linux-kernel - Re: [PATCH v4 3.0-rc2-tip 14/22] 14: x86: uprobes exception notifier for x86.

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Message-ID: <20110622145424.GG16471@linux.vnet.ibm.com>
Date:	Wed, 22 Jun 2011 20:24:24 +0530
From:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Ingo Molnar <mingo@...e.hu>, Steven Rostedt <rostedt@...dmis.org>,
	Linux-mm <linux-mm@...ck.org>,
	Arnaldo Carvalho de Melo <acme@...radead.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	Hugh Dickins <hughd@...gle.com>,
	Christoph Hellwig <hch@...radead.org>,
	Andi Kleen <andi@...stfloor.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Jonathan Corbet <corbet@....net>,
	Oleg Nesterov <oleg@...hat.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Roland McGrath <roland@...k.frob.com>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 3.0-rc2-tip 14/22] 14: x86: uprobes exception
 notifier for x86.

* Peter Zijlstra <peterz@...radead.org> [2011-06-21 15:32:47]:

> On Tue, 2011-06-21 at 15:31 +0200, Peter Zijlstra wrote:
> > On Tue, 2011-06-07 at 18:31 +0530, Srikar Dronamraju wrote:
> > > @@ -844,6 +845,19 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
> > >         if (thread_info_flags & _TIF_SIGPENDING)
> > >                 do_signal(regs);
> > >  
> > > +       if (thread_info_flags & _TIF_UPROBE) {
> > > +               clear_thread_flag(TIF_UPROBE);
> > > +#ifdef CONFIG_X86_32
> > > +               /*
> > > +                * On x86_32, do_notify_resume() gets called with
> > > +                * interrupts disabled. Hence enable interrupts if they
> > > +                * are still disabled.
> > > +                */
> > > +               local_irq_enable();
> > > +#endif
> > > +               uprobe_notify_resume(regs);
> > > +       } 
> > 
> > Would it make sense to do TIF_UPROBE before TIF_SIGPENDING? That way
> > when uprobe decides it ought to have send a signal we don't have to do
> > another loop through all this.
> 

Okay, 

> 
> Also, it might be good to unify x86_86 and i386 on the interrupt thing,
> instead of propagating this difference (unless of course there's a good
> reason they're different, but I really don't know this code well).

I am not sure if this has changed lately. So I will try removing the
local_irq_enable. 

Oleg, Roland, do you know why do_notify_resume() gets called with
interrupts disabled on i386? 

-- 
Thanks and Regards
Srikar
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