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Subject: Re: [PATCH v5 3.1.0-rc4-tip 13/26] x86: define a x86 specific
 exception notifier.
From: Peter Zijlstra <peterz@infradead.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
        Linux-mm <linux-mm@kvack.org>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Andi Kleen <andi@firstfloor.org>, Hugh Dickins <hughd@google.com>,
        Christoph Hellwig <hch@infradead.org>,
        Jonathan Corbet <corbet@lwn.net>, Thomas Gleixner <tglx@linutronix.de>,
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        Oleg Nesterov <oleg@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        Jim Keniston <jkenisto@linux.vnet.ibm.com>,
        Roland McGrath <roland@hack.frob.com>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Andrew Morton <akpm@linux-foundation.org>
Date: Tue, 27 Sep 2011 13:46:15 +0200
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On Mon, 2011-09-26 at 21:22 +0530, Srikar Dronamraju wrote:
> * Peter Zijlstra <peterz@infradead.org> [2011-09-26 16:19:51]:
> 
> > On Tue, 2011-09-20 at 17:32 +0530, Srikar Dronamraju wrote:
> > > @@ -820,6 +821,19 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
> > >                 mce_notify_process();
> > >  #endif /* CONFIG_X86_64 && CONFIG_X86_MCE */
> > >  
> > > +       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);
> > > +       }
> > > +
> > >         /* deal with pending signal delivery */
> > >         if (thread_info_flags & _TIF_SIGPENDING)
> > >                 do_signal(regs); 
> > 
> > It would be good to remove this difference between i386 and x86_64.
> 
> 
> I think, we have already discussed this. I tried getting to know why we
> have this difference in behaviour. However I havent been able to find
> the answer.
> 
> If you can get somebody to answer this, I would be happy to modify as
> required.

The Changelog failed to mention this. Afaict there really is no reason
other than that touching entry_32.S is a pain.