Re: [RFC PATCH v1 08/16] drm/radeon: use common fence implementation for fences

From: Christian König
Date: Wed May 14 2014 - 11:29:35 EST

+ /* did fence get signaled after we enabled the sw irq? */
+ if (atomic64_read(&fence->rdev->fence_drv[fence->ring].last_seq) >= fence->seq) {
+ radeon_irq_kms_sw_irq_put(fence->rdev, fence->ring);
+ return false;
+ }
+
+ fence->fence_wake.flags = 0;
+ fence->fence_wake.private = NULL;
+ fence->fence_wake.func = radeon_fence_check_signaled;
+ __add_wait_queue(&fence->rdev->fence_queue, &fence->fence_wake);
+ fence_get(f);
That looks like a race condition to me. The fence needs to be added to the wait queue before the check, not after.

Apart from that the whole approach looks like a really bad idea to me. How for example is lockup detection supposed to happen with this?

Christian.

Am 14.05.2014 16:58, schrieb Maarten Lankhorst:
Signed-off-by: Maarten Lankhorst <maarten.lankhorst@xxxxxxxxxxxxx>
---
drivers/gpu/drm/radeon/radeon.h | 15 +--
drivers/gpu/drm/radeon/radeon_device.c | 1
drivers/gpu/drm/radeon/radeon_fence.c | 189 +++++++++++++++++++++++++-------
3 files changed, 153 insertions(+), 52 deletions(-)

diff --git a/drivers/gpu/drm/radeon/radeon.h b/drivers/gpu/drm/radeon/radeon.h
index 68528619834a..a7d839a158ae 100644
--- a/drivers/gpu/drm/radeon/radeon.h
+++ b/drivers/gpu/drm/radeon/radeon.h
@@ -64,6 +64,7 @@
#include <linux/wait.h>
#include <linux/list.h>
#include <linux/kref.h>
+#include <linux/fence.h>
#include <ttm/ttm_bo_api.h>
#include <ttm/ttm_bo_driver.h>
@@ -113,9 +114,6 @@ extern int radeon_hard_reset;
#define RADEONFB_CONN_LIMIT 4
#define RADEON_BIOS_NUM_SCRATCH 8
-/* fence seq are set to this number when signaled */
-#define RADEON_FENCE_SIGNALED_SEQ 0LL
-
/* internal ring indices */
/* r1xx+ has gfx CP ring */
#define RADEON_RING_TYPE_GFX_INDEX 0
@@ -347,12 +345,15 @@ struct radeon_fence_driver {
};
struct radeon_fence {
+ struct fence base;
+
struct radeon_device *rdev;
- struct kref kref;
/* protected by radeon_fence.lock */
uint64_t seq;
/* RB, DMA, etc. */
unsigned ring;
+
+ wait_queue_t fence_wake;
};
int radeon_fence_driver_start_ring(struct radeon_device *rdev, int ring);
@@ -2256,6 +2257,7 @@ struct radeon_device {
struct radeon_mman mman;
struct radeon_fence_driver fence_drv[RADEON_NUM_RINGS];
wait_queue_head_t fence_queue;
+ unsigned fence_context;
struct mutex ring_lock;
struct radeon_ring ring[RADEON_NUM_RINGS];
bool ib_pool_ready;
@@ -2346,11 +2348,6 @@ u32 cik_mm_rdoorbell(struct radeon_device *rdev, u32 index);
void cik_mm_wdoorbell(struct radeon_device *rdev, u32 index, u32 v);
/*
- * Cast helper
- */
-#define to_radeon_fence(p) ((struct radeon_fence *)(p))
-
-/*
* Registers read & write functions.
*/
#define RREG8(reg) readb((rdev->rmmio) + (reg))
diff --git a/drivers/gpu/drm/radeon/radeon_device.c b/drivers/gpu/drm/radeon/radeon_device.c
index 0e770bbf7e29..501d0cf9eb8b 100644
--- a/drivers/gpu/drm/radeon/radeon_device.c
+++ b/drivers/gpu/drm/radeon/radeon_device.c
@@ -1175,6 +1175,7 @@ int radeon_device_init(struct radeon_device *rdev,
for (i = 0; i < RADEON_NUM_RINGS; i++) {
rdev->ring[i].idx = i;
}
+ rdev->fence_context = fence_context_alloc(RADEON_NUM_RINGS);
DRM_INFO("initializing kernel modesetting (%s 0x%04X:0x%04X 0x%04X:0x%04X).\n",
radeon_family_name[rdev->family], pdev->vendor, pdev->device,
diff --git a/drivers/gpu/drm/radeon/radeon_fence.c b/drivers/gpu/drm/radeon/radeon_fence.c
index a77b1c13ea43..bc844f300d3f 100644
--- a/drivers/gpu/drm/radeon/radeon_fence.c
+++ b/drivers/gpu/drm/radeon/radeon_fence.c
@@ -39,6 +39,15 @@
#include "radeon.h"
#include "radeon_trace.h"
+static const struct fence_ops radeon_fence_ops;
+
+#define to_radeon_fence(p) \
+ ({ \
+ struct radeon_fence *__f; \
+ __f = container_of((p), struct radeon_fence, base); \
+ __f->base.ops == &radeon_fence_ops ? __f : NULL; \
+ })
+
/*
* Fences
* Fences mark an event in the GPUs pipeline and are used
@@ -111,30 +120,55 @@ int radeon_fence_emit(struct radeon_device *rdev,
struct radeon_fence **fence,
int ring)
{
+ u64 seq = ++rdev->fence_drv[ring].sync_seq[ring];
+
/* we are protected by the ring emission mutex */
*fence = kmalloc(sizeof(struct radeon_fence), GFP_KERNEL);
if ((*fence) == NULL) {
return -ENOMEM;
}
- kref_init(&((*fence)->kref));
- (*fence)->rdev = rdev;
- (*fence)->seq = ++rdev->fence_drv[ring].sync_seq[ring];
(*fence)->ring = ring;
+ __fence_init(&(*fence)->base, &radeon_fence_ops,
+ &rdev->fence_queue.lock, rdev->fence_context + ring, seq);
+ (*fence)->rdev = rdev;
+ (*fence)->seq = seq;
radeon_fence_ring_emit(rdev, ring, *fence);
trace_radeon_fence_emit(rdev->ddev, ring, (*fence)->seq);
return 0;
}
/**
- * radeon_fence_process - process a fence
+ * radeon_fence_check_signaled - callback from fence_queue
*
- * @rdev: radeon_device pointer
- * @ring: ring index the fence is associated with
- *
- * Checks the current fence value and wakes the fence queue
- * if the sequence number has increased (all asics).
+ * this function is called with fence_queue lock held, which is also used
+ * for the fence locking itself, so unlocked variants are used for
+ * fence_signal, and remove_wait_queue.
*/
-void radeon_fence_process(struct radeon_device *rdev, int ring)
+static int radeon_fence_check_signaled(wait_queue_t *wait, unsigned mode, int flags, void *key)
+{
+ struct radeon_fence *fence;
+ u64 seq;
+
+ fence = container_of(wait, struct radeon_fence, fence_wake);
+
+ seq = atomic64_read(&fence->rdev->fence_drv[fence->ring].last_seq);
+ if (seq >= fence->seq) {
+ int ret = __fence_signal(&fence->base);
+
+ if (!ret)
+ FENCE_TRACE(&fence->base, "signaled from irq context\n");
+ else
+ FENCE_TRACE(&fence->base, "was already signaled\n");
+
+ radeon_irq_kms_sw_irq_put(fence->rdev, fence->ring);
+ __remove_wait_queue(&fence->rdev->fence_queue, &fence->fence_wake);
+ fence_put(&fence->base);
+ } else
+ FENCE_TRACE(&fence->base, "pending\n");
+ return 0;
+}
+
+static bool __radeon_fence_process(struct radeon_device *rdev, int ring)
{
uint64_t seq, last_seq, last_emitted;
unsigned count_loop = 0;
@@ -190,23 +224,22 @@ void radeon_fence_process(struct radeon_device *rdev, int ring)
}
} while (atomic64_xchg(&rdev->fence_drv[ring].last_seq, seq) > seq);
- if (wake)
- wake_up_all(&rdev->fence_queue);
+ return wake;
}
/**
- * radeon_fence_destroy - destroy a fence
+ * radeon_fence_process - process a fence
*
- * @kref: fence kref
+ * @rdev: radeon_device pointer
+ * @ring: ring index the fence is associated with
*
- * Frees the fence object (all asics).
+ * Checks the current fence value and wakes the fence queue
+ * if the sequence number has increased (all asics).
*/
-static void radeon_fence_destroy(struct kref *kref)
+void radeon_fence_process(struct radeon_device *rdev, int ring)
{
- struct radeon_fence *fence;
-
- fence = container_of(kref, struct radeon_fence, kref);
- kfree(fence);
+ if (__radeon_fence_process(rdev, ring))
+ wake_up_all(&rdev->fence_queue);
}
/**
@@ -237,6 +270,49 @@ static bool radeon_fence_seq_signaled(struct radeon_device *rdev,
return false;
}
+static bool __radeon_fence_signaled(struct fence *f)
+{
+ struct radeon_fence *fence = to_radeon_fence(f);
+
+ return radeon_fence_seq_signaled(fence->rdev, fence->seq, fence->ring);
+}
+
+/**
+ * radeon_fence_enable_signaling - enable signalling on fence
+ * @fence: fence
+ *
+ * This function is called with fence_queue lock held, and adds a callback
+ * to fence_queue that checks if this fence is signaled, and if so it
+ * signals the fence and removes itself.
+ */
+static bool radeon_fence_enable_signaling(struct fence *f)
+{
+ struct radeon_fence *fence = to_radeon_fence(f);
+
+ if (atomic64_read(&fence->rdev->fence_drv[fence->ring].last_seq) >= fence->seq ||
+ !fence->rdev->ddev->irq_enabled)
+ return false;
+
+ radeon_irq_kms_sw_irq_get(fence->rdev, fence->ring);
+
+ if (__radeon_fence_process(fence->rdev, fence->ring))
+ wake_up_all_locked(&fence->rdev->fence_queue);
+
+ /* did fence get signaled after we enabled the sw irq? */
+ if (atomic64_read(&fence->rdev->fence_drv[fence->ring].last_seq) >= fence->seq) {
+ radeon_irq_kms_sw_irq_put(fence->rdev, fence->ring);
+ return false;
+ }
+
+ fence->fence_wake.flags = 0;
+ fence->fence_wake.private = NULL;
+ fence->fence_wake.func = radeon_fence_check_signaled;
+ __add_wait_queue(&fence->rdev->fence_queue, &fence->fence_wake);
+ fence_get(f);
+
+ return true;
+}
+
/**
* radeon_fence_signaled - check if a fence has signaled
*
@@ -250,11 +326,13 @@ bool radeon_fence_signaled(struct radeon_fence *fence)
if (!fence) {
return true;
}
- if (fence->seq == RADEON_FENCE_SIGNALED_SEQ) {
- return true;
- }
+
if (radeon_fence_seq_signaled(fence->rdev, fence->seq, fence->ring)) {
- fence->seq = RADEON_FENCE_SIGNALED_SEQ;
+ int ret;
+
+ ret = fence_signal(&fence->base);
+ if (!ret)
+ FENCE_TRACE(&fence->base, "signaled from radeon_fence_signaled\n");
return true;
}
return false;
@@ -386,7 +464,7 @@ static int radeon_fence_wait_seq(struct radeon_device *rdev, u64 *target_seq,
* radeon_fence_wait - wait for a fence to signal
*
* @fence: radeon fence object
- * @intr: use interruptable sleep
+ * @intr: use interruptible sleep
*
* Wait for the requested fence to signal (all asics).
* @intr selects whether to use interruptable (true) or non-interruptable
@@ -398,20 +476,17 @@ int radeon_fence_wait(struct radeon_fence *fence, bool intr)
uint64_t seq[RADEON_NUM_RINGS] = {};
int r;
- if (fence == NULL) {
- WARN(1, "Querying an invalid fence : %p !\n", fence);
- return -EINVAL;
- }
-
- seq[fence->ring] = fence->seq;
- if (seq[fence->ring] == RADEON_FENCE_SIGNALED_SEQ)
+ if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fence->base.flags))
return 0;
+ seq[fence->ring] = fence->seq;
r = radeon_fence_wait_seq(fence->rdev, seq, intr);
- if (r)
+ if (r) {
return r;
-
- fence->seq = RADEON_FENCE_SIGNALED_SEQ;
+ }
+ r = fence_signal(&fence->base);
+ if (!r)
+ FENCE_TRACE(&fence->base, "signaled from fence_wait\n");
return 0;
}
@@ -443,12 +518,13 @@ int radeon_fence_wait_any(struct radeon_device *rdev,
continue;
}
+ if (test_bit(FENCE_FLAG_SIGNALED_BIT, &fences[i]->base.flags)) {
+ /* already signaled */
+ return 0;
+ }
+
seq[i] = fences[i]->seq;
++num_rings;
-
- /* test if something was allready signaled */
- if (seq[i] == RADEON_FENCE_SIGNALED_SEQ)
- return 0;
}
/* nothing to wait for ? */
@@ -525,7 +601,7 @@ int radeon_fence_wait_empty(struct radeon_device *rdev, int ring)
*/
struct radeon_fence *radeon_fence_ref(struct radeon_fence *fence)
{
- kref_get(&fence->kref);
+ fence_get(&fence->base);
return fence;
}
@@ -541,9 +617,8 @@ void radeon_fence_unref(struct radeon_fence **fence)
struct radeon_fence *tmp = *fence;
*fence = NULL;
- if (tmp) {
- kref_put(&tmp->kref, radeon_fence_destroy);
- }
+ if (tmp)
+ fence_put(&tmp->base);
}
/**
@@ -832,3 +907,31 @@ int radeon_debugfs_fence_init(struct radeon_device *rdev)
return 0;
#endif
}
+
+static const char *radeon_fence_get_driver_name(struct fence *fence)
+{
+ return "radeon";
+}
+
+static const char *radeon_fence_get_timeline_name(struct fence *f)
+{
+ struct radeon_fence *fence = to_radeon_fence(f);
+ switch (fence->ring) {
+ case RADEON_RING_TYPE_GFX_INDEX: return "radeon.gfx";
+ case CAYMAN_RING_TYPE_CP1_INDEX: return "radeon.cp1";
+ case CAYMAN_RING_TYPE_CP2_INDEX: return "radeon.cp2";
+ case R600_RING_TYPE_DMA_INDEX: return "radeon.dma";
+ case CAYMAN_RING_TYPE_DMA1_INDEX: return "radeon.dma1";
+ case R600_RING_TYPE_UVD_INDEX: return "radeon.uvd";
+ default: WARN_ON_ONCE(1); return "radeon.unk";
+ }
+}
+
+static const struct fence_ops radeon_fence_ops = {
+ .get_driver_name = radeon_fence_get_driver_name,
+ .get_timeline_name = radeon_fence_get_timeline_name,
+ .enable_signaling = radeon_fence_enable_signaling,
+ .signaled = __radeon_fence_signaled,
+ .wait = fence_default_wait,
+ .release = NULL,
+};

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