![Guenter Roeck](/assets/img/avatar_default.png)
lockdep reports the following circular locking dependency.
======================================================
INFO: possible circular locking dependency detected ]
4.6.0-rc3-00191-gfabf418 #162 Not tainted
-------------------------------------------------------
systemd/1 is trying to acquire lock:
((&(&wd_data->work)->work)){+.+...}, at: [<80141650>] flush_work+0x0/0x280
but task is already holding lock:
(&wd_data->lock){+.+...}, at: [<804acfa8>] watchdog_release+0x18/0x190
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&wd_data->lock){+.+...}:
[<80662310>] mutex_lock_nested+0x64/0x4a8
[<804aca4c>] watchdog_ping_work+0x18/0x4c
[<80143128>] process_one_work+0x1ac/0x500
[<801434b4>] worker_thread+0x38/0x554
[<80149510>] kthread+0xf4/0x108
[<80107c10>] ret_from_fork+0x14/0x24
-> #0 ((&(&wd_data->work)->work)){+.+...}:
[<8017c4e8>] lock_acquire+0x70/0x90
[<8014169c>] flush_work+0x4c/0x280
[<801440f8>] __cancel_work_timer+0x9c/0x1e0
[<804acfcc>] watchdog_release+0x3c/0x190
[<8022c5e8>] __fput+0x80/0x1c8
[<80147b28>] task_work_run+0x94/0xc8
[<8010b998>] do_work_pending+0x8c/0xb4
[<80107ba8>] slow_work_pending+0xc/0x20
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0 CPU1
---- ----
lock(&wd_data->lock);
lock((&(&wd_data->work)->work));
lock(&wd_data->lock);
lock((&(&wd_data->work)->work));
*** DEADLOCK ***
1 lock held by systemd/1:
stack backtrace:
CPU: 2 PID: 1 Comm: systemd Not tainted 4.6.0-rc3-00191-gfabf418 #162
Hardware name: Freescale i.MX6 Quad/DualLite (Device Tree)
[<8010f5e4>] (unwind_backtrace) from [<8010c038>] (show_stack+0x10/0x14)
[<8010c038>] (show_stack) from [<8039d7fc>] (dump_stack+0xa8/0xd4)
[<8039d7fc>] (dump_stack) from [<80177ee0>] (print_circular_bug+0x214/0x334)
[<80177ee0>] (print_circular_bug) from [<80179230>] (check_prevs_add+0x4dc/0x8e8)
[<80179230>] (check_prevs_add) from [<8017b3d8>] (__lock_acquire+0xc6c/0x14ec)
[<8017b3d8>] (__lock_acquire) from [<8017c4e8>] (lock_acquire+0x70/0x90)
[<8017c4e8>] (lock_acquire) from [<8014169c>] (flush_work+0x4c/0x280)
[<8014169c>] (flush_work) from [<801440f8>] (__cancel_work_timer+0x9c/0x1e0)
[<801440f8>] (__cancel_work_timer) from [<804acfcc>] (watchdog_release+0x3c/0x190)
[<804acfcc>] (watchdog_release) from [<8022c5e8>] (__fput+0x80/0x1c8)
[<8022c5e8>] (__fput) from [<80147b28>] (task_work_run+0x94/0xc8)
[<80147b28>] (task_work_run) from [<8010b998>] (do_work_pending+0x8c/0xb4)
[<8010b998>] (do_work_pending) from [<80107ba8>] (slow_work_pending+0xc/0x20)
Turns out the call to cancel_delayed_work_sync() in watchdog_release()
is not necessary and can be dropped. If the worker is no longer necessary,
the subsequent call to watchdog_update_worker() will cancel it. If it is
already running, it won't do anything, since the worker function checks
if it needs to ping the watchdog or not.
Reported-by: Clemens Gruber <clemens.gruber@pqgruber.com>
Tested-by: Clemens Gruber <clemens.gruber@pqgruber.com>
Fixes: 11d7aba9ce
("watchdog: imx2: Convert to use infrastructure triggered keepalives")
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Wim Van Sebroeck <wim@iguana.be>
Cc: stable <stable@vger.kernel.org>
976 lines
24 KiB
C
976 lines
24 KiB
C
/*
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* watchdog_dev.c
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*
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* (c) Copyright 2008-2011 Alan Cox <alan@lxorguk.ukuu.org.uk>,
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* All Rights Reserved.
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*
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* (c) Copyright 2008-2011 Wim Van Sebroeck <wim@iguana.be>.
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*
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*
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* This source code is part of the generic code that can be used
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* by all the watchdog timer drivers.
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*
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* This part of the generic code takes care of the following
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* misc device: /dev/watchdog.
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*
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* Based on source code of the following authors:
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* Matt Domsch <Matt_Domsch@dell.com>,
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* Rob Radez <rob@osinvestor.com>,
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* Rusty Lynch <rusty@linux.co.intel.com>
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* Satyam Sharma <satyam@infradead.org>
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* Randy Dunlap <randy.dunlap@oracle.com>
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*
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* This program is free software; you can redistribute it and/or
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* modify it under the terms of the GNU General Public License
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* as published by the Free Software Foundation; either version
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* 2 of the License, or (at your option) any later version.
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*
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* Neither Alan Cox, CymruNet Ltd., Wim Van Sebroeck nor Iguana vzw.
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* admit liability nor provide warranty for any of this software.
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* This material is provided "AS-IS" and at no charge.
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*/
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#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
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#include <linux/cdev.h> /* For character device */
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#include <linux/errno.h> /* For the -ENODEV/... values */
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#include <linux/fs.h> /* For file operations */
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#include <linux/init.h> /* For __init/__exit/... */
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#include <linux/jiffies.h> /* For timeout functions */
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#include <linux/kernel.h> /* For printk/panic/... */
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#include <linux/kref.h> /* For data references */
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#include <linux/miscdevice.h> /* For handling misc devices */
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#include <linux/module.h> /* For module stuff/... */
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#include <linux/mutex.h> /* For mutexes */
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#include <linux/slab.h> /* For memory functions */
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#include <linux/types.h> /* For standard types (like size_t) */
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#include <linux/watchdog.h> /* For watchdog specific items */
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#include <linux/workqueue.h> /* For workqueue */
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#include <linux/uaccess.h> /* For copy_to_user/put_user/... */
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#include "watchdog_core.h"
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/*
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* struct watchdog_core_data - watchdog core internal data
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* @kref: Reference count.
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* @cdev: The watchdog's Character device.
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* @wdd: Pointer to watchdog device.
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* @lock: Lock for watchdog core.
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* @status: Watchdog core internal status bits.
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*/
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struct watchdog_core_data {
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struct kref kref;
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struct cdev cdev;
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struct watchdog_device *wdd;
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struct mutex lock;
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unsigned long last_keepalive;
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unsigned long last_hw_keepalive;
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struct delayed_work work;
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unsigned long status; /* Internal status bits */
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#define _WDOG_DEV_OPEN 0 /* Opened ? */
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#define _WDOG_ALLOW_RELEASE 1 /* Did we receive the magic char ? */
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};
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/* the dev_t structure to store the dynamically allocated watchdog devices */
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static dev_t watchdog_devt;
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/* Reference to watchdog device behind /dev/watchdog */
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static struct watchdog_core_data *old_wd_data;
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static struct workqueue_struct *watchdog_wq;
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static inline bool watchdog_need_worker(struct watchdog_device *wdd)
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{
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/* All variables in milli-seconds */
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unsigned int hm = wdd->max_hw_heartbeat_ms;
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unsigned int t = wdd->timeout * 1000;
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/*
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* A worker to generate heartbeat requests is needed if all of the
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* following conditions are true.
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* - Userspace activated the watchdog.
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* - The driver provided a value for the maximum hardware timeout, and
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* thus is aware that the framework supports generating heartbeat
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* requests.
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* - Userspace requests a longer timeout than the hardware can handle.
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*/
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return hm && ((watchdog_active(wdd) && t > hm) ||
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(t && !watchdog_active(wdd) && watchdog_hw_running(wdd)));
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}
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static long watchdog_next_keepalive(struct watchdog_device *wdd)
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{
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struct watchdog_core_data *wd_data = wdd->wd_data;
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unsigned int timeout_ms = wdd->timeout * 1000;
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unsigned long keepalive_interval;
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unsigned long last_heartbeat;
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unsigned long virt_timeout;
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unsigned int hw_heartbeat_ms;
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virt_timeout = wd_data->last_keepalive + msecs_to_jiffies(timeout_ms);
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hw_heartbeat_ms = min(timeout_ms, wdd->max_hw_heartbeat_ms);
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keepalive_interval = msecs_to_jiffies(hw_heartbeat_ms / 2);
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if (!watchdog_active(wdd))
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return keepalive_interval;
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/*
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* To ensure that the watchdog times out wdd->timeout seconds
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* after the most recent ping from userspace, the last
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* worker ping has to come in hw_heartbeat_ms before this timeout.
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*/
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last_heartbeat = virt_timeout - msecs_to_jiffies(hw_heartbeat_ms);
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return min_t(long, last_heartbeat - jiffies, keepalive_interval);
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}
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static inline void watchdog_update_worker(struct watchdog_device *wdd)
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{
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struct watchdog_core_data *wd_data = wdd->wd_data;
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if (watchdog_need_worker(wdd)) {
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long t = watchdog_next_keepalive(wdd);
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if (t > 0)
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mod_delayed_work(watchdog_wq, &wd_data->work, t);
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} else {
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cancel_delayed_work(&wd_data->work);
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}
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}
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static int __watchdog_ping(struct watchdog_device *wdd)
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{
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struct watchdog_core_data *wd_data = wdd->wd_data;
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unsigned long earliest_keepalive = wd_data->last_hw_keepalive +
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msecs_to_jiffies(wdd->min_hw_heartbeat_ms);
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int err;
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if (time_is_after_jiffies(earliest_keepalive)) {
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mod_delayed_work(watchdog_wq, &wd_data->work,
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earliest_keepalive - jiffies);
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return 0;
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}
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wd_data->last_hw_keepalive = jiffies;
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if (wdd->ops->ping)
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err = wdd->ops->ping(wdd); /* ping the watchdog */
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else
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err = wdd->ops->start(wdd); /* restart watchdog */
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watchdog_update_worker(wdd);
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return err;
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}
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/*
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* watchdog_ping: ping the watchdog.
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* @wdd: the watchdog device to ping
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*
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* The caller must hold wd_data->lock.
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*
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* If the watchdog has no own ping operation then it needs to be
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* restarted via the start operation. This wrapper function does
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* exactly that.
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* We only ping when the watchdog device is running.
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*/
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static int watchdog_ping(struct watchdog_device *wdd)
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{
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struct watchdog_core_data *wd_data = wdd->wd_data;
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if (!watchdog_active(wdd) && !watchdog_hw_running(wdd))
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return 0;
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wd_data->last_keepalive = jiffies;
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return __watchdog_ping(wdd);
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}
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static void watchdog_ping_work(struct work_struct *work)
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{
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struct watchdog_core_data *wd_data;
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struct watchdog_device *wdd;
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wd_data = container_of(to_delayed_work(work), struct watchdog_core_data,
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work);
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mutex_lock(&wd_data->lock);
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wdd = wd_data->wdd;
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if (wdd && (watchdog_active(wdd) || watchdog_hw_running(wdd)))
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__watchdog_ping(wdd);
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mutex_unlock(&wd_data->lock);
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}
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/*
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* watchdog_start: wrapper to start the watchdog.
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* @wdd: the watchdog device to start
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*
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* The caller must hold wd_data->lock.
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*
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* Start the watchdog if it is not active and mark it active.
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* This function returns zero on success or a negative errno code for
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* failure.
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*/
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static int watchdog_start(struct watchdog_device *wdd)
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{
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struct watchdog_core_data *wd_data = wdd->wd_data;
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unsigned long started_at;
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int err;
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if (watchdog_active(wdd))
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return 0;
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started_at = jiffies;
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if (watchdog_hw_running(wdd) && wdd->ops->ping)
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err = wdd->ops->ping(wdd);
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else
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err = wdd->ops->start(wdd);
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if (err == 0) {
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set_bit(WDOG_ACTIVE, &wdd->status);
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wd_data->last_keepalive = started_at;
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watchdog_update_worker(wdd);
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}
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return err;
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}
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/*
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* watchdog_stop: wrapper to stop the watchdog.
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* @wdd: the watchdog device to stop
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*
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* The caller must hold wd_data->lock.
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*
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* Stop the watchdog if it is still active and unmark it active.
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* This function returns zero on success or a negative errno code for
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* failure.
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* If the 'nowayout' feature was set, the watchdog cannot be stopped.
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*/
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static int watchdog_stop(struct watchdog_device *wdd)
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{
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int err = 0;
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if (!watchdog_active(wdd))
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return 0;
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if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
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pr_info("watchdog%d: nowayout prevents watchdog being stopped!\n",
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wdd->id);
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return -EBUSY;
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}
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if (wdd->ops->stop)
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err = wdd->ops->stop(wdd);
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else
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set_bit(WDOG_HW_RUNNING, &wdd->status);
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if (err == 0) {
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clear_bit(WDOG_ACTIVE, &wdd->status);
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watchdog_update_worker(wdd);
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}
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return err;
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}
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/*
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* watchdog_get_status: wrapper to get the watchdog status
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* @wdd: the watchdog device to get the status from
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*
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* The caller must hold wd_data->lock.
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*
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* Get the watchdog's status flags.
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*/
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static unsigned int watchdog_get_status(struct watchdog_device *wdd)
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{
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if (!wdd->ops->status)
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return 0;
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return wdd->ops->status(wdd);
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}
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/*
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* watchdog_set_timeout: set the watchdog timer timeout
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* @wdd: the watchdog device to set the timeout for
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* @timeout: timeout to set in seconds
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*
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* The caller must hold wd_data->lock.
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*/
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static int watchdog_set_timeout(struct watchdog_device *wdd,
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unsigned int timeout)
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{
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int err = 0;
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if (!(wdd->info->options & WDIOF_SETTIMEOUT))
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return -EOPNOTSUPP;
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if (watchdog_timeout_invalid(wdd, timeout))
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return -EINVAL;
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if (wdd->ops->set_timeout)
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err = wdd->ops->set_timeout(wdd, timeout);
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else
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wdd->timeout = timeout;
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watchdog_update_worker(wdd);
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return err;
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}
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/*
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* watchdog_get_timeleft: wrapper to get the time left before a reboot
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* @wdd: the watchdog device to get the remaining time from
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* @timeleft: the time that's left
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*
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* The caller must hold wd_data->lock.
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*
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* Get the time before a watchdog will reboot (if not pinged).
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*/
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static int watchdog_get_timeleft(struct watchdog_device *wdd,
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unsigned int *timeleft)
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{
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*timeleft = 0;
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if (!wdd->ops->get_timeleft)
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return -EOPNOTSUPP;
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*timeleft = wdd->ops->get_timeleft(wdd);
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return 0;
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}
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#ifdef CONFIG_WATCHDOG_SYSFS
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static ssize_t nowayout_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct watchdog_device *wdd = dev_get_drvdata(dev);
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return sprintf(buf, "%d\n", !!test_bit(WDOG_NO_WAY_OUT, &wdd->status));
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}
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static DEVICE_ATTR_RO(nowayout);
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static ssize_t status_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct watchdog_device *wdd = dev_get_drvdata(dev);
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struct watchdog_core_data *wd_data = wdd->wd_data;
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unsigned int status;
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mutex_lock(&wd_data->lock);
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status = watchdog_get_status(wdd);
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mutex_unlock(&wd_data->lock);
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return sprintf(buf, "%u\n", status);
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}
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static DEVICE_ATTR_RO(status);
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static ssize_t bootstatus_show(struct device *dev,
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struct device_attribute *attr, char *buf)
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{
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struct watchdog_device *wdd = dev_get_drvdata(dev);
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return sprintf(buf, "%u\n", wdd->bootstatus);
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}
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static DEVICE_ATTR_RO(bootstatus);
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static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct watchdog_device *wdd = dev_get_drvdata(dev);
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struct watchdog_core_data *wd_data = wdd->wd_data;
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ssize_t status;
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unsigned int val;
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mutex_lock(&wd_data->lock);
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status = watchdog_get_timeleft(wdd, &val);
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mutex_unlock(&wd_data->lock);
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if (!status)
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status = sprintf(buf, "%u\n", val);
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return status;
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}
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static DEVICE_ATTR_RO(timeleft);
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static ssize_t timeout_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct watchdog_device *wdd = dev_get_drvdata(dev);
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return sprintf(buf, "%u\n", wdd->timeout);
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}
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static DEVICE_ATTR_RO(timeout);
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static ssize_t identity_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct watchdog_device *wdd = dev_get_drvdata(dev);
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return sprintf(buf, "%s\n", wdd->info->identity);
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}
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static DEVICE_ATTR_RO(identity);
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static ssize_t state_show(struct device *dev, struct device_attribute *attr,
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char *buf)
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{
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struct watchdog_device *wdd = dev_get_drvdata(dev);
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if (watchdog_active(wdd))
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return sprintf(buf, "active\n");
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return sprintf(buf, "inactive\n");
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}
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static DEVICE_ATTR_RO(state);
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|
|
static umode_t wdt_is_visible(struct kobject *kobj, struct attribute *attr,
|
|
int n)
|
|
{
|
|
struct device *dev = container_of(kobj, struct device, kobj);
|
|
struct watchdog_device *wdd = dev_get_drvdata(dev);
|
|
umode_t mode = attr->mode;
|
|
|
|
if (attr == &dev_attr_status.attr && !wdd->ops->status)
|
|
mode = 0;
|
|
else if (attr == &dev_attr_timeleft.attr && !wdd->ops->get_timeleft)
|
|
mode = 0;
|
|
|
|
return mode;
|
|
}
|
|
static struct attribute *wdt_attrs[] = {
|
|
&dev_attr_state.attr,
|
|
&dev_attr_identity.attr,
|
|
&dev_attr_timeout.attr,
|
|
&dev_attr_timeleft.attr,
|
|
&dev_attr_bootstatus.attr,
|
|
&dev_attr_status.attr,
|
|
&dev_attr_nowayout.attr,
|
|
NULL,
|
|
};
|
|
|
|
static const struct attribute_group wdt_group = {
|
|
.attrs = wdt_attrs,
|
|
.is_visible = wdt_is_visible,
|
|
};
|
|
__ATTRIBUTE_GROUPS(wdt);
|
|
#else
|
|
#define wdt_groups NULL
|
|
#endif
|
|
|
|
/*
|
|
* watchdog_ioctl_op: call the watchdog drivers ioctl op if defined
|
|
* @wdd: the watchdog device to do the ioctl on
|
|
* @cmd: watchdog command
|
|
* @arg: argument pointer
|
|
*
|
|
* The caller must hold wd_data->lock.
|
|
*/
|
|
|
|
static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
|
|
unsigned long arg)
|
|
{
|
|
if (!wdd->ops->ioctl)
|
|
return -ENOIOCTLCMD;
|
|
|
|
return wdd->ops->ioctl(wdd, cmd, arg);
|
|
}
|
|
|
|
/*
|
|
* watchdog_write: writes to the watchdog.
|
|
* @file: file from VFS
|
|
* @data: user address of data
|
|
* @len: length of data
|
|
* @ppos: pointer to the file offset
|
|
*
|
|
* A write to a watchdog device is defined as a keepalive ping.
|
|
* Writing the magic 'V' sequence allows the next close to turn
|
|
* off the watchdog (if 'nowayout' is not set).
|
|
*/
|
|
|
|
static ssize_t watchdog_write(struct file *file, const char __user *data,
|
|
size_t len, loff_t *ppos)
|
|
{
|
|
struct watchdog_core_data *wd_data = file->private_data;
|
|
struct watchdog_device *wdd;
|
|
int err;
|
|
size_t i;
|
|
char c;
|
|
|
|
if (len == 0)
|
|
return 0;
|
|
|
|
/*
|
|
* Note: just in case someone wrote the magic character
|
|
* five months ago...
|
|
*/
|
|
clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
|
|
|
|
/* scan to see whether or not we got the magic character */
|
|
for (i = 0; i != len; i++) {
|
|
if (get_user(c, data + i))
|
|
return -EFAULT;
|
|
if (c == 'V')
|
|
set_bit(_WDOG_ALLOW_RELEASE, &wd_data->status);
|
|
}
|
|
|
|
/* someone wrote to us, so we send the watchdog a keepalive ping */
|
|
|
|
err = -ENODEV;
|
|
mutex_lock(&wd_data->lock);
|
|
wdd = wd_data->wdd;
|
|
if (wdd)
|
|
err = watchdog_ping(wdd);
|
|
mutex_unlock(&wd_data->lock);
|
|
|
|
if (err < 0)
|
|
return err;
|
|
|
|
return len;
|
|
}
|
|
|
|
/*
|
|
* watchdog_ioctl: handle the different ioctl's for the watchdog device.
|
|
* @file: file handle to the device
|
|
* @cmd: watchdog command
|
|
* @arg: argument pointer
|
|
*
|
|
* The watchdog API defines a common set of functions for all watchdogs
|
|
* according to their available features.
|
|
*/
|
|
|
|
static long watchdog_ioctl(struct file *file, unsigned int cmd,
|
|
unsigned long arg)
|
|
{
|
|
struct watchdog_core_data *wd_data = file->private_data;
|
|
void __user *argp = (void __user *)arg;
|
|
struct watchdog_device *wdd;
|
|
int __user *p = argp;
|
|
unsigned int val;
|
|
int err;
|
|
|
|
mutex_lock(&wd_data->lock);
|
|
|
|
wdd = wd_data->wdd;
|
|
if (!wdd) {
|
|
err = -ENODEV;
|
|
goto out_ioctl;
|
|
}
|
|
|
|
err = watchdog_ioctl_op(wdd, cmd, arg);
|
|
if (err != -ENOIOCTLCMD)
|
|
goto out_ioctl;
|
|
|
|
switch (cmd) {
|
|
case WDIOC_GETSUPPORT:
|
|
err = copy_to_user(argp, wdd->info,
|
|
sizeof(struct watchdog_info)) ? -EFAULT : 0;
|
|
break;
|
|
case WDIOC_GETSTATUS:
|
|
val = watchdog_get_status(wdd);
|
|
err = put_user(val, p);
|
|
break;
|
|
case WDIOC_GETBOOTSTATUS:
|
|
err = put_user(wdd->bootstatus, p);
|
|
break;
|
|
case WDIOC_SETOPTIONS:
|
|
if (get_user(val, p)) {
|
|
err = -EFAULT;
|
|
break;
|
|
}
|
|
if (val & WDIOS_DISABLECARD) {
|
|
err = watchdog_stop(wdd);
|
|
if (err < 0)
|
|
break;
|
|
}
|
|
if (val & WDIOS_ENABLECARD)
|
|
err = watchdog_start(wdd);
|
|
break;
|
|
case WDIOC_KEEPALIVE:
|
|
if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
|
|
err = -EOPNOTSUPP;
|
|
break;
|
|
}
|
|
err = watchdog_ping(wdd);
|
|
break;
|
|
case WDIOC_SETTIMEOUT:
|
|
if (get_user(val, p)) {
|
|
err = -EFAULT;
|
|
break;
|
|
}
|
|
err = watchdog_set_timeout(wdd, val);
|
|
if (err < 0)
|
|
break;
|
|
/* If the watchdog is active then we send a keepalive ping
|
|
* to make sure that the watchdog keep's running (and if
|
|
* possible that it takes the new timeout) */
|
|
err = watchdog_ping(wdd);
|
|
if (err < 0)
|
|
break;
|
|
/* Fall */
|
|
case WDIOC_GETTIMEOUT:
|
|
/* timeout == 0 means that we don't know the timeout */
|
|
if (wdd->timeout == 0) {
|
|
err = -EOPNOTSUPP;
|
|
break;
|
|
}
|
|
err = put_user(wdd->timeout, p);
|
|
break;
|
|
case WDIOC_GETTIMELEFT:
|
|
err = watchdog_get_timeleft(wdd, &val);
|
|
if (err < 0)
|
|
break;
|
|
err = put_user(val, p);
|
|
break;
|
|
default:
|
|
err = -ENOTTY;
|
|
break;
|
|
}
|
|
|
|
out_ioctl:
|
|
mutex_unlock(&wd_data->lock);
|
|
return err;
|
|
}
|
|
|
|
/*
|
|
* watchdog_open: open the /dev/watchdog* devices.
|
|
* @inode: inode of device
|
|
* @file: file handle to device
|
|
*
|
|
* When the /dev/watchdog* device gets opened, we start the watchdog.
|
|
* Watch out: the /dev/watchdog device is single open, so we make sure
|
|
* it can only be opened once.
|
|
*/
|
|
|
|
static int watchdog_open(struct inode *inode, struct file *file)
|
|
{
|
|
struct watchdog_core_data *wd_data;
|
|
struct watchdog_device *wdd;
|
|
int err;
|
|
|
|
/* Get the corresponding watchdog device */
|
|
if (imajor(inode) == MISC_MAJOR)
|
|
wd_data = old_wd_data;
|
|
else
|
|
wd_data = container_of(inode->i_cdev, struct watchdog_core_data,
|
|
cdev);
|
|
|
|
/* the watchdog is single open! */
|
|
if (test_and_set_bit(_WDOG_DEV_OPEN, &wd_data->status))
|
|
return -EBUSY;
|
|
|
|
wdd = wd_data->wdd;
|
|
|
|
/*
|
|
* If the /dev/watchdog device is open, we don't want the module
|
|
* to be unloaded.
|
|
*/
|
|
if (!watchdog_hw_running(wdd) && !try_module_get(wdd->ops->owner)) {
|
|
err = -EBUSY;
|
|
goto out_clear;
|
|
}
|
|
|
|
err = watchdog_start(wdd);
|
|
if (err < 0)
|
|
goto out_mod;
|
|
|
|
file->private_data = wd_data;
|
|
|
|
if (!watchdog_hw_running(wdd))
|
|
kref_get(&wd_data->kref);
|
|
|
|
/* dev/watchdog is a virtual (and thus non-seekable) filesystem */
|
|
return nonseekable_open(inode, file);
|
|
|
|
out_mod:
|
|
module_put(wd_data->wdd->ops->owner);
|
|
out_clear:
|
|
clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
|
|
return err;
|
|
}
|
|
|
|
static void watchdog_core_data_release(struct kref *kref)
|
|
{
|
|
struct watchdog_core_data *wd_data;
|
|
|
|
wd_data = container_of(kref, struct watchdog_core_data, kref);
|
|
|
|
kfree(wd_data);
|
|
}
|
|
|
|
/*
|
|
* watchdog_release: release the watchdog device.
|
|
* @inode: inode of device
|
|
* @file: file handle to device
|
|
*
|
|
* This is the code for when /dev/watchdog gets closed. We will only
|
|
* stop the watchdog when we have received the magic char (and nowayout
|
|
* was not set), else the watchdog will keep running.
|
|
*/
|
|
|
|
static int watchdog_release(struct inode *inode, struct file *file)
|
|
{
|
|
struct watchdog_core_data *wd_data = file->private_data;
|
|
struct watchdog_device *wdd;
|
|
int err = -EBUSY;
|
|
bool running;
|
|
|
|
mutex_lock(&wd_data->lock);
|
|
|
|
wdd = wd_data->wdd;
|
|
if (!wdd)
|
|
goto done;
|
|
|
|
/*
|
|
* We only stop the watchdog if we received the magic character
|
|
* or if WDIOF_MAGICCLOSE is not set. If nowayout was set then
|
|
* watchdog_stop will fail.
|
|
*/
|
|
if (!test_bit(WDOG_ACTIVE, &wdd->status))
|
|
err = 0;
|
|
else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &wd_data->status) ||
|
|
!(wdd->info->options & WDIOF_MAGICCLOSE))
|
|
err = watchdog_stop(wdd);
|
|
|
|
/* If the watchdog was not stopped, send a keepalive ping */
|
|
if (err < 0) {
|
|
pr_crit("watchdog%d: watchdog did not stop!\n", wdd->id);
|
|
watchdog_ping(wdd);
|
|
}
|
|
|
|
watchdog_update_worker(wdd);
|
|
|
|
/* make sure that /dev/watchdog can be re-opened */
|
|
clear_bit(_WDOG_DEV_OPEN, &wd_data->status);
|
|
|
|
done:
|
|
running = wdd && watchdog_hw_running(wdd);
|
|
mutex_unlock(&wd_data->lock);
|
|
/*
|
|
* Allow the owner module to be unloaded again unless the watchdog
|
|
* is still running. If the watchdog is still running, it can not
|
|
* be stopped, and its driver must not be unloaded.
|
|
*/
|
|
if (!running) {
|
|
module_put(wd_data->cdev.owner);
|
|
kref_put(&wd_data->kref, watchdog_core_data_release);
|
|
}
|
|
return 0;
|
|
}
|
|
|
|
static const struct file_operations watchdog_fops = {
|
|
.owner = THIS_MODULE,
|
|
.write = watchdog_write,
|
|
.unlocked_ioctl = watchdog_ioctl,
|
|
.open = watchdog_open,
|
|
.release = watchdog_release,
|
|
};
|
|
|
|
static struct miscdevice watchdog_miscdev = {
|
|
.minor = WATCHDOG_MINOR,
|
|
.name = "watchdog",
|
|
.fops = &watchdog_fops,
|
|
};
|
|
|
|
/*
|
|
* watchdog_cdev_register: register watchdog character device
|
|
* @wdd: watchdog device
|
|
* @devno: character device number
|
|
*
|
|
* Register a watchdog character device including handling the legacy
|
|
* /dev/watchdog node. /dev/watchdog is actually a miscdevice and
|
|
* thus we set it up like that.
|
|
*/
|
|
|
|
static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
|
|
{
|
|
struct watchdog_core_data *wd_data;
|
|
int err;
|
|
|
|
wd_data = kzalloc(sizeof(struct watchdog_core_data), GFP_KERNEL);
|
|
if (!wd_data)
|
|
return -ENOMEM;
|
|
kref_init(&wd_data->kref);
|
|
mutex_init(&wd_data->lock);
|
|
|
|
wd_data->wdd = wdd;
|
|
wdd->wd_data = wd_data;
|
|
|
|
if (!watchdog_wq)
|
|
return -ENODEV;
|
|
|
|
INIT_DELAYED_WORK(&wd_data->work, watchdog_ping_work);
|
|
|
|
if (wdd->id == 0) {
|
|
old_wd_data = wd_data;
|
|
watchdog_miscdev.parent = wdd->parent;
|
|
err = misc_register(&watchdog_miscdev);
|
|
if (err != 0) {
|
|
pr_err("%s: cannot register miscdev on minor=%d (err=%d).\n",
|
|
wdd->info->identity, WATCHDOG_MINOR, err);
|
|
if (err == -EBUSY)
|
|
pr_err("%s: a legacy watchdog module is probably present.\n",
|
|
wdd->info->identity);
|
|
old_wd_data = NULL;
|
|
kfree(wd_data);
|
|
return err;
|
|
}
|
|
}
|
|
|
|
/* Fill in the data structures */
|
|
cdev_init(&wd_data->cdev, &watchdog_fops);
|
|
wd_data->cdev.owner = wdd->ops->owner;
|
|
|
|
/* Add the device */
|
|
err = cdev_add(&wd_data->cdev, devno, 1);
|
|
if (err) {
|
|
pr_err("watchdog%d unable to add device %d:%d\n",
|
|
wdd->id, MAJOR(watchdog_devt), wdd->id);
|
|
if (wdd->id == 0) {
|
|
misc_deregister(&watchdog_miscdev);
|
|
old_wd_data = NULL;
|
|
kref_put(&wd_data->kref, watchdog_core_data_release);
|
|
}
|
|
return err;
|
|
}
|
|
|
|
/* Record time of most recent heartbeat as 'just before now'. */
|
|
wd_data->last_hw_keepalive = jiffies - 1;
|
|
|
|
/*
|
|
* If the watchdog is running, prevent its driver from being unloaded,
|
|
* and schedule an immediate ping.
|
|
*/
|
|
if (watchdog_hw_running(wdd)) {
|
|
__module_get(wdd->ops->owner);
|
|
kref_get(&wd_data->kref);
|
|
queue_delayed_work(watchdog_wq, &wd_data->work, 0);
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* watchdog_cdev_unregister: unregister watchdog character device
|
|
* @watchdog: watchdog device
|
|
*
|
|
* Unregister watchdog character device and if needed the legacy
|
|
* /dev/watchdog device.
|
|
*/
|
|
|
|
static void watchdog_cdev_unregister(struct watchdog_device *wdd)
|
|
{
|
|
struct watchdog_core_data *wd_data = wdd->wd_data;
|
|
|
|
cdev_del(&wd_data->cdev);
|
|
if (wdd->id == 0) {
|
|
misc_deregister(&watchdog_miscdev);
|
|
old_wd_data = NULL;
|
|
}
|
|
|
|
mutex_lock(&wd_data->lock);
|
|
wd_data->wdd = NULL;
|
|
wdd->wd_data = NULL;
|
|
mutex_unlock(&wd_data->lock);
|
|
|
|
cancel_delayed_work_sync(&wd_data->work);
|
|
|
|
kref_put(&wd_data->kref, watchdog_core_data_release);
|
|
}
|
|
|
|
static struct class watchdog_class = {
|
|
.name = "watchdog",
|
|
.owner = THIS_MODULE,
|
|
.dev_groups = wdt_groups,
|
|
};
|
|
|
|
/*
|
|
* watchdog_dev_register: register a watchdog device
|
|
* @wdd: watchdog device
|
|
*
|
|
* Register a watchdog device including handling the legacy
|
|
* /dev/watchdog node. /dev/watchdog is actually a miscdevice and
|
|
* thus we set it up like that.
|
|
*/
|
|
|
|
int watchdog_dev_register(struct watchdog_device *wdd)
|
|
{
|
|
struct device *dev;
|
|
dev_t devno;
|
|
int ret;
|
|
|
|
devno = MKDEV(MAJOR(watchdog_devt), wdd->id);
|
|
|
|
ret = watchdog_cdev_register(wdd, devno);
|
|
if (ret)
|
|
return ret;
|
|
|
|
dev = device_create_with_groups(&watchdog_class, wdd->parent,
|
|
devno, wdd, wdd->groups,
|
|
"watchdog%d", wdd->id);
|
|
if (IS_ERR(dev)) {
|
|
watchdog_cdev_unregister(wdd);
|
|
return PTR_ERR(dev);
|
|
}
|
|
|
|
return ret;
|
|
}
|
|
|
|
/*
|
|
* watchdog_dev_unregister: unregister a watchdog device
|
|
* @watchdog: watchdog device
|
|
*
|
|
* Unregister watchdog device and if needed the legacy
|
|
* /dev/watchdog device.
|
|
*/
|
|
|
|
void watchdog_dev_unregister(struct watchdog_device *wdd)
|
|
{
|
|
device_destroy(&watchdog_class, wdd->wd_data->cdev.dev);
|
|
watchdog_cdev_unregister(wdd);
|
|
}
|
|
|
|
/*
|
|
* watchdog_dev_init: init dev part of watchdog core
|
|
*
|
|
* Allocate a range of chardev nodes to use for watchdog devices
|
|
*/
|
|
|
|
int __init watchdog_dev_init(void)
|
|
{
|
|
int err;
|
|
|
|
watchdog_wq = alloc_workqueue("watchdogd",
|
|
WQ_HIGHPRI | WQ_MEM_RECLAIM, 0);
|
|
if (!watchdog_wq) {
|
|
pr_err("Failed to create watchdog workqueue\n");
|
|
return -ENOMEM;
|
|
}
|
|
|
|
err = class_register(&watchdog_class);
|
|
if (err < 0) {
|
|
pr_err("couldn't register class\n");
|
|
return err;
|
|
}
|
|
|
|
err = alloc_chrdev_region(&watchdog_devt, 0, MAX_DOGS, "watchdog");
|
|
if (err < 0) {
|
|
pr_err("watchdog: unable to allocate char dev region\n");
|
|
class_unregister(&watchdog_class);
|
|
return err;
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* watchdog_dev_exit: exit dev part of watchdog core
|
|
*
|
|
* Release the range of chardev nodes used for watchdog devices
|
|
*/
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|
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void __exit watchdog_dev_exit(void)
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|
{
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|
unregister_chrdev_region(watchdog_devt, MAX_DOGS);
|
|
class_unregister(&watchdog_class);
|
|
destroy_workqueue(watchdog_wq);
|
|
}
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