linux-kernel - Re: [PATCH] powerpc/xmon: Fix data-breakpoint

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Date:   Tue, 14 Feb 2017 14:17:19 +0530
From:   Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
To:     mpe@...erman.id.au
Cc:     benh@...nel.crashing.org, paulus@...ba.org, npiggin@...il.com,
        peterz@...radead.org, linuxppc-dev@...ts.ozlabs.org,
        linux-kernel@...r.kernel.org, naveen.n.rao@...ux.vnet.ibm.com,
        Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
Subject: Re: [PATCH] powerpc/xmon: Fix data-breakpoint

Hi Michael,

Can you please pull this patch.

Thanks,
Ravi

On Tuesday 22 November 2016 02:55 PM, Ravi Bangoria wrote:
> Xmon data-breakpoint feature is broken.
>
> Whenever there is a watchpoint match occurs, hw_breakpoint_handler will
> be called by do_break via notifier chains mechanism. If watchpoint is
> registered by xmon, hw_breakpoint_handler won't find any associated
> perf_event and returns immediately with NOTIFY_STOP. Similarly, do_break
> also returns without notifying to xmon.
>
> Solve this by returning NOTIFY_DONE when hw_breakpoint_handler does not
> find any perf_event associated with matched watchpoint.
>
> Signed-off-by: Ravi Bangoria <ravi.bangoria@...ux.vnet.ibm.com>
> ---
>  arch/powerpc/kernel/hw_breakpoint.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
>
> diff --git a/arch/powerpc/kernel/hw_breakpoint.c b/arch/powerpc/kernel/hw_breakpoint.c
> index 03d089b..469d86d 100644
> --- a/arch/powerpc/kernel/hw_breakpoint.c
> +++ b/arch/powerpc/kernel/hw_breakpoint.c
> @@ -228,8 +228,10 @@ int hw_breakpoint_handler(struct die_args *args)
>  	rcu_read_lock();
>
>  	bp = __this_cpu_read(bp_per_reg);
> -	if (!bp)
> +	if (!bp) {
> +		rc = NOTIFY_DONE;
>  		goto out;
> +	}
>  	info = counter_arch_bp(bp);
>
>  	/*