// SPDX-License-Identifier: GPL-2.0-only
/*
* Fence mechanism for dma-buf and to allow for asynchronous dma access
*
* Copyright (C) 2012 Canonical Ltd
* Copyright (C) 2012 Texas Instruments
*
* Authors:
* Rob Clark <robdclark@gmail.com>
* Maarten Lankhorst <maarten.lankhorst@canonical.com>
*/
#include <linux/slab.h>
#include <linux/export.h>
#include <linux/atomic.h>
#include <linux/dma-fence.h>
#include <linux/sched/signal.h>
#define CREATE_TRACE_POINTS
#include <trace/events/dma_fence.h>
EXPORT_TRACEPOINT_SYMBOL(dma_fence_emit);
EXPORT_TRACEPOINT_SYMBOL(dma_fence_enable_signal);
EXPORT_TRACEPOINT_SYMBOL(dma_fence_signaled);
static DEFINE_SPINLOCK(dma_fence_stub_lock);
static struct dma_fence dma_fence_stub;
/*
* fence context counter: each execution context should have its own
* fence context, this allows checking if fences belong to the same
* context or not. One device can have multiple separate contexts,
* and they're used if some engine can run independently of another.
*/
static atomic64_t dma_fence_context_counter = ATOMIC64_INIT(1);
/**
* DOC: DMA fences overview
*
* DMA fences, represented by &struct dma_fence, are the kernel internal
* synchronization primitive for DMA operations like GPU rendering, video
* encoding/decoding, or displaying buffers on a screen.
*
* A fence is initialized using dma_fence_init() and completed using
* dma_fence_signal(). Fences are associated with a context, allocated through
* dma_fence_context_alloc(), and all fences on the same context are
* fully ordered.
*
* Since the purposes of fences is to facilitate cross-device and
* cross-application synchronization, there's multiple ways to use one:
*
* - Individual fences can be exposed as a &sync_file, accessed as a file
* descriptor from userspace, created by calling sync_file_create(). This is
* called explicit fencing, since userspace passes around explicit
* synchronization points.
*
* - Some subsystems also have their own explicit fencing primitives, like
* &drm_syncobj. Compared to &sync_file, a &drm_syncobj allows the underlying
* fence to be updated.
*
* - Then there's also implicit fencing, where the synchronization points are
* implicitly passed around as part of shared &dma_buf instances. Such
* implicit fences are stored in &struct reservation_object through the
* &dma_buf.resv pointer.
*/
static const char *dma_fence_stub_get_name(struct dma_fence *fence)
{
return "stub";
}
static const struct dma_fence_ops dma_fence_stub_ops = {
.get_driver_name = dma_fence_stub_get_name,
.get_timeline_name = dma_fence_stub_get_name,
};
/**
* dma_fence_get_stub - return a signaled fence
*
* Return a stub fence which is already signaled.
*/
struct dma_fence *dma_fence_get_stub(void)
{
spin_lock(&dma_fence_stub_lock);
if (!dma_fence_stub.ops) {
dma_fence_init(&dma_fence_stub,
&dma_fence_stub_ops,
&dma_fence_stub_lock,
0, 0);
dma_fence_signal_locked(&dma_fence_stub);
}
spin_unlock(&dma_fence_stub_lock);
return dma_fence_get(&dma_fence_stub);
}
EXPORT_SYMBOL(dma_fence_get_stub);
/**
* dma_fence_context_alloc - allocate an array of fence contexts
* @num: amount of contexts to allocate
*
* This function will return the first index of the number of fence contexts
* allocated. The fence context is used for setting &dma_fence.context to a
* unique number by passing the context to dma_fence_init().
*/
u64 dma_fence_context_alloc(unsigned num)
{
WARN_ON(!num);
return atomic64_add_return(num, &dma_fence_context_counter) - num;
}
EXPORT_SYMBOL(dma_fence_context_alloc);
/**
* dma_fence_signal_locked - signal completion of a fence
* @fence: the fence to signal
*
* Signal completion for software callbacks on a fence, this will unblock
* dma_fence_wait() calls and run all the callbacks added with
* dma_fence_add_callback(). Can be called multiple times, but since a fence
* can only go from the unsignaled to the signaled state and not back, it will
* only be effective the first time.
*
* Unlike dma_fence_signal(), this function must be called with &dma_fence.lock
* held.
*
* Returns 0 on success and a negative error value when @fence has been
* signalled already.
*/
int dma_fence_signal_locked(struct dma_fence *fence)
{
struct dma_fence_cb *cur, *tmp;
int ret = 0;
lockdep_assert_held(fence->lock);
if (WARN_ON(!fence))
return -EINVAL;
if (test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
ret = -EINVAL;
/*
* we might have raced with the unlocked dma_fence_signal,
* still run through all callbacks
*/
} else {
fence->timestamp = ktime_get();
set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
trace_dma_fence_signaled(fence);
}
list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
list_del_init(&cur->node);
cur->func(fence, cur);
}
return ret;
}
EXPORT_SYMBOL(dma_fence_signal_locked);
/**
* dma_fence_signal - signal completion of a fence
* @fence: the fence to signal
*
* Signal completion for software callbacks on a fence, this will unblock
* dma_fence_wait() calls and run all the callbacks added with
* dma_fence_add_callback(). Can be called multiple times, but since a fence
* can only go from the unsignaled to the signaled state and not back, it will
* only be effective the first time.
*
* Returns 0 on success and a negative error value when @fence has been
* signalled already.
*/
int dma_fence_signal(struct dma_fence *fence)
{
unsigned long flags;
if (!fence)
return -EINVAL;
if (test_and_set_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
return -EINVAL;
fence->timestamp = ktime_get();
set_bit(DMA_FENCE_FLAG_TIMESTAMP_BIT, &fence->flags);
trace_dma_fence_signaled(fence);
if (test_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT, &fence->flags)) {
struct dma_fence_cb *cur, *tmp;
spin_lock_irqsave(fence->lock, flags);
list_for_each_entry_safe(cur, tmp, &fence->cb_list, node) {
list_del_init(&cur->node);
cur->func(fence, cur);
}
spin_unlock_irqrestore(fence->lock, flags);
}
return 0;
}
EXPORT_SYMBOL(dma_fence_signal);
/**
* dma_fence_wait_timeout - sleep until the fence gets signaled
* or until timeout elapses
* @fence: the fence to wait on
* @intr: if true, do an interruptible wait
* @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
*
* Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
* remaining timeout in jiffies on success. Other error values may be
* returned on custom implementations.
*
* Performs a synchronous wait on this fence. It is assumed the caller
* directly or indirectly (buf-mgr between reservation and committing)
* holds a reference to the fence, otherwise the fence might be
* freed before return, resulting in undefined behavior.
*
* See also dma_fence_wait() and dma_fence_wait_any_timeout().
*/
signed long
dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
{
signed long ret;
if (WARN_ON(timeout < 0))
return -EINVAL;
trace_dma_fence_wait_start(fence);
if (fence->ops->wait)
ret = fence->ops->wait(fence, intr, timeout);
else
ret = dma_fence_default_wait(fence, intr, timeout);
trace_dma_fence_wait_end(fence);
return ret;
}
EXPORT_SYMBOL(dma_fence_wait_timeout);
/**
* dma_fence_release - default relese function for fences
* @kref: &dma_fence.recfount
*
* This is the default release functions for &dma_fence. Drivers shouldn't call
* this directly, but instead call dma_fence_put().
*/
void dma_fence_release(struct kref *kref)
{
struct dma_fence *fence =
container_of(kref, struct dma_fence, refcount);
trace_dma_fence_destroy(fence);
if (WARN(!list_empty(&fence->cb_list),
"Fence %s:%s:%llx:%llx released with pending signals!\n",
fence->ops->get_driver_name(fence),
fence->ops->get_timeline_name(fence),
fence->context, fence->seqno)) {
unsigned long flags;
/*
* Failed to signal before release, likely a refcounting issue.
*
* This should never happen, but if it does make sure that we
* don't leave chains dangling. We set the error flag first
* so that the callbacks know this signal is due to an error.
*/
spin_lock_irqsave(fence->lock, flags);
fence->error = -EDEADLK;
dma_fence_signal_locked(fence);
spin_unlock_irqrestore(fence->lock, flags);
}
if (fence->ops->release)
fence->ops->release(fence);
else
dma_fence_free(fence);
}
EXPORT_SYMBOL(dma_fence_release);
/**
* dma_fence_free - default release function for &dma_fence.
* @fence: fence to release
*
* This is the default implementation for &dma_fence_ops.release. It calls
* kfree_rcu() on @fence.
*/
void dma_fence_free(struct dma_fence *fence)
{
kfree_rcu(fence, rcu);
}
EXPORT_SYMBOL(dma_fence_free);
/**
* dma_fence_enable_sw_signaling - enable signaling on fence
* @fence: the fence to enable
*
* This will request for sw signaling to be enabled, to make the fence
* complete as soon as possible. This calls &dma_fence_ops.enable_signaling
* internally.
*/
void dma_fence_enable_sw_signaling(struct dma_fence *fence)
{
unsigned long flags;
if (!test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
&fence->flags) &&
!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) &&
fence->ops->enable_signaling) {
trace_dma_fence_enable_signal(fence);
spin_lock_irqsave(fence->lock, flags);
if (!fence->ops->enable_signaling(fence))
dma_fence_signal_locked(fence);
spin_unlock_irqrestore(fence->lock, flags);
}
}
EXPORT_SYMBOL(dma_fence_enable_sw_signaling);
/**
* dma_fence_add_callback - add a callback to be called when the fence
* is signaled
* @fence: the fence to wait on
* @cb: the callback to register
* @func: the function to call
*
* @cb will be initialized by dma_fence_add_callback(), no initialization
* by the caller is required. Any number of callbacks can be registered
* to a fence, but a callback can only be registered to one fence at a time.
*
* Note that the callback can be called from an atomic context. If
* fence is already signaled, this function will return -ENOENT (and
* *not* call the callback).
*
* Add a software callback to the fence. Same restrictions apply to
* refcount as it does to dma_fence_wait(), however the caller doesn't need to
* keep a refcount to fence afterward dma_fence_add_callback() has returned:
* when software access is enabled, the creator of the fence is required to keep
* the fence alive until after it signals with dma_fence_signal(). The callback
* itself can be called from irq context.
*
* Returns 0 in case of success, -ENOENT if the fence is already signaled
* and -EINVAL in case of error.
*/
int dma_fence_add_callback(struct dma_fence *fence, struct dma_fence_cb *cb,
dma_fence_func_t func)
{
unsigned long flags;
int ret = 0;
bool was_set;
if (WARN_ON(!fence || !func))
return -EINVAL;
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
INIT_LIST_HEAD(&cb->node);
return -ENOENT;
}
spin_lock_irqsave(fence->lock, flags);
was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
&fence->flags);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
ret = -ENOENT;
else if (!was_set && fence->ops->enable_signaling) {
trace_dma_fence_enable_signal(fence);
if (!fence->ops->enable_signaling(fence)) {
dma_fence_signal_locked(fence);
ret = -ENOENT;
}
}
if (!ret) {
cb->func = func;
list_add_tail(&cb->node, &fence->cb_list);
} else
INIT_LIST_HEAD(&cb->node);
spin_unlock_irqrestore(fence->lock, flags);
return ret;
}
EXPORT_SYMBOL(dma_fence_add_callback);
/**
* dma_fence_get_status - returns the status upon completion
* @fence: the dma_fence to query
*
* This wraps dma_fence_get_status_locked() to return the error status
* condition on a signaled fence. See dma_fence_get_status_locked() for more
* details.
*
* Returns 0 if the fence has not yet been signaled, 1 if the fence has
* been signaled without an error condition, or a negative error code
* if the fence has been completed in err.
*/
int dma_fence_get_status(struct dma_fence *fence)
{
unsigned long flags;
int status;
spin_lock_irqsave(fence->lock, flags);
status = dma_fence_get_status_locked(fence);
spin_unlock_irqrestore(fence->lock, flags);
return status;
}
EXPORT_SYMBOL(dma_fence_get_status);
/**
* dma_fence_remove_callback - remove a callback from the signaling list
* @fence: the fence to wait on
* @cb: the callback to remove
*
* Remove a previously queued callback from the fence. This function returns
* true if the callback is successfully removed, or false if the fence has
* already been signaled.
*
* *WARNING*:
* Cancelling a callback should only be done if you really know what you're
* doing, since deadlocks and race conditions could occur all too easily. For
* this reason, it should only ever be done on hardware lockup recovery,
* with a reference held to the fence.
*
* Behaviour is undefined if @cb has not been added to @fence using
* dma_fence_add_callback() beforehand.
*/
bool
dma_fence_remove_callback(struct dma_fence *fence, struct dma_fence_cb *cb)
{
unsigned long flags;
bool ret;
spin_lock_irqsave(fence->lock, flags);
ret = !list_empty(&cb->node);
if (ret)
list_del_init(&cb->node);
spin_unlock_irqrestore(fence->lock, flags);
return ret;
}
EXPORT_SYMBOL(dma_fence_remove_callback);
struct default_wait_cb {
struct dma_fence_cb base;
struct task_struct *task;
};
static void
dma_fence_default_wait_cb(struct dma_fence *fence, struct dma_fence_cb *cb)
{
struct default_wait_cb *wait =
container_of(cb, struct default_wait_cb, base);
wake_up_state(wait->task, TASK_NORMAL);
}
/**
* dma_fence_default_wait - default sleep until the fence gets signaled
* or until timeout elapses
* @fence: the fence to wait on
* @intr: if true, do an interruptible wait
* @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
*
* Returns -ERESTARTSYS if interrupted, 0 if the wait timed out, or the
* remaining timeout in jiffies on success. If timeout is zero the value one is
* returned if the fence is already signaled for consistency with other
* functions taking a jiffies timeout.
*/
signed long
dma_fence_default_wait(struct dma_fence *fence, bool intr, signed long timeout)
{
struct default_wait_cb cb;
unsigned long flags;
signed long ret = timeout ? timeout : 1;
bool was_set;
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
return ret;
spin_lock_irqsave(fence->lock, flags);
if (intr && signal_pending(current)) {
ret = -ERESTARTSYS;
goto out;
}
was_set = test_and_set_bit(DMA_FENCE_FLAG_ENABLE_SIGNAL_BIT,
&fence->flags);
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags))
goto out;
if (!was_set && fence->ops->enable_signaling) {
trace_dma_fence_enable_signal(fence);
if (!fence->ops->enable_signaling(fence)) {
dma_fence_signal_locked(fence);
goto out;
}
}
if (!timeout) {
ret = 0;
goto out;
}
cb.base.func = dma_fence_default_wait_cb;
cb.task = current;
list_add(&cb.base.node, &fence->cb_list);
while (!test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags) && ret > 0) {
if (intr)
__set_current_state(TASK_INTERRUPTIBLE);
else
__set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock_irqrestore(fence->lock, flags);
ret = schedule_timeout(ret);
spin_lock_irqsave(fence->lock, flags);
if (ret > 0 && intr && signal_pending(current))
ret = -ERESTARTSYS;
}
if (!list_empty(&cb.base.node))
list_del(&cb.base.node);
__set_current_state(TASK_RUNNING);
out:
spin_unlock_irqrestore(fence->lock, flags);
return ret;
}
EXPORT_SYMBOL(dma_fence_default_wait);
static bool
dma_fence_test_signaled_any(struct dma_fence **fences, uint32_t count,
uint32_t *idx)
{
int i;
for (i = 0; i < count; ++i) {
struct dma_fence *fence = fences[i];
if (test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &fence->flags)) {
if (idx)
*idx = i;
return true;
}
}
return false;
}
/**
* dma_fence_wait_any_timeout - sleep until any fence gets signaled
* or until timeout elapses
* @fences: array of fences to wait on
* @count: number of fences to wait on
* @intr: if true, do an interruptible wait
* @timeout: timeout value in jiffies, or MAX_SCHEDULE_TIMEOUT
* @idx: used to store the first signaled fence index, meaningful only on
* positive return
*
* Returns -EINVAL on custom fence wait implementation, -ERESTARTSYS if
* interrupted, 0 if the wait timed out, or the remaining timeout in jiffies
* on success.
*
* Synchronous waits for the first fence in the array to be signaled. The
* caller needs to hold a reference to all fences in the array, otherwise a
* fence might be freed before return, resulting in undefined behavior.
*
* See also dma_fence_wait() and dma_fence_wait_timeout().
*/
signed long
dma_fence_wait_any_timeout(struct dma_fence **fences, uint32_t count,
bool intr, signed long timeout, uint32_t *idx)
{
struct default_wait_cb *cb;
signed long ret = timeout;
unsigned i;
if (WARN_ON(!fences || !count || timeout < 0))
return -EINVAL;
if (timeout == 0) {
for (i = 0; i < count; ++i)
if (dma_fence_is_signaled(fences[i])) {
if (idx)
*idx = i;
return 1;
}
return 0;
}
cb = kcalloc(count, sizeof(struct default_wait_cb), GFP_KERNEL);
if (cb == NULL) {
ret = -ENOMEM;
goto err_free_cb;
}
for (i = 0; i < count; ++i) {
struct dma_fence *fence = fences[i];
cb[i].task = current;
if (dma_fence_add_callback(fence, &cb[i].base,
dma_fence_default_wait_cb)) {
/* This fence is already signaled */
if (idx)
*idx = i;
goto fence_rm_cb;
}
}
while (ret > 0) {
if (intr)
set_current_state(TASK_INTERRUPTIBLE);
else
set_current_state(TASK_UNINTERRUPTIBLE);
if (dma_fence_test_signaled_any(fences, count, idx))
break;
ret = schedule_timeout(ret);
if (ret > 0 && intr && signal_pending(current))
ret = -ERESTARTSYS;
}
__set_current_state(TASK_RUNNING);
fence_rm_cb:
while (i-- > 0)
dma_fence_remove_callback(fences[i], &cb[i].base);
err_free_cb:
kfree(cb);
return ret;
}
EXPORT_SYMBOL(dma_fence_wait_any_timeout);
/**
* dma_fence_init - Initialize a custom fence.
* @fence: the fence to initialize
* @ops: the dma_fence_ops for operations on this fence
* @lock: the irqsafe spinlock to use for locking this fence
* @context: the execution context this fence is run on
* @seqno: a linear increasing sequence number for this context
*
* Initializes an allocated fence, the caller doesn't have to keep its
* refcount after committing with this fence, but it will need to hold a
* refcount again if &dma_fence_ops.enable_signaling gets called.
*
* context and seqno are used for easy comparison between fences, allowing
* to check which fence is later by simply using dma_fence_later().
*/
void
dma_fence_init(struct dma_fence *fence, const struct dma_fence_ops *ops,
spinlock_t *lock, u64 context, u64 seqno)
{
BUG_ON(!lock);
BUG_ON(!ops || !ops->get_driver_name || !ops->get_timeline_name);
kref_init(&fence->refcount);
fence->ops = ops;
INIT_LIST_HEAD(&fence->cb_list);
fence->lock = lock;
fence->context = context;
fence->seqno = seqno;
fence->flags = 0UL;
fence->error = 0;
trace_dma_fence_init(fence);
}
EXPORT_SYMBOL(dma_fence_init);
