linux-kernel - Re: [PATCH 4/3] rtmutex: Avoid barrier in rt_mutex_handle

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:	Tue, 22 Mar 2016 13:20:50 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Davidlohr Bueso <dave@...olabs.net>, tglx@...utronix.de,
	mingo@...nel.org, bigeasy@...utronix.de, umgwanakikbuti@...il.com,
	paulmck@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org,
	kmo@...erainc.com
Subject: Re: [PATCH 4/3] rtmutex: Avoid barrier in rt_mutex_handle_deadlock

On Tue, Mar 22, 2016 at 12:32:21PM +0100, Heiko Carstens wrote:
> On Tue, Mar 22, 2016 at 11:21:53AM +0100, Peter Zijlstra wrote:

> > And s390 does something entirely vile, no idea what.
> 
> For the two s390 usages tsk equals current. So it could be easily replaced
> with set_current_state().

Hmm indeed, I only saw tsk = find_task_by_pid_ns() and didn't look
further, but you do indeed have an assertion later that ensures task ==
current.

I still don't get that code though; why would you set the current task
state to UNINTERRUPTIBLE, also set need_resched, but then not call
schedule() at all.

Clearly something magical is going on and its not clear.