linux-kernel - Re: [PATCH v3] watchdog: Add tracing events for the most usual watchdog events

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Date:   Sat, 8 Oct 2022 15:13:21 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Uwe Kleine-König <u.kleine-koenig@...gutronix.de>,
        Wim Van Sebroeck <wim@...ux-watchdog.org>
Cc:     Ingo Molnar <mingo@...hat.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        linux-watchdog@...r.kernel.org, kernel@...gutronix.de,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3] watchdog: Add tracing events for the most usual
 watchdog events

On 10/8/22 10:46, Uwe Kleine-König wrote:
> To simplify debugging which process touches a watchdog and when, add
> tracing events for .start(), .set_timeout(), .ping() and .stop().
> 
> Signed-off-by: Uwe Kleine-König <u.kleine-koenig@...gutronix.de>

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

> ---
> Changes since v2 sent with Message-Id:
> 20221004091950.3419662-1-u.kleine-koenig@...gutronix.de:
> 
>   - Reorder events in the header to have all DEFINE_EVENTS near their
>     DECLARE_EVENT_CLASS.
> 
> Changes since (implict) v1 sent with Message-Id:
> 20220930144935.3373366-1-u.kleine-koenig@...gutronix.de:
> 
>   - Make use of DECLARE_EVENT_CLASS as {requ,sugg}ested by Steven.
> 
>   MAINTAINERS                      |  1 +
>   drivers/watchdog/watchdog_core.c |  4 ++
>   drivers/watchdog/watchdog_dev.c  | 12 +++++-
>   include/trace/events/watchdog.h  | 66 ++++++++++++++++++++++++++++++++
>   4 files changed, 81 insertions(+), 2 deletions(-)
>   create mode 100644 include/trace/events/watchdog.h
> 
> diff --git a/MAINTAINERS b/MAINTAINERS
> index 72b9654f764c..507de599116b 100644
> --- a/MAINTAINERS
> +++ b/MAINTAINERS
> @@ -21890,6 +21890,7 @@ F:	Documentation/watchdog/
>   F:	drivers/watchdog/
>   F:	include/linux/watchdog.h
>   F:	include/uapi/linux/watchdog.h
> +F:	include/trace/events/watchdog.h
>   
>   WHISKEYCOVE PMIC GPIO DRIVER
>   M:	Kuppuswamy Sathyanarayanan <sathyanarayanan.kuppuswamy@...ux.intel.com>
> diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
> index 3fe8a7edc252..c777a612d932 100644
> --- a/drivers/watchdog/watchdog_core.c
> +++ b/drivers/watchdog/watchdog_core.c
> @@ -38,6 +38,9 @@
>   
>   #include "watchdog_core.h"	/* For watchdog_dev_register/... */
>   
> +#define CREATE_TRACE_POINTS
> +#include <trace/events/watchdog.h>
> +
>   static DEFINE_IDA(watchdog_ida);
>   
>   static int stop_on_reboot = -1;
> @@ -163,6 +166,7 @@ static int watchdog_reboot_notifier(struct notifier_block *nb,
>   			int ret;
>   
>   			ret = wdd->ops->stop(wdd);
> +			trace_watchdog_stop(wdd, ret);
>   			if (ret)
>   				return NOTIFY_BAD;
>   		}
> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> index 54903f3c851e..3323309c913c 100644
> --- a/drivers/watchdog/watchdog_dev.c
> +++ b/drivers/watchdog/watchdog_dev.c
> @@ -47,6 +47,8 @@
>   #include "watchdog_core.h"
>   #include "watchdog_pretimeout.h"
>   
> +#include <trace/events/watchdog.h>
> +
>   /* the dev_t structure to store the dynamically allocated watchdog devices */
>   static dev_t watchdog_devt;
>   /* Reference to watchdog device behind /dev/watchdog */
> @@ -157,10 +159,13 @@ static int __watchdog_ping(struct watchdog_device *wdd)
>   
>   	wd_data->last_hw_keepalive = now;
>   
> -	if (wdd->ops->ping)
> +	if (wdd->ops->ping) {
>   		err = wdd->ops->ping(wdd);  /* ping the watchdog */
> -	else
> +		trace_watchdog_ping(wdd, err);
> +	} else {
>   		err = wdd->ops->start(wdd); /* restart watchdog */
> +		trace_watchdog_start(wdd, err);
> +	}
>   
>   	if (err == 0)
>   		watchdog_hrtimer_pretimeout_start(wdd);
> @@ -259,6 +264,7 @@ static int watchdog_start(struct watchdog_device *wdd)
>   		}
>   	} else {
>   		err = wdd->ops->start(wdd);
> +		trace_watchdog_start(wdd, err);
>   		if (err == 0) {
>   			set_bit(WDOG_ACTIVE, &wdd->status);
>   			wd_data->last_keepalive = started_at;
> @@ -297,6 +303,7 @@ static int watchdog_stop(struct watchdog_device *wdd)
>   	if (wdd->ops->stop) {
>   		clear_bit(WDOG_HW_RUNNING, &wdd->status);
>   		err = wdd->ops->stop(wdd);
> +		trace_watchdog_stop(wdd, err);
>   	} else {
>   		set_bit(WDOG_HW_RUNNING, &wdd->status);
>   	}
> @@ -369,6 +376,7 @@ static int watchdog_set_timeout(struct watchdog_device *wdd,
>   
>   	if (wdd->ops->set_timeout) {
>   		err = wdd->ops->set_timeout(wdd, timeout);
> +		trace_watchdog_set_timeout(wdd, timeout, err);
>   	} else {
>   		wdd->timeout = timeout;
>   		/* Disable pretimeout if it doesn't fit the new timeout */
> diff --git a/include/trace/events/watchdog.h b/include/trace/events/watchdog.h
> new file mode 100644
> index 000000000000..beb9bb3424c8
> --- /dev/null
> +++ b/include/trace/events/watchdog.h
> @@ -0,0 +1,66 @@
> +/* SPDX-License-Identifier: GPL-2.0-only */
> +#undef TRACE_SYSTEM
> +#define TRACE_SYSTEM watchdog
> +
> +#if !defined(_TRACE_WATCHDOG_H) || defined(TRACE_HEADER_MULTI_READ)
> +#define _TRACE_WATCHDOG_H
> +
> +#include <linux/watchdog.h>
> +#include <linux/tracepoint.h>
> +
> +DECLARE_EVENT_CLASS(watchdog_template,
> +
> +	TP_PROTO(struct watchdog_device *wdd, int err),
> +
> +	TP_ARGS(wdd, err),
> +
> +	TP_STRUCT__entry(
> +		__field(int, id)
> +		__field(int, err)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->id = wdd->id;
> +		__entry->err = err;
> +	),
> +
> +	TP_printk("watchdog%d err=%d", __entry->id, __entry->err)
> +);
> +
> +DEFINE_EVENT(watchdog_template, watchdog_start,
> +	TP_PROTO(struct watchdog_device *wdd, int err),
> +	TP_ARGS(wdd, err));
> +
> +DEFINE_EVENT(watchdog_template, watchdog_ping,
> +	TP_PROTO(struct watchdog_device *wdd, int err),
> +	TP_ARGS(wdd, err));
> +
> +DEFINE_EVENT(watchdog_template, watchdog_stop,
> +	TP_PROTO(struct watchdog_device *wdd, int err),
> +	TP_ARGS(wdd, err));
> +
> +TRACE_EVENT(watchdog_set_timeout,
> +
> +	TP_PROTO(struct watchdog_device *wdd, unsigned int timeout, int err),
> +
> +	TP_ARGS(wdd, timeout, err),
> +
> +	TP_STRUCT__entry(
> +		__field(int, id)
> +		__field(unsigned int, timeout)
> +		__field(int, err)
> +	),
> +
> +	TP_fast_assign(
> +		__entry->id = wdd->id;
> +		__entry->timeout = timeout;
> +		__entry->err = err;
> +	),
> +
> +	TP_printk("watchdog%d timeout=%u err=%d", __entry->id, __entry->timeout, __entry->err)
> +);
> +
> +#endif /* !defined(_TRACE_WATCHDOG_H) || defined(TRACE_HEADER_MULTI_READ) */
> +
> +/* This part must be outside protection */
> +#include <trace/define_trace.h>
> 
> base-commit: 4fe89d07dcc2804c8b562f6c7896a45643d34b2f