linux-kernel - Re: schedule() && prev/current (Was: [PATCH 3/3] Make get_current() __attribute_

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:	Wed, 19 May 2010 08:21:19 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	David Howells <dhowells@...hat.com>, Ingo Molnar <mingo@...e.hu>,
	Yong Zhang <yong.zhang0@...il.com>, linux-arch@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: schedule() && prev/current (Was: [PATCH 3/3] Make
 get_current() __attribute__((const)))

On Tue, 2010-05-18 at 23:22 +0200, Oleg Nesterov wrote:

> And, looking at this patch I think that schedule() can be simplified
> a little bit.
> 
> "sched: Reassign prev and switch_count when reacquire_kernel_lock() fail"
> commit 6d558c3ac9b6508d26fd5cadccce51fc9d726b1c says:
> 
> 	Assume A->B schedule is processing,
> 	...
> 	Then on B's context,
> 	...
> 	prev and switch_count are related to A
> 
> How so? switch_count - yes, we should change it. But prev must be
> equal to B, and it must be equal to current. When we return from
> switch_to() registers/stack should be restored correctly, so we
> can do

What if schedule() got called at a different stack depth than we are
now?

I don't think we can assume anything about the stack context we just
switched to.
--
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/