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Date: Wed, 7 Feb 2024 09:24:57 +0530
From: Vimal Kumar <vimal.kumar32@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: "Rafael J. Wysocki" <rafael@kernel.org>, Pavel Machek <pavel@ucw.cz>,
	Len Brown <len.brown@intel.com>, linux-pm@vger.kernel.org,
	linux-kernel@vger.kernel.org, chinmoyghosh2001@gmail.com,
	badolevishal1116@gmail.com, mintupatel89@gmail.com
Subject: Re: [PATCH v4] PM / sleep: Mechanism to find source aborting kernel
 suspend transition
Message-ID: <20240207035457.GA19804@DESKTOP-KA7F9LU.localdomain>
References: <20240205170747.19748-1-vimal.kumar32@gmail.com>
 <2024020555-usable-hardy-345e@gregkh>
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In-Reply-To: <2024020555-usable-hardy-345e@gregkh>

On Mon, Feb 05, 2024 at 07:33:17PM +0000, Greg Kroah-Hartman wrote:
> On Mon, Feb 05, 2024 at 10:37:45PM +0530, Vimal Kumar wrote:
> > Sometimes kernel suspend transitions can be aborted unconditionally by
> > manipulating pm_abort_suspend value using "hard" wakeup triggers or
> > through "pm_system_wakeup()".
> > 
> > There is no way to trace the source path of module or subsystem which
> > aborted the suspend transitions. This change will create a list of
> > wakeup sources aborting suspend in progress through "hard" events as
> > well as subsytems aborting suspend using "pm_system_wakeup()".
> > 
> > Example: Existing suspend failure logs:
> > [  349.708359] PM: Some devices failed to suspend, or early wake event detected
> > [  350.327842] PM: suspend exit
> > 
> > Suspend failure logs with this change:
> > [  518.761835] PM: Some devices failed to suspend, or early wake event detected
> > [  519.486939] PM: wakeup source or subsystem uart_suspend_port aborted suspend
> > [  519.500594] PM: suspend exit
> > 
> > Here we can clearly identify the module triggerring abort suspend.
> > 
> > Co-developed-by: Chinmoy Ghosh <chinmoyghosh2001@gmail.com>
> > Signed-off-by: Chinmoy Ghosh <chinmoyghosh2001@gmail.com>
> > Co-developed-by: Mintu Patel <mintupatel89@gmail.com>
> > Signed-off-by: Mintu Patel <mintupatel89@gmail.com>
> > Co-developed-by: Vishal Badole <badolevishal1116@gmail.com>
> > Signed-off-by: Vishal Badole <badolevishal1116@gmail.com>
> > Signed-off-by: Vimal Kumar <vimal.kumar32@gmail.com>
> > ---
> > Changes in v4:
> > - Changed GFP_KERNEL flag to GFP_ATOMIC
> > - Changed mutex_lock to raw_spin_lock
> 
> why raw?
>
 As mutex_lock might sleep, we need to use lock that is suitable for usages in atomic context. raw_spin_lock is already being used for other list in
this driver, so I used the same. If suggested we can switch to spin_lock_irqsave as well.
> 
> > ---
> >  drivers/base/power/wakeup.c | 100 +++++++++++++++++++++++++++++++++++-
> >  1 file changed, 99 insertions(+), 1 deletion(-)
> > 
> > diff --git a/drivers/base/power/wakeup.c b/drivers/base/power/wakeup.c
> > index a917219feea6..b04794557eef 100644
> > --- a/drivers/base/power/wakeup.c
> > +++ b/drivers/base/power/wakeup.c
> > @@ -73,6 +73,16 @@ static struct wakeup_source deleted_ws = {
> > 
> >  static DEFINE_IDA(wakeup_ida);
> > 
> > +#ifdef CONFIG_PM_DEBUG
> > +static DEFINE_RAW_SPINLOCK(pm_abort_suspend_list_lock);
> > +
> > +struct pm_abort_suspend_source {
> > +	struct list_head list;
> > +	char *source_triggering_abort_suspend;
> > +};
> > +static LIST_HEAD(pm_abort_suspend_list);
> > +#endif
> > +
> >  /**
> >   * wakeup_source_create - Create a struct wakeup_source object.
> >   * @name: Name of the new wakeup source.
> > @@ -575,6 +585,54 @@ static void wakeup_source_activate(struct wakeup_source *ws)
> > 	trace_wakeup_source_activate(ws->name, cec);
> >  }
> > 
> > +#ifdef CONFIG_PM_DEBUG
> 
> Please do not add #ifdef to .c files, this makes this file even messier.
> 
> > @@ -590,8 +648,13 @@ static void wakeup_source_report_event(struct wakeup_source *ws, bool hard)
> > 	if (!ws->active)
> > 		wakeup_source_activate(ws);
> > 
> > -	if (hard)
> > +	if (hard) {
> > +#ifdef CONFIG_PM_DEBUG
> > +		if (pm_suspend_target_state != PM_SUSPEND_ON)
> > +			pm_abort_suspend_source_add(ws->name);
> > +#endif
> 
> Especially for stuff like this, if you write your .h files properly, no
> #ifdef are needed.
>
 Thanks. We can move it to .h file.
> 
> 
> 
> > 		pm_system_wakeup();
> > +	}
> >  }
> > 
> >  /**
> > @@ -893,12 +956,47 @@ bool pm_wakeup_pending(void)
> > 		pm_print_active_wakeup_sources();
> > 	}
> > 
> > +#ifdef CONFIG_PM_DEBUG
> > +	if (atomic_read(&pm_abort_suspend) > 0) {
> > +		struct pm_abort_suspend_source *info;
> > +
> > +		raw_spin_lock_irqsave(&pm_abort_suspend_list_lock, flags);
> > +		list_for_each_entry(info, &pm_abort_suspend_list, list) {
> > +			pm_pr_dbg("wakeup source or subsystem %s aborted suspend\n",
> > +					info->source_triggering_abort_suspend);
> > +		}
> > +		raw_spin_unlock_irqrestore(&pm_abort_suspend_list_lock, flags);
> > +		pm_abort_suspend_list_clear();
> > +	}
> > +#endif
> > +
> > 	return ret || atomic_read(&pm_abort_suspend) > 0;
> >  }
> >  EXPORT_SYMBOL_GPL(pm_wakeup_pending);
> > 
> >  void pm_system_wakeup(void)
> >  {
> > +
> > +#ifdef CONFIG_PM_DEBUG
> > +#ifdef CONFIG_DEBUG_INFO
> > +	if (pm_suspend_target_state != PM_SUSPEND_ON) {
> > +		char *source_name = kasprintf(GFP_ATOMIC,
> > +					"%ps",
> > +					__builtin_return_address(0));
> > +		if (!source_name)
> > +			goto exit;
> > +
> > +		if (strcmp(source_name, "pm_wakeup_ws_event"))
> > +			pm_abort_suspend_source_add(source_name);
> > +
> > +		kfree(source_name);
> > +	}
> > +exit:
> > +#else
> > +	if (pm_suspend_target_state != PM_SUSPEND_ON)
> > +		pm_pr_dbg("Some wakeup source or subsystem aborted suspend\n");
> > +#endif
> > +#endif
> 
> Would you want to maintain this #ifdef nesting mess for the next 20
> years?  Please do not do this.
> 
 I was hoping if we can remove the "CONFIG_PM_DEBUG" as this functionality can exist by default as well.
 We can avoid nesting and usage for CONFIG_DEBUG_INFO move to .h files.

 Please share your perspective on this.


> thanks,
> 
> greg k-h


Warm Regards,
Vimal Kumar