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 01:36:50 +0300 [thread overview]
Message-ID: <20191129223650.GO19879@uranus> (raw)
In-Reply-To: <20191129191708.GN19879@uranus>
On Fri, Nov 29, 2019 at 10:17:08PM +0300, Cyrill Gorcunov wrote:
> >
> > We discussed this and pid reuse is impossible unless you collect
> > the status of a child. You can easily mark the handle as dead as
> > soon as you get sigchild and collect it. I don't see any issue
> > here.
>
> 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.
You know, without signal blocking I fear we simply won't be able
to tack children properly. Look here is an example
pid = vfork();
if (pid == 0) {
_exit(1);
here sigchld already delivered to the libev
and it reaped it, vanishing from the system
so that anyother application can reuse it
} else {
ev_child_init(&handle->ev_sigchld, ev_sigchld_cb, pid, 0);
ev_child_start(EV_DEFAULT_ &handle->ev_sigchld);
but pid already dead and reused by someone else,
as I said wait() called under the hood, we simply
don't control it
}
and without signal blocking we can't order pid livetime anyhow.
You know in my first versions I setup ev_child_init with pid=0
and been expecting the sgnal handler catches _any_ sigchld but
it didn't work :/ Thus early _exit(1) in child process was
simply invisible to the rest of tarantool code.
next prev parent reply other threads:[~2019-11-29 22:36 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 [this message]
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
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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