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From: Cyrill Gorcunov <gorcunov@gmail.com>
To: Konstantin Osipov <kostja.osipov@gmail.com>
Cc: tml <tarantool-patches@dev.tarantool.org>
Subject: Re: [Tarantool-patches] [PATCH 1/5] popen: Introduce a backend engine
Date: Sat, 30 Nov 2019 10:36:28 +0300	[thread overview]
Message-ID: <20191130073628.GP19879@uranus> (raw)
In-Reply-To: <20191130041405.GB31199@atlas>

On Sat, Nov 30, 2019 at 07:14:05AM +0300, Konstantin Osipov wrote:
> * Cyrill Gorcunov <gorcunov@gmail.com> [19/11/30 07:03]:
> > Once we sart using non-blocking IO the read() could return -EAGAIN.
> > I think I need to find out how python is handling this situation,
> > is their read is blocking or not.
> 
> Take a look at how coio works. It adds the descriptor to the event
> loop and yields the current fiber.

I will, thanks! You know there is another problem with nonblocking
descriptors: consider a case where user runs a script like in my
test "input=''; read -n 5 input; echo $input". If you run it inside
a regular terminal the script will wait for input to apprear first,
but if we provide nonblocking pipe the "read" will exit with
-EAGAIN and script fail. Actually my first implementations have been
creating pipes with O_NONBLOCK and since such test case start to fail
I dropped O_NONBLOCK then.

> > The eio reaps children itself, ie calls for wait. Thus imagine a situation,
> > we start killing the process like
> > 
> > popen_kill(handle)
> > 	...
> > 	kill(handle->pid)
> > 	...
> > 
> > but before we reach kill() this process exited by self or killed
> > by a user on the node. The signal handler sets pid = -1 and we
> > call kill(-1). Which is wrong of course.
> 
> Can't you check the pid > 0 before you send the signal?

This won't work, a signal can interrupt us in any moment and
set the pid to -1 between if() and kill().

  reply	other threads:[~2019-11-30  7:36 UTC|newest]

Thread overview: 34+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-11-28 20:45 [Tarantool-patches] [PATCH 0/5] popen: Add ability to run external process Cyrill Gorcunov
2019-11-28 20:45 ` [Tarantool-patches] [PATCH 1/5] popen: Introduce a backend engine Cyrill Gorcunov
2019-11-29  5:52   ` Konstantin Osipov
2019-11-29  9:57     ` Cyrill Gorcunov
2019-11-29  5:59   ` Konstantin Osipov
2019-11-29  9:40     ` Cyrill Gorcunov
2019-11-29 11:19       ` Konstantin Osipov
2019-11-29 11:36         ` Cyrill Gorcunov
2019-11-29 14:50           ` Konstantin Osipov
2019-11-29 15:14             ` Cyrill Gorcunov
2019-11-29 15:17               ` Cyrill Gorcunov
2019-11-29 18:31               ` Konstantin Osipov
2019-11-29 19:17                 ` Cyrill Gorcunov
2019-11-29 22:36                   ` Cyrill Gorcunov
2019-11-30  4:21                     ` Konstantin Osipov
2019-11-30  7:48                       ` Cyrill Gorcunov
2019-11-30  4:14                   ` Konstantin Osipov
2019-11-30  7:36                     ` Cyrill Gorcunov [this message]
2019-11-30 10:04                       ` Konstantin Osipov
2019-11-30 10:47                         ` Cyrill Gorcunov
2019-11-30 10:54                           ` Cyrill Gorcunov
2019-11-30 12:16                             ` Cyrill Gorcunov
2019-11-30 20:30                             ` Konstantin Osipov
2019-11-30 20:36                               ` Cyrill Gorcunov
2019-12-13  2:50   ` Alexander Turenko
2019-11-28 20:45 ` [Tarantool-patches] [PATCH 2/5] lua/fio: Add lbox_fio_push_error as a separate helper Cyrill Gorcunov
2019-11-29  6:02   ` Konstantin Osipov
2019-11-29  9:47     ` Cyrill Gorcunov
2019-11-29 11:22       ` Konstantin Osipov
2019-11-29 11:42         ` Cyrill Gorcunov
2019-11-29 14:51           ` Konstantin Osipov
2019-11-28 20:45 ` [Tarantool-patches] [PATCH 3/5] popen/fio: Merge popen engine into fio internal module Cyrill Gorcunov
2019-11-28 20:45 ` [Tarantool-patches] [PATCH 4/5] popen/fio: Implement lua interface for a popen object Cyrill Gorcunov
2019-11-28 20:45 ` [Tarantool-patches] [PATCH 5/5] test: Add app/popen test Cyrill Gorcunov

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