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Date: Thu, 16 Jun 2022 16:55:19 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Daniel Bristot de Oliveira <bristot@...nel.org>,
Steven Rostedt <rostedt@...dmis.org>
Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>,
Jonathan Corbet <corbet@....net>,
Ingo Molnar <mingo@...hat.com>,
Thomas Gleixner <tglx@...utronix.de>,
Peter Zijlstra <peterz@...radead.org>,
Will Deacon <will@...nel.org>,
Catalin Marinas <catalin.marinas@....com>,
Marco Elver <elver@...gle.com>,
Dmitry Vyukov <dvyukov@...gle.com>,
"Paul E. McKenney" <paulmck@...nel.org>,
Shuah Khan <skhan@...uxfoundation.org>,
Gabriele Paoloni <gpaoloni@...hat.com>,
Juri Lelli <juri.lelli@...hat.com>,
Clark Williams <williams@...hat.com>,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org,
linux-trace-devel@...r.kernel.org
Subject: Re: [PATCH V4 17/20] watchdog/dev: Add tracepoints
On 6/16/22 08:47, Daniel Bristot de Oliveira wrote:
> On 6/16/22 15:44, Guenter Roeck wrote:
>> On 6/16/22 01:44, Daniel Bristot de Oliveira wrote:
>>> Add a set of tracepoints, enabling the observability of the watchdog
>>> device interactions with user-space.
>>>
>>> The events are:
>>> watchdog:watchdog_open
>>> watchdog:watchdog_close
>>> watchdog:watchdog_start
>>> watchdog:watchdog_stop
>>> watchdog:watchdog_set_timeout
>>> watchdog:watchdog_ping
>>> watchdog:watchdog_nowayout
>>> watchdog:watchdog_set_keep_alive
>>> watchdog:watchdog_keep_alive
>>> watchdog:watchdog_set_pretimeout
>>> watchdog:watchdog_pretimeout
>>>
>>> Cc: Wim Van Sebroeck <wim@...ux-watchdog.org>
>>> Cc: Guenter Roeck <linux@...ck-us.net>
>>> Cc: Jonathan Corbet <corbet@....net>
>>> Cc: Steven Rostedt <rostedt@...dmis.org>
>>> Cc: Ingo Molnar <mingo@...hat.com>
>>> Cc: Thomas Gleixner <tglx@...utronix.de>
>>> Cc: Peter Zijlstra <peterz@...radead.org>
>>> Cc: Will Deacon <will@...nel.org>
>>> Cc: Catalin Marinas <catalin.marinas@....com>
>>> Cc: Marco Elver <elver@...gle.com>
>>> Cc: Dmitry Vyukov <dvyukov@...gle.com>
>>> Cc: "Paul E. McKenney" <paulmck@...nel.org>
>>> Cc: Shuah Khan <skhan@...uxfoundation.org>
>>> Cc: Gabriele Paoloni <gpaoloni@...hat.com>
>>> Cc: Juri Lelli <juri.lelli@...hat.com>
>>> Cc: Clark Williams <williams@...hat.com>
>>> Cc: linux-doc@...r.kernel.org
>>> Cc: linux-kernel@...r.kernel.org
>>> Cc: linux-trace-devel@...r.kernel.org
>>> Signed-off-by: Daniel Bristot de Oliveira <bristot@...nel.org>
>>> ---
>>> drivers/watchdog/watchdog_dev.c | 43 ++++++++++-
>>> drivers/watchdog/watchdog_pretimeout.c | 2 +
>>> include/linux/watchdog.h | 7 +-
>>> include/trace/events/watchdog.h | 101 +++++++++++++++++++++++++
>>> 4 files changed, 143 insertions(+), 10 deletions(-)
>>> create mode 100644 include/trace/events/watchdog.h
>>>
>>> diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
>>> index 54903f3c851e..2f28dc5ab763 100644
>>> --- a/drivers/watchdog/watchdog_dev.c
>>> +++ b/drivers/watchdog/watchdog_dev.c
>>> @@ -44,6 +44,9 @@
>>> #include <linux/watchdog.h> /* For watchdog specific items */
>>> #include <linux/uaccess.h> /* For copy_to_user/put_user/... */
>>> +#define CREATE_TRACE_POINTS
>>> +#include <trace/events/watchdog.h>
>>> +
>>> #include "watchdog_core.h"
>>> #include "watchdog_pretimeout.h"
>>> @@ -130,9 +133,11 @@ static inline void watchdog_update_worker(struct
>>> watchdog_device *wdd)
>>> if (watchdog_need_worker(wdd)) {
>>> ktime_t t = watchdog_next_keepalive(wdd);
>>> - if (t > 0)
>>> + if (t > 0) {
>>> hrtimer_start(&wd_data->timer, t,
>>> HRTIMER_MODE_REL_HARD);
>>> + trace_watchdog_set_keep_alive(wdd, ktime_to_ms(t));
>>> + }
>>> } else {
>>> hrtimer_cancel(&wd_data->timer);
>>> }
>>> @@ -141,7 +146,7 @@ static inline void watchdog_update_worker(struct
>>> watchdog_device *wdd)
>>> static int __watchdog_ping(struct watchdog_device *wdd)
>>> {
>>> struct watchdog_core_data *wd_data = wdd->wd_data;
>>> - ktime_t earliest_keepalive, now;
>>> + ktime_t earliest_keepalive, now, next_keepalive;
>>> int err;
>>> earliest_keepalive = ktime_add(wd_data->last_hw_keepalive,
>>> @@ -149,14 +154,16 @@ static int __watchdog_ping(struct watchdog_device *wdd)
>>> now = ktime_get();
>>> if (ktime_after(earliest_keepalive, now)) {
>>> - hrtimer_start(&wd_data->timer,
>>> - ktime_sub(earliest_keepalive, now),
>>> + next_keepalive = ktime_sub(earliest_keepalive, now);
>>> + hrtimer_start(&wd_data->timer, next_keepalive,
>>> HRTIMER_MODE_REL_HARD);
>>> + trace_watchdog_set_keep_alive(wdd, ktime_to_ms(next_keepalive));
>>> return 0;
>>> }
>>> wd_data->last_hw_keepalive = now;
>>> + trace_watchdog_ping(wdd);
>>> if (wdd->ops->ping)
>>> err = wdd->ops->ping(wdd); /* ping the watchdog */
>>> else
>>> @@ -215,6 +222,7 @@ static void watchdog_ping_work(struct kthread_work *work)
>>> wd_data = container_of(work, struct watchdog_core_data, work);
>>> mutex_lock(&wd_data->lock);
>>> + trace_watchdog_keep_alive(wd_data->wdd);
>>> if (watchdog_worker_should_ping(wd_data))
>>> __watchdog_ping(wd_data->wdd);
>>> mutex_unlock(&wd_data->lock);
>>> @@ -250,6 +258,8 @@ static int watchdog_start(struct watchdog_device *wdd)
>>> set_bit(_WDOG_KEEPALIVE, &wd_data->status);
>>> + trace_watchdog_start(wdd);
>>> +
>>> started_at = ktime_get();
>>> if (watchdog_hw_running(wdd) && wdd->ops->ping) {
>>> err = __watchdog_ping(wdd);
>>> @@ -294,6 +304,7 @@ static int watchdog_stop(struct watchdog_device *wdd)
>>> return -EBUSY;
>>> }
>>> + trace_watchdog_stop(wdd);
>>> if (wdd->ops->stop) {
>>> clear_bit(WDOG_HW_RUNNING, &wdd->status);
>>> err = wdd->ops->stop(wdd);
>>> @@ -367,6 +378,7 @@ static int watchdog_set_timeout(struct watchdog_device *wdd,
>>> if (watchdog_timeout_invalid(wdd, timeout))
>>> return -EINVAL;
>>> + trace_watchdog_set_timeout(wdd, timeout);
>>
>> The driver has no obligation to set the timeout to the
>> requested value. It might be more valuable to report both
>> the requested and the actual values.
>>
>>
>
> Ack! how do I get the actual value?
>
Read it from the data structure after the driver function returned.
>>> if (wdd->ops->set_timeout) {
>>> err = wdd->ops->set_timeout(wdd, timeout);
>>> } else {
>>> @@ -399,6 +411,8 @@ static int watchdog_set_pretimeout(struct watchdog_device
>>> *wdd,
>>> if (watchdog_pretimeout_invalid(wdd, timeout))
>>> return -EINVAL;
>>> + trace_watchdog_set_pretimeout(wdd, timeout);
>>> +
>>
>> Again, the driver has no obligation to set the timeout to the
>> requested value.
>
> /me takes note.
>
>>
>>> if (wdd->ops->set_pretimeout && (wdd->info->options & WDIOF_PRETIMEOUT))
>>> err = wdd->ops->set_pretimeout(wdd, timeout);
>>> else
>>> @@ -430,6 +444,23 @@ static int watchdog_get_timeleft(struct watchdog_device
>>> *wdd,
>>> return 0;
>>> }
>>> +/**
>>> + * watchdog_set_nowayout - set nowaout bit
>>> + * @wdd: The watchdog device to set nowayoutbit
>>> + * @nowayout A boolean on/off switcher
>>> + *
>>> + * If nowayout boolean is true, the nowayout option is set. No action is
>>> + * taken if nowayout is false.
>>> + */
>>> +void watchdog_set_nowayout(struct watchdog_device *wdd, bool nowayout)
>>> +{
>>> + if (nowayout) {
>>> + set_bit(WDOG_NO_WAY_OUT, &wdd->status);
>>> + trace_watchdog_nowayout(wdd);
>>> + }
>>> +}
>>> +EXPORT_SYMBOL(watchdog_set_nowayout);
>>> +
>>> #ifdef CONFIG_WATCHDOG_SYSFS
>>> static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
>>> char *buf)
>>> @@ -861,6 +892,8 @@ static int watchdog_open(struct inode *inode, struct file
>>> *file)
>>> goto out_clear;
>>> }
>>> + trace_watchdog_open(wdd);
>>> +
>>> err = watchdog_start(wdd);
>>> if (err < 0)
>>> goto out_mod;
>>> @@ -883,6 +916,7 @@ static int watchdog_open(struct inode *inode, struct file
>>> *file)
>>> return stream_open(inode, file);
>>> out_mod:
>>> + trace_watchdog_close(wdd);
>>> module_put(wd_data->wdd->ops->owner);
>>> out_clear:
>>> clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
>>> @@ -944,6 +978,7 @@ static int watchdog_release(struct inode *inode, struct
>>> file *file)
>>> /* make sure that /dev/watchdog can be re-opened */
>>> clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
>>> + trace_watchdog_close(wdd);
>>> done:
>>> running = wdd && watchdog_hw_running(wdd);
>>> mutex_unlock(&wd_data->lock);
>>> diff --git a/drivers/watchdog/watchdog_pretimeout.c
>>> b/drivers/watchdog/watchdog_pretimeout.c
>>> index 376a495ab80c..58c391ed2205 100644
>>> --- a/drivers/watchdog/watchdog_pretimeout.c
>>> +++ b/drivers/watchdog/watchdog_pretimeout.c
>>> @@ -8,6 +8,7 @@
>>> #include <linux/spinlock.h>
>>> #include <linux/string.h>
>>> #include <linux/watchdog.h>
>>> +#include <trace/events/watchdog.h>
>>> #include "watchdog_core.h"
>>> #include "watchdog_pretimeout.h"
>>> @@ -107,6 +108,7 @@ void watchdog_notify_pretimeout(struct watchdog_device *wdd)
>>> return;
>>> }
>>> + trace_watchdog_pretimeout(wdd);
>>> wdd->gov->pretimeout(wdd);
>>> spin_unlock_irqrestore(&pretimeout_lock, flags);
>>> }
>>> diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
>>> index 99660197a36c..11d93407e492 100644
>>> --- a/include/linux/watchdog.h
>>> +++ b/include/linux/watchdog.h
>>> @@ -139,12 +139,7 @@ static inline bool watchdog_hw_running(struct
>>> watchdog_device *wdd)
>>> return test_bit(WDOG_HW_RUNNING, &wdd->status);
>>> }
>>> -/* Use the following function to set the nowayout feature */
>>> -static inline void watchdog_set_nowayout(struct watchdog_device *wdd, bool
>>> nowayout)
>>> -{
>>> - if (nowayout)
>>> - set_bit(WDOG_NO_WAY_OUT, &wdd->status);
>>> -}
>>> +void watchdog_set_nowayout(struct watchdog_device *wdd, bool nowayout);
>>> /* Use the following function to stop the watchdog on reboot */
>>> static inline void watchdog_stop_on_reboot(struct watchdog_device *wdd)
>>> diff --git a/include/trace/events/watchdog.h b/include/trace/events/watchdog.h
>>> new file mode 100644
>>> index 000000000000..145cd6cfaa02
>>> --- /dev/null
>>> +++ b/include/trace/events/watchdog.h
>>> @@ -0,0 +1,101 @@
>>> +/* SPDX-License-Identifier: GPL-2.0 */
>>> +#undef TRACE_SYSTEM
>>> +#define TRACE_SYSTEM watchdog
>>> +
>>> +#if !defined(_TRACE_WATCHDOG_H) || defined(TRACE_HEADER_MULTI_READ)
>>> +#define _TRACE_WATCHDOG_H
>>> +
>>> +#include <linux/tracepoint.h>
>>> +
>>> +/*
>>> + * These are all events whose sole argument is the watchdog id.
>>> + */
>>> +DECLARE_EVENT_CLASS(dev_operations_template,
>>> +
>>> + TP_PROTO(struct watchdog_device *wdd),
>>> +
>>> + TP_ARGS(wdd),
>>> +
>>> + TP_STRUCT__entry(
>>> + __field(__u32, id)
>>> + ),
>>> +
>>> + TP_fast_assign(
>>> + __entry->id = wdd->id;
>>> + ),
>>> +
>>> + TP_printk("id=%d",
>>> + __entry->id)
>>> +);
>>> +
>>> +DEFINE_EVENT(dev_operations_template, watchdog_open,
>>> + TP_PROTO(struct watchdog_device *wdd),
>>> + TP_ARGS(wdd));
>>> +
>>> +DEFINE_EVENT(dev_operations_template, watchdog_close,
>>> + TP_PROTO(struct watchdog_device *wdd),
>>> + TP_ARGS(wdd));
>>> +
>>> +DEFINE_EVENT(dev_operations_template, watchdog_start,
>>> + TP_PROTO(struct watchdog_device *wdd),
>>> + TP_ARGS(wdd));
>>> +
>>> +DEFINE_EVENT(dev_operations_template, watchdog_stop,
>>> + TP_PROTO(struct watchdog_device *wdd),
>>> + TP_ARGS(wdd));
>>> +
>>> +DEFINE_EVENT(dev_operations_template, watchdog_ping,
>>> + TP_PROTO(struct watchdog_device *wdd),
>>> + TP_ARGS(wdd));
>>> +
>>> +DEFINE_EVENT(dev_operations_template, watchdog_nowayout,
>>> + TP_PROTO(struct watchdog_device *wdd),
>>> + TP_ARGS(wdd));
>>> +
>>> +DEFINE_EVENT(dev_operations_template, watchdog_keep_alive,
>>> + TP_PROTO(struct watchdog_device *wdd),
>>> + TP_ARGS(wdd));
>>> +
>>> +DEFINE_EVENT(dev_operations_template, watchdog_pretimeout,
>>> + TP_PROTO(struct watchdog_device *wdd),
>>> + TP_ARGS(wdd));
>>> +
>>> +/*
>>> + * These are all events with a device ID and a given timeout.
>>> + */
>>> +DECLARE_EVENT_CLASS(watchdog_timeout_template,
>>> +
>>> + TP_PROTO(struct watchdog_device *wdd, u64 timeout),
>>> +
>>> + TP_ARGS(wdd, timeout),
>>> +
>>> + TP_STRUCT__entry(
>>> + __field(__u32, id)
>>> + __field(__u64, timeout)
>>
>>
>> Why u64 ? timeout is unsigned long.
>
> ack! I will change it. (I am seeing unsigned int, am I missing something?).
Yes, you are correct.
Guenter
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