linux-kernel - Re: [patch] x86: unify/rewrite SMP TSC sync code

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]

Message-Id: <200611241813.13205.ak@suse.de>
Date:	Fri, 24 Nov 2006 18:13:13 +0100
From:	Andi Kleen <ak@...e.de>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	linux-kernel@...r.kernel.org, Andrew Morton <akpm@...l.org>,
	Arjan van de Ven <arjan@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [patch] x86: unify/rewrite SMP TSC sync code


> make the TSC synchronization code more robust, and unify it between 
> x86_64 and i386.
> 
> The biggest change is the removal of the 'fix up TSCs' code on x86_64 
> and i386, in some rare cases it was /causing/ time-warps on SMP systems.

On x86-64 I don't think it can since it doesn't check anymore on sync Intel.

> The new code only checks for TSC asynchronity - and if it can prove a 
> time-warp (if it can observe the TSC going backwards when going from one 
> CPU to another within a critical section), then the TSC clock-source is 
> turned off.

The trouble is that people are using the RDTSC anyways even if the
kernel doesn't. So some synchronization is probably a good idea.

-Andi
-
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/