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This adds the option to use a hrtimer to generate a watchdog pretimeout event for hardware watchdogs that do not natively support watchdog pretimeouts. With this enabled, all watchdogs will appear to have pretimeout support in userspace. If no pretimeout value is set, there will be no change in the watchdog's behavior. If a pretimeout value is set for a specific watchdog that does not have built-in pretimeout support, a timer will be started that should fire at the specified time before the watchdog timeout would occur. When the watchdog is successfully pinged, the timer will be restarted. If the timer is allowed to fire it will generate a pretimeout event. However because a software timer is used, it may not be able to fire in every circumstance. If the watchdog does support a pretimeout natively, that functionality will be used instead of the hrtimer. The general design of this feaure was inspired by the software watchdog, specifically its own pretimeout implementation. However the software watchdog and this feature are completely independent. They can be used together; with or without CONFIG_SOFT_WATCHDOG_PRETIMEOUT enabled. The main advantage of using the hrtimer pretimeout with a hardware watchdog, compared to running the software watchdog with a hardware watchdog, is that if the hardware watchdog driver is unable to ping the watchdog (e.g. due to a bus or communication error), then the hrtimer pretimeout would still fire whereas the software watchdog would not. Signed-off-by: Curtis Klein <curtis.klein@hpe.com> Reviewed-by: Guenter Roeck <linux@roeck-us.net> Link: https://lore.kernel.org/r/1612383090-27110-1-git-send-email-curtis.klein@hpe.com Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Wim Van Sebroeck <wim@linux-watchdog.org>
217 lines
4.5 KiB
C
217 lines
4.5 KiB
C
// SPDX-License-Identifier: GPL-2.0-or-later
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/*
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* Copyright (C) 2015-2016 Mentor Graphics
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*/
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#include <linux/list.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/string.h>
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#include <linux/watchdog.h>
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#include "watchdog_core.h"
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#include "watchdog_pretimeout.h"
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/* Default watchdog pretimeout governor */
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static struct watchdog_governor *default_gov;
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/* The spinlock protects default_gov, wdd->gov and pretimeout_list */
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static DEFINE_SPINLOCK(pretimeout_lock);
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/* List of watchdog devices, which can generate a pretimeout event */
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static LIST_HEAD(pretimeout_list);
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struct watchdog_pretimeout {
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struct watchdog_device *wdd;
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struct list_head entry;
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};
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/* The mutex protects governor list and serializes external interfaces */
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static DEFINE_MUTEX(governor_lock);
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/* List of the registered watchdog pretimeout governors */
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static LIST_HEAD(governor_list);
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struct governor_priv {
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struct watchdog_governor *gov;
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struct list_head entry;
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};
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static struct governor_priv *find_governor_by_name(const char *gov_name)
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{
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struct governor_priv *priv;
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list_for_each_entry(priv, &governor_list, entry)
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if (sysfs_streq(gov_name, priv->gov->name))
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return priv;
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return NULL;
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}
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int watchdog_pretimeout_available_governors_get(char *buf)
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{
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struct governor_priv *priv;
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int count = 0;
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mutex_lock(&governor_lock);
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list_for_each_entry(priv, &governor_list, entry)
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count += sysfs_emit_at(buf, count, "%s\n", priv->gov->name);
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mutex_unlock(&governor_lock);
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return count;
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}
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int watchdog_pretimeout_governor_get(struct watchdog_device *wdd, char *buf)
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{
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int count = 0;
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spin_lock_irq(&pretimeout_lock);
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if (wdd->gov)
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count = sysfs_emit(buf, "%s\n", wdd->gov->name);
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spin_unlock_irq(&pretimeout_lock);
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return count;
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}
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int watchdog_pretimeout_governor_set(struct watchdog_device *wdd,
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const char *buf)
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{
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struct governor_priv *priv;
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mutex_lock(&governor_lock);
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priv = find_governor_by_name(buf);
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if (!priv) {
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mutex_unlock(&governor_lock);
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return -EINVAL;
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}
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spin_lock_irq(&pretimeout_lock);
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wdd->gov = priv->gov;
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spin_unlock_irq(&pretimeout_lock);
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mutex_unlock(&governor_lock);
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return 0;
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}
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void watchdog_notify_pretimeout(struct watchdog_device *wdd)
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{
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unsigned long flags;
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spin_lock_irqsave(&pretimeout_lock, flags);
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if (!wdd->gov) {
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spin_unlock_irqrestore(&pretimeout_lock, flags);
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return;
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}
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wdd->gov->pretimeout(wdd);
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spin_unlock_irqrestore(&pretimeout_lock, flags);
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}
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EXPORT_SYMBOL_GPL(watchdog_notify_pretimeout);
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int watchdog_register_governor(struct watchdog_governor *gov)
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{
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struct watchdog_pretimeout *p;
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struct governor_priv *priv;
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priv = kzalloc(sizeof(*priv), GFP_KERNEL);
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if (!priv)
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return -ENOMEM;
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mutex_lock(&governor_lock);
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if (find_governor_by_name(gov->name)) {
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mutex_unlock(&governor_lock);
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kfree(priv);
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return -EBUSY;
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}
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priv->gov = gov;
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list_add(&priv->entry, &governor_list);
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if (!strncmp(gov->name, WATCHDOG_PRETIMEOUT_DEFAULT_GOV,
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WATCHDOG_GOV_NAME_MAXLEN)) {
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spin_lock_irq(&pretimeout_lock);
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default_gov = gov;
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list_for_each_entry(p, &pretimeout_list, entry)
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if (!p->wdd->gov)
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p->wdd->gov = default_gov;
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spin_unlock_irq(&pretimeout_lock);
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}
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mutex_unlock(&governor_lock);
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return 0;
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}
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EXPORT_SYMBOL(watchdog_register_governor);
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void watchdog_unregister_governor(struct watchdog_governor *gov)
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{
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struct watchdog_pretimeout *p;
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struct governor_priv *priv, *t;
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mutex_lock(&governor_lock);
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list_for_each_entry_safe(priv, t, &governor_list, entry) {
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if (priv->gov == gov) {
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list_del(&priv->entry);
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kfree(priv);
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break;
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}
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}
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spin_lock_irq(&pretimeout_lock);
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list_for_each_entry(p, &pretimeout_list, entry)
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if (p->wdd->gov == gov)
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p->wdd->gov = default_gov;
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spin_unlock_irq(&pretimeout_lock);
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mutex_unlock(&governor_lock);
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}
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EXPORT_SYMBOL(watchdog_unregister_governor);
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int watchdog_register_pretimeout(struct watchdog_device *wdd)
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{
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struct watchdog_pretimeout *p;
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if (!watchdog_have_pretimeout(wdd))
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return 0;
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p = kzalloc(sizeof(*p), GFP_KERNEL);
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if (!p)
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return -ENOMEM;
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spin_lock_irq(&pretimeout_lock);
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list_add(&p->entry, &pretimeout_list);
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p->wdd = wdd;
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wdd->gov = default_gov;
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spin_unlock_irq(&pretimeout_lock);
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return 0;
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}
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void watchdog_unregister_pretimeout(struct watchdog_device *wdd)
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{
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struct watchdog_pretimeout *p, *t;
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if (!watchdog_have_pretimeout(wdd))
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return;
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spin_lock_irq(&pretimeout_lock);
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wdd->gov = NULL;
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list_for_each_entry_safe(p, t, &pretimeout_list, entry) {
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if (p->wdd == wdd) {
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list_del(&p->entry);
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break;
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}
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}
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spin_unlock_irq(&pretimeout_lock);
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kfree(p);
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}
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