linux-kernel - Re: Q: schedule() and implied barriers on arm64

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: <20151019152108.GC11226@e104818-lin.cambridge.arm.com>
Date:	Mon, 19 Oct 2015 16:21:08 +0100
From:	Catalin Marinas <catalin.marinas@....com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Peter Zijlstra <peterz@...radead.org>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Will Deacon <will.deacon@....com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Q: schedule() and implied barriers on arm64

On Mon, Oct 19, 2015 at 09:06:05AM +0200, Ingo Molnar wrote:
> * Peter Zijlstra <peterz@...radead.org> wrote:
> 
> > In any case, its all moot now, since Paul no longer requires schedule() to imply 
> > a full barrier.
> >
> > [...]
> 
> Nevertheless from a least-surprise POV it might be worth guaranteeing it, because 
> I bet there's tons of code that assumes that schedule() is a heavy operation and 
> it's such an easy mistake to make. Since we are so close to having that guarantee, 
> we might as well codify it?

FWIW, the arm64 __switch_to() has a heavy barrier (DSB) but the reason
for this was to cope with potentially interrupted cache or TLB
maintenance (which require a DSB on the same CPU) and thread migration
to another CPU.

-- 
Catalin

--
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/