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Date:   Thu, 13 Oct 2011 15:11:38 +0530
From:   Ananth N Mavinakayanahalli <ananth@in.ibm.com>
To:     Maneesh Soni <manesoni@cisco.com>
Cc:     ralf@linux-mips.org, linux-kernel@vger.kernel.org,
        linux-mips@linux-mips.org, david.daney@cavium.com,
        kamensky@cisco.com
Subject: Re: [PATCH] MIPS Kprobes: Support branch instructions probing
Message-ID: <20111013094137.GA19054@in.ibm.com>
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References: <20111013090749.GB16761@cisco.com>
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On Thu, Oct 13, 2011 at 02:37:49PM +0530, Maneesh Soni wrote:

...

I know nothing of MIPS internals, but...
 
>  static int __kprobes kprobe_handler(struct pt_regs *regs)
> @@ -239,8 +531,13 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
>  			save_previous_kprobe(kcb);
>  			set_current_kprobe(p, regs, kcb);
>  			kprobes_inc_nmissed_count(p);
> -			prepare_singlestep(p, regs);
> +			prepare_singlestep(p, regs, kcb);
>  			kcb->kprobe_status = KPROBE_REENTER;
> +			if (kcb->flags & SKIP_DELAYSLOT) {
> +				resume_execution(p, regs, kcb);
> +				restore_previous_kprobe(kcb);
> +				preempt_enable_no_resched();
> +			}
>  			return 1;
>  		} else {
>  			if (addr->word != breakpoint_insn.word) {
> @@ -284,8 +581,15 @@ static int __kprobes kprobe_handler(struct pt_regs *regs)
>  	}
> 
>  ss_probe:
> -	prepare_singlestep(p, regs);
> -	kcb->kprobe_status = KPROBE_HIT_SS;
> +	prepare_singlestep(p, regs, kcb);
> +	if (kcb->flags & SKIP_DELAYSLOT) {
> +		kcb->kprobe_status = KPROBE_HIT_SSDONE;
> +		if (p->post_handler)
> +			p->post_handler(p, regs, 0);
> +		resume_execution(p, regs, kcb);

You are missing a preempt_disable_no_resched() here.

Ananth