Alex Bin Xie
*From:*amd-gfx [mailto:[email protected]] *On
Behalf Of *Jason Ekstrand
*Sent:* Monday, July 10, 2017 11:53 AM
*To:* Christian König <[email protected]>
*Cc:* Dave Airlie <[email protected]>; Maling list - DRI developers
<[email protected]>; amd-gfx mailing list
<[email protected]>
*Subject:* Re: [PATCH] drm/syncobj: add sync obj wait interface. (v6)
On Mon, Jul 10, 2017 at 8:45 AM, Christian König
<[email protected] <mailto:[email protected]>> wrote:
Am 10.07.2017 um 17:28 schrieb Jason Ekstrand:
On Wed, Jul 5, 2017 at 6:04 PM, Dave Airlie <[email protected]
<mailto:[email protected]>> wrote:
From: Dave Airlie <[email protected]
<mailto:[email protected]>>
This interface will allow sync object to be used to back
Vulkan fences. This API is pretty much the vulkan fence
waiting
API, and I've ported the code from amdgpu.
v2: accept relative timeout, pass remaining time back
to userspace.
v3: return to absolute timeouts.
v4: absolute zero = poll,
rewrite any/all code to have same operation for arrays
return -EINVAL for 0 fences.
v4.1: fixup fences allocation check, use u64_to_user_ptr
v5: move to sec/nsec, and use timespec64 for calcs.
v6: use -ETIME and drop the out status flag. (-ETIME
is suggested by ickle, I can feel a shed painting)
Signed-off-by: Dave Airlie <[email protected]
<mailto:[email protected]>>
---
drivers/gpu/drm/drm_internal.h | 2 +
drivers/gpu/drm/drm_ioctl.c | 2 +
drivers/gpu/drm/drm_syncobj.c | 142
+++++++++++++++++++++++++++++++++++++++++
include/uapi/drm/drm.h | 13 ++++
4 files changed, 159 insertions(+)
diff --git a/drivers/gpu/drm/drm_internal.h
b/drivers/gpu/drm/drm_internal.h
index 5cecc97..d71b50d 100644
--- a/drivers/gpu/drm/drm_internal.h
+++ b/drivers/gpu/drm/drm_internal.h
@@ -157,3 +157,5 @@ int
drm_syncobj_handle_to_fd_ioctl(struct drm_device *dev,
void *data,
struct drm_file *file_private);
int drm_syncobj_fd_to_handle_ioctl(struct drm_device
*dev, void *data,
struct drm_file *file_private);
+int drm_syncobj_wait_ioctl(struct drm_device *dev, void
*data,
+ struct drm_file *file_private);
diff --git a/drivers/gpu/drm/drm_ioctl.c
b/drivers/gpu/drm/drm_ioctl.c
index f1e5681..385ce74 100644
--- a/drivers/gpu/drm/drm_ioctl.c
+++ b/drivers/gpu/drm/drm_ioctl.c
@@ -657,6 +657,8 @@ static const struct drm_ioctl_desc
drm_ioctls[] = {
DRM_UNLOCKED|DRM_RENDER_ALLOW),
DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE,
drm_syncobj_fd_to_handle_ioctl,
DRM_UNLOCKED|DRM_RENDER_ALLOW),
+ DRM_IOCTL_DEF(DRM_IOCTL_SYNCOBJ_WAIT,
drm_syncobj_wait_ioctl,
+ DRM_UNLOCKED|DRM_RENDER_ALLOW),
};
#define DRM_CORE_IOCTL_COUNT ARRAY_SIZE( drm_ioctls )
diff --git a/drivers/gpu/drm/drm_syncobj.c
b/drivers/gpu/drm/drm_syncobj.c
index 89441bc..2d5a7a1 100644
--- a/drivers/gpu/drm/drm_syncobj.c
+++ b/drivers/gpu/drm/drm_syncobj.c
@@ -1,5 +1,7 @@
/*
* Copyright 2017 Red Hat
+ * Parts ported from amdgpu (fence wait code).
+ * Copyright 2016 Advanced Micro Devices, Inc.
*
* Permission is hereby granted, free of charge, to any
person obtaining a
* copy of this software and associated documentation
files (the "Software"),
@@ -31,6 +33,9 @@
* that contain an optional fence. The fence can be
updated with a new
* fence, or be NULL.
*
+ * syncobj's can be waited upon, where it will wait for
the underlying
+ * fence.
+ *
* syncobj's can be export to fd's and back, these fd's
are opaque and
* have no other use case, except passing the syncobj
between processes.
*
@@ -451,3 +456,140 @@
drm_syncobj_fd_to_handle_ioctl(struct drm_device *dev,
void *data,
return drm_syncobj_fd_to_handle(file_private,
args->fd,
&args->handle);
}
+
+/**
+ * drm_timeout_abs_to_jiffies - calculate jiffies timeout
from absolute value
+ *
+ * @timeout_sec: timeout sec component, 0 for poll
+ * @timeout_nsec: timeout nsec component in ns, 0 for poll
+ * both must be 0 for poll.
+ *
+ * Calculate the timeout in jiffies from an absolute time
in sec/nsec.
+ */
+static unsigned long drm_timeout_abs_to_jiffies(int64_t
timeout_sec, uint64_t timeout_nsec)
+{
+ struct timespec64 abs_timeout, timeout,
max_jiffy_timespec;
+ unsigned long timeout_jiffies;
+
+ /* make 0 timeout means poll - absolute 0 doesn't
seem valid */
+ if (timeout_sec == 0 && timeout_nsec == 0)
+ return 0;
+
+ abs_timeout.tv_sec = timeout_sec;
+ abs_timeout.tv_nsec = timeout_nsec;
+
+ /* clamp timeout if it's to large */
+ if (!timespec64_valid_strict(&abs_timeout))
+ return MAX_SCHEDULE_TIMEOUT - 1;
+
+ timeout = timespec64_sub(abs_timeout,
ktime_to_timespec64(ktime_get()));
+ if (!timespec64_valid(&timeout))
+ return 0;
+
+ jiffies_to_timespec64(MAX_JIFFY_OFFSET,
&max_jiffy_timespec);
+ if (timespec64_compare(&timeout,
&max_jiffy_timespec) >= 0)
+ return MAX_SCHEDULE_TIMEOUT - 1;
+
+ timeout_jiffies = timespec64_to_jiffies(&timeout);
+ /* clamp timeout to avoid infinite timeout */
+ if (timeout_jiffies >= MAX_SCHEDULE_TIMEOUT)
+ return MAX_SCHEDULE_TIMEOUT - 1;
+
+ return timeout_jiffies + 1;
+}
+
+static int drm_syncobj_wait_fences(struct drm_device *dev,
+ struct drm_file *file_private,
+ struct drm_syncobj_wait *wait,
+ struct dma_fence **fences)
+{
+ unsigned long timeout =
drm_timeout_abs_to_jiffies(wait->timeout_sec,
wait->timeout_nsec);
+ int ret = 0;
+ uint32_t first = ~0;
+
+ if (wait->flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL) {
+ int i;
+ for (i = 0; i < wait->count_handles; i++) {
+ ret =
dma_fence_wait_timeout(fences[i], true, timeout);
+
+ if (ret < 0)
+ return ret;
+ if (ret == 0)
+ break;
+ timeout = ret;
+ }
+ first = 0;
+ } else {
+ ret = dma_fence_wait_any_timeout(fences,
+ wait->count_handles,
+ true, timeout,
+ &first);
+ }
+
+ if (ret < 0)
+ return ret;
+
+ wait->first_signaled = first;
+ if (ret == 0)
+ return -ETIME;
+ return 0;
+}
+
+int
+drm_syncobj_wait_ioctl(struct drm_device *dev, void *data,
+ struct drm_file *file_private)
+{
+ struct drm_syncobj_wait *args = data;
+ uint32_t *handles;
+ struct dma_fence **fences;
+ int ret = 0;
+ int i;
+
+ if (!drm_core_check_feature(dev, DRIVER_SYNCOBJ))
+ return -ENODEV;
+
+ if (args->flags != 0 && args->flags !=
DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL)
+ return -EINVAL;
+
+ if (args->count_handles == 0)
+ return -EINVAL;
+
+ /* Get the handles from userspace */
+ handles = kmalloc_array(args->count_handles,
sizeof(uint32_t),
+ GFP_KERNEL);
+ if (handles == NULL)
+ return -ENOMEM;
+
+ if (copy_from_user(handles,
+ u64_to_user_ptr(args->handles),
+ sizeof(uint32_t) * args->count_handles)) {
+ ret = -EFAULT;
+ goto err_free_handles;
+ }
+
+ fences = kcalloc(args->count_handles,
+ sizeof(struct dma_fence *),
GFP_KERNEL);
+ if (!fences) {
+ ret = -ENOMEM;
+ goto err_free_handles;
+ }
+
+ for (i = 0; i < args->count_handles; i++) {
+ ret = drm_syncobj_fence_get(file_private,
handles[i],
+ &fences[i]);
+ if (ret)
+ goto err_free_fence_array;
+ }
+
+ ret = drm_syncobj_wait_fences(dev, file_private,
+ args, fences);
So, reading some CTS tests again, and I think we have a
problem here. The Vulkan spec allows you to wait on a fence
that is in the unsignaled state.
At least on the closed source driver that would be illegal as far
as I know.
Then they are doing workarounds in userspace. There are definitely
CTS tests for this:
https://github.com/KhronosGroup/VK-GL-CTS/blob/master/external/vulkancts/modules/vulkan/synchronization/vktSynchronizationBasicFenceTests.cpp#L74
You can't wait on a semaphore before the signal operation is send
down to the kerel.
We (Intel) deal with this today by tracking whether or not the fence
has been submitted and using a condition variable in userspace to sort
it all out. If we ever want to share fences across processes (which
we do), then this needs to be sorted in the kernel.
--Jason
Regards,
Christian.
In theory, you could have thread A start waiting on a fence
before thread B submits the work which triggers that fence.
This means that the dma_fence may not exist yet when
vkWaitForFences gets called. If we really want to support the
full Vulkan usage, we need to somehow support missing
dma_fences by waiting for the dma_fence to show up.
Unfortunately, I don't know enough about the internal kernel
APIs to know what that would look like.
+
+err_free_fence_array:
+ for (i = 0; i < args->count_handles; i++)
+ dma_fence_put(fences[i]);
+ kfree(fences);
+err_free_handles:
+ kfree(handles);
+
+ return ret;
+}
diff --git a/include/uapi/drm/drm.h b/include/uapi/drm/drm.h
index 101593a..91746a7 100644
--- a/include/uapi/drm/drm.h
+++ b/include/uapi/drm/drm.h
@@ -718,6 +718,18 @@ struct drm_syncobj_handle {
__u32 pad;
};
+#define DRM_SYNCOBJ_WAIT_FLAGS_WAIT_ALL (1 << 0)
+struct drm_syncobj_wait {
+ __u64 handles;
+ /* absolute timeout */
+ __s64 timeout_sec;
+ __s64 timeout_nsec;
+ __u32 count_handles;
+ __u32 flags;
+ __u32 first_signaled; /* only valid when not
waiting all */
+ __u32 pad;
+};
+
#if defined(__cplusplus)
}
#endif
@@ -840,6 +852,7 @@ extern "C" {
#define DRM_IOCTL_SYNCOBJ_DESTROY DRM_IOWR(0xC0, struct
drm_syncobj_destroy)
#define DRM_IOCTL_SYNCOBJ_HANDLE_TO_FD DRM_IOWR(0xC1,
struct drm_syncobj_handle)
#define DRM_IOCTL_SYNCOBJ_FD_TO_HANDLE DRM_IOWR(0xC2,
struct drm_syncobj_handle)
+#define DRM_IOCTL_SYNCOBJ_WAIT DRM_IOWR(0xC3, struct
drm_syncobj_wait)
/**
* Device specific ioctls should only be in their
respective headers
--
2.9.4
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