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From: Szabolcs Nagy <nsz@port70.net>
To: Florian Weimer <fweimer@redhat.com>
Cc: Nick Peng <pymumu@gmail.com>, musl@lists.openwall.com
Subject: Re: [musl] BUG: Calling readdir/dirfd after vfork will cause deadlock.
Date: Mon, 27 Jun 2022 10:37:37 +0200	[thread overview]
Message-ID: <20220627083737.GW1320090@port70.net> (raw)
In-Reply-To: <87k092eem6.fsf@oldenburg.str.redhat.com>

* Florian Weimer <fweimer@redhat.com> [2022-06-27 09:42:57 +0200]:
> * Szabolcs Nagy:
> 
> > * Nick Peng <pymumu@gmail.com> [2022-06-25 11:40:17 +0800]:
> >> Description:  After vfork, calling functions such as readdir/dirfd may
> >> cause deadlock. GNU C is OK.
> >
> > why do you think "GNU C is OK"? is this from some real software?
> 
> glibc supports opendir/readdir/closedir after vfork as an extension.
> The JVM depends on it.

how does that work? i think glibc just calls vfork syscall (or
clone(CLONE_VM|CLONE_VFORK)) from asm and opendir allocates.
so i'd expect a deadlock where the parent waits for the child
to exec while holding the malloc lock.

> 
> Of course it's undefined, but I really see no way around keeping support
> for it for the time being.
> 
> Thanks,
> Florian

  reply	other threads:[~2022-06-27  8:37 UTC|newest]

Thread overview: 13+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-06-25  3:40 Nick Peng
2022-06-25 12:51 ` Szabolcs Nagy
2022-06-27  4:05   ` Nick Peng
2022-06-27 10:38     ` Laurent Bercot
2022-06-27 14:21     ` Rich Felker
2022-06-27 14:29     ` Markus Wichmann
2022-06-27  7:42   ` Florian Weimer
2022-06-27  8:37     ` Szabolcs Nagy [this message]
2022-06-27  9:23       ` Florian Weimer
2022-06-27 17:33         ` Szabolcs Nagy
2022-06-25 12:56 ` Alex Xu (Hello71)
2022-06-27  7:44   ` Florian Weimer
2022-06-27 12:28     ` Alex Xu (Hello71)

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