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Message-ID: <20201015085024.GR2947641@port70.net>
Date: Thu, 15 Oct 2020 10:50:24 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: Alexey Izbyshev <izbyshev@...ras.ru>
Cc: musl@...ts.openwall.com
Subject: Re: Why is setrlimit() considered to have per-thread effect?
* Alexey Izbyshev <izbyshev@...ras.ru> [2020-10-15 08:01:00 +0300]:
> Commit 544ee752cd[1] claims that setrlimit() is per-thread on Linux,
> similarly to setxid() calls, so it should be called via __synccall(). But
> this appears to be wrong: the kernel code operates on tsk->signal[2], which
> is a per-thread-group structure. Glibc doesn't call setrlimit() for each
> thread either. Am I missing something?
note that prlimit does not have synccall in
musl: the kernel implemented the per process
rlimit setting when prlimit was added.
(i think this is linux commit
1c1e618ddd15f69fd87ccea596769f78c8065504 )
but older kernels don't have that.
>
> Tangentially, setgroups() is not called via __synccall(), though it does
> have per-thread effect. Is this intentional?
that may be a bug, but it's not a posix api
so not a conformance issue, but a linux issue:
if other linux libcs don't do synccall then
that's the defacto interface contract.
>
> Alexey
>
> [1] https://git.musl-libc.org/cgit/musl/commit/?id=544ee752cd38febfa3aa3798b4dfb6fabd13846b
> [2] https://elixir.bootlin.com/linux/v5.9/source/kernel/sys.c#L1566
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