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: <20081118144751.GA30358@elte.hu>
Date:	Tue, 18 Nov 2008 15:47:51 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Heiko Carstens <heiko.carstens@...ibm.com>,
	linux-kernel@...r.kernel.org,
	Martin Schwidefsky <schwidefsky@...ibm.com>
Subject: Re: ftrace: preemptoff selftest not working


* Steven Rostedt <rostedt@...dmis.org> wrote:

> 
> On Tue, 18 Nov 2008, Ingo Molnar wrote:
> > 
> > * Steven Rostedt <rostedt@...dmis.org> wrote:
> > 
> > > > Hence the trace buffer will be empty. The patch below makes the 
> > > > selftests working for me, since then they run in preemptible 
> > > > context. But it is ugly and I'm not proposing it for upstream ;)
> > > > 
> > > > Just wanted to make you aware that there is a bug.
> > > 
> > > Yep, this might be a better answer than what I put into linux-tip 
> > > (and my git repo).
> > > 
> > > See:
> > > 
> > >   ftrace: force pass of preemptoff selftest
> > > 
> > > The cause of the bug was the conversion of the BKL back to a 
> > > spinlock, and making it non preempt.  The initcall code is called 
> > > with the BKL applied which now means it can not preempt. This breaks 
> > > the preempt tracer selftest.
> > > 
> > > My solution was to just force a pass if this is detected. Perhaps 
> > > moving the test might be better.
> > 
> > it would be better to just drop the BKL in that selftest. (or in all 
> > selftests - an elevated preempt count will skew a number of things)
> 
> I have no problem with that, but does the BKL play any role for 
> being held? I have no idea why it is taken in boot up, so I'm 
> hestiant to touch it.

we can drop it in selected initcalls just fine. Its only role is 
old-style init functions racing with other async contexts of 
themselves.

	Ingo
--
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/

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ