linux-kernel - Re: [PATCH v5 3.1.0-rc4-tip 13/26] x86: define a x86 specific exception notifier.

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Date:	Mon, 26 Sep 2011 16:05:17 -0600
From:	Shuah Khan <shuah.khan@...com>
To:	srikar@...ux.vnet.ibm.com
Cc:	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 3.1.0-rc4-tip 13/26] x86: define a x86 specific
 exception notifier.

> 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.

The reason for the difference between X86_64 and i386 is because of a bug
that went to address delayed signals on x86_64. More details can be found
at:

http://kerneltrap.org/mailarchive/git-commits-head/2008/7/15/2490384

It appears for some reason i386 code path left unchanged, maybe desire to
not fix it when it ain't broken.

-- Shuah



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