From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Frank Rowand <frank.rowand@am.sony.com>,
Tim Sander <tim01@vlsi.informatik.tu-darmstadt.de>,
"linux-rt-users@vger.kernel.org" <linux-rt-users@vger.kernel.org>
Subject: Re: bugsplat 3.6.7-rt18
Date: Mon, 3 Dec 2012 05:50:23 -0800 [thread overview]
Message-ID: <20121203135023.GD2605@linux.vnet.ibm.com> (raw)
In-Reply-To: <alpine.LFD.2.02.1212031051370.2701@ionos>
On Mon, Dec 03, 2012 at 10:54:02AM +0100, Thomas Gleixner wrote:
> On Fri, 30 Nov 2012, Paul E. McKenney wrote:
> > On Fri, Nov 30, 2012 at 04:15:09PM -0800, Frank Rowand wrote:
> > > > Possible unsafe locking scenario:
> > > >
> > > > CPU0
> > > > ----
> > > > lock(rcu_kthread_wq.lock.lock.wait_lock);
> > > > <Interrupt>
> > > > lock(rcu_kthread_wq.lock.lock.wait_lock);
> >
> > ???
> >
> > These are all spin_lock_irqsave() calls, so how would the interrupt
> > happen? Or do these need to be changed to raw_spinlock_t?
> >
> > Hmmm... In include/linux/wait.h, doesn't struct __wait_queue_head
> > need to have raw_spinlock_t rather than spinlock_t? Please try that
> > change and let me know what happens.
>
> No. We can't do that. The reason is that some wait queue wakeups have
> callbacks which can't be called with interrupts disabled on RT.
>
> IIRC, I restructured the RCU code in 3.0-rt so it won't be affected by
> this. I'll have a look.
I guess I am once again getting out of touch with -rt... Apologies for
the noise.
Thanx, Paul
prev parent reply other threads:[~2012-12-03 13:50 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-11-30 23:50 bugsplat 3.6.7-rt18 Tim Sander
2012-12-01 0:15 ` Frank Rowand
2012-12-01 1:59 ` Paul E. McKenney
2012-12-03 9:28 ` Tim Sander
2012-12-03 9:54 ` Thomas Gleixner
2012-12-03 13:50 ` Paul E. McKenney [this message]
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