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Message-ID: <CA+i0qc4-DZvFpOEyJBhMzi=HOc-KowNTf8tebTOh5oinav1S8A@mail.gmail.com>
Date: Tue, 22 Dec 2015 01:36:41 +0200
From: Tomas Winkler <tomasw@...il.com>
To: Damien Riegel <damien.riegel@...oirfairelinux.com>,
Guenter Roeck <linux@...ck-us.net>,
Linux Watchdog Mailing List <linux-watchdog@...r.kernel.org>,
Wim Van Sebroeck <wim@...ana.be>,
Pratyush Anand <panand@...hat.com>,
Hans de Goede <hdegoede@...hat.com>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 2/5] watchdog: Separate and maintain variables based on
variable lifetime
On Mon, Dec 21, 2015 at 7:28 PM, Damien Riegel
<damien.riegel@...oirfairelinux.com> wrote:
>
> On Sun, Dec 20, 2015 at 01:05:00PM -0800, Guenter Roeck wrote:
> > All variables required by the watchdog core to manage a watchdog are
> > currently stored in struct watchdog_device. The lifetime of those
> > variables is determined by the watchdog driver. However, the lifetime
> > of variables used by the watchdog core differs from the lifetime of
> > struct watchdog_device. To remedy this situation, watchdog drivers
> > can implement ref and unref callbacks, to be used by the watchdog
> > core to lock struct watchdog_device in memory.
> >
> > While this solves the immediate problem, it depends on watchdog drivers
> > to actually implement the ref/unref callbacks. This is error prone,
> > often not implemented in the first place, or not implemented correctly.
> >
> > To solve the problem without requiring driver support, split the variables
> > in struct watchdog_device into two data structures - one for variables
> > associated with the watchdog driver, one for variables associated with
> > the watchdog core. With this approach, the watchdog core can keep track
> > of its variable lifetime and no longer depends on ref/unref callbacks
> > in the driver. As a side effect, some of the variables originally in
> > struct watchdog_driver are now private to the watchdog core and no longer
> > visible in watchdog drivers.
> >
> > The 'ref' and 'unref' callbacks in struct watchdog_driver are no longer
> > used and marked as deprecated.
>
> Two comments below. It's great to see that unbinding a driver no longer
> triggers a kernel panic.
>
> >
> > Signed-off-by: Guenter Roeck <linux@...ck-us.net>
> > ---
> > Documentation/watchdog/watchdog-kernel-api.txt | 45 +--
> > drivers/watchdog/watchdog_core.c | 2 -
> > drivers/watchdog/watchdog_core.h | 23 ++
> > drivers/watchdog/watchdog_dev.c | 377 +++++++++++++------------
> > include/linux/watchdog.h | 21 +-
> > 5 files changed, 239 insertions(+), 229 deletions(-)
> >
> > diff --git a/Documentation/watchdog/watchdog-kernel-api.txt b/Documentation/watchdog/watchdog-kernel-api.txt
> > index 0a37da76acef..3db5092924e5 100644
> > --- a/Documentation/watchdog/watchdog-kernel-api.txt
> > +++ b/Documentation/watchdog/watchdog-kernel-api.txt
> > @@ -44,7 +44,6 @@ The watchdog device structure looks like this:
> >
> > struct watchdog_device {
> > int id;
> > - struct cdev cdev;
> > struct device *dev;
> > struct device *parent;
> > const struct watchdog_info *info;
> > @@ -56,7 +55,7 @@ struct watchdog_device {
> > struct notifier_block reboot_nb;
> > struct notifier_block restart_nb;
> > void *driver_data;
> > - struct mutex lock;
> > + void *wdd_data;
> > unsigned long status;
> > struct list_head deferred;
> > };
> > @@ -66,8 +65,6 @@ It contains following fields:
> > /dev/watchdog0 cdev (dynamic major, minor 0) as well as the old
> > /dev/watchdog miscdev. The id is set automatically when calling
> > watchdog_register_device.
> > -* cdev: cdev for the dynamic /dev/watchdog<id> device nodes. This
> > - field is also populated by watchdog_register_device.
> > * dev: device under the watchdog class (created by watchdog_register_device).
> > * parent: set this to the parent device (or NULL) before calling
> > watchdog_register_device.
> > @@ -89,11 +86,10 @@ It contains following fields:
> > * driver_data: a pointer to the drivers private data of a watchdog device.
> > This data should only be accessed via the watchdog_set_drvdata and
> > watchdog_get_drvdata routines.
> > -* lock: Mutex for WatchDog Timer Driver Core internal use only.
> > +* wdd_data: a pointer to watchdog core internal data.
> > * status: this field contains a number of status bits that give extra
> > information about the status of the device (Like: is the watchdog timer
> > - running/active, is the nowayout bit set, is the device opened via
> > - the /dev/watchdog interface or not, ...).
> > + running/active, or is the nowayout bit set).
> > * deferred: entry in wtd_deferred_reg_list which is used to
> > register early initialized watchdogs.
> >
> > @@ -110,8 +106,8 @@ struct watchdog_ops {
> > int (*set_timeout)(struct watchdog_device *, unsigned int);
> > unsigned int (*get_timeleft)(struct watchdog_device *);
> > int (*restart)(struct watchdog_device *);
> > - void (*ref)(struct watchdog_device *);
> > - void (*unref)(struct watchdog_device *);
> > + void (*ref)(struct watchdog_device *) __deprecated;
> > + void (*unref)(struct watchdog_device *) __deprecated;
> > long (*ioctl)(struct watchdog_device *, unsigned int, unsigned long);
> > };
> >
> > @@ -120,20 +116,6 @@ driver's operations. This module owner will be used to lock the module when
> > the watchdog is active. (This to avoid a system crash when you unload the
> > module and /dev/watchdog is still open).
> >
> > -If the watchdog_device struct is dynamically allocated, just locking the module
> > -is not enough and a driver also needs to define the ref and unref operations to
> > -ensure the structure holding the watchdog_device does not go away.
> > -
> > -The simplest (and usually sufficient) implementation of this is to:
> > -1) Add a kref struct to the same structure which is holding the watchdog_device
> > -2) Define a release callback for the kref which frees the struct holding both
> > -3) Call kref_init on this kref *before* calling watchdog_register_device()
> > -4) Define a ref operation calling kref_get on this kref
> > -5) Define a unref operation calling kref_put on this kref
> > -6) When it is time to cleanup:
> > - * Do not kfree() the struct holding both, the last kref_put will do this!
> > - * *After* calling watchdog_unregister_device() call kref_put on the kref
> > -
> > Some operations are mandatory and some are optional. The mandatory operations
> > are:
> > * start: this is a pointer to the routine that starts the watchdog timer
> > @@ -176,34 +158,21 @@ they are supported. These optional routines/operations are:
> > * get_timeleft: this routines returns the time that's left before a reset.
> > * restart: this routine restarts the machine. It returns 0 on success or a
> > negative errno code for failure.
> > -* ref: the operation that calls kref_get on the kref of a dynamically
> > - allocated watchdog_device struct.
> > -* unref: the operation that calls kref_put on the kref of a dynamically
> > - allocated watchdog_device struct.
> > * ioctl: if this routine is present then it will be called first before we do
> > our own internal ioctl call handling. This routine should return -ENOIOCTLCMD
> > if a command is not supported. The parameters that are passed to the ioctl
> > call are: watchdog_device, cmd and arg.
> >
> > +The 'ref' and 'unref' operations are no longer used and deprecated.
> > +
> > The status bits should (preferably) be set with the set_bit and clear_bit alike
> > bit-operations. The status bits that are defined are:
> > * WDOG_ACTIVE: this status bit indicates whether or not a watchdog timer device
> > is active or not. When the watchdog is active after booting, then you should
> > set this status bit (Note: when you register the watchdog timer device with
> > this bit set, then opening /dev/watchdog will skip the start operation)
> > -* WDOG_DEV_OPEN: this status bit shows whether or not the watchdog device
> > - was opened via /dev/watchdog.
> > - (This bit should only be used by the WatchDog Timer Driver Core).
> > -* WDOG_ALLOW_RELEASE: this bit stores whether or not the magic close character
> > - has been sent (so that we can support the magic close feature).
> > - (This bit should only be used by the WatchDog Timer Driver Core).
> > * WDOG_NO_WAY_OUT: this bit stores the nowayout setting for the watchdog.
> > If this bit is set then the watchdog timer will not be able to stop.
> > -* WDOG_UNREGISTERED: this bit gets set by the WatchDog Timer Driver Core
> > - after calling watchdog_unregister_device, and then checked before calling
> > - any watchdog_ops, so that you can be sure that no operations (other then
> > - unref) will get called after unregister, even if userspace still holds a
> > - reference to /dev/watchdog
> >
> > To set the WDOG_NO_WAY_OUT status bit (before registering your watchdog
> > timer device) you can either:
> > diff --git a/drivers/watchdog/watchdog_core.c b/drivers/watchdog/watchdog_core.c
> > index f0293f7d2b80..ec1ab6c1a80b 100644
> > --- a/drivers/watchdog/watchdog_core.c
> > +++ b/drivers/watchdog/watchdog_core.c
> > @@ -210,8 +210,6 @@ static int __watchdog_register_device(struct watchdog_device *wdd)
> > * corrupted in a later stage then we expect a kernel panic!
> > */
> >
> > - mutex_init(&wdd->lock);
> > -
> > /* Use alias for watchdog id if possible */
> > if (wdd->parent) {
> > ret = of_alias_get_id(wdd->parent->of_node, "watchdog");
> > diff --git a/drivers/watchdog/watchdog_core.h b/drivers/watchdog/watchdog_core.h
> > index 86ff962d1e15..c9b0656284de 100644
> > --- a/drivers/watchdog/watchdog_core.h
> > +++ b/drivers/watchdog/watchdog_core.h
> > @@ -26,9 +26,32 @@
> > * This material is provided "AS-IS" and at no charge.
> > */
> >
> > +#include <linux/cdev.h>
> > +#include <linux/kref.h>
> > +#include <linux/mutex.h>
> > +#include <linux/watchdog.h>
> > +
> > #define MAX_DOGS 32 /* Maximum number of watchdog devices */
> >
> > /*
> > + * struct _watchdog_device - watchdog core internal data
>
> Think it should be /**. Anyway, I find it confusing to have both
> _watchdog_device and watchdog_device, but I can't think of a better
> name right now.
>
> > + * @kref: Reference count.
> > + * @cdev: The watchdog's Character device.
> > + * @wdd: Pointer to watchdog device.
> > + * @lock: Lock for watchdog core.
> > + * @status: Watchdog core internal status bits.
> > + */
> > +struct _watchdog_device {
We should probably find a better name for this structure... watchdog
_adapter, _descriptor, or even _data
Also this style is quite confusing when __func() is wrapping func(),
usually this would be otherway around
> > + struct kref kref;
> > + struct cdev cdev;
> > + struct watchdog_device *wdd;
> > + struct mutex lock;
> > + unsigned long status; /* Internal status bits */
> > +#define _WDOG_DEV_OPEN 0 /* Opened ? */
> > +#define _WDOG_ALLOW_RELEASE 1 /* Did we receive the magic char ? */
> > +};
> > +
> > +/*
> > * Functions/procedures to be called by the core
> > */
> > extern int watchdog_dev_register(struct watchdog_device *);
> > diff --git a/drivers/watchdog/watchdog_dev.c b/drivers/watchdog/watchdog_dev.c
> > index c24392623e98..e8416bdc7037 100644
> > --- a/drivers/watchdog/watchdog_dev.c
> > +++ b/drivers/watchdog/watchdog_dev.c
> > @@ -37,6 +37,7 @@
> > #include <linux/errno.h> /* For the -ENODEV/... values */
> > #include <linux/kernel.h> /* For printk/panic/... */
> > #include <linux/fs.h> /* For file operations */
> > +#include <linux/slab.h> /* For memory functions */
> > #include <linux/watchdog.h> /* For watchdog specific items */
> > #include <linux/miscdevice.h> /* For handling misc devices */
> > #include <linux/init.h> /* For __init/__exit/... */
> > @@ -47,12 +48,14 @@
> > /* the dev_t structure to store the dynamically allocated watchdog devices */
> > static dev_t watchdog_devt;
> > /* the watchdog device behind /dev/watchdog */
> > -static struct watchdog_device *old_wdd;
> > +static struct _watchdog_device *_old_wdd;
> >
> > /*
> > * watchdog_ping: ping the watchdog.
> > * @wdd: the watchdog device to ping
> > *
> > + * The caller must hold _wdd->lock.
> > + *
> > * If the watchdog has no own ping operation then it needs to be
> > * restarted via the start operation. This wrapper function does
> > * exactly that.
> > @@ -61,25 +64,37 @@ static struct watchdog_device *old_wdd;
> >
> > static int watchdog_ping(struct watchdog_device *wdd)
> > {
Not sure this lockless wrappers are really needed.
> > - int err = 0;
> > -
> > - mutex_lock(&wdd->lock);
> > -
> > - if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
> > - err = -ENODEV;
> > - goto out_ping;
> > - }
> > + int err;
> >
> > if (!watchdog_active(wdd))
> > - goto out_ping;
> > + return 0;
> >
> > if (wdd->ops->ping)
> > err = wdd->ops->ping(wdd); /* ping the watchdog */
> > else
> > err = wdd->ops->start(wdd); /* restart watchdog */
> >
> > -out_ping:
> > - mutex_unlock(&wdd->lock);
> > + return err;
> > +}
> > +
> > +/*
> > + * _watchdog_ping: ping the watchdog.
> > + * @_wdd: Watchdog core device data
> > + *
> > + * Acquire _wdd->lock and call watchdog_ping() unless the watchdog
> > + * driver has been unregistered.
> > + */
> > +static int _watchdog_ping(struct _watchdog_device *_wdd)
Use of double underscore __ is more comon .
> > +{
> > + struct watchdog_device *wdd;
> > + int err = -ENODEV;
> > +
> > + mutex_lock(&_wdd->lock);
> > + wdd = _wdd->wdd;
> > + if (wdd)
> > + err = watchdog_ping(wdd);
> > + mutex_unlock(&_wdd->lock);
> > +
> > return err;
> > }
> >
> > @@ -87,6 +102,8 @@ out_ping:
> > * watchdog_start: wrapper to start the watchdog.
> > * @wdd: the watchdog device to start
> > *
> > + * The caller must hold _wdd->lock.
> > + *
> > * Start the watchdog if it is not active and mark it active.
> > * This function returns zero on success or a negative errno code for
> > * failure.
> > @@ -94,24 +111,15 @@ out_ping:
> >
> > static int watchdog_start(struct watchdog_device *wdd)
> > {
> > - int err = 0;
> > -
> > - mutex_lock(&wdd->lock);
> > -
> > - if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
> > - err = -ENODEV;
> > - goto out_start;
> > - }
> > + int err;
> >
> > if (watchdog_active(wdd))
> > - goto out_start;
> > + return 0;
> >
> > err = wdd->ops->start(wdd);
> > if (err == 0)
> > set_bit(WDOG_ACTIVE, &wdd->status);
> >
> > -out_start:
> > - mutex_unlock(&wdd->lock);
> > return err;
> > }
> >
> > @@ -119,6 +127,8 @@ out_start:
> > * watchdog_stop: wrapper to stop the watchdog.
> > * @wdd: the watchdog device to stop
> > *
> > + * The caller must hold _wdd->lock.
> > + *
> > * Stop the watchdog if it is still active and unmark it active.
> > * This function returns zero on success or a negative errno code for
> > * failure.
> > @@ -127,93 +137,58 @@ out_start:
> >
> > static int watchdog_stop(struct watchdog_device *wdd)
> > {
> > - int err = 0;
> > -
> > - mutex_lock(&wdd->lock);
> > -
> > - if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
> > - err = -ENODEV;
> > - goto out_stop;
> > - }
> > + int err;
> >
> > if (!watchdog_active(wdd))
> > - goto out_stop;
> > + return 0;
> >
> > if (test_bit(WDOG_NO_WAY_OUT, &wdd->status)) {
> > dev_info(wdd->dev, "nowayout prevents watchdog being stopped!\n");
> > - err = -EBUSY;
> > - goto out_stop;
> > + return -EBUSY;
> > }
> >
> > err = wdd->ops->stop(wdd);
> > if (err == 0)
> > clear_bit(WDOG_ACTIVE, &wdd->status);
> >
> > -out_stop:
> > - mutex_unlock(&wdd->lock);
> > return err;
> > }
> >
> > /*
> > * watchdog_get_status: wrapper to get the watchdog status
> > * @wdd: the watchdog device to get the status from
> > - * @status: the status of the watchdog device
> > + *
> > + * The caller must hold _wdd->lock.
> > *
> > * Get the watchdog's status flags.
> > */
> >
> > -static int watchdog_get_status(struct watchdog_device *wdd,
> > - unsigned int *status)
> > +static unsigned int watchdog_get_status(struct watchdog_device *wdd)
> > {
> > - int err = 0;
> > -
> > - *status = 0;
> > if (!wdd->ops->status)
> > - return -EOPNOTSUPP;
> > -
> > - mutex_lock(&wdd->lock);
> > -
> > - if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
> > - err = -ENODEV;
> > - goto out_status;
> > - }
> > -
> > - *status = wdd->ops->status(wdd);
> > + return 0;
> >
> > -out_status:
> > - mutex_unlock(&wdd->lock);
> > - return err;
> > + return wdd->ops->status(wdd);
> > }
> >
> > /*
> > * watchdog_set_timeout: set the watchdog timer timeout
> > * @wdd: the watchdog device to set the timeout for
> > * @timeout: timeout to set in seconds
> > + *
> > + * The caller must hold _wdd->lock.
> > */
> >
> > static int watchdog_set_timeout(struct watchdog_device *wdd,
> > unsigned int timeout)
> > {
> > - int err;
> > -
> > if (!wdd->ops->set_timeout || !(wdd->info->options & WDIOF_SETTIMEOUT))
> > return -EOPNOTSUPP;
> >
> > if (watchdog_timeout_invalid(wdd, timeout))
> > return -EINVAL;
> >
> > - mutex_lock(&wdd->lock);
> > -
> > - if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
> > - err = -ENODEV;
> > - goto out_timeout;
> > - }
> > -
> > - err = wdd->ops->set_timeout(wdd, timeout);
> > -
> > -out_timeout:
> > - mutex_unlock(&wdd->lock);
> > - return err;
> > + return wdd->ops->set_timeout(wdd, timeout);
> > }
> >
> > /*
> > @@ -221,30 +196,22 @@ out_timeout:
> > * @wdd: the watchdog device to get the remaining time from
> > * @timeleft: the time that's left
> > *
> > + * The caller must hold _wdd->lock.
> > + *
> > * Get the time before a watchdog will reboot (if not pinged).
> > */
> >
> > static int watchdog_get_timeleft(struct watchdog_device *wdd,
> > unsigned int *timeleft)
> > {
> > - int err = 0;
> > -
> > *timeleft = 0;
> > +
> > if (!wdd->ops->get_timeleft)
> > return -EOPNOTSUPP;
> >
> > - mutex_lock(&wdd->lock);
> > -
> > - if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
> > - err = -ENODEV;
> > - goto out_timeleft;
> > - }
> > -
> > *timeleft = wdd->ops->get_timeleft(wdd);
> >
> > -out_timeleft:
> > - mutex_unlock(&wdd->lock);
> > - return err;
> > + return 0;
> > }
> >
> > #ifdef CONFIG_WATCHDOG_SYSFS
> > @@ -261,14 +228,14 @@ static ssize_t status_show(struct device *dev, struct device_attribute *attr,
> > char *buf)
> > {
> > struct watchdog_device *wdd = dev_get_drvdata(dev);
> > - ssize_t status;
> > - unsigned int val;
> > + struct _watchdog_device *_wdd = wdd->wdd_data;
> > + unsigned int status;
> >
> > - status = watchdog_get_status(wdd, &val);
> > - if (!status)
> > - status = sprintf(buf, "%u\n", val);
> > + mutex_lock(&_wdd->lock);
> > + status = watchdog_get_status(wdd);
> > + mutex_unlock(&_wdd->lock);
> >
> > - return status;
> > + return sprintf(buf, "%u\n", status);
> > }
> > static DEVICE_ATTR_RO(status);
> >
> > @@ -285,10 +252,13 @@ static ssize_t timeleft_show(struct device *dev, struct device_attribute *attr,
> > char *buf)
> > {
> > struct watchdog_device *wdd = dev_get_drvdata(dev);
> > + struct _watchdog_device *_wdd = wdd->wdd_data;
> > ssize_t status;
> > unsigned int val;
> >
> > + mutex_lock(&_wdd->lock);
> > status = watchdog_get_timeleft(wdd, &val);
> > + mutex_unlock(&_wdd->lock);
> > if (!status)
> > status = sprintf(buf, "%u\n", val);
> >
> > @@ -363,28 +333,17 @@ __ATTRIBUTE_GROUPS(wdt);
> > * @wdd: the watchdog device to do the ioctl on
> > * @cmd: watchdog command
> > * @arg: argument pointer
> > + *
> > + * The caller must hold _wdd->lock.
> > */
> >
> > static int watchdog_ioctl_op(struct watchdog_device *wdd, unsigned int cmd,
> > unsigned long arg)
> > {
> > - int err;
> > -
> > if (!wdd->ops->ioctl)
> > return -ENOIOCTLCMD;
> >
> > - mutex_lock(&wdd->lock);
> > -
> > - if (test_bit(WDOG_UNREGISTERED, &wdd->status)) {
> > - err = -ENODEV;
> > - goto out_ioctl;
> > - }
> > -
> > - err = wdd->ops->ioctl(wdd, cmd, arg);
> > -
> > -out_ioctl:
> > - mutex_unlock(&wdd->lock);
> > - return err;
> > + return wdd->ops->ioctl(wdd, cmd, arg);
> > }
> >
> > /*
> > @@ -402,7 +361,7 @@ out_ioctl:
> > static ssize_t watchdog_write(struct file *file, const char __user *data,
> > size_t len, loff_t *ppos)
> > {
> > - struct watchdog_device *wdd = file->private_data;
> > + struct _watchdog_device *_wdd = file->private_data;
> > size_t i;
> > char c;
> > int err;
> > @@ -414,18 +373,18 @@ static ssize_t watchdog_write(struct file *file, const char __user *data,
> > * Note: just in case someone wrote the magic character
> > * five months ago...
> > */
> > - clear_bit(WDOG_ALLOW_RELEASE, &wdd->status);
> > + clear_bit(_WDOG_ALLOW_RELEASE, &_wdd->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, &wdd->status);
> > + set_bit(_WDOG_ALLOW_RELEASE, &_wdd->status);
> > }
> >
> > /* someone wrote to us, so we send the watchdog a keepalive ping */
> > - err = watchdog_ping(wdd);
> > + err = _watchdog_ping(_wdd);
> > if (err < 0)
> > return err;
> >
> > @@ -445,71 +404,94 @@ static ssize_t watchdog_write(struct file *file, const char __user *data,
> > static long watchdog_ioctl(struct file *file, unsigned int cmd,
> > unsigned long arg)
> > {
> > - struct watchdog_device *wdd = file->private_data;
> > + struct _watchdog_device *_wdd = file->private_data;
> > void __user *argp = (void __user *)arg;
> > + struct watchdog_device *wdd;
> > int __user *p = argp;
> > unsigned int val;
> > - int err;
> > + int err = 0;
> > +
> > + mutex_lock(&_wdd->lock);
> > +
> > + wdd = _wdd->wdd;
> > + if (!wdd) {
> > + err = -ENODEV;
> > + goto out_ioctl;
> > + }
> >
> > err = watchdog_ioctl_op(wdd, cmd, arg);
> > if (err != -ENOIOCTLCMD)
> > - return err;
> > + goto out_ioctl;
> >
> > switch (cmd) {
> > case WDIOC_GETSUPPORT:
> > - return copy_to_user(argp, wdd->info,
> > + err = copy_to_user(argp, wdd->info,
> > sizeof(struct watchdog_info)) ? -EFAULT : 0;
> > + break;
> > case WDIOC_GETSTATUS:
> > - err = watchdog_get_status(wdd, &val);
> > - if (err == -ENODEV)
> > - return err;
> > - return put_user(val, p);
> > + val = watchdog_get_status(wdd);
> > + err = put_user(val, p);
> > + break;
> > case WDIOC_GETBOOTSTATUS:
> > - return put_user(wdd->bootstatus, p);
> > + err = put_user(wdd->bootstatus, p);
> > + break;
> > case WDIOC_SETOPTIONS:
> > - if (get_user(val, p))
> > - return -EFAULT;
> > + if (get_user(val, p)) {
> > + err = -EFAULT;
> > + break;
> > + }
> > if (val & WDIOS_DISABLECARD) {
> > err = watchdog_stop(wdd);
> > if (err < 0)
> > - return err;
> > + break;
> > }
> > - if (val & WDIOS_ENABLECARD) {
> > + if (val & WDIOS_ENABLECARD)
> > err = watchdog_start(wdd);
> > - if (err < 0)
> > - return err;
> > - }
> > - return 0;
> > + break;
> > case WDIOC_KEEPALIVE:
> > - if (!(wdd->info->options & WDIOF_KEEPALIVEPING))
> > - return -EOPNOTSUPP;
> > - return watchdog_ping(wdd);
> > + if (!(wdd->info->options & WDIOF_KEEPALIVEPING)) {
> > + err = -EOPNOTSUPP;
> > + break;
> > + }
> > + err = watchdog_ping(wdd);
> > + break;
> > case WDIOC_SETTIMEOUT:
> > - if (get_user(val, p))
> > - return -EFAULT;
> > + if (get_user(val, p)) {
> > + err = -EFAULT;
> > + break;
> > + }
> > err = watchdog_set_timeout(wdd, val);
> > if (err < 0)
> > - return err;
> > + 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)
> > - return err;
> > + break;
You are changing behaviour for the driver here as you are keeping lock
over two driver op calls.
> > /* Fall */
> > case WDIOC_GETTIMEOUT:
> > /* timeout == 0 means that we don't know the timeout */
> > - if (wdd->timeout == 0)
> > - return -EOPNOTSUPP;
> > - return put_user(wdd->timeout, p);
> > + 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)
> > - return err;
> > - return put_user(val, p);
> > + if (err < 0)
> > + break;
> > + err = put_user(val, p);
> > + break;
> > default:
> > - return -ENOTTY;
> > + err = -ENOTTY;
> > + break;
> > }
> > +
> > +out_ioctl:
> > + mutex_unlock(&_wdd->lock);
> > + return err;
> > }
> >
> > /*
> > @@ -524,45 +506,68 @@ static long watchdog_ioctl(struct file *file, unsigned int cmd,
> >
> > static int watchdog_open(struct inode *inode, struct file *file)
> > {
> > - int err = -EBUSY;
> > + struct _watchdog_device *_wdd;
> > struct watchdog_device *wdd;
> > + int err;
> >
> > /* Get the corresponding watchdog device */
> > if (imajor(inode) == MISC_MAJOR)
> > - wdd = old_wdd;
> > + _wdd = _old_wdd;
> > else
> > - wdd = container_of(inode->i_cdev, struct watchdog_device, cdev);
> > + _wdd = container_of(inode->i_cdev, struct _watchdog_device,
> > + cdev);
> >
> > /* the watchdog is single open! */
> > - if (test_and_set_bit(WDOG_DEV_OPEN, &wdd->status))
> > + if (test_and_set_bit(_WDOG_DEV_OPEN, &_wdd->status))
> > return -EBUSY;
> >
> > + mutex_lock(&_wdd->lock);
> > +
> > + wdd = _wdd->wdd;
> > + if (!wdd) {
> > + err = -ENODEV;
> > + goto out_clear;
> > + }
> > +
> > /*
> > * If the /dev/watchdog device is open, we don't want the module
> > * to be unloaded.
> > */
> > - if (!try_module_get(wdd->ops->owner))
> > - goto out;
> > + if (!try_module_get(wdd->ops->owner)) {
> > + err = -EBUSY;
> > + goto out_clear;
> > + }
> >
> > err = watchdog_start(wdd);
> > if (err < 0)
> > goto out_mod;
> >
> > - file->private_data = wdd;
> > + file->private_data = _wdd;
> >
> > - if (wdd->ops->ref)
> > - wdd->ops->ref(wdd);
> > + kref_get(&_wdd->kref);
> >
> > /* dev/watchdog is a virtual (and thus non-seekable) filesystem */
> > - return nonseekable_open(inode, file);
> > + err = nonseekable_open(inode, file);
> > + goto out_unlock;
> >
> > out_mod:
> > - module_put(wdd->ops->owner);
> > -out:
> > - clear_bit(WDOG_DEV_OPEN, &wdd->status);
> > + module_put(_wdd->wdd->ops->owner);
> > +out_clear:
> > + clear_bit(_WDOG_DEV_OPEN, &_wdd->status);
> > +out_unlock:
> > + mutex_unlock(&_wdd->lock);
> > return err;
> > }
> >
> > +static void watchdog_wdd_release(struct kref *kref)
> > +{
> > + struct _watchdog_device *_wdd;
> > +
> > + _wdd = container_of(kref, struct _watchdog_device, kref);
> > +
> > + kfree(_wdd);
> > +}
> > +
> > /*
> > * watchdog_release: release the watchdog device.
> > * @inode: inode of device
> > @@ -575,9 +580,16 @@ out:
> >
> > static int watchdog_release(struct inode *inode, struct file *file)
> > {
> > - struct watchdog_device *wdd = file->private_data;
> > + struct _watchdog_device *_wdd = file->private_data;
> > + struct watchdog_device *wdd;
> > int err = -EBUSY;
> >
> > + mutex_lock(&_wdd->lock);
> > +
> > + wdd = _wdd->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
> > @@ -585,29 +597,24 @@ static int watchdog_release(struct inode *inode, struct file *file)
> > */
> > if (!test_bit(WDOG_ACTIVE, &wdd->status))
> > err = 0;
> > - else if (test_and_clear_bit(WDOG_ALLOW_RELEASE, &wdd->status) ||
> > + else if (test_and_clear_bit(_WDOG_ALLOW_RELEASE, &_wdd->status) ||
> > !(wdd->info->options & WDIOF_MAGICCLOSE))
> > err = watchdog_stop(wdd);
> >
> > /* If the watchdog was not stopped, send a keepalive ping */
> > if (err < 0) {
> > - mutex_lock(&wdd->lock);
> > - if (!test_bit(WDOG_UNREGISTERED, &wdd->status))
> > - dev_crit(wdd->dev, "watchdog did not stop!\n");
> > - mutex_unlock(&wdd->lock);
> > + dev_crit(wdd->dev, "watchdog did not stop!\n");
> > watchdog_ping(wdd);
> > }
> >
> > - /* Allow the owner module to be unloaded again */
> > - module_put(wdd->ops->owner);
> > -
> > /* make sure that /dev/watchdog can be re-opened */
> > - clear_bit(WDOG_DEV_OPEN, &wdd->status);
> > -
> > - /* Note wdd may be gone after this, do not use after this! */
> > - if (wdd->ops->unref)
> > - wdd->ops->unref(wdd);
> > + clear_bit(_WDOG_DEV_OPEN, &_wdd->status);
> >
> > +done:
> > + mutex_unlock(&_wdd->lock);
> > + /* Allow the owner module to be unloaded again */
> > + module_put(_wdd->cdev.owner);
> > + kref_put(&_wdd->kref, watchdog_wdd_release);
> > return 0;
> > }
> >
> > @@ -637,10 +644,20 @@ static struct miscdevice watchdog_miscdev = {
> >
> > static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
> > {
> > + struct _watchdog_device *_wdd;
> > int err;
> >
> > + _wdd = kzalloc(sizeof(struct _watchdog_device), GFP_KERNEL);
> > + if (!_wdd)
> > + return -ENOMEM;
> > + kref_init(&_wdd->kref);
> > + mutex_init(&_wdd->lock);
> > +
> > + _wdd->wdd = wdd;
> > + wdd->wdd_data = _wdd;
> > +
> > if (wdd->id == 0) {
> > - old_wdd = wdd;
> > + _old_wdd = _wdd;
> > watchdog_miscdev.parent = wdd->parent;
> > err = misc_register(&watchdog_miscdev);
> > if (err != 0) {
> > @@ -649,23 +666,25 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
> > if (err == -EBUSY)
> > pr_err("%s: a legacy watchdog module is probably present.\n",
> > wdd->info->identity);
> > - old_wdd = NULL;
> > + _old_wdd = NULL;
> > + kfree(_wdd);
> > return err;
> > }
> > }
> >
> > /* Fill in the data structures */
> > - cdev_init(&wdd->cdev, &watchdog_fops);
> > - wdd->cdev.owner = wdd->ops->owner;
> > + cdev_init(&_wdd->cdev, &watchdog_fops);
> > + _wdd->cdev.owner = wdd->ops->owner;
> >
> > /* Add the device */
> > - err = cdev_add(&wdd->cdev, devno, 1);
> > + err = cdev_add(&_wdd->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_wdd = NULL;
> > + _old_wdd = NULL;
> > + kref_put(&_wdd->kref, watchdog_wdd_release);
> > }
> > }
> > return err;
> > @@ -681,15 +700,23 @@ static int watchdog_cdev_register(struct watchdog_device *wdd, dev_t devno)
> >
> > static void watchdog_cdev_unregister(struct watchdog_device *wdd)
> > {
> > - mutex_lock(&wdd->lock);
> > - set_bit(WDOG_UNREGISTERED, &wdd->status);
> > - mutex_unlock(&wdd->lock);
> > + struct _watchdog_device *_wdd = wdd->wdd_data;
> >
> > - cdev_del(&wdd->cdev);
> > + cdev_del(&_wdd->cdev);
> > if (wdd->id == 0) {
> > misc_deregister(&watchdog_miscdev);
> > - old_wdd = NULL;
> > + _old_wdd = NULL;
> > }
> > +
> > + if (watchdog_active(wdd))
> > + pr_crit("watchdog%d: watchdog still running!\n", wdd->id);
>
> As it is now safe to unbind and rebind a driver, it means that a
> watchdog driver probe function can now be called with a running
> watchdog. Some drivers handle this situation, but I think that most of
> them expect the watchdog to be off at this point.
>
> > +
> > + mutex_lock(&_wdd->lock);
> > + _wdd->wdd = NULL;
> > + wdd->wdd_data = NULL;
> > + mutex_unlock(&_wdd->lock);
> > +
> > + kref_put(&_wdd->kref, watchdog_wdd_release);
> > }
> >
> > static struct class watchdog_class = {
> > @@ -742,9 +769,9 @@ int watchdog_dev_register(struct watchdog_device *wdd)
> >
> > void watchdog_dev_unregister(struct watchdog_device *wdd)
> > {
> > - watchdog_cdev_unregister(wdd);
> > device_destroy(&watchdog_class, wdd->dev->devt);
> > wdd->dev = NULL;
> > + watchdog_cdev_unregister(wdd);
> > }
> >
> > /*
> > diff --git a/include/linux/watchdog.h b/include/linux/watchdog.h
> > index a88f955fde92..1d3363aeb6e4 100644
> > --- a/include/linux/watchdog.h
> > +++ b/include/linux/watchdog.h
> > @@ -28,8 +28,6 @@ struct watchdog_device;
> > * @set_timeout:The routine for setting the watchdog devices timeout value (in seconds).
> > * @get_timeleft:The routine that gets the time left before a reset (in seconds).
> > * @restart: The routine for restarting the machine.
> > - * @ref: The ref operation for dyn. allocated watchdog_device structs
> > - * @unref: The unref operation for dyn. allocated watchdog_device structs
> > * @ioctl: The routines that handles extra ioctl calls.
> > *
> > * The watchdog_ops structure contains a list of low-level operations
> > @@ -48,15 +46,14 @@ struct watchdog_ops {
> > int (*set_timeout)(struct watchdog_device *, unsigned int);
> > unsigned int (*get_timeleft)(struct watchdog_device *);
> > int (*restart)(struct watchdog_device *);
> > - void (*ref)(struct watchdog_device *);
> > - void (*unref)(struct watchdog_device *);
> > + void (*ref)(struct watchdog_device *) __deprecated;
> > + void (*unref)(struct watchdog_device *) __deprecated;
> > long (*ioctl)(struct watchdog_device *, unsigned int, unsigned long);
> > };
> >
> > /** struct watchdog_device - The structure that defines a watchdog device
> > *
> > * @id: The watchdog's ID. (Allocated by watchdog_register_device)
> > - * @cdev: The watchdog's Character device.
> > * @dev: The device for our watchdog
> > * @parent: The parent bus device
> > * @info: Pointer to a watchdog_info structure.
> > @@ -67,8 +64,8 @@ struct watchdog_ops {
> > * @max_timeout:The watchdog devices maximum timeout value (in seconds).
> > * @reboot_nb: The notifier block to stop watchdog on reboot.
> > * @restart_nb: The notifier block to register a restart function.
> > - * @driver-data:Pointer to the drivers private data.
> > - * @lock: Lock for watchdog core internal use only.
> > + * @driver_data:Pointer to the drivers private data.
> > + * @wdd_data: Pointer to watchdog core internal data.
> > * @status: Field that contains the devices internal status bits.
> > * @deferred: entry in wtd_deferred_reg_list which is used to
> > * register early initialized watchdogs.
> > @@ -84,7 +81,6 @@ struct watchdog_ops {
> > */
> > struct watchdog_device {
> > int id;
> > - struct cdev cdev;
> > struct device *dev;
> > struct device *parent;
> > const struct watchdog_info *info;
> > @@ -96,15 +92,12 @@ struct watchdog_device {
> > struct notifier_block reboot_nb;
> > struct notifier_block restart_nb;
> > void *driver_data;
> > - struct mutex lock;
> > + void *wdd_data;
> > unsigned long status;
> > /* Bit numbers for status flags */
> > #define WDOG_ACTIVE 0 /* Is the watchdog running/active */
> > -#define WDOG_DEV_OPEN 1 /* Opened via /dev/watchdog ? */
> > -#define WDOG_ALLOW_RELEASE 2 /* Did we receive the magic char ? */
> > -#define WDOG_NO_WAY_OUT 3 /* Is 'nowayout' feature set ? */
> > -#define WDOG_UNREGISTERED 4 /* Has the device been unregistered */
> > -#define WDOG_STOP_ON_REBOOT 5 /* Should be stopped on reboot */
> > +#define WDOG_NO_WAY_OUT 1 /* Is 'nowayout' feature set ? */
> > +#define WDOG_STOP_ON_REBOOT 2 /* Should be stopped on reboot */
> > struct list_head deferred;
> > };
> >
> > --
> > 2.1.4
> >
> --
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