/*
* Copyright © 2008-2018 Intel Corporation
*
* Permission is hereby granted, free of charge, to any person obtaining a
* copy of this software and associated documentation files (the "Software"),
* to deal in the Software without restriction, including without limitation
* the rights to use, copy, modify, merge, publish, distribute, sublicense,
* and/or sell copies of the Software, and to permit persons to whom the
* Software is furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice (including the next
* paragraph) shall be included in all copies or substantial portions of the
* Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL
* THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*
*/
#ifndef I915_REQUEST_H
#define I915_REQUEST_H
#include <linux/dma-fence.h>
#include "i915_gem.h"
#include "i915_scheduler.h"
#include "i915_sw_fence.h"
#include "i915_scheduler.h"
#include <uapi/drm/i915_drm.h>
struct drm_file;
struct drm_i915_gem_object;
struct i915_request;
struct i915_timeline;
struct intel_wait {
struct rb_node node;
struct task_struct *tsk;
struct i915_request *request;
u32 seqno;
};
struct intel_signal_node {
struct intel_wait wait;
struct list_head link;
};
struct i915_capture_list {
struct i915_capture_list *next;
struct i915_vma *vma;
};
/**
* Request queue structure.
*
* The request queue allows us to note sequence numbers that have been emitted
* and may be associated with active buffers to be retired.
*
* By keeping this list, we can avoid having to do questionable sequence
* number comparisons on buffer last_read|write_seqno. It also allows an
* emission time to be associated with the request for tracking how far ahead
* of the GPU the submission is.
*
* When modifying this structure be very aware that we perform a lockless
* RCU lookup of it that may race against reallocation of the struct
* from the slab freelist. We intentionally do not zero the structure on
* allocation so that the lookup can use the dangling pointers (and is
* cogniscent that those pointers may be wrong). Instead, everything that
* needs to be initialised must be done so explicitly.
*
* The requests are reference counted.
*/
struct i915_request {
struct dma_fence fence;
spinlock_t lock;
/** On Which ring this request was generated */
struct drm_i915_private *i915;
/**
* Context and ring buffer related to this request
* Contexts are refcounted, so when this request is associated with a
* context, we must increment the context's refcount, to guarantee that
* it persists while any request is linked to it. Requests themselves
* are also refcounted, so the request will only be freed when the last
* reference to it is dismissed, and the code in
* i915_request_free() will then decrement the refcount on the
* context.
*/
struct i915_gem_context *gem_context;
struct intel_engine_cs *engine;
struct intel_context *hw_context;
struct intel_ring *ring;
struct i915_timeline *timeline;
struct intel_signal_node signaling;
/*
* Fences for the various phases in the request's lifetime.
*
* The submit fence is used to await upon all of the request's
* dependencies. When it is signaled, the request is ready to run.
* It is used by the driver to then queue the request for execution.
*/
struct i915_sw_fence submit;
wait_queue_entry_t submitq;
wait_queue_head_t execute;
/*
* A list of everyone we wait upon, and everyone who waits upon us.
* Even though we will not be submitted to the hardware before the
* submit fence is signaled (it waits for all external events as well
* as our own requests), the scheduler still needs to know the
* dependency tree for the lifetime of the request (from execbuf
* to retirement), i.e. bidirectional dependency information for the
* request not tied to individual fences.
*/
struct i915_sched_node sched;
struct i915_dependency dep;
/**
* GEM sequence number associated with this request on the
* global execution timeline. It is zero when the request is not
* on the HW queue (i.e. not on the engine timeline list).
* Its value is guarded by the timeline spinlock.
*/
u32 global_seqno;
/** Position in the ring of the start of the request */
u32 head;
/** Position in the ring of the start of the user packets */
u32 infix;
/**
* Position in the ring of the start of the postfix.
* This is required to calculate the maximum available ring space
* without overwriting the postfix.
*/
u32 postfix;
/** Position in the ring of the end of the whole request */
u32 tail;
/** Position in the ring of the end of any workarounds after the tail */
u32 wa_tail;
/** Preallocate space in the ring for the emitting the request */
u32 reserved_space;
/** Batch buffer related to this request if any (used for
* error state dump only).
*/
struct i915_vma *batch;
/**
* Additional buffers requested by userspace to be captured upon
* a GPU hang. The vma/obj on this list are protected by their
* active reference - all objects on this list must also be
* on the active_list (of their final request).
*/
struct i915_capture_list *capture_list;
struct list_head active_list;
/** Time at which this request was emitted, in jiffies. */
unsigned long emitted_jiffies;
bool waitboost;
/** engine->request_list entry for this request */
struct list_head link;
/** ring->request_list entry for this request */
struct list_head ring_link;
struct drm_i915_file_private *file_priv;
/** file_priv list entry for this request */
struct list_head client_link;
};
#define I915_FENCE_GFP (GFP_KERNEL | __GFP_RETRY_MAYFAIL | __GFP_NOWARN)
extern const struct dma_fence_ops i915_fence_ops;
static inline bool dma_fence_is_i915(const struct dma_fence *fence)
{
return fence->ops == &i915_fence_ops;
}
struct i915_request * __must_check
i915_request_alloc(struct intel_engine_cs *engine,
struct i915_gem_context *ctx);
void i915_request_retire_upto(struct i915_request *rq);
static inline struct i915_request *
to_request(struct dma_fence *fence)
{
/* We assume that NULL fence/request are interoperable */
BUILD_BUG_ON(offsetof(struct i915_request, fence) != 0);
GEM_BUG_ON(fence && !dma_fence_is_i915(fence));
return container_of(fence, struct i915_request, fence);
}
static inline struct i915_request *
i915_request_get(struct i915_request *rq)
{
return to_request(dma_fence_get(&rq->fence));
}
static inline struct i915_request *
i915_request_get_rcu(struct i915_request *rq)
{
return to_request(dma_fence_get_rcu(&rq->fence));
}
static inline void
i915_request_put(struct i915_request *rq)
{
dma_fence_put(&rq->fence);
}
/**
* i915_request_global_seqno - report the current global seqno
* @request - the request
*
* A request is assigned a global seqno only when it is on the hardware
* execution queue. The global seqno can be used to maintain a list of
* requests on the same engine in retirement order, for example for
* constructing a priority queue for waiting. Prior to its execution, or
* if it is subsequently removed in the event of preemption, its global
* seqno is zero. As both insertion and removal from the execution queue
* may operate in IRQ context, it is not guarded by the usual struct_mutex
* BKL. Instead those relying on the global seqno must be prepared for its
* value to change between reads. Only when the request is complete can
* the global seqno be stable (due to the memory barriers on submitting
* the commands to the hardware to write the breadcrumb, if the HWS shows
* that it has passed the global seqno and the global seqno is unchanged
* after the read, it is indeed complete).
*/
static u32
i915_request_global_seqno(const struct i915_request *request)
{
return READ_ONCE(request->global_seqno);
}
int i915_request_await_object(struct i915_request *to,
struct drm_i915_gem_object *obj,
bool write);
int i915_request_await_dma_fence(struct i915_request *rq,
struct dma_fence *fence);
void i915_request_add(struct i915_request *rq);
void __i915_request_submit(struct i915_request *request);
void i915_request_submit(struct i915_request *request);
void i915_request_skip(struct i915_request *request, int error);
void __i915_request_unsubmit(struct i915_request *request);
void i915_request_unsubmit(struct i915_request *request);
long i915_request_wait(struct i915_request *rq,
unsigned int flags,
long timeout)
__attribute__((nonnull(1)));
#define I915_WAIT_INTERRUPTIBLE BIT(0)
#define I915_WAIT_LOCKED BIT(1) /* struct_mutex held, handle GPU reset */
#define I915_WAIT_ALL BIT(2) /* used by i915_gem_object_wait() */
#define I915_WAIT_FOR_IDLE_BOOST BIT(3)
static inline u32 intel_engine_get_seqno(struct intel_engine_cs *engine);
/**
* Returns true if seq1 is later than seq2.
*/
static inline bool i915_seqno_passed(u32 seq1, u32 seq2)
{
return (s32)(seq1 - seq2) >= 0;
}
static inline bool
__i915_request_completed(const struct i915_request *rq, u32 seqno)
{
GEM_BUG_ON(!seqno);
return i915_seqno_passed(intel_engine_get_seqno(rq->engine), seqno) &&
seqno == i915_request_global_seqno(rq);
}
static inline bool i915_request_completed(const struct i915_request *rq)
{
u32 seqno;
seqno = i915_request_global_seqno(rq);
if (!seqno)
return false;
return __i915_request_completed(rq, seqno);
}
static inline bool i915_request_started(const struct i915_request *rq)
{
u32 seqno;
seqno = i915_request_global_seqno(rq);
if (!seqno)
return false;
return i915_seqno_passed(intel_engine_get_seqno(rq->engine),
seqno - 1);
}
static inline bool i915_sched_node_signaled(const struct i915_sched_node *node)
{
const struct i915_request *rq =
container_of(node, const struct i915_request, sched);
return i915_request_completed(rq);
}
void i915_retire_requests(struct drm_i915_private *i915);
/*
* We treat requests as fences. This is not be to confused with our
* "fence registers" but pipeline synchronisation objects ala GL_ARB_sync.
* We use the fences to synchronize access from the CPU with activity on the
* GPU, for example, we should not rewrite an object's PTE whilst the GPU
* is reading them. We also track fences at a higher level to provide
* implicit synchronisation around GEM objects, e.g. set-domain will wait
* for outstanding GPU rendering before marking the object ready for CPU
* access, or a pageflip will wait until the GPU is complete before showing
* the frame on the scanout.
*
* In order to use a fence, the object must track the fence it needs to
* serialise with. For example, GEM objects want to track both read and
* write access so that we can perform concurrent read operations between
* the CPU and GPU engines, as well as waiting for all rendering to
* complete, or waiting for the last GPU user of a "fence register". The
* object then embeds a #i915_gem_active to track the most recent (in
* retirement order) request relevant for the desired mode of access.
* The #i915_gem_active is updated with i915_gem_active_set() to track the
* most recent fence request, typically this is done as part of
* i915_vma_move_to_active().
*
* When the #i915_gem_active completes (is retired), it will
* signal its completion to the owner through a callback as well as mark
* itself as idle (i915_gem_active.request == NULL). The owner
* can then perform any action, such as delayed freeing of an active
* resource including itself.
*/
struct i915_gem_active;
typedef void (*i915_gem_retire_fn)(struct i915_gem_active *,
struct i915_request *);
struct i915_gem_active {
struct i915_request __rcu *request;
struct list_head link;
i915_gem_retire_fn retire;
};
void i915_gem_retire_noop(struct i915_gem_active *,
struct i915_request *request);
/**
* init_request_active - prepares the activity tracker for use
* @active - the active tracker
* @func - a callback when then the tracker is retired (becomes idle),
* can be NULL
*
* init_request_active() prepares the embedded @active struct for use as
* an activity tracker, that is for tracking the last known active request
* associated with it. When the last request becomes idle, when it is retired
* after completion, the optional callback @func is invoked.
*/
static inline void
init_request_active(struct i915_gem_active *active,
i915_gem_retire_fn retire)
{
RCU_INIT_POINTER(active->request, NULL);
INIT_LIST_HEAD(&active->link);
active->retire = retire ?: i915_gem_retire_noop;
}
/**
* i915_gem_active_set - updates the tracker to watch the current request
* @active - the active tracker
* @request - the request to watch
*
* i915_gem_active_set() watches the given @request for completion. Whilst
* that @request is busy, the @active reports busy. When that @request is
* retired, the @active tracker is updated to report idle.
*/
static inline void
i915_gem_active_set(struct i915_gem_active *active,
struct i915_request *request)
{
list_move(&active->link, &request->active_list);
rcu_assign_pointer(active->request, request);
}
/**
* i915_gem_active_set_retire_fn - updates the retirement callback
* @active - the active tracker
* @fn - the routine called when the request is retired
* @mutex - struct_mutex used to guard retirements
*
* i915_gem_active_set_retire_fn() updates the function pointer that
* is called when the final request associated with the @active tracker
* is retired.
*/
static inline void
i915_gem_active_set_retire_fn(struct i915_gem_active *active,
i915_gem_retire_fn fn,
struct mutex *mutex)
{
lockdep_assert_held(mutex);
active->retire = fn ?: i915_gem_retire_noop;
}
static inline struct i915_request *
__i915_gem_active_peek(const struct i915_gem_active *active)
{
/*
* Inside the error capture (running with the driver in an unknown
* state), we want to bend the rules slightly (a lot).
*
* Work is in progress to make it safer, in the meantime this keeps
* the known issue from spamming the logs.
*/
return rcu_dereference_protected(active->request, 1);
}
/**
* i915_gem_active_raw - return the active request
* @active - the active tracker
*
* i915_gem_active_raw() returns the current request being tracked, or NULL.
* It does not obtain a reference on the request for the caller, so the caller
* must hold struct_mutex.
*/
static inline struct i915_request *
i915_gem_active_raw(const struct i915_gem_active *active, struct mutex *mutex)
{
return rcu_dereference_protected(active->request,
lockdep_is_held(mutex));
}
/**
* i915_gem_active_peek - report the active request being monitored
* @active - the active tracker
*
* i915_gem_active_peek() returns the current request being tracked if
* still active, or NULL. It does not obtain a reference on the request
* for the caller, so the caller must hold struct_mutex.
*/
static inline struct i915_request *
i915_gem_active_peek(const struct i915_gem_active *active, struct mutex *mutex)
{
struct i915_request *request;
request = i915_gem_active_raw(active, mutex);
if (!request || i915_request_completed(request))
return NULL;
return request;
}
/**
* i915_gem_active_get - return a reference to the active request
* @active - the active tracker
*
* i915_gem_active_get() returns a reference to the active request, or NULL
* if the active tracker is idle. The caller must hold struct_mutex.
*/
static inline struct i915_request *
i915_gem_active_get(const struct i915_gem_active *active, struct mutex *mutex)
{
return i915_request_get(i915_gem_active_peek(active, mutex));
}
/**
* __i915_gem_active_get_rcu - return a reference to the active request
* @active - the active tracker
*
* __i915_gem_active_get() returns a reference to the active request, or NULL
* if the active tracker is idle. The caller must hold the RCU read lock, but
* the returned pointer is safe to use outside of RCU.
*/
static inline struct i915_request *
__i915_gem_active_get_rcu(const struct i915_gem_active *active)
{
/*
* Performing a lockless retrieval of the active request is super
* tricky. SLAB_TYPESAFE_BY_RCU merely guarantees that the backing
* slab of request objects will not be freed whilst we hold the
* RCU read lock. It does not guarantee that the request itself
* will not be freed and then *reused*. Viz,
*
* Thread A Thread B
*
* rq = active.request
* retire(rq) -> free(rq);
* (rq is now first on the slab freelist)
* active.request = NULL
*
* rq = new submission on a new object
* ref(rq)
*
* To prevent the request from being reused whilst the caller
* uses it, we take a reference like normal. Whilst acquiring
* the reference we check that it is not in a destroyed state
* (refcnt == 0). That prevents the request being reallocated
* whilst the caller holds on to it. To check that the request
* was not reallocated as we acquired the reference we have to
* check that our request remains the active request across
* the lookup, in the same manner as a seqlock. The visibility
* of the pointer versus the reference counting is controlled
* by using RCU barriers (rcu_dereference and rcu_assign_pointer).
*
* In the middle of all that, we inspect whether the request is
* complete. Retiring is lazy so the request may be completed long
* before the active tracker is updated. Querying whether the
* request is complete is far cheaper (as it involves no locked
* instructions setting cachelines to exclusive) than acquiring
* the reference, so we do it first. The RCU read lock ensures the
* pointer dereference is valid, but does not ensure that the
* seqno nor HWS is the right one! However, if the request was
* reallocated, that means the active tracker's request was complete.
* If the new request is also complete, then both are and we can
* just report the active tracker is idle. If the new request is
* incomplete, then we acquire a reference on it and check that
* it remained the active request.
*
* It is then imperative that we do not zero the request on
* reallocation, so that we can chase the dangling pointers!
* See i915_request_alloc().
*/
do {
struct i915_request *request;
request = rcu_dereference(active->request);
if (!request || i915_request_completed(request))
return NULL;
/*
* An especially silly compiler could decide to recompute the
* result of i915_request_completed, more specifically
* re-emit the load for request->fence.seqno. A race would catch
* a later seqno value, which could flip the result from true to
* false. Which means part of the instructions below might not
* be executed, while later on instructions are executed. Due to
* barriers within the refcounting the inconsistency can't reach
* past the call to i915_request_get_rcu, but not executing
* that while still executing i915_request_put() creates
* havoc enough. Prevent this with a compiler barrier.
*/
barrier();
request = i915_request_get_rcu(request);
/*
* What stops the following rcu_access_pointer() from occurring
* before the above i915_request_get_rcu()? If we were
* to read the value before pausing to get the reference to
* the request, we may not notice a change in the active
* tracker.
*
* The rcu_access_pointer() is a mere compiler barrier, which
* means both the CPU and compiler are free to perform the
* memory read without constraint. The compiler only has to
* ensure that any operations after the rcu_access_pointer()
* occur afterwards in program order. This means the read may
* be performed earlier by an out-of-order CPU, or adventurous
* compiler.
*
* The atomic operation at the heart of
* i915_request_get_rcu(), see dma_fence_get_rcu(), is
* atomic_inc_not_zero() which is only a full memory barrier
* when successful. That is, if i915_request_get_rcu()
* returns the request (and so with the reference counted
* incremented) then the following read for rcu_access_pointer()
* must occur after the atomic operation and so confirm
* that this request is the one currently being tracked.
*
* The corresponding write barrier is part of
* rcu_assign_pointer().
*/
if (!request || request == rcu_access_pointer(active->request))
return rcu_pointer_handoff(request);
i915_request_put(request);
} while (1);
}
/**
* i915_gem_active_get_unlocked - return a reference to the active request
* @active - the active tracker
*
* i915_gem_active_get_unlocked() returns a reference to the active request,
* or NULL if the active tracker is idle. The reference is obtained under RCU,
* so no locking is required by the caller.
*
* The reference should be freed with i915_request_put().
*/
static inline struct i915_request *
i915_gem_active_get_unlocked(const struct i915_gem_active *active)
{
struct i915_request *request;
rcu_read_lock();
request = __i915_gem_active_get_rcu(active);
rcu_read_unlock();
return request;
}
/**
* i915_gem_active_isset - report whether the active tracker is assigned
* @active - the active tracker
*
* i915_gem_active_isset() returns true if the active tracker is currently
* assigned to a request. Due to the lazy retiring, that request may be idle
* and this may report stale information.
*/
static inline bool
i915_gem_active_isset(const struct i915_gem_active *active)
{
return rcu_access_pointer(active->request);
}
/**
* i915_gem_active_wait - waits until the request is completed
* @active - the active request on which to wait
* @flags - how to wait
* @timeout - how long to wait at most
* @rps - userspace client to charge for a waitboost
*
* i915_gem_active_wait() waits until the request is completed before
* returning, without requiring any locks to be held. Note that it does not
* retire any requests before returning.
*
* This function relies on RCU in order to acquire the reference to the active
* request without holding any locks. See __i915_gem_active_get_rcu() for the
* glory details on how that is managed. Once the reference is acquired, we
* can then wait upon the request, and afterwards release our reference,
* free of any locking.
*
* This function wraps i915_request_wait(), see it for the full details on
* the arguments.
*
* Returns 0 if successful, or a negative error code.
*/
static inline int
i915_gem_active_wait(const struct i915_gem_active *active, unsigned int flags)
{
struct i915_request *request;
long ret = 0;
request = i915_gem_active_get_unlocked(active);
if (request) {
ret = i915_request_wait(request, flags, MAX_SCHEDULE_TIMEOUT);
i915_request_put(request);
}
return ret < 0 ? ret : 0;
}
/**
* i915_gem_active_retire - waits until the request is retired
* @active - the active request on which to wait
*
* i915_gem_active_retire() waits until the request is completed,
* and then ensures that at least the retirement handler for this
* @active tracker is called before returning. If the @active
* tracker is idle, the function returns immediately.
*/
static inline int __must_check
i915_gem_active_retire(struct i915_gem_active *active,
struct mutex *mutex)
{
struct i915_request *request;
long ret;
request = i915_gem_active_raw(active, mutex);
if (!request)
return 0;
ret = i915_request_wait(request,
I915_WAIT_INTERRUPTIBLE | I915_WAIT_LOCKED,
MAX_SCHEDULE_TIMEOUT);
if (ret < 0)
return ret;
list_del_init(&active->link);
RCU_INIT_POINTER(active->request, NULL);
active->retire(active, request);
return 0;
}
#define for_each_active(mask, idx) \
for (; mask ? idx = ffs(mask) - 1, 1 : 0; mask &= ~BIT(idx))
#endif /* I915_REQUEST_H */
