoph Hellwig
2018-05-22 11:30 ` [PATCH 08/31] aio: implement IOCB_CMD_POLL Christoph Hellwig
2018-05-22 22:05   ` Al Viro
2018-05-23  0:45     ` Al Viro
2018-05-23  0:49       ` Al Viro
2018-05-23  1:43         ` YAaioRace (was Re: [PATCH 08/31] aio: implement IOCB_CMD_POLL) Al Viro
2018-05-22 11:30 ` Christoph Hellwig [this message]
2018-05-22 11:30 ` [PATCH 10/31] net: refactor socket_poll Christoph Hellwig
2018-05-22 11:30 ` [PATCH 11/31] net: add support for ->poll_mask in proto_ops Christoph Hellwig
2018-05-22 11:30 ` [PATCH 12/31] net: remove sock_no_poll Christoph Hellwig
2018-05-22 11:30 ` [PATCH 13/31] net/tcp: convert to ->poll_mask Christoph Hellwig
2018-05-22 11:30 ` [PATCH 14/31] net/unix: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 15/31] net: convert datagram_poll users tp ->poll_mask Christoph Hellwig
2018-05-22 11:30 ` [PATCH 16/31] net/dccp: convert to ->poll_mask Christoph Hellwig
2018-05-22 11:30 ` [PATCH 17/31] net/atm: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 18/31] net/vmw_vsock: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 19/31] net/tipc: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 20/31] net/sctp: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 21/31] net/bluetooth: " Christoph Hellwig
2018-05-22 11:30 ` [PATCH 22/31] net/caif: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 23/31] net/nfc: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 24/31] net/phonet: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 25/31] net/iucv: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 26/31] net/rxrpc: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 27/31] crypto: af_alg: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 28/31] pipe: " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 29/31] eventfd: switch " Christoph Hellwig
2018-05-22 11:31 ` [PATCH 30/31] timerfd: convert " Christoph Hellwig
2018-05-22 16:59   ` Sergei Shtylyov
2018-05-22 11:31 ` [PATCH 31/31] random: " Christoph Hellwig
2018-05-22 22:07 ` aio poll and a new in-kernel poll API V12 Al Viro

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