Re: [PATCH] PM / devfreq: Rework freq_table to be local to devfreq struct
From: Christian Marangi
Date: Fri Jul 01 2022 - 07:29:01 EST
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@xxxxxxxxxxxxxxx
> > Signed-off-by: Christian Marangi <ansuelsmth@xxxxxxxxx>
> > ---
>
> 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);
> > 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