linux-kernel - Re: [PATCH -tip 0/2] Temporary RCU fixes for notrace and hotplug CPU

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: <20090825162549.GB25058@Krystal>
Date:	Tue, 25 Aug 2009 12:25:49 -0400
From:	Mathieu Desnoyers <mathieu.desnoyers@...ymtl.ca>
To:	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>
Cc:	Ingo Molnar <mingo@...e.hu>, Lai Jiangshan <laijs@...fujitsu.com>,
	linux-kernel@...r.kernel.org, dipankar@...ibm.com,
	akpm@...ux-foundation.org, josht@...ux.vnet.ibm.com,
	dvhltc@...ibm.com, niv@...ibm.com, tglx@...utronix.de,
	peterz@...radead.org, rostedt@...dmis.org,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH -tip 0/2] Temporary RCU fixes for notrace and hotplug
	CPU

* Paul E. McKenney (paulmck@...ux.vnet.ibm.com) wrote:
> On Tue, Aug 25, 2009 at 10:00:47AM +0200, Ingo Molnar wrote:
> > 
> > btw., i'm still seeing crashes with the latest RCU bits:
> > 
> > [   20.621740] Testing event sys_enter_futex: OK
> > [   20.629738] Testing event sys_exit_futex: OK
> > [   20.637737] Testing event lock_acquire: [reboot]
> > 
> > Possibly due to infinite recursion as well. Config attached.
> 
> Color me confused...
> 
> Unless someone has a better idea, I will send in a patch that adds
> "notrace" to every RCU API member used by any file in the kernel
> that has "trace" in its name (excluding ptrace.c and rcutree_trace.c,
> of course).  This list is as follows:
> 
> 	call_rcu()
> 	call_rcu_sched()
> 	rcu_read_lock()
> 	rcu_read_unlock()
> 
> So, any better ideas?

Tracers using RCU should use the _notrace() version of read_lock/unlock.
I think the callers should be fixed rather than RCU.

Tracepoints have been designed to use the _notrace variant on the
instrumentation site. The core of tracepoint management use
call_rcu_sched(), which can be traced without any problem.

I have not followed the late tracing development as closely though, so
errors might have crept in.

Mathieu

> 
> 							Thanx, Paul

-- 
Mathieu Desnoyers
OpenPGP key fingerprint: 8CD5 52C3 8E3C 4140 715F  BA06 3F25 A8FE 3BAE 9A68
--
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/