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Message-ID: <62bede4c.1c69fb81.1709a.b7f7@mx.google.com>
Date:   Fri, 1 Jul 2022 13:45:15 +0200
From:   Christian Marangi <ansuelsmth@gmail.com>
To:     Marek Szyprowski <m.szyprowski@samsung.com>
Cc:     MyungJoo Ham <myungjoo.ham@samsung.com>,
        Kyungmin Park <kyungmin.park@samsung.com>,
        Chanwoo Choi <cw00.choi@samsung.com>, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org,
        'Linux Samsung SOC' <linux-samsung-soc@vger.kernel.org>,
        Krzysztof Kozlowski <krzk@kernel.org>, stable@vger.kernel.org
Subject: Re: [PATCH] PM / devfreq: Rework freq_table to be local to devfreq
 struct
References: <20220619220351.29891-1-ansuelsmth@gmail.com>
 <CGME20220701080154eucas1p2c545476306b23c62ebddcabf2616b828@eucas1p2.samsung.com>
 <4ea890c9-7df1-b5b2-0e13-0f23eb452d49@samsung.com>
 <62beda74.1c69fb81.bace6.3899@mx.google.com>
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On Fri, Jul 01, 2022 at 01:28:50PM +0200, Christian Marangi wrote:
> On Fri, Jul 01, 2022 at 10:01:52AM +0200, Marek Szyprowski wrote:
> > Hi All,
> > 
> > On 20.06.2022 00:03, Christian Marangi wrote:
> > > On a devfreq PROBE_DEFER, the freq_table in the driver profile struct,
> > > is never reset and may be leaved in an undefined state.
> > >
> > > This comes from the fact that we store the freq_table in the driver
> > > profile struct that is commonly defined as static and not reset on
> > > PROBE_DEFER.
> > > We currently skip the reinit of the freq_table if we found
> > > it's already defined since a driver may declare his own freq_table.
> > >
> > > This logic is flawed in the case devfreq core generate a freq_table, set
> > > it in the profile struct and then PROBE_DEFER, freeing the freq_table.
> > > In this case devfreq will found a NOT NULL freq_table that has been
> > > freed, skip the freq_table generation and probe the driver based on the
> > > wrong table.
> > >
> > > To fix this and correctly handle PROBE_DEFER, use a local freq_table and
> > > max_state in the devfreq struct and never modify the freq_table present
> > > in the profile struct if it does provide it.
> > >
> > > Fixes: 0ec09ac2cebe ("PM / devfreq: Set the freq_table of devfreq device")
> > > Cc: stable@vger.kernel.org
> > > Signed-off-by: Christian Marangi <ansuelsmth@gmail.com>
> > > ---
> > 
> > This patch landed in linux next-20220630 as commit b5d281f6c16d ("PM / 
> > devfreq: Rework freq_table to be local to devfreq struct"). 
> > Unfortunately it causes the following regression on my Exynos based test 
> > systems:
> > 
> > 8<--- cut here ---
> > Unable to handle kernel NULL pointer dereference at virtual address 00000000
> > [00000000] *pgd=00000000
> > Internal error: Oops: 5 [#1] PREEMPT SMP ARM
> > Modules linked in:
> > CPU: 3 PID: 49 Comm: kworker/u8:3 Not tainted 5.19.0-rc4-next-20220630 #5312
> > Hardware name: Samsung Exynos (Flattened Device Tree)
> > Workqueue: events_unbound deferred_probe_work_func
> > PC is at exynos_bus_probe+0x604/0x684
> > LR is at device_add+0x14c/0x908
> > pc : [<c090aef4>]??? lr : [<c06cf77c>]??? psr: 80000053
> > ...
> > Process kworker/u8:3 (pid: 49, stack limit = 0x(ptrval))
> > Stack: (0xf0a15d30 to 0xf0a16000)
> > ...
> >  ?exynos_bus_probe from platform_probe+0x5c/0xb8
> >  ?platform_probe from really_probe+0xe0/0x414
> >  ?really_probe from __driver_probe_device+0xa0/0x208
> >  ?__driver_probe_device from driver_probe_device+0x30/0xc0
> >  ?driver_probe_device from __device_attach_driver+0xa4/0x11c
> >  ?__device_attach_driver from bus_for_each_drv+0x7c/0xc0
> >  ?bus_for_each_drv from __device_attach+0xac/0x20c
> >  ?__device_attach from bus_probe_device+0x88/0x90
> >  ?bus_probe_device from deferred_probe_work_func+0x98/0xe0
> >  ?deferred_probe_work_func from process_one_work+0x288/0x774
> >  ?process_one_work from worker_thread+0x44/0x504
> >  ?worker_thread from kthread+0xf4/0x128
> >  ?kthread from ret_from_fork+0x14/0x2c
> > Exception stack(0xf0a15fb0 to 0xf0a15ff8)
> > ...
> > ---[ end trace 0000000000000000 ]---
> > 
> > This issue is caused by bus->devfreq->profile->freq_table being NULL here:
> > 
> > https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/drivers/devfreq/exynos-bus.c?h=next-20220630#n451
> > 
> >
> 
> I just checked this and the bug is caused by a simple pr_info...
> 
> Can you test the following patch just to make sure?
> 
> diff --git a/drivers/devfreq/exynos-bus.c b/drivers/devfreq/exynos-bus.c
> index b5615e667e31..79725bbb4bb0 100644
> --- a/drivers/devfreq/exynos-bus.c
> +++ b/drivers/devfreq/exynos-bus.c
> @@ -447,9 +447,9 @@ static int exynos_bus_probe(struct platform_device *pdev)
>                 }
>         }
> 
> -       max_state = bus->devfreq->profile->max_state;
> -       min_freq = (bus->devfreq->profile->freq_table[0] / 1000);
> -       max_freq = (bus->devfreq->profile->freq_table[max_state - 1] / 1000);
> +       max_state = bus->devfreq->max_state;
> +       min_freq = (bus->devfreq->freq_table[0] / 1000);
> +       max_freq = (bus->devfreq->freq_table[max_state - 1] / 1000);
>         pr_info("exynos-bus: new bus device registered: %s (%6ld KHz ~ %6ld KHz)\n",
>                         dev_name(dev), min_freq, max_freq);
>  
>

(BTW patch is ready, just waiting for your test and I will send it)

> > >   drivers/devfreq/devfreq.c          | 71 ++++++++++++++----------------
> > >   drivers/devfreq/governor_passive.c | 14 +++---
> > >   include/linux/devfreq.h            |  5 +++
> > >   3 files changed, 46 insertions(+), 44 deletions(-)
> > >
> > > diff --git a/drivers/devfreq/devfreq.c b/drivers/devfreq/devfreq.c
> > > index 01474daf4548..2e2b3b414d67 100644
> > > --- a/drivers/devfreq/devfreq.c
> > > +++ b/drivers/devfreq/devfreq.c
> > > @@ -123,7 +123,7 @@ void devfreq_get_freq_range(struct devfreq *devfreq,
> > >   			    unsigned long *min_freq,
> > >   			    unsigned long *max_freq)
> > >   {
> > > -	unsigned long *freq_table = devfreq->profile->freq_table;
> > > +	unsigned long *freq_table = devfreq->freq_table;
> > >   	s32 qos_min_freq, qos_max_freq;
> > >   
> > >   	lockdep_assert_held(&devfreq->lock);
> > > @@ -133,11 +133,11 @@ void devfreq_get_freq_range(struct devfreq *devfreq,
> > >   	 * The devfreq drivers can initialize this in either ascending or
> > >   	 * descending order and devfreq core supports both.
> > >   	 */
> > > -	if (freq_table[0] < freq_table[devfreq->profile->max_state - 1]) {
> > > +	if (freq_table[0] < freq_table[devfreq->max_state - 1]) {
> > >   		*min_freq = freq_table[0];
> > > -		*max_freq = freq_table[devfreq->profile->max_state - 1];
> > > +		*max_freq = freq_table[devfreq->max_state - 1];
> > >   	} else {
> > > -		*min_freq = freq_table[devfreq->profile->max_state - 1];
> > > +		*min_freq = freq_table[devfreq->max_state - 1];
> > >   		*max_freq = freq_table[0];
> > >   	}
> > >   
> > > @@ -169,8 +169,8 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
> > >   {
> > >   	int lev;
> > >   
> > > -	for (lev = 0; lev < devfreq->profile->max_state; lev++)
> > > -		if (freq == devfreq->profile->freq_table[lev])
> > > +	for (lev = 0; lev < devfreq->max_state; lev++)
> > > +		if (freq == devfreq->freq_table[lev])
> > >   			return lev;
> > >   
> > >   	return -EINVAL;
> > > @@ -178,7 +178,6 @@ static int devfreq_get_freq_level(struct devfreq *devfreq, unsigned long freq)
> > >   
> > >   static int set_freq_table(struct devfreq *devfreq)
> > >   {
> > > -	struct devfreq_dev_profile *profile = devfreq->profile;
> > >   	struct dev_pm_opp *opp;
> > >   	unsigned long freq;
> > >   	int i, count;
> > > @@ -188,25 +187,22 @@ static int set_freq_table(struct devfreq *devfreq)
> > >   	if (count <= 0)
> > >   		return -EINVAL;
> > >   
> > > -	profile->max_state = count;
> > > -	profile->freq_table = devm_kcalloc(devfreq->dev.parent,
> > > -					profile->max_state,
> > > -					sizeof(*profile->freq_table),
> > > -					GFP_KERNEL);
> > > -	if (!profile->freq_table) {
> > > -		profile->max_state = 0;
> > > +	devfreq->max_state = count;
> > > +	devfreq->freq_table = devm_kcalloc(devfreq->dev.parent,
> > > +					   devfreq->max_state,
> > > +					   sizeof(*devfreq->freq_table),
> > > +					   GFP_KERNEL);
> > > +	if (!devfreq->freq_table)
> > >   		return -ENOMEM;
> > > -	}
> > >   
> > > -	for (i = 0, freq = 0; i < profile->max_state; i++, freq++) {
> > > +	for (i = 0, freq = 0; i < devfreq->max_state; i++, freq++) {
> > >   		opp = dev_pm_opp_find_freq_ceil(devfreq->dev.parent, &freq);
> > >   		if (IS_ERR(opp)) {
> > > -			devm_kfree(devfreq->dev.parent, profile->freq_table);
> > > -			profile->max_state = 0;
> > > +			devm_kfree(devfreq->dev.parent, devfreq->freq_table);
> > >   			return PTR_ERR(opp);
> > >   		}
> > >   		dev_pm_opp_put(opp);
> > > -		profile->freq_table[i] = freq;
> > > +		devfreq->freq_table[i] = freq;
> > >   	}
> > >   
> > >   	return 0;
> > > @@ -246,7 +242,7 @@ int devfreq_update_status(struct devfreq *devfreq, unsigned long freq)
> > >   
> > >   	if (lev != prev_lev) {
> > >   		devfreq->stats.trans_table[
> > > -			(prev_lev * devfreq->profile->max_state) + lev]++;
> > > +			(prev_lev * devfreq->max_state) + lev]++;
> > >   		devfreq->stats.total_trans++;
> > >   	}
> > >   
> > > @@ -835,6 +831,9 @@ struct devfreq *devfreq_add_device(struct device *dev,
> > >   		if (err < 0)
> > >   			goto err_dev;
> > >   		mutex_lock(&devfreq->lock);
> > > +	} else {
> > > +		devfreq->freq_table = devfreq->profile->freq_table;
> > > +		devfreq->max_state = devfreq->profile->max_state;
> > >   	}
> > >   
> > >   	devfreq->scaling_min_freq = find_available_min_freq(devfreq);
> > > @@ -870,8 +869,8 @@ struct devfreq *devfreq_add_device(struct device *dev,
> > >   
> > >   	devfreq->stats.trans_table = devm_kzalloc(&devfreq->dev,
> > >   			array3_size(sizeof(unsigned int),
> > > -				    devfreq->profile->max_state,
> > > -				    devfreq->profile->max_state),
> > > +				    devfreq->max_state,
> > > +				    devfreq->max_state),
> > >   			GFP_KERNEL);
> > >   	if (!devfreq->stats.trans_table) {
> > >   		mutex_unlock(&devfreq->lock);
> > > @@ -880,7 +879,7 @@ struct devfreq *devfreq_add_device(struct device *dev,
> > >   	}
> > >   
> > >   	devfreq->stats.time_in_state = devm_kcalloc(&devfreq->dev,
> > > -			devfreq->profile->max_state,
> > > +			devfreq->max_state,
> > >   			sizeof(*devfreq->stats.time_in_state),
> > >   			GFP_KERNEL);
> > >   	if (!devfreq->stats.time_in_state) {
> > > @@ -1665,9 +1664,9 @@ static ssize_t available_frequencies_show(struct device *d,
> > >   
> > >   	mutex_lock(&df->lock);
> > >   
> > > -	for (i = 0; i < df->profile->max_state; i++)
> > > +	for (i = 0; i < df->max_state; i++)
> > >   		count += scnprintf(&buf[count], (PAGE_SIZE - count - 2),
> > > -				"%lu ", df->profile->freq_table[i]);
> > > +				"%lu ", df->freq_table[i]);
> > >   
> > >   	mutex_unlock(&df->lock);
> > >   	/* Truncate the trailing space */
> > > @@ -1690,7 +1689,7 @@ static ssize_t trans_stat_show(struct device *dev,
> > >   
> > >   	if (!df->profile)
> > >   		return -EINVAL;
> > > -	max_state = df->profile->max_state;
> > > +	max_state = df->max_state;
> > >   
> > >   	if (max_state == 0)
> > >   		return sprintf(buf, "Not Supported.\n");
> > > @@ -1707,19 +1706,17 @@ static ssize_t trans_stat_show(struct device *dev,
> > >   	len += sprintf(buf + len, "           :");
> > >   	for (i = 0; i < max_state; i++)
> > >   		len += sprintf(buf + len, "%10lu",
> > > -				df->profile->freq_table[i]);
> > > +				df->freq_table[i]);
> > >   
> > >   	len += sprintf(buf + len, "   time(ms)\n");
> > >   
> > >   	for (i = 0; i < max_state; i++) {
> > > -		if (df->profile->freq_table[i]
> > > -					== df->previous_freq) {
> > > +		if (df->freq_table[i] == df->previous_freq)
> > >   			len += sprintf(buf + len, "*");
> > > -		} else {
> > > +		else
> > >   			len += sprintf(buf + len, " ");
> > > -		}
> > > -		len += sprintf(buf + len, "%10lu:",
> > > -				df->profile->freq_table[i]);
> > > +
> > > +		len += sprintf(buf + len, "%10lu:", df->freq_table[i]);
> > >   		for (j = 0; j < max_state; j++)
> > >   			len += sprintf(buf + len, "%10u",
> > >   				df->stats.trans_table[(i * max_state) + j]);
> > > @@ -1743,7 +1740,7 @@ static ssize_t trans_stat_store(struct device *dev,
> > >   	if (!df->profile)
> > >   		return -EINVAL;
> > >   
> > > -	if (df->profile->max_state == 0)
> > > +	if (df->max_state == 0)
> > >   		return count;
> > >   
> > >   	err = kstrtoint(buf, 10, &value);
> > > @@ -1751,11 +1748,11 @@ static ssize_t trans_stat_store(struct device *dev,
> > >   		return -EINVAL;
> > >   
> > >   	mutex_lock(&df->lock);
> > > -	memset(df->stats.time_in_state, 0, (df->profile->max_state *
> > > +	memset(df->stats.time_in_state, 0, (df->max_state *
> > >   					sizeof(*df->stats.time_in_state)));
> > >   	memset(df->stats.trans_table, 0, array3_size(sizeof(unsigned int),
> > > -					df->profile->max_state,
> > > -					df->profile->max_state));
> > > +					df->max_state,
> > > +					df->max_state));
> > >   	df->stats.total_trans = 0;
> > >   	df->stats.last_update = get_jiffies_64();
> > >   	mutex_unlock(&df->lock);
> > > diff --git a/drivers/devfreq/governor_passive.c b/drivers/devfreq/governor_passive.c
> > > index 72c67979ebe1..ce24a262aa16 100644
> > > --- a/drivers/devfreq/governor_passive.c
> > > +++ b/drivers/devfreq/governor_passive.c
> > > @@ -131,18 +131,18 @@ static int get_target_freq_with_devfreq(struct devfreq *devfreq,
> > >   		goto out;
> > >   
> > >   	/* Use interpolation if required opps is not available */
> > > -	for (i = 0; i < parent_devfreq->profile->max_state; i++)
> > > -		if (parent_devfreq->profile->freq_table[i] == *freq)
> > > +	for (i = 0; i < parent_devfreq->max_state; i++)
> > > +		if (parent_devfreq->freq_table[i] == *freq)
> > >   			break;
> > >   
> > > -	if (i == parent_devfreq->profile->max_state)
> > > +	if (i == parent_devfreq->max_state)
> > >   		return -EINVAL;
> > >   
> > > -	if (i < devfreq->profile->max_state) {
> > > -		child_freq = devfreq->profile->freq_table[i];
> > > +	if (i < devfreq->max_state) {
> > > +		child_freq = devfreq->freq_table[i];
> > >   	} else {
> > > -		count = devfreq->profile->max_state;
> > > -		child_freq = devfreq->profile->freq_table[count - 1];
> > > +		count = devfreq->max_state;
> > > +		child_freq = devfreq->freq_table[count - 1];
> > >   	}
> > >   
> > >   out:
> > > diff --git a/include/linux/devfreq.h b/include/linux/devfreq.h
> > > index dc10bee75a72..34aab4dd336c 100644
> > > --- a/include/linux/devfreq.h
> > > +++ b/include/linux/devfreq.h
> > > @@ -148,6 +148,8 @@ struct devfreq_stats {
> > >    *		reevaluate operable frequencies. Devfreq users may use
> > >    *		devfreq.nb to the corresponding register notifier call chain.
> > >    * @work:	delayed work for load monitoring.
> > > + * @freq_table:		current frequency table used by the devfreq driver.
> > > + * @max_state:		count of entry present in the frequency table.
> > >    * @previous_freq:	previously configured frequency value.
> > >    * @last_status:	devfreq user device info, performance statistics
> > >    * @data:	Private data of the governor. The devfreq framework does not
> > > @@ -185,6 +187,9 @@ struct devfreq {
> > >   	struct notifier_block nb;
> > >   	struct delayed_work work;
> > >   
> > > +	unsigned long *freq_table;
> > > +	unsigned int max_state;
> > > +
> > >   	unsigned long previous_freq;
> > >   	struct devfreq_dev_status last_status;
> > >   
> > 
> > Best regards
> > -- 
> > Marek Szyprowski, PhD
> > Samsung R&D Institute Poland
> > 
> 
> -- 
> 	Ansuel

-- 
	Ansuel