diff mbox series

ntp: Use freezable workqueue for RTC synchronization

Message ID 20210125143039.1051912-1-geert+renesas@glider.be (mailing list archive)
State Mainlined
Commit 24c242ec7abb3d21fa0b1da6bb251521dc1717b5
Delegated to: Geert Uytterhoeven
Headers show
Series ntp: Use freezable workqueue for RTC synchronization | expand

Commit Message

Geert Uytterhoeven Jan. 25, 2021, 2:30 p.m. UTC
The bug fixed by commit e3fab2f3de081e98 ("ntp: Fix RTC synchronization
on 32-bit platforms") revealed an underlying issue: RTC synchronization
may happen anytime, even while the system is partially suspended.

On systems where the RTC is connected to an I2C bus, the I2C bus
controller may already or still be suspended, triggering a WARNING
during suspend or resume from s2ram:

    WARNING: CPU: 0 PID: 124 at drivers/i2c/i2c-core.h:54 __i2c_transfer+0x634/0x680
    i2c i2c-6: Transfer while suspended
    [...]
    Workqueue: events_power_efficient sync_hw_clock
    [...]
    [<c0738e08>] (__i2c_transfer) from [<c0738eac>] (i2c_transfer+0x58/0xf8)
    [<c0738eac>] (i2c_transfer) from [<c065202c>] (regmap_i2c_read+0x58/0x94)
    [<c065202c>] (regmap_i2c_read) from [<c064de40>] (_regmap_raw_read+0x19c/0x2f4)
    [<c064de40>] (_regmap_raw_read) from [<c064dfdc>] (_regmap_bus_read+0x44/0x68)
    [<c064dfdc>] (_regmap_bus_read) from [<c064ccb4>] (_regmap_read+0x84/0x1a4)
    [<c064ccb4>] (_regmap_read) from [<c064d334>] (_regmap_update_bits+0xa8/0xf4)
    [<c064d334>] (_regmap_update_bits) from [<c064d464>] (_regmap_select_page+0xe4/0x100)
    [<c064d464>] (_regmap_select_page) from [<c064d554>] (_regmap_raw_write_impl+0xd4/0x6c4)
    [<c064d554>] (_regmap_raw_write_impl) from [<c064ec10>] (_regmap_raw_write+0xd8/0x114)
    [<c064ec10>] (_regmap_raw_write) from [<c064eca4>] (regmap_raw_write+0x58/0x7c)
    [<c064eca4>] (regmap_raw_write) from [<c064ede0>] (regmap_bulk_write+0x118/0x13c)
    [<c064ede0>] (regmap_bulk_write) from [<c073660c>] (da9063_rtc_set_time+0x44/0x8c)
    [<c073660c>] (da9063_rtc_set_time) from [<c0734164>] (rtc_set_time+0xc8/0x228)
    [<c0734164>] (rtc_set_time) from [<c02abe78>] (sync_hw_clock+0x128/0x1fc)
    [<c02abe78>] (sync_hw_clock) from [<c023e6a0>] (process_one_work+0x330/0x550)
    [<c023e6a0>] (process_one_work) from [<c023f0a8>] (worker_thread+0x22c/0x2ec)

Fix this race condition by using the freezable instead of the normal
power-efficient workqueue.

Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>
---
 kernel/time/ntp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

Comments

Rafael J. Wysocki Feb. 5, 2021, 12:43 p.m. UTC | #1
On Tue, Jan 26, 2021 at 6:48 AM Geert Uytterhoeven
<geert+renesas@glider.be> wrote:
>
> The bug fixed by commit e3fab2f3de081e98 ("ntp: Fix RTC synchronization
> on 32-bit platforms") revealed an underlying issue: RTC synchronization
> may happen anytime, even while the system is partially suspended.
>
> On systems where the RTC is connected to an I2C bus, the I2C bus
> controller may already or still be suspended, triggering a WARNING
> during suspend or resume from s2ram:
>
>     WARNING: CPU: 0 PID: 124 at drivers/i2c/i2c-core.h:54 __i2c_transfer+0x634/0x680
>     i2c i2c-6: Transfer while suspended
>     [...]
>     Workqueue: events_power_efficient sync_hw_clock
>     [...]
>     [<c0738e08>] (__i2c_transfer) from [<c0738eac>] (i2c_transfer+0x58/0xf8)
>     [<c0738eac>] (i2c_transfer) from [<c065202c>] (regmap_i2c_read+0x58/0x94)
>     [<c065202c>] (regmap_i2c_read) from [<c064de40>] (_regmap_raw_read+0x19c/0x2f4)
>     [<c064de40>] (_regmap_raw_read) from [<c064dfdc>] (_regmap_bus_read+0x44/0x68)
>     [<c064dfdc>] (_regmap_bus_read) from [<c064ccb4>] (_regmap_read+0x84/0x1a4)
>     [<c064ccb4>] (_regmap_read) from [<c064d334>] (_regmap_update_bits+0xa8/0xf4)
>     [<c064d334>] (_regmap_update_bits) from [<c064d464>] (_regmap_select_page+0xe4/0x100)
>     [<c064d464>] (_regmap_select_page) from [<c064d554>] (_regmap_raw_write_impl+0xd4/0x6c4)
>     [<c064d554>] (_regmap_raw_write_impl) from [<c064ec10>] (_regmap_raw_write+0xd8/0x114)
>     [<c064ec10>] (_regmap_raw_write) from [<c064eca4>] (regmap_raw_write+0x58/0x7c)
>     [<c064eca4>] (regmap_raw_write) from [<c064ede0>] (regmap_bulk_write+0x118/0x13c)
>     [<c064ede0>] (regmap_bulk_write) from [<c073660c>] (da9063_rtc_set_time+0x44/0x8c)
>     [<c073660c>] (da9063_rtc_set_time) from [<c0734164>] (rtc_set_time+0xc8/0x228)
>     [<c0734164>] (rtc_set_time) from [<c02abe78>] (sync_hw_clock+0x128/0x1fc)
>     [<c02abe78>] (sync_hw_clock) from [<c023e6a0>] (process_one_work+0x330/0x550)
>     [<c023e6a0>] (process_one_work) from [<c023f0a8>] (worker_thread+0x22c/0x2ec)
>
> Fix this race condition by using the freezable instead of the normal
> power-efficient workqueue.
>
> Signed-off-by: Geert Uytterhoeven <geert+renesas@glider.be>

LGTM

Acked-by: Rafael J. Wysocki <rafael@kernel.org>

> ---
>  kernel/time/ntp.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
> index 54d52fab201d283e..6310328fe398406a 100644
> --- a/kernel/time/ntp.c
> +++ b/kernel/time/ntp.c
> @@ -502,7 +502,7 @@ static struct hrtimer sync_hrtimer;
>
>  static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer)
>  {
> -       queue_work(system_power_efficient_wq, &sync_work);
> +       queue_work(system_freezable_power_efficient_wq, &sync_work);
>
>         return HRTIMER_NORESTART;
>  }
> @@ -668,7 +668,7 @@ void ntp_notify_cmos_timer(void)
>          * just a pointless work scheduled.
>          */
>         if (ntp_synced() && !hrtimer_is_queued(&sync_hrtimer))
> -               queue_work(system_power_efficient_wq, &sync_work);
> +               queue_work(system_freezable_power_efficient_wq, &sync_work);
>  }
>
>  static void __init ntp_init_cmos_sync(void)
> --
> 2.25.1
>
diff mbox series

Patch

diff --git a/kernel/time/ntp.c b/kernel/time/ntp.c
index 54d52fab201d283e..6310328fe398406a 100644
--- a/kernel/time/ntp.c
+++ b/kernel/time/ntp.c
@@ -502,7 +502,7 @@  static struct hrtimer sync_hrtimer;
 
 static enum hrtimer_restart sync_timer_callback(struct hrtimer *timer)
 {
-	queue_work(system_power_efficient_wq, &sync_work);
+	queue_work(system_freezable_power_efficient_wq, &sync_work);
 
 	return HRTIMER_NORESTART;
 }
@@ -668,7 +668,7 @@  void ntp_notify_cmos_timer(void)
 	 * just a pointless work scheduled.
 	 */
 	if (ntp_synced() && !hrtimer_is_queued(&sync_hrtimer))
-		queue_work(system_power_efficient_wq, &sync_work);
+		queue_work(system_freezable_power_efficient_wq, &sync_work);
 }
 
 static void __init ntp_init_cmos_sync(void)