From: Ken Brown <kbrown@cornell.edu>
To: cygwin@cygwin.com
Subject: Re: Synchronization problem with posix_spawn
Date: Wed, 29 Jul 2020 19:12:50 -0400 [thread overview]
Message-ID: <864b3031-9fc8-beb3-ba7c-1ade4c31a288@cornell.edu> (raw)
In-Reply-To: <b1992e8b-d2e8-9c44-8f93-a270d5a879ed@cornell.edu>
On 7/29/2020 4:17 PM, Ken Brown via Cygwin wrote:
> posix_spawn(p) returns before the spawned process is fully up and running. As a
> result, the spawned process can fail to receive signals. The attached test case
> illustrates the problem. It spawns a sleep process and then tries to kill it.
> On exit, the sleep process is still running.
>
> The following excerpts from the strace output show the issue: The SIGTERM signal
> is sent after the main program has forked a subprocess (and posix_spawnp has
> returned), but before the forked subprocess has exec'd the sleep process:
>
> 559 32069 [main] spawn_test 4125 vfork: stub called
> 257 48437 [main] spawn_test 4125 dofork: 4126 = fork()
> 754 9511 [main] spawn_test 4126 dofork: 0 = fork()
> 66 48503 [main] spawn_test 4125 kill0: kill (4126, 15)
> 44 9555 [main] spawn_test 4126 find_exec: find_exec (/usr/bin/sleep)
> 42 10835 [main] spawn_test 4126 spawnve: spawnve (/usr/bin/sleep, sleep,
> 0x8000281A0)
> 45 3149 [main] sleep 4126 child_info::ready: signalled 0x164 that I was
> ready
> 6475 21055 [main] spawn_test 4126! child_info::sync: pid 45028, WFMO
> returned 0, exit_code 0x103, res 1
> --- Process 45028 (pid: 4126) thread 41444 created
I just took a look at the source, and I see that posix_spawn was taken from
FreeBSD. Does FreeBSD have the same problem? Should applications just be aware
of this issue and insert a sleep after posix_spawn before sending signals?
Ken
next prev parent reply other threads:[~2020-07-29 23:12 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-29 20:17 Ken Brown
2020-07-29 23:12 ` Ken Brown [this message]
2020-07-30 11:59 ` Corinna Vinschen
2020-07-30 17:17 ` Corinna Vinschen
2020-07-30 23:04 ` Ken Brown
2020-07-31 8:10 ` Corinna Vinschen
2020-08-03 9:10 ` Peter Dons Tychsen
2020-08-03 10:50 ` Corinna Vinschen
2020-08-20 5:40 ` Peter Dons Tychsen
2020-08-20 12:50 ` Corinna Vinschen
2020-08-21 7:58 ` Peter Dons Tychsen
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