Re: [RFC PATCH] x86: use new exception_enter()/exception_exit() API in do_device_not_available()

[Sergey Senozhatsky <sergey.senozhatsky@gmail.com>]

On (08/29/12 00:11), Borislav Petkov wrote:
> Date: Wed, 29 Aug 2012 00:11:13 +0200
> From: Borislav Petkov <bp@alien8.de>
> To: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> Cc: Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
>  "H. Peter Anvin" <hpa@zytor.com>, x86@kernel.org, Steven Rostedt
>  <rostedt@goodmis.org>, Srikar Dronamraju <srikar@linux.vnet.ibm.com>,
>  Peter Zijlstra <a.p.zijlstra@chello.nl>, "Paul E. McKenney"
>  <paulmck@linux.vnet.ibm.com>, linux-kernel@vger.kernel.org
> Subject: Re: [RFC PATCH] x86: use new exception_enter()/exception_exit()
>  API in do_device_not_available()
> User-Agent: Mutt/1.5.21 (2010-09-15)
> 
> On Wed, Aug 29, 2012 at 12:00:47AM +0300, Sergey Senozhatsky wrote:
> >  x86: use new exception_enter()/exception_exit() API in do_device_not_available()
> > 
> >  RCU can be in extended quiescent state when do_device_not_available() called.
> > 
> > [  676.400274] RCU used illegally from idle CPU!
> > [  676.400274] rcu_scheduler_active = 1, debug_locks = 0
> > [  676.400278] RCU used illegally from extended quiescent state!
> > [  676.400282] 2 locks held by sed/9468:
> > [  676.400285]  #0:  (&rq->lock){-.-.-.}, at: [<ffffffff814c67cf>] __schedule+0x1c0/0x992
> > [  676.400304]  #1:  (rcu_read_lock){.+.+..}, at: [<ffffffff8106a880>] cpuacct_charge+0x27/0x1e0
> > [  676.400321] 
> > [  676.400329] Call Trace:
> > [  676.400340]  [<ffffffff8108933a>] lockdep_rcu_suspicious+0x109/0x112
> > [  676.400347]  [<ffffffff8106a8f7>] cpuacct_charge+0x9e/0x1e0
> > [  676.400353]  [<ffffffff8106a880>] ? cpuacct_charge+0x27/0x1e0
> > [  676.400359]  [<ffffffff814c67cf>] ? __schedule+0x1c0/0x992
> > [  676.400366]  [<ffffffff8106d525>] update_curr+0x159/0x200
> > [  676.400375]  [<ffffffff8100a04f>] ? init_fpu+0x4e/0x8f
> > [  676.400382]  [<ffffffff8106e0da>] put_prev_task_fair+0x2a/0xac
> > [  676.400388]  [<ffffffff814c69a7>] __schedule+0x398/0x992
> > [  676.400397]  [<ffffffff810b4f0a>] ? rcu_irq_exit+0x83/0x99
> > [  676.400404]  [<ffffffff814c8bf0>] ? retint_restore_args+0x13/0x13
> > [  676.400411]  [<ffffffff810889e9>] ? lock_is_held+0x2d/0xa5
> > [  676.400414]  [<ffffffff8100a04f>] ? init_fpu+0x4e/0x8f
> > [  676.400417]  [<ffffffff81065d0a>] __cond_resched+0x28/0x34
> > [  676.400420]  [<ffffffff814c701a>] _cond_resched+0x2e/0x35
> > [  676.400425]  [<ffffffff8111cad4>] kmem_cache_alloc+0x4c/0x1c5
> > [  676.400430]  [<ffffffff810021ff>] ? math_state_restore+0x1f/0xdc
> > [  676.400433]  [<ffffffff8100a04f>] init_fpu+0x4e/0x8f
> > [  676.400437]  [<ffffffff8100220e>] math_state_restore+0x2e/0xdc
> > [  676.400440]  [<ffffffff814c982e>] do_device_not_available+0xe/0x10
> > [  676.400445]  [<ffffffff814d161b>] device_not_available+0x1b/0x20
> > 
> > 
> > Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
> > 
> > ---
> > 
> >  arch/x86/kernel/traps.c | 2 ++
> >  1 file changed, 2 insertions(+)
> > 
> > diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c
> > index ab82cbd..dff3e72 100644
> > --- a/arch/x86/kernel/traps.c
> > +++ b/arch/x86/kernel/traps.c
> > @@ -654,7 +654,9 @@ do_device_not_available(struct pt_regs *regs, long error_code)
> >  		return;
> >  	}
> >  #endif
> > +	exception_enter(regs);
> >  	math_state_restore(); /* interrupts still off */
> > +	exception_enter(regs);
> 
> Shouldn't that be exception_exit actually?
>

OH! NO WAY I did that mistake! That was some last minute in-text-editor
changes and somehow I screwed this up. Will re-send in a second.

Sorry, and thank you.
 
	-ss