From: Alexey Izbyshev <izbyshev@ispras.ru>
To: musl@lists.openwall.com
Cc: Szabolcs Nagy <nsz@port70.net>
Subject: Re: __synccall: deadlock and reliance on racy /proc/self/task
Date: Sun, 10 Feb 2019 01:29:32 +0300 [thread overview]
Message-ID: <a59e1e62e62949e5b99e74188bea8645@ispras.ru> (raw)
In-Reply-To: <20190209214045.GO21289@port70.net>
On 2019-02-10 00:40, Szabolcs Nagy wrote:
> the attached patch fixes the issue on my machine.
> i don't know if this is just luck.
>
> the assumption is that if /proc/self/task is read twice such that
> all tids in it seem to be active and caught, then all the active
> threads of the process are caught (no new threads that are already
> started but not visible there yet)
>
> anyway i had to retry until there are no exiting threads in dir to
> reliably fix the deadlock.
Unfortunately, on 4.15.x kernel, I've got both the deadlock (~23000
iterations) and the mismatch (after I removed kill() loop; ~19000
iterations).
On 4.4.x, it took ~30 mln. iterations to get the mismatch (on
deadlock-free version):
--iter: 30198000
--iter: 30199000
mismatch: tid 539: 1000 != 0
Alexey
next prev parent reply other threads:[~2019-02-09 22:29 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-02-02 21:40 Alexey Izbyshev
2019-02-07 18:36 ` Rich Felker
2019-02-08 18:14 ` Alexey Izbyshev
2019-02-08 18:33 ` Rich Felker
2019-02-09 16:21 ` Szabolcs Nagy
2019-02-09 18:33 ` Alexey Izbyshev
2019-02-09 21:40 ` Szabolcs Nagy
2019-02-09 22:29 ` Alexey Izbyshev [this message]
2019-02-10 0:52 ` Rich Felker
2019-02-10 1:16 ` Szabolcs Nagy
2019-02-10 1:20 ` Rich Felker
2019-02-10 4:01 ` Rich Felker
2019-02-10 12:32 ` Szabolcs Nagy
2019-02-10 15:05 ` Rich Felker
2019-02-10 12:15 ` Alexey Izbyshev
2019-02-10 14:57 ` Rich Felker
2019-02-10 21:04 ` Alexey Izbyshev
2019-02-12 18:48 ` Rich Felker
2019-02-21 0:41 ` Rich Felker
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