From: Christoph Hellwig <hch@lst.de>
To: Benjamin LaHaise <ben@communityfibre.ca>
Cc: Christoph Hellwig <hch@lst.de>,
viro@zeniv.linux.org.uk, 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: Re: aio poll, io_pgetevents and a new in-kernel poll API V4
Date: Fri, 26 Jan 2018 13:31:23 +0100 [thread overview]
Message-ID: <20180126123123.GA6985@lst.de> (raw)
In-Reply-To: <20180125201025.GN23664@kvack.org>
On Thu, Jan 25, 2018 at 03:10:25PM -0500, Benjamin LaHaise wrote:
> I implemented something similar back in December, but did so without
> changing the in-kernel poll API. See below for the patch that implements
> it. Is changing the in-kernel poll API really desirable given how many
> drivers that will touch?
I had various previous versions that did not touch the driver API,
but there are a couple issues with that:
(1) you cannot make the API race free. With the existing convoluted
poll_table_struct-based API you can't check for pending items
before adding yourself to the waitqueue in a race free manner.
(2) you cannot make the submit non-blocking without deferring to
a workqueue or similar and thus incurring another context switch
(3) you cannot deliver events from the wakeup callback, incurring
another context switch, this time in the wakeup path that actually
matters for some applications
(3) the in-kernel poll API really is broken to start with and needs
to be fixed anyway. I'd rather rely on that instead of working
around decades old cruft that has no reason to exist.
prev parent reply other threads:[~2018-01-26 12:31 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-22 20:12 aio poll, io_pgetevents and a new in-kernel poll API V4 Christoph Hellwig
2018-01-22 20:12 ` [PATCH 01/36] aio: don't print the page size at boot time Christoph Hellwig
2018-01-22 20:12 ` [PATCH 02/36] aio: remove an outdated comment in aio_complete Christoph Hellwig
2018-01-22 20:12 ` [PATCH 03/36] aio: refactor read/write iocb setup Christoph Hellwig
2018-01-22 20:12 ` [PATCH 04/36] aio: sanitize ki_list handling Christoph Hellwig
2018-01-22 20:12 ` [PATCH 05/36] aio: simplify cancellation Christoph Hellwig
2018-01-22 20:12 ` [PATCH 06/36] aio: delete iocbs from the active_reqs list in kiocb_cancel Christoph Hellwig
2018-01-22 20:12 ` [PATCH 07/36] aio: add delayed cancel support Christoph Hellwig
2018-01-22 20:12 ` [PATCH 08/36] aio: implement io_pgetevents Christoph Hellwig
2018-01-24 19:24 ` Jeff Moyer
2018-01-22 20:12 ` [PATCH 09/36] fs: unexport poll_schedule_timeout Christoph Hellwig
2018-01-22 20:12 ` [PATCH 10/36] fs: cleanup do_pollfd Christoph Hellwig
2018-01-22 20:12 ` [PATCH 11/36] fs: update documentation for __poll_t Christoph Hellwig
2018-01-22 20:12 ` [PATCH 12/36] fs: add new vfs_poll and file_can_poll helpers Christoph Hellwig
2018-01-22 20:12 ` [PATCH 13/36] fs: introduce new ->get_poll_head and ->poll_mask methods Christoph Hellwig
2018-01-22 20:12 ` [PATCH 14/36] aio: implement IOCB_CMD_POLL Christoph Hellwig
2018-01-24 19:24 ` Jeff Moyer
2018-01-22 20:12 ` [PATCH 15/36] net: refactor socket_poll Christoph Hellwig
2018-01-22 20:12 ` [PATCH 16/36] net: add support for ->poll_mask in proto_ops Christoph Hellwig
2018-01-22 20:12 ` [PATCH 17/36] net: remove sock_no_poll Christoph Hellwig
2018-01-22 20:12 ` [PATCH 18/36] net/tcp: convert to ->poll_mask Christoph Hellwig
2018-01-22 20:12 ` [PATCH 19/36] net/unix: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 20/36] net: convert datagram_poll users tp ->poll_mask Christoph Hellwig
2018-01-22 20:12 ` [PATCH 21/36] net/dccp: convert to ->poll_mask Christoph Hellwig
2018-01-22 20:12 ` [PATCH 22/36] net/atm: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 23/36] net/vmw_vsock: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 24/36] net/tipc: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 25/36] net/sctp: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 26/36] net/bluetooth: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 27/36] net/caif: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 28/36] net/nfc: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 29/36] net/phonet: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 30/36] net/iucv: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 31/36] net/rxrpc: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 32/36] crypto: af_alg: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 33/36] pipe: " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 34/36] eventfd: switch " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 35/36] timerfd: convert " Christoph Hellwig
2018-01-22 20:12 ` [PATCH 36/36] random: " Christoph Hellwig
2018-01-25 20:10 ` aio poll, io_pgetevents and a new in-kernel poll API V4 Benjamin LaHaise
2018-01-26 12:31 ` Christoph Hellwig [this message]
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