diff --git a/drivers/gpu/drm/i915/Makefile b/drivers/gpu/drm/i915/Makefile
index a3d2b789c9ec8493e95772b7e4794e8495b80711..618293c8c9d93daf84a8890ec9afbdbc523e8e02 100644
--- a/drivers/gpu/drm/i915/Makefile
+++ b/drivers/gpu/drm/i915/Makefile
@@ -38,6 +38,7 @@ i915-y += i915_cmd_parser.o \
i915_gem_userptr.o \
i915_gpu_error.o \
i915_trace_points.o \
+ intel_breadcrumbs.o \
intel_lrc.o \
intel_mocs.o \
intel_ringbuffer.o \
diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
index f664884ad27fc267b8a47b33fa9abfec4877682e..f522a366223d310d764678fa92afe9f9c9b8a111 100644
--- a/drivers/gpu/drm/i915/i915_debugfs.c
+++ b/drivers/gpu/drm/i915/i915_debugfs.c
@@ -788,10 +788,22 @@ static int i915_gem_request_info(struct seq_file *m, void *data)
static void i915_ring_seqno_info(struct seq_file *m,
struct intel_engine_cs *engine)
{
+ struct intel_breadcrumbs *b = &engine->breadcrumbs;
+ struct rb_node *rb;
+
seq_printf(m, "Current sequence (%s): %x\n",
engine->name, engine->get_seqno(engine));
seq_printf(m, "Current user interrupts (%s): %x\n",
engine->name, READ_ONCE(engine->user_interrupts));
+
+ spin_lock(&b->lock);
+ for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
+ struct intel_wait *w = container_of(rb, typeof(*w), node);
+
+ seq_printf(m, "Waiting (%s): %s [%d] on %x\n",
+ engine->name, w->tsk->comm, w->tsk->pid, w->seqno);
+ }
+ spin_unlock(&b->lock);
}
static int i915_gem_seqno_info(struct seq_file *m, void *data)
@@ -1428,6 +1440,8 @@ static int i915_hangcheck_info(struct seq_file *m, void *unused)
engine->hangcheck.seqno,
seqno[id],
engine->last_submitted_seqno);
+ seq_printf(m, "\twaiters? %d\n",
+ intel_engine_has_waiter(engine));
seq_printf(m, "\tuser interrupts = %x [current %x]\n",
engine->hangcheck.user_interrupts,
READ_ONCE(engine->user_interrupts));
@@ -2415,7 +2429,7 @@ static int count_irq_waiters(struct drm_i915_private *i915)
int count = 0;
for_each_engine(engine, i915)
- count += engine->irq_refcount;
+ count += intel_engine_has_waiter(engine);
return count;
}
diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index 0d0e4ac4dadba2e2c77f20fd0f822da3cc79de71..1fefa8c495f2001789ff7ce3cae9303895702ff7 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -506,6 +506,7 @@ struct drm_i915_error_state {
bool valid;
/* Software tracked state */
bool waiting;
+ int num_waiters;
int hangcheck_score;
enum intel_ring_hangcheck_action hangcheck_action;
int num_requests;
@@ -551,6 +552,12 @@ struct drm_i915_error_state {
u32 tail;
} *requests;
+ struct drm_i915_error_waiter {
+ char comm[TASK_COMM_LEN];
+ pid_t pid;
+ u32 seqno;
+ } *waiters;
+
struct {
u32 gfx_mode;
union {
@@ -1429,7 +1436,7 @@ struct i915_gpu_error {
#define I915_STOP_RING_ALLOW_WARN (1 << 30)
/* For missed irq/seqno simulation. */
- unsigned int test_irq_rings;
+ unsigned long test_irq_rings;
};
enum modeset_restore {
@@ -3064,7 +3071,6 @@ ibx_disable_display_interrupt(struct drm_i915_private *dev_priv, uint32_t bits)
ibx_display_interrupt_update(dev_priv, bits, 0);
}
-
/* i915_gem.c */
int i915_gem_create_ioctl(struct drm_device *dev, void *data,
struct drm_file *file_priv);
@@ -3975,4 +3981,34 @@ static inline void i915_trace_irq_get(struct intel_engine_cs *engine,
i915_gem_request_assign(&engine->trace_irq_req, req);
}
+static inline bool __i915_request_irq_complete(struct drm_i915_gem_request *req)
+{
+ /* Ensure our read of the seqno is coherent so that we
+ * do not "miss an interrupt" (i.e. if this is the last
+ * request and the seqno write from the GPU is not visible
+ * by the time the interrupt fires, we will see that the
+ * request is incomplete and go back to sleep awaiting
+ * another interrupt that will never come.)
+ *
+ * Strictly, we only need to do this once after an interrupt,
+ * but it is easier and safer to do it every time the waiter
+ * is woken.
+ */
+ if (i915_gem_request_completed(req, false))
+ return true;
+
+ /* We need to check whether any gpu reset happened in between
+ * the request being submitted and now. If a reset has occurred,
+ * the seqno will have been advance past ours and our request
+ * is complete. If we are in the process of handling a reset,
+ * the request is effectively complete as the rendering will
+ * be discarded, but we need to return in order to drop the
+ * struct_mutex.
+ */
+ if (i915_reset_in_progress(&req->i915->gpu_error))
+ return true;
+
+ return false;
+}
+
#endif
diff --git a/drivers/gpu/drm/i915/i915_gem.c b/drivers/gpu/drm/i915/i915_gem.c
index b5278d117ea046f24e3b48856dd35045e60a9c80..c9814572e346b5853847e864a646d5f7e803a0b5 100644
--- a/drivers/gpu/drm/i915/i915_gem.c
+++ b/drivers/gpu/drm/i915/i915_gem.c
@@ -1343,17 +1343,6 @@ i915_gem_check_wedge(unsigned reset_counter, bool interruptible)
return 0;
}
-static void fake_irq(unsigned long data)
-{
- wake_up_process((struct task_struct *)data);
-}
-
-static bool missed_irq(struct drm_i915_private *dev_priv,
- struct intel_engine_cs *engine)
-{
- return test_bit(engine->id, &dev_priv->gpu_error.missed_irq_rings);
-}
-
static unsigned long local_clock_us(unsigned *cpu)
{
unsigned long t;
@@ -1386,7 +1375,7 @@ static bool busywait_stop(unsigned long timeout, unsigned cpu)
return this_cpu != cpu;
}
-static int __i915_spin_request(struct drm_i915_gem_request *req, int state)
+static bool __i915_spin_request(struct drm_i915_gem_request *req, int state)
{
unsigned long timeout;
unsigned cpu;
@@ -1401,17 +1390,14 @@ static int __i915_spin_request(struct drm_i915_gem_request *req, int state)
* takes to sleep on a request, on the order of a microsecond.
*/
- if (req->engine->irq_refcount)
- return -EBUSY;
-
/* Only spin if we know the GPU is processing this request */
if (!i915_gem_request_started(req, true))
- return -EAGAIN;
+ return false;
timeout = local_clock_us(&cpu) + 5;
- while (!need_resched()) {
+ do {
if (i915_gem_request_completed(req, true))
- return 0;
+ return true;
if (signal_pending_state(state, current))
break;
@@ -1420,12 +1406,9 @@ static int __i915_spin_request(struct drm_i915_gem_request *req, int state)
break;
cpu_relax_lowlatency();
- }
-
- if (i915_gem_request_completed(req, false))
- return 0;
+ } while (!need_resched());
- return -EAGAIN;
+ return false;
}
/**
@@ -1450,18 +1433,14 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
s64 *timeout,
struct intel_rps_client *rps)
{
- struct intel_engine_cs *engine = i915_gem_request_get_engine(req);
- struct drm_i915_private *dev_priv = req->i915;
- const bool irq_test_in_progress =
- ACCESS_ONCE(dev_priv->gpu_error.test_irq_rings) & intel_engine_flag(engine);
int state = interruptible ? TASK_INTERRUPTIBLE : TASK_UNINTERRUPTIBLE;
DEFINE_WAIT(reset);
- DEFINE_WAIT(wait);
- unsigned long timeout_expire;
+ struct intel_wait wait;
+ unsigned long timeout_remain;
s64 before = 0; /* Only to silence a compiler warning. */
- int ret;
+ int ret = 0;
- WARN(!intel_irqs_enabled(dev_priv), "IRQs disabled");
+ might_sleep();
if (list_empty(&req->list))
return 0;
@@ -1469,7 +1448,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
if (i915_gem_request_completed(req, true))
return 0;
- timeout_expire = 0;
+ timeout_remain = MAX_SCHEDULE_TIMEOUT;
if (timeout) {
if (WARN_ON(*timeout < 0))
return -EINVAL;
@@ -1477,7 +1456,7 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
if (*timeout == 0)
return -ETIME;
- timeout_expire = jiffies + nsecs_to_jiffies_timeout(*timeout);
+ timeout_remain = nsecs_to_jiffies_timeout(*timeout);
/*
* Record current time in case interrupted by signal, or wedged.
@@ -1485,55 +1464,32 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
before = ktime_get_raw_ns();
}
- if (INTEL_INFO(dev_priv)->gen >= 6)
- gen6_rps_boost(dev_priv, rps, req->emitted_jiffies);
-
trace_i915_gem_request_wait_begin(req);
- /* Optimistic spin for the next jiffie before touching IRQs */
- ret = __i915_spin_request(req, state);
- if (ret == 0)
- goto out;
+ if (INTEL_INFO(req->i915)->gen >= 6)
+ gen6_rps_boost(req->i915, rps, req->emitted_jiffies);
- if (!irq_test_in_progress && WARN_ON(!engine->irq_get(engine))) {
- ret = -ENODEV;
- goto out;
- }
+ /* Optimistic spin for the next ~jiffie before touching IRQs */
+ if (__i915_spin_request(req, state))
+ goto complete;
- add_wait_queue(&dev_priv->gpu_error.wait_queue, &reset);
- for (;;) {
- struct timer_list timer;
+ set_current_state(state);
+ add_wait_queue(&req->i915->gpu_error.wait_queue, &reset);
- prepare_to_wait(&engine->irq_queue, &wait, state);
-
- /* We need to check whether any gpu reset happened in between
- * the request being submitted and now. If a reset has occurred,
- * the seqno will have been advance past ours and our request
- * is complete. If we are in the process of handling a reset,
- * the request is effectively complete as the rendering will
- * be discarded, but we need to return in order to drop the
- * struct_mutex.
+ intel_wait_init(&wait, req->seqno);
+ if (intel_engine_add_wait(req->engine, &wait))
+ /* In order to check that we haven't missed the interrupt
+ * as we enabled it, we need to kick ourselves to do a
+ * coherent check on the seqno before we sleep.
*/
- if (i915_reset_in_progress(&dev_priv->gpu_error)) {
- ret = 0;
- break;
- }
-
- if (i915_gem_request_completed(req, false)) {
- ret = 0;
- break;
- }
+ goto wakeup;
+ for (;;) {
if (signal_pending_state(state, current)) {
ret = -ERESTARTSYS;
break;
}
- if (timeout && time_after_eq(jiffies, timeout_expire)) {
- ret = -ETIME;
- break;
- }
-
/* Ensure that even if the GPU hangs, we get woken up.
*
* However, note that if no one is waiting, we never notice
@@ -1541,32 +1497,33 @@ int __i915_wait_request(struct drm_i915_gem_request *req,
* held by the GPU and so trigger a hangcheck. In the most
* pathological case, this will be upon memory starvation!
*/
- i915_queue_hangcheck(dev_priv);
-
- timer.function = NULL;
- if (timeout || missed_irq(dev_priv, engine)) {
- unsigned long expire;
+ i915_queue_hangcheck(req->i915);
- setup_timer_on_stack(&timer, fake_irq, (unsigned long)current);
- expire = missed_irq(dev_priv, engine) ? jiffies + 1 : timeout_expire;
- mod_timer(&timer, expire);
+ timeout_remain = io_schedule_timeout(timeout_remain);
+ if (timeout_remain == 0) {
+ ret = -ETIME;
+ break;
}
- io_schedule();
-
- if (timer.function) {
- del_singleshot_timer_sync(&timer);
- destroy_timer_on_stack(&timer);
- }
- }
- remove_wait_queue(&dev_priv->gpu_error.wait_queue, &reset);
+ if (intel_wait_complete(&wait))
+ break;
- if (!irq_test_in_progress)
- engine->irq_put(engine);
+ set_current_state(state);
- finish_wait(&engine->irq_queue, &wait);
+wakeup:
+ /* Carefully check if the request is complete, giving time
+ * for the seqno to be visible following the interrupt.
+ * We also have to check in case we are kicked by the GPU
+ * reset in order to drop the struct_mutex.
+ */
+ if (__i915_request_irq_complete(req))
+ break;
+ }
+ remove_wait_queue(&req->i915->gpu_error.wait_queue, &reset);
-out:
+ intel_engine_remove_wait(req->engine, &wait);
+ __set_current_state(TASK_RUNNING);
+complete:
trace_i915_gem_request_wait_end(req);
if (timeout) {
@@ -2796,6 +2753,12 @@ i915_gem_init_seqno(struct drm_i915_private *dev_priv, u32 seqno)
}
i915_gem_retire_requests(dev_priv);
+ /* If the seqno wraps around, we need to clear the breadcrumb rbtree */
+ if (!i915_seqno_passed(seqno, dev_priv->next_seqno)) {
+ while (intel_kick_waiters(dev_priv))
+ yield();
+ }
+
/* Finally reset hw state */
for_each_engine(engine, dev_priv)
intel_ring_init_seqno(engine, seqno);
diff --git a/drivers/gpu/drm/i915/i915_gpu_error.c b/drivers/gpu/drm/i915/i915_gpu_error.c
index 34ff2459ceea3aab4147b75b0d3a36723444d99c..250f0b8180990369b85a77c9aace12dd2fcac2f0 100644
--- a/drivers/gpu/drm/i915/i915_gpu_error.c
+++ b/drivers/gpu/drm/i915/i915_gpu_error.c
@@ -463,6 +463,18 @@ int i915_error_state_to_str(struct drm_i915_error_state_buf *m,
}
}
+ if (error->ring[i].num_waiters) {
+ err_printf(m, "%s --- %d waiters\n",
+ dev_priv->engine[i].name,
+ error->ring[i].num_waiters);
+ for (j = 0; j < error->ring[i].num_waiters; j++) {
+ err_printf(m, " seqno 0x%08x for %s [%d]\n",
+ error->ring[i].waiters[j].seqno,
+ error->ring[i].waiters[j].comm,
+ error->ring[i].waiters[j].pid);
+ }
+ }
+
if ((obj = error->ring[i].ringbuffer)) {
err_printf(m, "%s --- ringbuffer = 0x%08x\n",
dev_priv->engine[i].name,
@@ -605,8 +617,9 @@ static void i915_error_state_free(struct kref *error_ref)
i915_error_object_free(error->ring[i].ringbuffer);
i915_error_object_free(error->ring[i].hws_page);
i915_error_object_free(error->ring[i].ctx);
- kfree(error->ring[i].requests);
i915_error_object_free(error->ring[i].wa_ctx);
+ kfree(error->ring[i].requests);
+ kfree(error->ring[i].waiters);
}
i915_error_object_free(error->semaphore_obj);
@@ -892,6 +905,48 @@ static void gen6_record_semaphore_state(struct drm_i915_private *dev_priv,
}
}
+static void engine_record_waiters(struct intel_engine_cs *engine,
+ struct drm_i915_error_ring *ering)
+{
+ struct intel_breadcrumbs *b = &engine->breadcrumbs;
+ struct drm_i915_error_waiter *waiter;
+ struct rb_node *rb;
+ int count;
+
+ ering->num_waiters = 0;
+ ering->waiters = NULL;
+
+ spin_lock(&b->lock);
+ count = 0;
+ for (rb = rb_first(&b->waiters); rb != NULL; rb = rb_next(rb))
+ count++;
+ spin_unlock(&b->lock);
+
+ waiter = NULL;
+ if (count)
+ waiter = kmalloc_array(count,
+ sizeof(struct drm_i915_error_waiter),
+ GFP_ATOMIC);
+ if (!waiter)
+ return;
+
+ ering->waiters = waiter;
+
+ spin_lock(&b->lock);
+ for (rb = rb_first(&b->waiters); rb; rb = rb_next(rb)) {
+ struct intel_wait *w = container_of(rb, typeof(*w), node);
+
+ strcpy(waiter->comm, w->tsk->comm);
+ waiter->pid = w->tsk->pid;
+ waiter->seqno = w->seqno;
+ waiter++;
+
+ if (++ering->num_waiters == count)
+ break;
+ }
+ spin_unlock(&b->lock);
+}
+
static void i915_record_ring_state(struct drm_i915_private *dev_priv,
struct drm_i915_error_state *error,
struct intel_engine_cs *engine,
@@ -926,7 +981,7 @@ static void i915_record_ring_state(struct drm_i915_private *dev_priv,
ering->instdone = I915_READ(GEN2_INSTDONE);
}
- ering->waiting = waitqueue_active(&engine->irq_queue);
+ ering->waiting = intel_engine_has_waiter(engine);
ering->instpm = I915_READ(RING_INSTPM(engine->mmio_base));
ering->acthd = intel_ring_get_active_head(engine);
ering->seqno = engine->get_seqno(engine);
@@ -1032,6 +1087,7 @@ static void i915_gem_record_rings(struct drm_i915_private *dev_priv,
error->ring[i].valid = true;
i915_record_ring_state(dev_priv, error, engine, &error->ring[i]);
+ engine_record_waiters(engine, &error->ring[i]);
request = i915_gem_find_active_request(engine);
if (request) {
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
index 6c17596d75ddcc483ddae803d24b22b019c7623c..a11ab00cdee0900a5a09884008202d94a0447ebb 100644
--- a/drivers/gpu/drm/i915/i915_irq.c
+++ b/drivers/gpu/drm/i915/i915_irq.c
@@ -976,13 +976,10 @@ static void ironlake_rps_change_irq_handler(struct drm_i915_private *dev_priv)
static void notify_ring(struct intel_engine_cs *engine)
{
- if (!intel_engine_initialized(engine))
- return;
-
- trace_i915_gem_request_notify(engine);
- engine->user_interrupts++;
-
- wake_up_all(&engine->irq_queue);
+ if (intel_engine_wakeup(engine)) {
+ trace_i915_gem_request_notify(engine);
+ engine->user_interrupts++;
+ }
}
static void vlv_c0_read(struct drm_i915_private *dev_priv,
@@ -1063,7 +1060,7 @@ static bool any_waiters(struct drm_i915_private *dev_priv)
struct intel_engine_cs *engine;
for_each_engine(engine, dev_priv)
- if (engine->irq_refcount)
+ if (intel_engine_has_waiter(engine))
return true;
return false;
@@ -3074,13 +3071,14 @@ static unsigned kick_waiters(struct intel_engine_cs *engine)
if (engine->hangcheck.user_interrupts == user_interrupts &&
!test_and_set_bit(engine->id, &i915->gpu_error.missed_irq_rings)) {
- if (!(i915->gpu_error.test_irq_rings & intel_engine_flag(engine)))
+ if (!test_bit(engine->id, &i915->gpu_error.test_irq_rings))
DRM_ERROR("Hangcheck timer elapsed... %s idle\n",
engine->name);
else
DRM_INFO("Fake missed irq on %s\n",
engine->name);
- wake_up_all(&engine->irq_queue);
+
+ intel_engine_enable_fake_irq(engine);
}
return user_interrupts;
@@ -3124,7 +3122,7 @@ static void i915_hangcheck_elapsed(struct work_struct *work)
intel_uncore_arm_unclaimed_mmio_detection(dev_priv);
for_each_engine_id(engine, dev_priv, id) {
- bool busy = waitqueue_active(&engine->irq_queue);
+ bool busy = intel_engine_has_waiter(engine);
u64 acthd;
u32 seqno;
unsigned user_interrupts;
diff --git a/drivers/gpu/drm/i915/intel_breadcrumbs.c b/drivers/gpu/drm/i915/intel_breadcrumbs.c
new file mode 100644
index 0000000000000000000000000000000000000000..a3bbf2d90dce2d7739a285d42b14102ef328e680
--- /dev/null
+++ b/drivers/gpu/drm/i915/intel_breadcrumbs.c
@@ -0,0 +1,380 @@
+/*
+ * Copyright © 2015 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.
+ *
+ */
+
+#include "i915_drv.h"
+
+static void intel_breadcrumbs_fake_irq(unsigned long data)
+{
+ struct intel_engine_cs *engine = (struct intel_engine_cs *)data;
+
+ /*
+ * The timer persists in case we cannot enable interrupts,
+ * or if we have previously seen seqno/interrupt incoherency
+ * ("missed interrupt" syndrome). Here the worker will wake up
+ * every jiffie in order to kick the oldest waiter to do the
+ * coherent seqno check.
+ */
+ rcu_read_lock();
+ if (intel_engine_wakeup(engine))
+ mod_timer(&engine->breadcrumbs.fake_irq, jiffies + 1);
+ rcu_read_unlock();
+}
+
+static void irq_enable(struct intel_engine_cs *engine)
+{
+ WARN_ON(!engine->irq_get(engine));
+}
+
+static void irq_disable(struct intel_engine_cs *engine)
+{
+ engine->irq_put(engine);
+}
+
+static bool __intel_breadcrumbs_enable_irq(struct intel_breadcrumbs *b)
+{
+ struct intel_engine_cs *engine =
+ container_of(b, struct intel_engine_cs, breadcrumbs);
+ struct drm_i915_private *i915 = engine->i915;
+ bool irq_posted = false;
+
+ assert_spin_locked(&b->lock);
+ if (b->rpm_wakelock)
+ return false;
+
+ /* Since we are waiting on a request, the GPU should be busy
+ * and should have its own rpm reference. For completeness,
+ * record an rpm reference for ourselves to cover the
+ * interrupt we unmask.
+ */
+ intel_runtime_pm_get_noresume(i915);
+ b->rpm_wakelock = true;
+
+ /* No interrupts? Kick the waiter every jiffie! */
+ if (intel_irqs_enabled(i915)) {
+ if (!test_bit(engine->id, &i915->gpu_error.test_irq_rings)) {
+ irq_enable(engine);
+ irq_posted = true;
+ }
+ b->irq_enabled = true;
+ }
+
+ if (!b->irq_enabled ||
+ test_bit(engine->id, &i915->gpu_error.missed_irq_rings))
+ mod_timer(&b->fake_irq, jiffies + 1);
+
+ return irq_posted;
+}
+
+static void __intel_breadcrumbs_disable_irq(struct intel_breadcrumbs *b)
+{
+ struct intel_engine_cs *engine =
+ container_of(b, struct intel_engine_cs, breadcrumbs);
+
+ assert_spin_locked(&b->lock);
+ if (!b->rpm_wakelock)
+ return;
+
+ if (b->irq_enabled) {
+ irq_disable(engine);
+ b->irq_enabled = false;
+ }
+
+ intel_runtime_pm_put(engine->i915);
+ b->rpm_wakelock = false;
+}
+
+static inline struct intel_wait *to_wait(struct rb_node *node)
+{
+ return container_of(node, struct intel_wait, node);
+}
+
+static inline void __intel_breadcrumbs_finish(struct intel_breadcrumbs *b,
+ struct intel_wait *wait)
+{
+ assert_spin_locked(&b->lock);
+
+ /* This request is completed, so remove it from the tree, mark it as
+ * complete, and *then* wake up the associated task.
+ */
+ rb_erase(&wait->node, &b->waiters);
+ RB_CLEAR_NODE(&wait->node);
+
+ wake_up_process(wait->tsk); /* implicit smp_wmb() */
+}
+
+static bool __intel_engine_add_wait(struct intel_engine_cs *engine,
+ struct intel_wait *wait)
+{
+ struct intel_breadcrumbs *b = &engine->breadcrumbs;
+ struct rb_node **p, *parent, *completed;
+ bool first;
+ u32 seqno;
+
+ /* Insert the request into the retirement ordered list
+ * of waiters by walking the rbtree. If we are the oldest
+ * seqno in the tree (the first to be retired), then
+ * set ourselves as the bottom-half.
+ *
+ * As we descend the tree, prune completed branches since we hold the
+ * spinlock we know that the first_waiter must be delayed and can
+ * reduce some of the sequential wake up latency if we take action
+ * ourselves and wake up the completed tasks in parallel. Also, by
+ * removing stale elements in the tree, we may be able to reduce the
+ * ping-pong between the old bottom-half and ourselves as first-waiter.
+ */
+ first = true;
+ parent = NULL;
+ completed = NULL;
+ seqno = engine->get_seqno(engine);
+
+ /* If the request completed before we managed to grab the spinlock,
+ * return now before adding ourselves to the rbtree. We let the
+ * current bottom-half handle any pending wakeups and instead
+ * try and get out of the way quickly.
+ */
+ if (i915_seqno_passed(seqno, wait->seqno)) {
+ RB_CLEAR_NODE(&wait->node);
+ return first;
+ }
+
+ p = &b->waiters.rb_node;
+ while (*p) {
+ parent = *p;
+ if (wait->seqno == to_wait(parent)->seqno) {
+ /* We have multiple waiters on the same seqno, select
+ * the highest priority task (that with the smallest
+ * task->prio) to serve as the bottom-half for this
+ * group.
+ */
+ if (wait->tsk->prio > to_wait(parent)->tsk->prio) {
+ p = &parent->rb_right;
+ first = false;
+ } else {
+ p = &parent->rb_left;
+ }
+ } else if (i915_seqno_passed(wait->seqno,
+ to_wait(parent)->seqno)) {
+ p = &parent->rb_right;
+ if (i915_seqno_passed(seqno, to_wait(parent)->seqno))
+ completed = parent;
+ else
+ first = false;
+ } else {
+ p = &parent->rb_left;
+ }
+ }
+ rb_link_node(&wait->node, parent, p);
+ rb_insert_color(&wait->node, &b->waiters);
+ GEM_BUG_ON(!first && !b->tasklet);
+
+ if (completed) {
+ struct rb_node *next = rb_next(completed);
+
+ GEM_BUG_ON(!next && !first);
+ if (next && next != &wait->node) {
+ GEM_BUG_ON(first);
+ b->first_wait = to_wait(next);
+ smp_store_mb(b->tasklet, b->first_wait->tsk);
+ /* As there is a delay between reading the current
+ * seqno, processing the completed tasks and selecting
+ * the next waiter, we may have missed the interrupt
+ * and so need for the next bottom-half to wakeup.
+ *
+ * Also as we enable the IRQ, we may miss the
+ * interrupt for that seqno, so we have to wake up
+ * the next bottom-half in order to do a coherent check
+ * in case the seqno passed.
+ */
+ __intel_breadcrumbs_enable_irq(b);
+ wake_up_process(to_wait(next)->tsk);
+ }
+
+ do {
+ struct intel_wait *crumb = to_wait(completed);
+ completed = rb_prev(completed);
+ __intel_breadcrumbs_finish(b, crumb);
+ } while (completed);
+ }
+
+ if (first) {
+ GEM_BUG_ON(rb_first(&b->waiters) != &wait->node);
+ b->first_wait = wait;
+ smp_store_mb(b->tasklet, wait->tsk);
+ first = __intel_breadcrumbs_enable_irq(b);
+ }
+ GEM_BUG_ON(!b->tasklet);
+ GEM_BUG_ON(!b->first_wait);
+ GEM_BUG_ON(rb_first(&b->waiters) != &b->first_wait->node);
+
+ return first;
+}
+
+bool intel_engine_add_wait(struct intel_engine_cs *engine,
+ struct intel_wait *wait)
+{
+ struct intel_breadcrumbs *b = &engine->breadcrumbs;
+ bool first;
+
+ spin_lock(&b->lock);
+ first = __intel_engine_add_wait(engine, wait);
+ spin_unlock(&b->lock);
+
+ return first;
+}
+
+void intel_engine_enable_fake_irq(struct intel_engine_cs *engine)
+{
+ mod_timer(&engine->breadcrumbs.fake_irq, jiffies + 1);
+}
+
+static inline bool chain_wakeup(struct rb_node *rb, int priority)
+{
+ return rb && to_wait(rb)->tsk->prio <= priority;
+}
+
+void intel_engine_remove_wait(struct intel_engine_cs *engine,
+ struct intel_wait *wait)
+{
+ struct intel_breadcrumbs *b = &engine->breadcrumbs;
+
+ /* Quick check to see if this waiter was already decoupled from
+ * the tree by the bottom-half to avoid contention on the spinlock
+ * by the herd.
+ */
+ if (RB_EMPTY_NODE(&wait->node))
+ return;
+
+ spin_lock(&b->lock);
+
+ if (RB_EMPTY_NODE(&wait->node))
+ goto out_unlock;
+
+ if (b->first_wait == wait) {
+ struct rb_node *next;
+ const int priority = wait->tsk->prio;
+
+ GEM_BUG_ON(b->tasklet != wait->tsk);
+
+ /* We are the current bottom-half. Find the next candidate,
+ * the first waiter in the queue on the remaining oldest
+ * request. As multiple seqnos may complete in the time it
+ * takes us to wake up and find the next waiter, we have to
+ * wake up that waiter for it to perform its own coherent
+ * completion check.
+ */
+ next = rb_next(&wait->node);
+ if (chain_wakeup(next, priority)) {
+ /* If the next waiter is already complete,
+ * wake it up and continue onto the next waiter. So
+ * if have a small herd, they will wake up in parallel
+ * rather than sequentially, which should reduce
+ * the overall latency in waking all the completed
+ * clients.
+ *
+ * However, waking up a chain adds extra latency to
+ * the first_waiter. This is undesirable if that
+ * waiter is a high priority task.
+ */
+ u32 seqno = engine->get_seqno(engine);
+
+ while (i915_seqno_passed(seqno, to_wait(next)->seqno)) {
+ struct rb_node *n = rb_next(next);
+
+ __intel_breadcrumbs_finish(b, to_wait(next));
+ next = n;
+ if (!chain_wakeup(next, priority))
+ break;
+ }
+ }
+
+ if (next) {
+ /* In our haste, we may have completed the first waiter
+ * before we enabled the interrupt. Do so now as we
+ * have a second waiter for a future seqno. Afterwards,
+ * we have to wake up that waiter in case we missed
+ * the interrupt, or if we have to handle an
+ * exception rather than a seqno completion.
+ */
+ b->first_wait = to_wait(next);
+ smp_store_mb(b->tasklet, b->first_wait->tsk);
+ if (b->first_wait->seqno != wait->seqno)
+ __intel_breadcrumbs_enable_irq(b);
+ wake_up_process(b->tasklet);
+ } else {
+ b->first_wait = NULL;
+ WRITE_ONCE(b->tasklet, NULL);
+ __intel_breadcrumbs_disable_irq(b);
+ }
+ } else {
+ GEM_BUG_ON(rb_first(&b->waiters) == &wait->node);
+ }
+
+ GEM_BUG_ON(RB_EMPTY_NODE(&wait->node));
+ rb_erase(&wait->node, &b->waiters);
+
+out_unlock:
+ GEM_BUG_ON(b->first_wait == wait);
+ GEM_BUG_ON(rb_first(&b->waiters) !=
+ (b->first_wait ? &b->first_wait->node : NULL));
+ GEM_BUG_ON(!b->tasklet ^ RB_EMPTY_ROOT(&b->waiters));
+ spin_unlock(&b->lock);
+}
+
+int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine)
+{
+ struct intel_breadcrumbs *b = &engine->breadcrumbs;
+
+ spin_lock_init(&b->lock);
+ setup_timer(&b->fake_irq,
+ intel_breadcrumbs_fake_irq,
+ (unsigned long)engine);
+
+ return 0;
+}
+
+void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine)
+{
+ struct intel_breadcrumbs *b = &engine->breadcrumbs;
+
+ del_timer_sync(&b->fake_irq);
+}
+
+unsigned int intel_kick_waiters(struct drm_i915_private *i915)
+{
+ struct intel_engine_cs *engine;
+ unsigned int mask = 0;
+
+ /* To avoid the task_struct disappearing beneath us as we wake up
+ * the process, we must first inspect the task_struct->state under the
+ * RCU lock, i.e. as we call wake_up_process() we must be holding the
+ * rcu_read_lock().
+ */
+ rcu_read_lock();
+ for_each_engine(engine, i915)
+ if (unlikely(intel_engine_wakeup(engine)))
+ mask |= intel_engine_flag(engine);
+ rcu_read_unlock();
+
+ return mask;
+}
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index 339d8041075f8ce8d8bc67b5a7858509f3afd2dc..226bba22e4b4a53a001f6b30f4be00e2e6d05caa 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -1961,6 +1961,8 @@ void intel_logical_ring_cleanup(struct intel_engine_cs *engine)
i915_cmd_parser_fini_ring(engine);
i915_gem_batch_pool_fini(&engine->batch_pool);
+ intel_engine_fini_breadcrumbs(engine);
+
if (engine->status_page.obj) {
i915_gem_object_unpin_map(engine->status_page.obj);
engine->status_page.obj = NULL;
@@ -1998,7 +2000,6 @@ logical_ring_default_irqs(struct intel_engine_cs *engine, unsigned shift)
{
engine->irq_enable_mask = GT_RENDER_USER_INTERRUPT << shift;
engine->irq_keep_mask = GT_CONTEXT_SWITCH_INTERRUPT << shift;
- init_waitqueue_head(&engine->irq_queue);
}
static int
@@ -2025,6 +2026,10 @@ logical_ring_init(struct intel_engine_cs *engine)
struct i915_gem_context *dctx = engine->i915->kernel_context;
int ret;
+ ret = intel_engine_init_breadcrumbs(engine);
+ if (ret)
+ goto error;
+
ret = i915_cmd_parser_init_ring(engine);
if (ret)
goto error;
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
index 24cdc920f4b4cb50503048b113cfbc168638f990..af50aa01bcd92bf216f15410ae08dccef37fd2fa 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.c
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
@@ -2394,7 +2394,9 @@ static int intel_init_ring_buffer(struct drm_device *dev,
memset(engine->semaphore.sync_seqno, 0,
sizeof(engine->semaphore.sync_seqno));
- init_waitqueue_head(&engine->irq_queue);
+ ret = intel_engine_init_breadcrumbs(engine);
+ if (ret)
+ goto error;
/* We may need to do things with the shrinker which
* require us to immediately switch back to the default
@@ -2474,6 +2476,7 @@ void intel_cleanup_engine(struct intel_engine_cs *engine)
i915_cmd_parser_fini_ring(engine);
i915_gem_batch_pool_fini(&engine->batch_pool);
+ intel_engine_fini_breadcrumbs(engine);
intel_ring_context_unpin(dev_priv->kernel_context, engine);
@@ -2676,6 +2679,13 @@ void intel_ring_init_seqno(struct intel_engine_cs *engine, u32 seqno)
engine->last_submitted_seqno = seqno;
engine->hangcheck.seqno = seqno;
+
+ /* After manually advancing the seqno, fake the interrupt in case
+ * there are any waiters for that seqno.
+ */
+ rcu_read_lock();
+ intel_engine_wakeup(engine);
+ rcu_read_unlock();
}
static void gen6_bsd_ring_write_tail(struct intel_engine_cs *engine,
diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
index 113d5230a6de11c070cadba9dc028ff254605fae..6fd70a56e219b1b98dc4468c485096b70155878a 100644
--- a/drivers/gpu/drm/i915/intel_ringbuffer.h
+++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
@@ -148,6 +148,32 @@ struct intel_engine_cs {
struct intel_ringbuffer *buffer;
struct list_head buffers;
+ /* Rather than have every client wait upon all user interrupts,
+ * with the herd waking after every interrupt and each doing the
+ * heavyweight seqno dance, we delegate the task (of being the
+ * bottom-half of the user interrupt) to the first client. After
+ * every interrupt, we wake up one client, who does the heavyweight
+ * coherent seqno read and either goes back to sleep (if incomplete),
+ * or wakes up all the completed clients in parallel, before then
+ * transferring the bottom-half status to the next client in the queue.
+ *
+ * Compared to walking the entire list of waiters in a single dedicated
+ * bottom-half, we reduce the latency of the first waiter by avoiding
+ * a context switch, but incur additional coherent seqno reads when
+ * following the chain of request breadcrumbs. Since it is most likely
+ * that we have a single client waiting on each seqno, then reducing
+ * the overhead of waking that client is much preferred.
+ */
+ struct intel_breadcrumbs {
+ spinlock_t lock; /* protects the lists of requests */
+ struct rb_root waiters; /* sorted by retirement, priority */
+ struct intel_wait *first_wait; /* oldest waiter by retirement */
+ struct task_struct *tasklet; /* bh for user interrupts */
+ struct timer_list fake_irq; /* used after a missed interrupt */
+ bool irq_enabled;
+ bool rpm_wakelock;
+ } breadcrumbs;
+
/*
* A pool of objects to use as shadow copies of client batch buffers
* when the command parser is enabled. Prevents the client from
@@ -296,8 +322,6 @@ struct intel_engine_cs {
bool gpu_caches_dirty;
- wait_queue_head_t irq_queue;
-
struct i915_gem_context *last_context;
struct intel_ring_hangcheck hangcheck;
@@ -483,4 +507,55 @@ static inline u32 intel_hws_seqno_address(struct intel_engine_cs *engine)
return engine->status_page.gfx_addr + I915_GEM_HWS_INDEX_ADDR;
}
+/* intel_breadcrumbs.c -- user interrupt bottom-half for waiters */
+struct intel_wait {
+ struct rb_node node;
+ struct task_struct *tsk;
+ u32 seqno;
+};
+
+int intel_engine_init_breadcrumbs(struct intel_engine_cs *engine);
+
+static inline void intel_wait_init(struct intel_wait *wait, u32 seqno)
+{
+ wait->tsk = current;
+ wait->seqno = seqno;
+}
+
+static inline bool intel_wait_complete(const struct intel_wait *wait)
+{
+ return RB_EMPTY_NODE(&wait->node);
+}
+
+bool intel_engine_add_wait(struct intel_engine_cs *engine,
+ struct intel_wait *wait);
+void intel_engine_remove_wait(struct intel_engine_cs *engine,
+ struct intel_wait *wait);
+
+static inline bool intel_engine_has_waiter(struct intel_engine_cs *engine)
+{
+ return READ_ONCE(engine->breadcrumbs.tasklet);
+}
+
+static inline bool intel_engine_wakeup(struct intel_engine_cs *engine)
+{
+ bool wakeup = false;
+ struct task_struct *tsk = READ_ONCE(engine->breadcrumbs.tasklet);
+ /* Note that for this not to dangerously chase a dangling pointer,
+ * the caller is responsible for ensure that the task remain valid for
+ * wake_up_process() i.e. that the RCU grace period cannot expire.
+ *
+ * Also note that tsk is likely to be in !TASK_RUNNING state so an
+ * early test for tsk->state != TASK_RUNNING before wake_up_process()
+ * is unlikely to be beneficial.
+ */
+ if (tsk)
+ wakeup = wake_up_process(tsk);
+ return wakeup;
+}
+
+void intel_engine_enable_fake_irq(struct intel_engine_cs *engine);
+void intel_engine_fini_breadcrumbs(struct intel_engine_cs *engine);
+unsigned int intel_kick_waiters(struct drm_i915_private *i915);
+
#endif /* _INTEL_RINGBUFFER_H_ */