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* [PATCH] watchdog: qcom: Avoid context switch in restart handler
@ 2020-12-07  6:00 Manivannan Sadhasivam
  2020-12-07  7:13 ` Guenter Roeck
  0 siblings, 1 reply; 2+ messages in thread
From: Manivannan Sadhasivam @ 2020-12-07  6:00 UTC (permalink / raw)
  To: wim, linux
  Cc: agross, bjorn.andersson, linux-arm-msm, linux-watchdog,
	linux-kernel, Manivannan Sadhasivam

The use of msleep() in the restart handler will cause scheduler to
induce a context switch which is not desirable. This generates below
warning on SDX55 when WDT is the only available restart source:

[   39.800188] reboot: Restarting system
[   39.804115] ------------[ cut here ]------------
[   39.807855] WARNING: CPU: 0 PID: 678 at kernel/rcu/tree_plugin.h:297 rcu_note_context_switch+0x190/0x764
[   39.812538] Modules linked in:
[   39.821954] CPU: 0 PID: 678 Comm: reboot Not tainted 5.10.0-rc1-00063-g33a9990d1d66-dirty #47
[   39.824854] Hardware name: Generic DT based system
[   39.833470] [<c0310fbc>] (unwind_backtrace) from [<c030c544>] (show_stack+0x10/0x14)
[   39.838154] [<c030c544>] (show_stack) from [<c0c218f0>] (dump_stack+0x8c/0xa0)
[   39.846049] [<c0c218f0>] (dump_stack) from [<c0322f80>] (__warn+0xd8/0xf0)
[   39.853058] [<c0322f80>] (__warn) from [<c0c1dc08>] (warn_slowpath_fmt+0x64/0xc8)
[   39.859925] [<c0c1dc08>] (warn_slowpath_fmt) from [<c038b6f4>] (rcu_note_context_switch+0x190/0x764)
[   39.867503] [<c038b6f4>] (rcu_note_context_switch) from [<c0c2aa3c>] (__schedule+0x84/0x640)
[   39.876685] [<c0c2aa3c>] (__schedule) from [<c0c2b050>] (schedule+0x58/0x10c)
[   39.885095] [<c0c2b050>] (schedule) from [<c0c2eed0>] (schedule_timeout+0x1e8/0x3d4)
[   39.892135] [<c0c2eed0>] (schedule_timeout) from [<c039ad40>] (msleep+0x2c/0x38)
[   39.899947] [<c039ad40>] (msleep) from [<c0a59d0c>] (qcom_wdt_restart+0xc4/0xcc)
[   39.907319] [<c0a59d0c>] (qcom_wdt_restart) from [<c0a58290>] (watchdog_restart_notifier+0x18/0x28)
[   39.914715] [<c0a58290>] (watchdog_restart_notifier) from [<c03468e0>] (atomic_notifier_call_chain+0x60/0x84)
[   39.923487] [<c03468e0>] (atomic_notifier_call_chain) from [<c030ae64>] (machine_restart+0x78/0x7c)
[   39.933551] [<c030ae64>] (machine_restart) from [<c0348048>] (__do_sys_reboot+0xdc/0x1e0)
[   39.942397] [<c0348048>] (__do_sys_reboot) from [<c0300060>] (ret_fast_syscall+0x0/0x54)
[   39.950721] Exception stack(0xc3e0bfa8 to 0xc3e0bff0)
[   39.958855] bfa0:                   0001221c bed2fe24 fee1dead 28121969 01234567 00000000
[   39.963832] bfc0: 0001221c bed2fe24 00000003 00000058 000225e0 00000000 00000000 00000000
[   39.971985] bfe0: b6e62560 bed2fc84 00010fd8 b6e62580
[   39.980124] ---[ end trace 3f578288bad866e4 ]---

Hence, replace msleep() with mdelay() to fix this issue.

Fixes: 05e487d905ab ("watchdog: qcom: register a restart notifier")
Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
---
 drivers/watchdog/qcom-wdt.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
index ab7465d186fd..cdf754233e53 100644
--- a/drivers/watchdog/qcom-wdt.c
+++ b/drivers/watchdog/qcom-wdt.c
@@ -148,7 +148,7 @@ static int qcom_wdt_restart(struct watchdog_device *wdd, unsigned long action,
 	 */
 	wmb();
 
-	msleep(150);
+	mdelay(150);
 	return 0;
 }
 
-- 
2.25.1


^ permalink raw reply	[flat|nested] 2+ messages in thread

* Re: [PATCH] watchdog: qcom: Avoid context switch in restart handler
  2020-12-07  6:00 [PATCH] watchdog: qcom: Avoid context switch in restart handler Manivannan Sadhasivam
@ 2020-12-07  7:13 ` Guenter Roeck
  0 siblings, 0 replies; 2+ messages in thread
From: Guenter Roeck @ 2020-12-07  7:13 UTC (permalink / raw)
  To: Manivannan Sadhasivam, wim
  Cc: agross, bjorn.andersson, linux-arm-msm, linux-watchdog, linux-kernel

On 12/6/20 10:00 PM, Manivannan Sadhasivam wrote:
> The use of msleep() in the restart handler will cause scheduler to
> induce a context switch which is not desirable. This generates below
> warning on SDX55 when WDT is the only available restart source:
> 
> [   39.800188] reboot: Restarting system
> [   39.804115] ------------[ cut here ]------------
> [   39.807855] WARNING: CPU: 0 PID: 678 at kernel/rcu/tree_plugin.h:297 rcu_note_context_switch+0x190/0x764
> [   39.812538] Modules linked in:
> [   39.821954] CPU: 0 PID: 678 Comm: reboot Not tainted 5.10.0-rc1-00063-g33a9990d1d66-dirty #47
> [   39.824854] Hardware name: Generic DT based system
> [   39.833470] [<c0310fbc>] (unwind_backtrace) from [<c030c544>] (show_stack+0x10/0x14)
> [   39.838154] [<c030c544>] (show_stack) from [<c0c218f0>] (dump_stack+0x8c/0xa0)
> [   39.846049] [<c0c218f0>] (dump_stack) from [<c0322f80>] (__warn+0xd8/0xf0)
> [   39.853058] [<c0322f80>] (__warn) from [<c0c1dc08>] (warn_slowpath_fmt+0x64/0xc8)
> [   39.859925] [<c0c1dc08>] (warn_slowpath_fmt) from [<c038b6f4>] (rcu_note_context_switch+0x190/0x764)
> [   39.867503] [<c038b6f4>] (rcu_note_context_switch) from [<c0c2aa3c>] (__schedule+0x84/0x640)
> [   39.876685] [<c0c2aa3c>] (__schedule) from [<c0c2b050>] (schedule+0x58/0x10c)
> [   39.885095] [<c0c2b050>] (schedule) from [<c0c2eed0>] (schedule_timeout+0x1e8/0x3d4)
> [   39.892135] [<c0c2eed0>] (schedule_timeout) from [<c039ad40>] (msleep+0x2c/0x38)
> [   39.899947] [<c039ad40>] (msleep) from [<c0a59d0c>] (qcom_wdt_restart+0xc4/0xcc)
> [   39.907319] [<c0a59d0c>] (qcom_wdt_restart) from [<c0a58290>] (watchdog_restart_notifier+0x18/0x28)
> [   39.914715] [<c0a58290>] (watchdog_restart_notifier) from [<c03468e0>] (atomic_notifier_call_chain+0x60/0x84)
> [   39.923487] [<c03468e0>] (atomic_notifier_call_chain) from [<c030ae64>] (machine_restart+0x78/0x7c)
> [   39.933551] [<c030ae64>] (machine_restart) from [<c0348048>] (__do_sys_reboot+0xdc/0x1e0)
> [   39.942397] [<c0348048>] (__do_sys_reboot) from [<c0300060>] (ret_fast_syscall+0x0/0x54)
> [   39.950721] Exception stack(0xc3e0bfa8 to 0xc3e0bff0)
> [   39.958855] bfa0:                   0001221c bed2fe24 fee1dead 28121969 01234567 00000000
> [   39.963832] bfc0: 0001221c bed2fe24 00000003 00000058 000225e0 00000000 00000000 00000000
> [   39.971985] bfe0: b6e62560 bed2fc84 00010fd8 b6e62580
> [   39.980124] ---[ end trace 3f578288bad866e4 ]---
> 
> Hence, replace msleep() with mdelay() to fix this issue.
> 
> Fixes: 05e487d905ab ("watchdog: qcom: register a restart notifier")
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Reviewed-by: Guenter Roeck <linux@roeck-us.net>

> ---
>  drivers/watchdog/qcom-wdt.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/drivers/watchdog/qcom-wdt.c b/drivers/watchdog/qcom-wdt.c
> index ab7465d186fd..cdf754233e53 100644
> --- a/drivers/watchdog/qcom-wdt.c
> +++ b/drivers/watchdog/qcom-wdt.c
> @@ -148,7 +148,7 @@ static int qcom_wdt_restart(struct watchdog_device *wdd, unsigned long action,
>  	 */
>  	wmb();
>  
> -	msleep(150);
> +	mdelay(150);
>  	return 0;
>  }
>  
> 


^ permalink raw reply	[flat|nested] 2+ messages in thread

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2020-12-07  6:00 [PATCH] watchdog: qcom: Avoid context switch in restart handler Manivannan Sadhasivam
2020-12-07  7:13 ` Guenter Roeck

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