* [PATCH] drivers: rtc: handle OTF clock changes
@ 2026-06-24 12:31 Elad Nachman
2026-06-24 15:31 ` Alexandre Belloni
2026-08-07 13:05 ` Dan Carpenter
0 siblings, 2 replies; 4+ messages in thread
From: Elad Nachman @ 2026-06-24 12:31 UTC (permalink / raw)
To: alexandre.belloni, linux-rtc, linux-kernel; +Cc: enachman
From: Elad Nachman <enachman@marvell.com>
When processing expired RTC events and rearming them, use now
instead of expiry to prevent endless loops.
Issue seen with Armada 385 SOC.
Fixes commit 6610e0893b8b ("RTC: Rework RTC code to use timerqueue for events")
Signed-off-by: Elad Nachman <enachman@marvell.com>
---
drivers/rtc/interface.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
index 96626f8068f9..c32ef95a07d4 100644
--- a/drivers/rtc/interface.c
+++ b/drivers/rtc/interface.c
@@ -126,6 +126,7 @@ EXPORT_SYMBOL_GPL(rtc_read_time);
int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
{
int err, uie;
+ struct rtc_time new_tm;
err = rtc_valid_tm(tm);
if (err != 0)
@@ -159,6 +160,17 @@ int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
else
err = -EINVAL;
+ if (rtc && rtc->ops && rtc->ops->read_time) {
+ if (!rtc->ops->read_time(rtc->dev.parent, &new_tm)) {
+ pr_debug("new rtc time secs %d mins %d hours %d mday %d mon %d year %d way %d yday %d dst %d\n",
+ new_tm.tm_sec, new_tm.tm_min,
+ new_tm.tm_hour, new_tm.tm_mday,
+ new_tm.tm_mon, new_tm.tm_year,
+ new_tm.tm_wday, new_tm.tm_yday,
+ new_tm.tm_isdst);
+ }
+ }
+
pm_stay_awake(rtc->dev.parent);
mutex_unlock(&rtc->ops_lock);
/* A timer might have just expired */
@@ -999,7 +1011,7 @@ void rtc_timer_do_work(struct work_struct *work)
trace_rtc_timer_fired(timer);
/* Re-add/fwd periodic timers */
if (ktime_to_ns(timer->period)) {
- timer->node.expires = ktime_add(timer->node.expires,
+ timer->node.expires = ktime_add(now,
timer->period);
timer->enabled = 1;
timerqueue_add(&rtc->timerqueue, &timer->node);
--
2.25.1
^ permalink raw reply related [flat|nested] 4+ messages in thread
* Re: [PATCH] drivers: rtc: handle OTF clock changes
2026-06-24 12:31 [PATCH] drivers: rtc: handle OTF clock changes Elad Nachman
@ 2026-06-24 15:31 ` Alexandre Belloni
2026-06-28 17:34 ` [EXTERNAL] " Elad Nachman
2026-08-07 13:05 ` Dan Carpenter
1 sibling, 1 reply; 4+ messages in thread
From: Alexandre Belloni @ 2026-06-24 15:31 UTC (permalink / raw)
To: Elad Nachman; +Cc: linux-rtc, linux-kernel
On 24/06/2026 15:31:03+0300, Elad Nachman wrote:
> From: Elad Nachman <enachman@marvell.com>
>
> When processing expired RTC events and rearming them, use now
> instead of expiry to prevent endless loops.
> Issue seen with Armada 385 SOC.
The loop is not endless, it may be long however. How do you reproduce
this? Or maybe the question is what is enabling PIE on your system?
Your patch breaks existing code because it will expect to get one event
per elapsed period while your patch will cause events to be skipped.
>
> Fixes commit 6610e0893b8b ("RTC: Rework RTC code to use timerqueue for events")
> Signed-off-by: Elad Nachman <enachman@marvell.com>
> ---
> drivers/rtc/interface.c | 14 +++++++++++++-
> 1 file changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
> index 96626f8068f9..c32ef95a07d4 100644
> --- a/drivers/rtc/interface.c
> +++ b/drivers/rtc/interface.c
> @@ -126,6 +126,7 @@ EXPORT_SYMBOL_GPL(rtc_read_time);
> int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
> {
> int err, uie;
> + struct rtc_time new_tm;
>
> err = rtc_valid_tm(tm);
> if (err != 0)
> @@ -159,6 +160,17 @@ int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
> else
> err = -EINVAL;
>
> + if (rtc && rtc->ops && rtc->ops->read_time) {
> + if (!rtc->ops->read_time(rtc->dev.parent, &new_tm)) {
> + pr_debug("new rtc time secs %d mins %d hours %d mday %d mon %d year %d way %d yday %d dst %d\n",
> + new_tm.tm_sec, new_tm.tm_min,
> + new_tm.tm_hour, new_tm.tm_mday,
> + new_tm.tm_mon, new_tm.tm_year,
> + new_tm.tm_wday, new_tm.tm_yday,
> + new_tm.tm_isdst);
> + }
> + }
> +
This is unrelated to the patch.
> pm_stay_awake(rtc->dev.parent);
> mutex_unlock(&rtc->ops_lock);
> /* A timer might have just expired */
> @@ -999,7 +1011,7 @@ void rtc_timer_do_work(struct work_struct *work)
> trace_rtc_timer_fired(timer);
> /* Re-add/fwd periodic timers */
> if (ktime_to_ns(timer->period)) {
> - timer->node.expires = ktime_add(timer->node.expires,
> + timer->node.expires = ktime_add(now,
> timer->period);
> timer->enabled = 1;
> timerqueue_add(&rtc->timerqueue, &timer->node);
> --
> 2.25.1
>
--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com
^ permalink raw reply [flat|nested] 4+ messages in thread
* RE: [EXTERNAL] Re: [PATCH] drivers: rtc: handle OTF clock changes
2026-06-24 15:31 ` Alexandre Belloni
@ 2026-06-28 17:34 ` Elad Nachman
0 siblings, 0 replies; 4+ messages in thread
From: Elad Nachman @ 2026-06-28 17:34 UTC (permalink / raw)
To: Alexandre Belloni; +Cc: linux-rtc@vger.kernel.org, linux-kernel@vger.kernel.org
Hi Alexandre,
>
>
> From: Alexandre Belloni <alexandre.belloni@bootlin.com>
> Sent: Wednesday, June 24, 2026 6:31 PM
> To: Elad Nachman <enachman@marvell.com>
> Cc: linux-rtc@vger.kernel.org; linux-kernel@vger.kernel.org
> Subject: [EXTERNAL] Re: [PATCH] drivers: rtc: handle OTF clock changes
>
> > From: Elad Nachman <mailto:enachman@marvell.com>
> >
> > When processing expired RTC events and rearming them, use now
> > instead of expiry to prevent endless loops.
> > Issue seen with Armada 385 SOC.
>
> The loop is not endless, it may be long however. How do you reproduce
48 seconds are long enough to trigger RCU related watchdog which eventually causes NOS reboot...
> this? Or maybe the question is what is enabling PIE on your system?
Not only PIE but also UIE enablement leads to this behavior.
UIE is enabled by Chrony, and that is activated by SONIC NOS.
SONIC NOS was introduced a time modification test (forward/backward)
which triggers this issue, causing the following kernel soft lockup:
[ 409.188746] rcu: blocking rcu_node structures (internal RCU debug):
[ 436.242391] watchdog: BUG: soft lockup - CPU#1 stuck for 48s! [kworker/1:3:432]
[ 436.250173] Kernel panic - not syncing: softlockup: hung tasks
[ 436.256032] CPU: 1 PID: 432 Comm: kworker/1:3 Tainted: G O L 6.1.0-29-2-armmp
[ 436.272194] Workqueue: events rtc_timer_do_work
[ 436.377383] __irq_svc from _raw_spin_unlock_irqrestore+0x24/0x28
[ 436.383510] _raw_spin_unlock_irqrestore from __wake_up_common_lock+0x8c/0xc0
[ 436.390685] __wake_up_common_lock from __wake_up+0x20/0x28
[ 436.396286] __wake_up from rtc_handle_legacy_irq+0x58/0x6c
[ 436.401890] rtc_handle_legacy_irq from rtc_timer_do_work+0xe0/0x37c
[ 436.408275] rtc_timer_do_work from process_one_work+0x1f8/0x4b4
[ 436.414317] process_one_work from worker_thread+0x54/0x50c
[ 436.419924] worker_thread from kthread+0xd8/0xf4
>
> Your patch breaks existing code because it will expect to get one event
> per elapsed period while your patch will cause events to be skipped.
I realize that, but the alternative of having soft lockup followed by reboot is worse in my opinion...
If you have any better idea, I am more than open to suggestions...
>
> >
> > Fixes commit 6610e0893b8b ("RTC: Rework RTC code to use timerqueue for events")
> > Signed-off-by: Elad Nachman <mailto:enachman@marvell.com>
> > ---
> > drivers/rtc/interface.c | 14 +++++++++++++-
> > 1 file changed, 13 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/rtc/interface.c b/drivers/rtc/interface.c
> > index 96626f8068f9..c32ef95a07d4 100644
> > --- a/drivers/rtc/interface.c
> > +++ b/drivers/rtc/interface.c
> > @@ -126,6 +126,7 @@ EXPORT_SYMBOL_GPL(rtc_read_time);
> > int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
> > {
> > int err, uie;
> > + struct rtc_time new_tm;
> >
> > err = rtc_valid_tm(tm);
> > if (err != 0)
> > @@ -159,6 +160,17 @@ int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
> > else
> > err = -EINVAL;
> >
> > + if (rtc && rtc->ops && rtc->ops->read_time) {
> > + if (!rtc->ops->read_time(rtc->dev.parent, &new_tm)) {
> > + pr_debug("new rtc time secs %d mins %d hours %d mday %d mon %d year %d way %d yday %d dst %d\n",
> > + new_tm.tm_sec, new_tm.tm_min,
> > + new_tm.tm_hour, new_tm.tm_mday,
> > + new_tm.tm_mon, new_tm.tm_year,
> > + new_tm.tm_wday, new_tm.tm_yday,
> > + new_tm.tm_isdst);
> > + }
> > + }
> > +
>
>
> This is unrelated to the patch.
I can remove this easily once we find a solution to the main issue above...
>
> > pm_stay_awake(rtc->dev.parent);
> > mutex_unlock(&rtc->ops_lock);
> > /* A timer might have just expired */
> > @@ -999,7 +1011,7 @@ void rtc_timer_do_work(struct work_struct *work)
> > trace_rtc_timer_fired(timer);
> > /* Re-add/fwd periodic timers */
> > if (ktime_to_ns(timer->period)) {
> > - timer->node.expires = ktime_add(timer->node.expires,
> > + timer->node.expires = ktime_add(now,
> > timer->period);
> > timer->enabled = 1;
> > timerqueue_add(&rtc->timerqueue, &timer->node);
> > --
> > 2.25.1
> >
>
> --
> Alexandre Belloni, co-owner and COO, Bootlin
> Embedded Linux and Kernel engineering
> https://urldefense.proofpoint.com/v2/url?u=https-3A__bootlin.com&d=DwIBAg&c=nKjWec2b6R0mOyPaz7xtfQ&r=eTeNTLEK5-TxXczjOcKPhANIFtlB9pP4lq9qhdlFrwQ&m=6PDPbjuCmjWGjRiUxkS5sPKd4lHU_NypV7pVhoFdBcLnksTSMiVrFYs7blEViGJR&s=IQM9cBpCUzoV4ONJnQs4yjzbjygO7zRYDW1jpJL3zWM&e=
Thanks,
Elad.
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: [PATCH] drivers: rtc: handle OTF clock changes
2026-06-24 12:31 [PATCH] drivers: rtc: handle OTF clock changes Elad Nachman
2026-06-24 15:31 ` Alexandre Belloni
@ 2026-08-07 13:05 ` Dan Carpenter
1 sibling, 0 replies; 4+ messages in thread
From: Dan Carpenter @ 2026-08-07 13:05 UTC (permalink / raw)
To: oe-kbuild, Elad Nachman, alexandre.belloni, linux-rtc,
linux-kernel
Cc: lkp, oe-kbuild-all, enachman
Hi Elad,
kernel test robot noticed the following build warnings:
https://git-scm.com/docs/git-format-patch#_base_tree_information]
url: https://github.com/intel-lab-lkp/linux/commits/Elad-Nachman/drivers-rtc-handle-OTF-clock-changes/20260806-231215
base: https://git.kernel.org/pub/scm/linux/kernel/git/abelloni/linux.git rtc-next
patch link: https://lore.kernel.org/r/20260624123103.3523728-1-enachman%40marvell.com
patch subject: [PATCH] drivers: rtc: handle OTF clock changes
config: i386-randconfig-141 (https://download.01.org/0day-ci/archive/20260807/202608072059.hZ2oY5u0-lkp@intel.com/config)
compiler: gcc-14 (Debian 14.2.0-19) 14.2.0
smatch: v0.5.0-9187-g5189e3fb
If you fix the issue in a separate patch/commit (i.e. not just a new version of
the same patch/commit), kindly add following tags
| Reported-by: kernel test robot <lkp@intel.com>
| Reported-by: Dan Carpenter <error27@gmail.com>
| Closes: https://lore.kernel.org/r/202608072059.hZ2oY5u0-lkp@intel.com/
smatch warnings:
drivers/rtc/interface.c:163 rtc_set_time() warn: variable dereferenced before check 'rtc' (see line 135)
vim +/rtc +163 drivers/rtc/interface.c
ab6a2d70d18edc David Brownell 2007-05-08 126 int rtc_set_time(struct rtc_device *rtc, struct rtc_time *tm)
0c86edc0d49706 Alessandro Zummo 2006-03-27 127 {
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 128 int err, uie;
37b82b16c5f104 Elad Nachman 2026-06-24 129 struct rtc_time new_tm;
0c86edc0d49706 Alessandro Zummo 2006-03-27 130
0c86edc0d49706 Alessandro Zummo 2006-03-27 131 err = rtc_valid_tm(tm);
0c86edc0d49706 Alessandro Zummo 2006-03-27 132 if (err != 0)
0c86edc0d49706 Alessandro Zummo 2006-03-27 133 return err;
0c86edc0d49706 Alessandro Zummo 2006-03-27 134
4c4e5df1f346f7 Baolin Wang 2018-01-08 @135 err = rtc_valid_range(rtc, tm);
4c4e5df1f346f7 Baolin Wang 2018-01-08 136 if (err)
4c4e5df1f346f7 Baolin Wang 2018-01-08 137 return err;
71db049e7355f3 Alexandre Belloni 2018-02-17 138
989515647e7832 Baolin Wang 2018-01-08 139 rtc_subtract_offset(rtc, tm);
989515647e7832 Baolin Wang 2018-01-08 140
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 141 #ifdef CONFIG_RTC_INTF_DEV_UIE_EMUL
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 142 uie = rtc->uie_rtctimer.enabled || rtc->uie_irq_active;
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 143 #else
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 144 uie = rtc->uie_rtctimer.enabled;
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 145 #endif
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 146 if (uie) {
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 147 err = rtc_update_irq_enable(rtc, 0);
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 148 if (err)
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 149 return err;
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 150 }
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 151
0c86edc0d49706 Alessandro Zummo 2006-03-27 152 err = mutex_lock_interruptible(&rtc->ops_lock);
0c86edc0d49706 Alessandro Zummo 2006-03-27 153 if (err)
b68bb2632453a9 David Brownell 2008-07-29 154 return err;
0c86edc0d49706 Alessandro Zummo 2006-03-27 155
0c86edc0d49706 Alessandro Zummo 2006-03-27 156 if (!rtc->ops)
0c86edc0d49706 Alessandro Zummo 2006-03-27 157 err = -ENODEV;
bbccf83f6c4e1a Alessandro Zummo 2009-01-06 158 else if (rtc->ops->set_time)
cd9662094edf41 David Brownell 2007-05-08 159 err = rtc->ops->set_time(rtc->dev.parent, tm);
606cc43c720bde Alexandre Belloni 2019-03-20 160 else
bbccf83f6c4e1a Alessandro Zummo 2009-01-06 161 err = -EINVAL;
0c86edc0d49706 Alessandro Zummo 2006-03-27 162
37b82b16c5f104 Elad Nachman 2026-06-24 @163 if (rtc && rtc->ops && rtc->ops->read_time) {
^^^
There is no point in checking "rtc" after we have already dereferenced
it.
37b82b16c5f104 Elad Nachman 2026-06-24 164 if (!rtc->ops->read_time(rtc->dev.parent, &new_tm)) {
37b82b16c5f104 Elad Nachman 2026-06-24 165 pr_debug("new rtc time secs %d mins %d hours %d mday %d mon %d year %d way %d yday %d dst %d\n",
37b82b16c5f104 Elad Nachman 2026-06-24 166 new_tm.tm_sec, new_tm.tm_min,
37b82b16c5f104 Elad Nachman 2026-06-24 167 new_tm.tm_hour, new_tm.tm_mday,
37b82b16c5f104 Elad Nachman 2026-06-24 168 new_tm.tm_mon, new_tm.tm_year,
37b82b16c5f104 Elad Nachman 2026-06-24 169 new_tm.tm_wday, new_tm.tm_yday,
37b82b16c5f104 Elad Nachman 2026-06-24 170 new_tm.tm_isdst);
37b82b16c5f104 Elad Nachman 2026-06-24 171 }
37b82b16c5f104 Elad Nachman 2026-06-24 172 }
37b82b16c5f104 Elad Nachman 2026-06-24 173
14d0e347ea2db5 Zoran Markovic 2013-06-26 174 pm_stay_awake(rtc->dev.parent);
0c86edc0d49706 Alessandro Zummo 2006-03-27 175 mutex_unlock(&rtc->ops_lock);
5f9679d29c7959 NeilBrown 2011-12-09 176 /* A timer might have just expired */
5f9679d29c7959 NeilBrown 2011-12-09 177 schedule_work(&rtc->irqwork);
29a1f599c0cc37 Baolin Wang 2017-12-14 178
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 179 if (uie) {
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 180 err = rtc_update_irq_enable(rtc, 1);
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 181 if (err)
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 182 return err;
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 183 }
7e7c005b4b1f1f Alexandre Belloni 2019-10-21 184
29a1f599c0cc37 Baolin Wang 2017-12-14 185 trace_rtc_set_time(rtc_tm_to_time64(tm), err);
0c86edc0d49706 Alessandro Zummo 2006-03-27 186 return err;
0c86edc0d49706 Alessandro Zummo 2006-03-27 187 }
--
0-DAY CI Kernel Test Service
https://github.com/intel/lkp-tests/wiki
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~2026-08-07 13:05 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz follow: Atom feed
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2026-06-24 12:31 [PATCH] drivers: rtc: handle OTF clock changes Elad Nachman
2026-06-24 15:31 ` Alexandre Belloni
2026-06-28 17:34 ` [EXTERNAL] " Elad Nachman
2026-08-07 13:05 ` Dan Carpenter
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