linux-kernel - Re: [RFA][PATCH 02/27] PM / Sleep: Remove ftrace

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Date:	Sat, 28 Jun 2014 02:02:24 +0200
From:	"Rafael J. Wysocki" <rjw@...ysocki.net>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"H. Peter Anvin" <hpa@...or.com>, linux-arch@...r.kernel.org,
	Jiri Kosina <jkosina@...e.cz>,
	Josh Poimboeuf <notifications@...hub.com>
Subject: Re: [RFA][PATCH 02/27] PM / Sleep: Remove ftrace_stop/start() from suspend and hibernate

On Thursday, June 26, 2014 12:52:23 PM Steven Rostedt wrote:
> From: "Steven Rostedt (Red Hat)" <rostedt@...dmis.org>
> 
> ftrace_stop() and ftrace_start() were added to the suspend and hibernate
> process because there was some function within the work flow that caused
> the system to reboot if it was traced. This function has recently been
> found (restore_processor_state()). Now there's no reason to disable
> function tracing while we are going into suspend or hibernate, which means
> that being able to trace this will help tremendously in debugging any
> issues with suspend or hibernate.
> 
> This also means that the ftrace_stop/start() functions can be removed
> and simplify the function tracing code a bit.
> 
> Signed-off-by: Steven Rostedt <rostedt@...dmis.org>

ACK

> ---
>  kernel/power/hibernate.c | 6 ------
>  kernel/power/suspend.c   | 2 --
>  2 files changed, 8 deletions(-)
> 
> diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
> index 49e0a20fd010..ca7b1906c6c8 100644
> --- a/kernel/power/hibernate.c
> +++ b/kernel/power/hibernate.c
> @@ -365,7 +365,6 @@ int hibernation_snapshot(int platform_mode)
>  	}
>  
>  	suspend_console();
> -	ftrace_stop();
>  	pm_restrict_gfp_mask();
>  
>  	error = dpm_suspend(PMSG_FREEZE);
> @@ -391,7 +390,6 @@ int hibernation_snapshot(int platform_mode)
>  	if (error || !in_suspend)
>  		pm_restore_gfp_mask();
>  
> -	ftrace_start();
>  	resume_console();
>  	dpm_complete(msg);
>  
> @@ -494,7 +492,6 @@ int hibernation_restore(int platform_mode)
>  
>  	pm_prepare_console();
>  	suspend_console();
> -	ftrace_stop();
>  	pm_restrict_gfp_mask();
>  	error = dpm_suspend_start(PMSG_QUIESCE);
>  	if (!error) {
> @@ -502,7 +499,6 @@ int hibernation_restore(int platform_mode)
>  		dpm_resume_end(PMSG_RECOVER);
>  	}
>  	pm_restore_gfp_mask();
> -	ftrace_start();
>  	resume_console();
>  	pm_restore_console();
>  	return error;
> @@ -529,7 +525,6 @@ int hibernation_platform_enter(void)
>  
>  	entering_platform_hibernation = true;
>  	suspend_console();
> -	ftrace_stop();
>  	error = dpm_suspend_start(PMSG_HIBERNATE);
>  	if (error) {
>  		if (hibernation_ops->recover)
> @@ -573,7 +568,6 @@ int hibernation_platform_enter(void)
>   Resume_devices:
>  	entering_platform_hibernation = false;
>  	dpm_resume_end(PMSG_RESTORE);
> -	ftrace_start();
>  	resume_console();
>  
>   Close:
> diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
> index 4dd8822f732a..f6623da034d8 100644
> --- a/kernel/power/suspend.c
> +++ b/kernel/power/suspend.c
> @@ -248,7 +248,6 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
>  		goto Platform_wake;
>  	}
>  
> -	ftrace_stop();
>  	error = disable_nonboot_cpus();
>  	if (error || suspend_test(TEST_CPUS))
>  		goto Enable_cpus;
> @@ -275,7 +274,6 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
>  
>   Enable_cpus:
>  	enable_nonboot_cpus();
> -	ftrace_start();
>  
>   Platform_wake:
>  	if (need_suspend_ops(state) && suspend_ops->wake)
> 

-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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