lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  PHC 
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Date:	Tue, 6 Oct 2015 02:17:36 +0000 (UTC)
From:	Mathieu Desnoyers <>
To:	Rusty Russell <>
Cc:	Andrew Morton <>,, linux-api <>
Subject: Re: [PATCH 0/3] sys_membarrier (x86, generic)

----- On Oct 5, 2015, at 7:21 PM, Rusty Russell wrote:

> Mathieu Desnoyers <> writes:
>> Hi Andrew,
>> Here is a repost of sys_membarrier, rebased on top of Linus commit
>> c4b5fd3fb2058b650447372472ad24e2a989f9f6 without any change since the
>> last v19 post other that proceeding to further testing. When merging
>> with other system calls, system call number conflicts should be quite
>> straightforward to handle, there is nothing special there.
> Hi Mathieu,
>        Great to see this go in!  One small note: it talks about
> threads, but membarrier as currently implemented would cover any shared
> memory.  If you plan to optimize in future, that might not be the case:
> we'd want an address argument for those cases?

Hi Rusty,

Indeed, the current membarrier implementation only supports
the MEMBARRIER_CMD_SHARED flag, which works even with shared
memory across processes. If we ever want to optimize that for
single-process, multi-threaded cases, we would have to add
a new flag (e.g. MEMBARRIER_CMD_PRIVATE). This is quite
similar to what already exists in the futex system call.

I'm not sure I fully understand where the address argument
you are describing would be useful. So far, I see two
main use-cases: we either interact with memory that is
local to a single process, or with memory shared across

We could indeed think about sending a membarrier to all
processes using a specific shared memory area (hence the
possible need for an address argument). This could eventually
be supported by adding a specific flag for this (e.g.
MEMBARRIER_CMD_SHM), which would indicate that an extra
parameter is provided (an address).

Thoughts ?

Thanks for the feedback!


> Cheers,
> Rusty.

Mathieu Desnoyers
EfficiOS Inc.
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

Powered by blists - more mailing lists