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From: Anthony PERARD <anthony.perard@citrix.com>
To: Ian Jackson <ian.jackson@citrix.com>
Cc: xen-devel@lists.xenproject.org, Wei Liu <wei.liu2@citrix.com>
Subject: Re: [PATCH v7 01/14] libxl: Enhance libxl__sendmsg_fds to deal with EINTR and EWOULDBLOCK
Date: Fri, 4 Jan 2019 12:07:23 +0000	[thread overview]
Message-ID: <20190104120723.GC1508@perard.uk.xensource.com> (raw)
In-Reply-To: <23580.63725.92336.625926@mariner.uk.xensource.com>

On Fri, Dec 21, 2018 at 02:30:05PM +0000, Ian Jackson wrote:
> Anthony PERARD writes ("[PATCH v7 01/14] libxl: Enhance libxl__sendmsg_fds to deal with EINTR and EWOULDBLOCK"):
> > This patch change the behavior of libxl__sendmsg_fds to retry sendmsg on
> > EINTR error.
> > 
> > This patch also allow a caller of libxl__sendmsg_fds to deal with
> > EWOULDBLOCK. The function now requires to send only 1 byte of data so
> > that when dealing with non-blocking fds a EWOULDBLOCK error would mean
> > that the fds haven't been sent yet. Current caller already send only 1
> > byte.
> 
> Even with a blocking fd, sendmsg may in principle report a short
> write.  (So the commit message should talk about short writes in
> general.)

I have rewrite the commit message like this:

This patch change the behavior of libxl__sendmsg_fds to retry sendmsg on
EINTR error and return an error on short writes.

This patch allow a caller of libxl__sendmsg_fds to deal with EWOULDBLOCK
and short writes. The function now requires to send only 1 byte of data
so that when dealing with non-blocking fds a EWOULDBLOCK error would
mean that the fds haven't been sent yet. Current caller already send
only 1 byte.


> > Notes:
> >     v7:
> >         always assert datalen == 1, but only fail when sendmsg haven't send
> >         everything (r != datalen)
> >         check sendmsg return value on success as well (check for short write)
> 
> Rather than having a function which takes an argument which
> mandatorily takes the value 1, how about simply deleting that
> argument ?

I'll add a new patch to do that at the end of the series.

> You can do that in a followup patch if you like.  In the meantime:
> 
> Acked-by: Ian Jackson <ian.jackson@eu.citrix.com>

Thanks,

-- 
Anthony PERARD

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  reply	other threads:[~2019-01-04 12:07 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-11-23 13:53 [PATCH v7 00/14] libxl: Enable save/restore/migration of a restricted QEMU + libxl__ev_qmp_* Anthony PERARD
2018-11-23 13:53 ` [PATCH v7 01/14] libxl: Enhance libxl__sendmsg_fds to deal with EINTR and EWOULDBLOCK Anthony PERARD
2018-12-21 14:30   ` Ian Jackson
2019-01-04 12:07     ` Anthony PERARD [this message]
2019-01-04 15:58       ` Ian Jackson
2018-11-23 13:53 ` [PATCH v7 02/14] libxl_qmp: Separate QMP message generation from qmp_send_prepare Anthony PERARD
2018-12-21 14:32   ` Ian Jackson
2018-11-23 13:53 ` [PATCH v7 03/14] libxl_qmp: Change qmp_qemu_check_version to compare version Anthony PERARD
2018-11-23 13:53 ` [PATCH v7 04/14] libxl: Add wrapper around libxl__json_object_to_json JSON Anthony PERARD
2018-12-21 14:33   ` Ian Jackson
2018-11-23 13:53 ` [PATCH v7 05/14] libxl: Design of an async API to issue QMP commands to QEMU Anthony PERARD
2018-11-23 13:53 ` [PATCH v7 06/14] libxl_qmp: Implementation of libxl__ev_qmp_* Anthony PERARD
2018-12-21 15:36   ` Ian Jackson
2018-12-21 15:59     ` Ian Jackson
2019-01-03 12:40     ` Anthony PERARD
2019-01-04 11:14       ` Anthony PERARD
2019-01-04 11:21       ` Ian Jackson
2019-01-04 11:41         ` Anthony PERARD
2018-11-23 13:53 ` [PATCH v7 07/14] libxl_exec: Add libxl__spawn_initiate_failure Anthony PERARD
2018-12-21 15:57   ` Ian Jackson
2018-11-23 13:53 ` [PATCH v7 08/14] libxl: Add init/dispose of for libxl__domain_build_state Anthony PERARD
2018-12-21 16:00   ` Ian Jackson
2018-11-23 13:53 ` [PATCH v7 09/14] libxl_dm: Pre-open QMP socket for QEMU Anthony PERARD
2018-12-21 16:01   ` Ian Jackson
2018-11-23 13:53 ` [PATCH v7 10/14] libxl: Add dmss_init/dispose for libxl__dm_spawn_state Anthony PERARD
2018-11-23 13:53 ` [PATCH v7 11/14] libxl: QEMU startup sync based on QMP Anthony PERARD
2018-12-21 16:03   ` Ian Jackson
2018-11-23 13:53 ` [PATCH v7 12/14] libxl_qmp: Store advertised QEMU version in libxl__ev_qmp Anthony PERARD
2018-12-21 16:05   ` Ian Jackson
2018-11-23 13:53 ` [PATCH v7 13/14] libxl: Change libxl__domain_suspend_device_model() to be async Anthony PERARD
2018-12-21 16:09   ` Ian Jackson
2018-11-23 13:53 ` [PATCH v7 14/14] libxl: Re-implement domain_suspend_device_model using libxl__ev_qmp Anthony PERARD
2018-12-21 16:12   ` Ian Jackson
2018-11-23 13:57 ` [PATCH v7 00/14] libxl: Enable save/restore/migration of a restricted QEMU + libxl__ev_qmp_* Anthony PERARD
2018-12-21 16:13 ` Ian Jackson

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