linux-kernel - Re: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write

lists.openwall.net		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 linux-cve-announce 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:	Sun, 19 Jan 2014 11:56:02 -0800
From:	Linus Torvalds <torvalds@...ux-foundation.org>
To:	Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	Matt Turner <mattst88@...il.com>,
	Waiman Long <waiman.long@...com>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	Ivan Kokshaysky <ink@...assic.park.msu.ru>,
	Daniel J Blueman <daniel@...ascale.com>,
	Richard Henderson <rth@...ddle.net>
Subject: Re: [PATCH v8 4/4] qrwlock: Use smp_store_release() in write_unlock()

On Sun, Jan 19, 2014 at 12:04 AM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> wrote:
>
> OK, another approach would be to never add "select ARCH_USE_QUEUE_RWLOCK"
> on Alpha, at least if the queued rwlocks really do want to atomically
> manipulate bytes.  After all, the Alpha systems that I know about don't
> have enough CPUs to make queued rwlocks necessary anyway.
>
> Much simpler solution!
>
> Is this what you were getting at, or am I missing your point?

You're missing something.

Just make the "writer" field be an "int" on little-endian archiectures
(like alpha).

There is no reason for that field to be a "char" to begin with, as far
as I can tell, since the padding of the structure means that it
doesn't save any space. But even if that wasn't true, we could make an
arch-specific type for "minimum type for locking".

So my *point* was that it should be easy enough to just make sure that
any data structures used for locking have types that are appropriate
for that locking.

                      Linus
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/