linux-kernel - Re: [PATCH 39/40] debug_core: Turn off tracing while in the debugger

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Date:	Thu, 14 Jan 2010 19:10:10 -0500
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Jason Wessel <jason.wessel@...driver.com>
Cc:	linux-kernel@...r.kernel.org, kgdb-bugreport@...ts.sourceforge.net,
	mingo@...e.hu
Subject: Re: [PATCH 39/40] debug_core: Turn off tracing while in the
 debugger

On Thu, 2010-01-14 at 08:59 -0600, Jason Wessel wrote:
> The kernel debugger should turn off kernel tracing any time the
> debugger is active and restore it on resume.
> 
> CC: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Jason Wessel <jason.wessel@...driver.com>
> ---
>  kernel/debug/debug_core.c |    8 ++++++++
>  1 files changed, 8 insertions(+), 0 deletions(-)
> 
> diff --git a/kernel/debug/debug_core.c b/kernel/debug/debug_core.c
> index 6ca3f7c..464aa65 100644
> --- a/kernel/debug/debug_core.c
> +++ b/kernel/debug/debug_core.c
> @@ -474,6 +474,7 @@ static int kgdb_cpu_enter(struct kgdb_state *ks, struct pt_regs *regs)
>  	int sstep_tries = 100;
>  	int error;
>  	int i, cpu;
> +	int trace_on = 0;
>  acquirelock:
>  	/*
>  	 * Interrupts will be restored by the 'trap return' code, except when
> @@ -518,6 +519,8 @@ return_normal:
>  			 */
>  			if (arch_kgdb_ops.correct_hw_break)
>  				arch_kgdb_ops.correct_hw_break();
> +			if (trace_on)
> +				tracing_on();
>  			atomic_set(&cpu_in_kgdb[cpu], 0);
>  			touch_softlockup_watchdog_sync();
>  			clocksource_touch_watchdog();
> @@ -592,6 +595,9 @@ return_normal:
>  	kgdb_single_step = 0;
>  	kgdb_contthread = current;
>  	exception_level = 0;
> +	trace_on = tracing_is_on();
> +	if (trace_on)
> +		tracing_off();

Hmm, what happens if tracing gets turned on by something else? Will it
break this code? If so, we may need to do something different here.

-- Steve

>  
>  	while (1) {
>  cpu_master_loop:
> @@ -642,6 +648,8 @@ kgdb_restore:
>  		else
>  			kgdb_sstep_pid = 0;
>  	}
> +	if (trace_on)
> +		tracing_on();
>  	/* Free kgdb_active */
>  	atomic_set(&kgdb_active, -1);
>  	touch_softlockup_watchdog_sync();


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