linux-kernel - Re: [RFT][PATCH v2 2/2] PM / QoS: Fix device resume latency framework

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Date:   Fri, 3 Nov 2017 19:28:07 -0700
From:   Ramesh Thomas <ramesh.thomas@...el.com>
To:     Reinette Chatre <reinette.chatre@...el.com>
Cc:     "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Linux PM <linux-pm@...r.kernel.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Tero Kristo <t-kristo@...com>, Alex Shi <alex.shi@...aro.org>
Subject: Re: [RFT][PATCH v2 2/2] PM / QoS: Fix device resume latency framework

On 2017-11-03 at 09:39:08 -0700, Reinette Chatre wrote:
> Hi Rafael,
> 
> I started to test this but found myself triggering one of the warnings:
> 
> On 11/3/2017 4:50 AM, Rafael J. Wysocki wrote:
> > --- linux-pm.orig/include/linux/pm_qos.h
> > +++ linux-pm/include/linux/pm_qos.h
> > @@ -28,16 +28,19 @@ enum pm_qos_flags_status {
> >  	PM_QOS_FLAGS_ALL,
> >  };
> >  
> > -#define PM_QOS_DEFAULT_VALUE -1
> > +#define PM_QOS_DEFAULT_VALUE	(-1)
> 
> PM_QOS_DEFAULT_VALUE is -1 ...
> 
> 
> > ===================================================================
> > --- linux-pm.orig/drivers/base/power/qos.c
> > +++ linux-pm/drivers/base/power/qos.c
> > @@ -139,6 +139,9 @@ static int apply_constraint(struct dev_p
> >  
> >  	switch(req->type) {
> >  	case DEV_PM_QOS_RESUME_LATENCY:
> > +		if (WARN_ON(value < 0))
> > +			value = 0;
> > +
> 
> ... causing me to hit this WARN_ON because apply_constraint() is called by __dev_pm_qos_remove_request() with the value parameter set to PM_QOS_DEFAULT_VALUE.

That value does not get used if action is PM_QOS_REMOVE_REQ. May be just pass
0 or PM_QOS_RESUME_LATENCY_DEFAULT_VALUE everywhere apply_constraint is called
with PM_QOS_REMOVE_REQ action.