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Message-ID: <20260723213451.GE3520958@port70.net>
Date: Thu, 23 Jul 2026 23:34:51 +0200
From: Szabolcs Nagy <nsz@...t70.net>
To: Jake Adamson <jakeadamson@...gle.com>
Cc: musl@...ts.openwall.com
Subject: Re: Question: number of arguments of musl's membarrier does
not match Linux syscall
* Jake Adamson <jakeadamson@...gle.com> [2026-07-23 13:34:02 -0700]:
> Hi I'm adding membarrier() to Android's Bionic and I noticed that
> there are a different number of arguments in Musl than in Linux’s
> system call. Is there a reason for that and is there any nuisance that
> I should be thinking about when adding it? And do you plan on adding
> the cpu_id argument?
google broke it (silently)
https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=2a36ab717e8fe678d98f81c14a0b124712719840
good example why libc does not like wrapping new syscalls
(the contract is not documented and reasonable assumptions
get broken instead of using a new syscall number)
now it has to be var arg if we want backward compat.
>
> Linux: int cmd, unsigned int flags, int cpu_id
> https://man7.org/linux/man-pages/man2/membarrier.2.html
>
>
> Musl: int cmd, int flags
> https://git.musl-libc.org/cgit/musl/tree/src/linux/membarrier.c
>
> Jake Adamson
> Android Native Tools and Libraries, Software Engineer
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