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Date: Mon, 14 Jun 2010 13:54:23 -0400
From: Christoph Hellwig <hch@infradead.org>
To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
Cc: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@elte.hu>,
       Masami Hiramatsu <mhiramat@redhat.com>, Mel Gorman <mel@csn.ul.ie>,
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       Steven Rostedt <rostedt@goodmis.org>,
       Roland McGrath <roland@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
       Christoph Hellwig <hch@infradead.org>,
       Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
       Oleg Nesterov <oleg@redhat.com>, Mark Wielaard <mjw@redhat.com>,
       Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
       Andrew Morton <akpm@linux-foundation.org>,
       Linus Torvalds <torvalds@linux-foundation.org>,
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       "Rafael J. Wysocki" <rjw@sisk.pl>, "Frank Ch. Eigler" <fche@redhat.com>,
       LKML <linux-kernel@vger.kernel.org>,
       "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [PATCH v5 7/14] x86 support for Uprobes
Message-ID: <20100614175423.GG23754@infradead.org>
References: <20100614082748.29068.21995.sendpatchset@localhost6.localdomain6>
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On Mon, Jun 14, 2010 at 01:59:13PM +0530, Srikar Dronamraju wrote:
> @@ -850,7 +850,19 @@ do_notify_resume(struct pt_regs *regs, void *unused, __u32 thread_info_flags)
>  
>  	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.
> +		 */
> +		native_irq_enable();
> +#endif
>  		uprobe_notify_resume(regs);
> +
> +#ifdef CONFIG_X86_32
> +		native_irq_disable();
> +#endif

I'm no x86 port guru, but this looks rather worriesome to me.  Why does
do_notify_resume have different calling conventions on 32 vs 64-bit?
And if there is a good reason that 32-bit has them disabled, why is
enabling them in the middle of do_notify_resume okay?

> +void arch_uprobe_disable_sstep(struct pt_regs *regs)
> +{
> +		/* Disable single-stepping by clearing what we set */
> +		clear_thread_flag(TIF_SINGLESTEP);
> +		clear_thread_flag(TIF_FORCED_TF);
> +		regs->flags &= ~X86_EFLAGS_TF;
> +}

This seems to have one layer of indentation too much.
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