linux/drivers/iio/industrialio-trigger.c
Jonathan Cameron a18aeac73c iio: trigger: Fix a scheduling whilst atomic issue seen on tsc2046
commit 9020ef6598 upstream.

IIO triggers are software IRQ chips that split an incoming IRQ into
separate IRQs routed to all devices using the trigger.
When all consumers are done then a trigger callback reenable() is
called.  There are a few circumstances under which this can happen
in atomic context.

1) A single user of the trigger that calls the iio_trigger_done()
function from interrupt context.
2) A race between disconnecting the last device from a trigger and
the trigger itself sucessfully being disabled.

To avoid a resulting scheduling whilst atomic, close this second corner
by using schedule_work() to ensure the reenable is not done in atomic
context.

Note that drivers must be careful to manage the interaction of
set_state() and reenable() callbacks to ensure appropriate reference
counting if they are relying on the same hardware controls.

Deliberately taking this the slow path rather than via a fixes tree
because the error has hard to hit and I would like it to soak for a while
before hitting a release kernel.

Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Cc: Pengutronix Kernel Team <kernel@pengutronix.de>
Cc: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Tested-by: Oleksij Rempel <o.rempel@pengutronix.de>
Cc: <Stable@vger.kernel.org>
Link: https://lore.kernel.org/r/20211017172209.112387-1-jic23@kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2022-01-27 11:02:57 +01:00

749 lines
20 KiB
C

// SPDX-License-Identifier: GPL-2.0-only
/* The industrial I/O core, trigger handling functions
*
* Copyright (c) 2008 Jonathan Cameron
*/
#include <linux/kernel.h>
#include <linux/idr.h>
#include <linux/err.h>
#include <linux/device.h>
#include <linux/interrupt.h>
#include <linux/list.h>
#include <linux/slab.h>
#include <linux/iio/iio.h>
#include <linux/iio/iio-opaque.h>
#include <linux/iio/trigger.h>
#include "iio_core.h"
#include "iio_core_trigger.h"
#include <linux/iio/trigger_consumer.h>
/* RFC - Question of approach
* Make the common case (single sensor single trigger)
* simple by starting trigger capture from when first sensors
* is added.
*
* Complex simultaneous start requires use of 'hold' functionality
* of the trigger. (not implemented)
*
* Any other suggestions?
*/
static DEFINE_IDA(iio_trigger_ida);
/* Single list of all available triggers */
static LIST_HEAD(iio_trigger_list);
static DEFINE_MUTEX(iio_trigger_list_lock);
/**
* iio_trigger_read_name() - retrieve useful identifying name
* @dev: device associated with the iio_trigger
* @attr: pointer to the device_attribute structure that is
* being processed
* @buf: buffer to print the name into
*
* Return: a negative number on failure or the number of written
* characters on success.
*/
static ssize_t iio_trigger_read_name(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct iio_trigger *trig = to_iio_trigger(dev);
return sysfs_emit(buf, "%s\n", trig->name);
}
static DEVICE_ATTR(name, S_IRUGO, iio_trigger_read_name, NULL);
static struct attribute *iio_trig_dev_attrs[] = {
&dev_attr_name.attr,
NULL,
};
ATTRIBUTE_GROUPS(iio_trig_dev);
static struct iio_trigger *__iio_trigger_find_by_name(const char *name);
int __iio_trigger_register(struct iio_trigger *trig_info,
struct module *this_mod)
{
int ret;
trig_info->owner = this_mod;
trig_info->id = ida_simple_get(&iio_trigger_ida, 0, 0, GFP_KERNEL);
if (trig_info->id < 0)
return trig_info->id;
/* Set the name used for the sysfs directory etc */
dev_set_name(&trig_info->dev, "trigger%d", trig_info->id);
ret = device_add(&trig_info->dev);
if (ret)
goto error_unregister_id;
/* Add to list of available triggers held by the IIO core */
mutex_lock(&iio_trigger_list_lock);
if (__iio_trigger_find_by_name(trig_info->name)) {
pr_err("Duplicate trigger name '%s'\n", trig_info->name);
ret = -EEXIST;
goto error_device_del;
}
list_add_tail(&trig_info->list, &iio_trigger_list);
mutex_unlock(&iio_trigger_list_lock);
return 0;
error_device_del:
mutex_unlock(&iio_trigger_list_lock);
device_del(&trig_info->dev);
error_unregister_id:
ida_simple_remove(&iio_trigger_ida, trig_info->id);
return ret;
}
EXPORT_SYMBOL(__iio_trigger_register);
void iio_trigger_unregister(struct iio_trigger *trig_info)
{
mutex_lock(&iio_trigger_list_lock);
list_del(&trig_info->list);
mutex_unlock(&iio_trigger_list_lock);
ida_simple_remove(&iio_trigger_ida, trig_info->id);
/* Possible issue in here */
device_del(&trig_info->dev);
}
EXPORT_SYMBOL(iio_trigger_unregister);
int iio_trigger_set_immutable(struct iio_dev *indio_dev, struct iio_trigger *trig)
{
struct iio_dev_opaque *iio_dev_opaque;
if (!indio_dev || !trig)
return -EINVAL;
iio_dev_opaque = to_iio_dev_opaque(indio_dev);
mutex_lock(&indio_dev->mlock);
WARN_ON(iio_dev_opaque->trig_readonly);
indio_dev->trig = iio_trigger_get(trig);
iio_dev_opaque->trig_readonly = true;
mutex_unlock(&indio_dev->mlock);
return 0;
}
EXPORT_SYMBOL(iio_trigger_set_immutable);
/* Search for trigger by name, assuming iio_trigger_list_lock held */
static struct iio_trigger *__iio_trigger_find_by_name(const char *name)
{
struct iio_trigger *iter;
list_for_each_entry(iter, &iio_trigger_list, list)
if (!strcmp(iter->name, name))
return iter;
return NULL;
}
static struct iio_trigger *iio_trigger_acquire_by_name(const char *name)
{
struct iio_trigger *trig = NULL, *iter;
mutex_lock(&iio_trigger_list_lock);
list_for_each_entry(iter, &iio_trigger_list, list)
if (sysfs_streq(iter->name, name)) {
trig = iter;
iio_trigger_get(trig);
break;
}
mutex_unlock(&iio_trigger_list_lock);
return trig;
}
static void iio_reenable_work_fn(struct work_struct *work)
{
struct iio_trigger *trig = container_of(work, struct iio_trigger,
reenable_work);
/*
* This 'might' occur after the trigger state is set to disabled -
* in that case the driver should skip reenabling.
*/
trig->ops->reenable(trig);
}
/*
* In general, reenable callbacks may need to sleep and this path is
* not performance sensitive, so just queue up a work item
* to reneable the trigger for us.
*
* Races that can cause this.
* 1) A handler occurs entirely in interrupt context so the counter
* the final decrement is still in this interrupt.
* 2) The trigger has been removed, but one last interrupt gets through.
*
* For (1) we must call reenable, but not in atomic context.
* For (2) it should be safe to call reenanble, if drivers never blindly
* reenable after state is off.
*/
static void iio_trigger_notify_done_atomic(struct iio_trigger *trig)
{
if (atomic_dec_and_test(&trig->use_count) && trig->ops &&
trig->ops->reenable)
schedule_work(&trig->reenable_work);
}
void iio_trigger_poll(struct iio_trigger *trig)
{
int i;
if (!atomic_read(&trig->use_count)) {
atomic_set(&trig->use_count, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) {
if (trig->subirqs[i].enabled)
generic_handle_irq(trig->subirq_base + i);
else
iio_trigger_notify_done_atomic(trig);
}
}
}
EXPORT_SYMBOL(iio_trigger_poll);
irqreturn_t iio_trigger_generic_data_rdy_poll(int irq, void *private)
{
iio_trigger_poll(private);
return IRQ_HANDLED;
}
EXPORT_SYMBOL(iio_trigger_generic_data_rdy_poll);
void iio_trigger_poll_chained(struct iio_trigger *trig)
{
int i;
if (!atomic_read(&trig->use_count)) {
atomic_set(&trig->use_count, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) {
if (trig->subirqs[i].enabled)
handle_nested_irq(trig->subirq_base + i);
else
iio_trigger_notify_done(trig);
}
}
}
EXPORT_SYMBOL(iio_trigger_poll_chained);
void iio_trigger_notify_done(struct iio_trigger *trig)
{
if (atomic_dec_and_test(&trig->use_count) && trig->ops &&
trig->ops->reenable)
trig->ops->reenable(trig);
}
EXPORT_SYMBOL(iio_trigger_notify_done);
/* Trigger Consumer related functions */
static int iio_trigger_get_irq(struct iio_trigger *trig)
{
int ret;
mutex_lock(&trig->pool_lock);
ret = bitmap_find_free_region(trig->pool,
CONFIG_IIO_CONSUMERS_PER_TRIGGER,
ilog2(1));
mutex_unlock(&trig->pool_lock);
if (ret >= 0)
ret += trig->subirq_base;
return ret;
}
static void iio_trigger_put_irq(struct iio_trigger *trig, int irq)
{
mutex_lock(&trig->pool_lock);
clear_bit(irq - trig->subirq_base, trig->pool);
mutex_unlock(&trig->pool_lock);
}
/* Complexity in here. With certain triggers (datardy) an acknowledgement
* may be needed if the pollfuncs do not include the data read for the
* triggering device.
* This is not currently handled. Alternative of not enabling trigger unless
* the relevant function is in there may be the best option.
*/
/* Worth protecting against double additions? */
int iio_trigger_attach_poll_func(struct iio_trigger *trig,
struct iio_poll_func *pf)
{
struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(pf->indio_dev);
bool notinuse =
bitmap_empty(trig->pool, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
int ret = 0;
/* Prevent the module from being removed whilst attached to a trigger */
__module_get(iio_dev_opaque->driver_module);
/* Get irq number */
pf->irq = iio_trigger_get_irq(trig);
if (pf->irq < 0) {
pr_err("Could not find an available irq for trigger %s, CONFIG_IIO_CONSUMERS_PER_TRIGGER=%d limit might be exceeded\n",
trig->name, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
goto out_put_module;
}
/* Request irq */
ret = request_threaded_irq(pf->irq, pf->h, pf->thread,
pf->type, pf->name,
pf);
if (ret < 0)
goto out_put_irq;
/* Enable trigger in driver */
if (trig->ops && trig->ops->set_trigger_state && notinuse) {
ret = trig->ops->set_trigger_state(trig, true);
if (ret < 0)
goto out_free_irq;
}
/*
* Check if we just registered to our own trigger: we determine that
* this is the case if the IIO device and the trigger device share the
* same parent device.
*/
if (pf->indio_dev->dev.parent == trig->dev.parent)
trig->attached_own_device = true;
return ret;
out_free_irq:
free_irq(pf->irq, pf);
out_put_irq:
iio_trigger_put_irq(trig, pf->irq);
out_put_module:
module_put(iio_dev_opaque->driver_module);
return ret;
}
int iio_trigger_detach_poll_func(struct iio_trigger *trig,
struct iio_poll_func *pf)
{
struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(pf->indio_dev);
bool no_other_users =
bitmap_weight(trig->pool, CONFIG_IIO_CONSUMERS_PER_TRIGGER) == 1;
int ret = 0;
if (trig->ops && trig->ops->set_trigger_state && no_other_users) {
ret = trig->ops->set_trigger_state(trig, false);
if (ret)
return ret;
}
if (pf->indio_dev->dev.parent == trig->dev.parent)
trig->attached_own_device = false;
iio_trigger_put_irq(trig, pf->irq);
free_irq(pf->irq, pf);
module_put(iio_dev_opaque->driver_module);
return ret;
}
irqreturn_t iio_pollfunc_store_time(int irq, void *p)
{
struct iio_poll_func *pf = p;
pf->timestamp = iio_get_time_ns(pf->indio_dev);
return IRQ_WAKE_THREAD;
}
EXPORT_SYMBOL(iio_pollfunc_store_time);
struct iio_poll_func
*iio_alloc_pollfunc(irqreturn_t (*h)(int irq, void *p),
irqreturn_t (*thread)(int irq, void *p),
int type,
struct iio_dev *indio_dev,
const char *fmt,
...)
{
va_list vargs;
struct iio_poll_func *pf;
pf = kmalloc(sizeof *pf, GFP_KERNEL);
if (pf == NULL)
return NULL;
va_start(vargs, fmt);
pf->name = kvasprintf(GFP_KERNEL, fmt, vargs);
va_end(vargs);
if (pf->name == NULL) {
kfree(pf);
return NULL;
}
pf->h = h;
pf->thread = thread;
pf->type = type;
pf->indio_dev = indio_dev;
return pf;
}
EXPORT_SYMBOL_GPL(iio_alloc_pollfunc);
void iio_dealloc_pollfunc(struct iio_poll_func *pf)
{
kfree(pf->name);
kfree(pf);
}
EXPORT_SYMBOL_GPL(iio_dealloc_pollfunc);
/**
* iio_trigger_read_current() - trigger consumer sysfs query current trigger
* @dev: device associated with an industrial I/O device
* @attr: pointer to the device_attribute structure that
* is being processed
* @buf: buffer where the current trigger name will be printed into
*
* For trigger consumers the current_trigger interface allows the trigger
* used by the device to be queried.
*
* Return: a negative number on failure, the number of characters written
* on success or 0 if no trigger is available
*/
static ssize_t iio_trigger_read_current(struct device *dev,
struct device_attribute *attr,
char *buf)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
if (indio_dev->trig)
return sysfs_emit(buf, "%s\n", indio_dev->trig->name);
return 0;
}
/**
* iio_trigger_write_current() - trigger consumer sysfs set current trigger
* @dev: device associated with an industrial I/O device
* @attr: device attribute that is being processed
* @buf: string buffer that holds the name of the trigger
* @len: length of the trigger name held by buf
*
* For trigger consumers the current_trigger interface allows the trigger
* used for this device to be specified at run time based on the trigger's
* name.
*
* Return: negative error code on failure or length of the buffer
* on success
*/
static ssize_t iio_trigger_write_current(struct device *dev,
struct device_attribute *attr,
const char *buf,
size_t len)
{
struct iio_dev *indio_dev = dev_to_iio_dev(dev);
struct iio_dev_opaque *iio_dev_opaque = to_iio_dev_opaque(indio_dev);
struct iio_trigger *oldtrig = indio_dev->trig;
struct iio_trigger *trig;
int ret;
mutex_lock(&indio_dev->mlock);
if (indio_dev->currentmode == INDIO_BUFFER_TRIGGERED) {
mutex_unlock(&indio_dev->mlock);
return -EBUSY;
}
if (iio_dev_opaque->trig_readonly) {
mutex_unlock(&indio_dev->mlock);
return -EPERM;
}
mutex_unlock(&indio_dev->mlock);
trig = iio_trigger_acquire_by_name(buf);
if (oldtrig == trig) {
ret = len;
goto out_trigger_put;
}
if (trig && indio_dev->info->validate_trigger) {
ret = indio_dev->info->validate_trigger(indio_dev, trig);
if (ret)
goto out_trigger_put;
}
if (trig && trig->ops && trig->ops->validate_device) {
ret = trig->ops->validate_device(trig, indio_dev);
if (ret)
goto out_trigger_put;
}
indio_dev->trig = trig;
if (oldtrig) {
if (indio_dev->modes & INDIO_EVENT_TRIGGERED)
iio_trigger_detach_poll_func(oldtrig,
indio_dev->pollfunc_event);
iio_trigger_put(oldtrig);
}
if (indio_dev->trig) {
if (indio_dev->modes & INDIO_EVENT_TRIGGERED)
iio_trigger_attach_poll_func(indio_dev->trig,
indio_dev->pollfunc_event);
}
return len;
out_trigger_put:
if (trig)
iio_trigger_put(trig);
return ret;
}
static DEVICE_ATTR(current_trigger, S_IRUGO | S_IWUSR,
iio_trigger_read_current,
iio_trigger_write_current);
static struct attribute *iio_trigger_consumer_attrs[] = {
&dev_attr_current_trigger.attr,
NULL,
};
static const struct attribute_group iio_trigger_consumer_attr_group = {
.name = "trigger",
.attrs = iio_trigger_consumer_attrs,
};
static void iio_trig_release(struct device *device)
{
struct iio_trigger *trig = to_iio_trigger(device);
int i;
if (trig->subirq_base) {
for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) {
irq_modify_status(trig->subirq_base + i,
IRQ_NOAUTOEN,
IRQ_NOREQUEST | IRQ_NOPROBE);
irq_set_chip(trig->subirq_base + i,
NULL);
irq_set_handler(trig->subirq_base + i,
NULL);
}
irq_free_descs(trig->subirq_base,
CONFIG_IIO_CONSUMERS_PER_TRIGGER);
}
kfree(trig->name);
kfree(trig);
}
static const struct device_type iio_trig_type = {
.release = iio_trig_release,
.groups = iio_trig_dev_groups,
};
static void iio_trig_subirqmask(struct irq_data *d)
{
struct irq_chip *chip = irq_data_get_irq_chip(d);
struct iio_trigger *trig = container_of(chip, struct iio_trigger, subirq_chip);
trig->subirqs[d->irq - trig->subirq_base].enabled = false;
}
static void iio_trig_subirqunmask(struct irq_data *d)
{
struct irq_chip *chip = irq_data_get_irq_chip(d);
struct iio_trigger *trig = container_of(chip, struct iio_trigger, subirq_chip);
trig->subirqs[d->irq - trig->subirq_base].enabled = true;
}
static __printf(2, 0)
struct iio_trigger *viio_trigger_alloc(struct device *parent,
const char *fmt,
va_list vargs)
{
struct iio_trigger *trig;
int i;
trig = kzalloc(sizeof *trig, GFP_KERNEL);
if (!trig)
return NULL;
trig->dev.parent = parent;
trig->dev.type = &iio_trig_type;
trig->dev.bus = &iio_bus_type;
device_initialize(&trig->dev);
INIT_WORK(&trig->reenable_work, iio_reenable_work_fn);
mutex_init(&trig->pool_lock);
trig->subirq_base = irq_alloc_descs(-1, 0,
CONFIG_IIO_CONSUMERS_PER_TRIGGER,
0);
if (trig->subirq_base < 0)
goto free_trig;
trig->name = kvasprintf(GFP_KERNEL, fmt, vargs);
if (trig->name == NULL)
goto free_descs;
trig->subirq_chip.name = trig->name;
trig->subirq_chip.irq_mask = &iio_trig_subirqmask;
trig->subirq_chip.irq_unmask = &iio_trig_subirqunmask;
for (i = 0; i < CONFIG_IIO_CONSUMERS_PER_TRIGGER; i++) {
irq_set_chip(trig->subirq_base + i, &trig->subirq_chip);
irq_set_handler(trig->subirq_base + i, &handle_simple_irq);
irq_modify_status(trig->subirq_base + i,
IRQ_NOREQUEST | IRQ_NOAUTOEN, IRQ_NOPROBE);
}
return trig;
free_descs:
irq_free_descs(trig->subirq_base, CONFIG_IIO_CONSUMERS_PER_TRIGGER);
free_trig:
kfree(trig);
return NULL;
}
/**
* iio_trigger_alloc - Allocate a trigger
* @parent: Device to allocate iio_trigger for
* @fmt: trigger name format. If it includes format
* specifiers, the additional arguments following
* format are formatted and inserted in the resulting
* string replacing their respective specifiers.
* RETURNS:
* Pointer to allocated iio_trigger on success, NULL on failure.
*/
struct iio_trigger *iio_trigger_alloc(struct device *parent, const char *fmt, ...)
{
struct iio_trigger *trig;
va_list vargs;
va_start(vargs, fmt);
trig = viio_trigger_alloc(parent, fmt, vargs);
va_end(vargs);
return trig;
}
EXPORT_SYMBOL(iio_trigger_alloc);
void iio_trigger_free(struct iio_trigger *trig)
{
if (trig)
put_device(&trig->dev);
}
EXPORT_SYMBOL(iio_trigger_free);
static void devm_iio_trigger_release(struct device *dev, void *res)
{
iio_trigger_free(*(struct iio_trigger **)res);
}
/**
* devm_iio_trigger_alloc - Resource-managed iio_trigger_alloc()
* Managed iio_trigger_alloc. iio_trigger allocated with this function is
* automatically freed on driver detach.
* @parent: Device to allocate iio_trigger for
* @fmt: trigger name format. If it includes format
* specifiers, the additional arguments following
* format are formatted and inserted in the resulting
* string replacing their respective specifiers.
*
*
* RETURNS:
* Pointer to allocated iio_trigger on success, NULL on failure.
*/
struct iio_trigger *devm_iio_trigger_alloc(struct device *parent, const char *fmt, ...)
{
struct iio_trigger **ptr, *trig;
va_list vargs;
ptr = devres_alloc(devm_iio_trigger_release, sizeof(*ptr),
GFP_KERNEL);
if (!ptr)
return NULL;
/* use raw alloc_dr for kmalloc caller tracing */
va_start(vargs, fmt);
trig = viio_trigger_alloc(parent, fmt, vargs);
va_end(vargs);
if (trig) {
*ptr = trig;
devres_add(parent, ptr);
} else {
devres_free(ptr);
}
return trig;
}
EXPORT_SYMBOL_GPL(devm_iio_trigger_alloc);
static void devm_iio_trigger_unreg(void *trigger_info)
{
iio_trigger_unregister(trigger_info);
}
/**
* __devm_iio_trigger_register - Resource-managed iio_trigger_register()
* @dev: device this trigger was allocated for
* @trig_info: trigger to register
* @this_mod: module registering the trigger
*
* Managed iio_trigger_register(). The IIO trigger registered with this
* function is automatically unregistered on driver detach. This function
* calls iio_trigger_register() internally. Refer to that function for more
* information.
*
* RETURNS:
* 0 on success, negative error number on failure.
*/
int __devm_iio_trigger_register(struct device *dev,
struct iio_trigger *trig_info,
struct module *this_mod)
{
int ret;
ret = __iio_trigger_register(trig_info, this_mod);
if (ret)
return ret;
return devm_add_action_or_reset(dev, devm_iio_trigger_unreg, trig_info);
}
EXPORT_SYMBOL_GPL(__devm_iio_trigger_register);
bool iio_trigger_using_own(struct iio_dev *indio_dev)
{
return indio_dev->trig->attached_own_device;
}
EXPORT_SYMBOL(iio_trigger_using_own);
/**
* iio_trigger_validate_own_device - Check if a trigger and IIO device belong to
* the same device
* @trig: The IIO trigger to check
* @indio_dev: the IIO device to check
*
* This function can be used as the validate_device callback for triggers that
* can only be attached to their own device.
*
* Return: 0 if both the trigger and the IIO device belong to the same
* device, -EINVAL otherwise.
*/
int iio_trigger_validate_own_device(struct iio_trigger *trig,
struct iio_dev *indio_dev)
{
if (indio_dev->dev.parent != trig->dev.parent)
return -EINVAL;
return 0;
}
EXPORT_SYMBOL(iio_trigger_validate_own_device);
int iio_device_register_trigger_consumer(struct iio_dev *indio_dev)
{
return iio_device_register_sysfs_group(indio_dev,
&iio_trigger_consumer_attr_group);
}
void iio_device_unregister_trigger_consumer(struct iio_dev *indio_dev)
{
/* Clean up an associated but not attached trigger reference */
if (indio_dev->trig)
iio_trigger_put(indio_dev->trig);
}