llvmpipe: Implement EGL_ANDROID_native_fence_sync

Add support for the native fence extension through the use
of udmabuf's dmabuffers. Thanks to the fact that llvmpipe
is synchronous we can export a sync file from a dmabuf that
is always signalled and use this to implement the extension.
For importing sync files we can simply poll the sync file
to wait until it is signalled.

Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/28735>

src/gallium/drivers/llvmpipe/lp_context.c

@@ -253,6 +253,10 @@ llvmpipe_create_context(struct pipe_screen *screen, void *priv,
 
    llvmpipe_init_sampler_matrix(llvmpipe);
 
+#ifdef HAVE_LIBDRM
+   llvmpipe_init_fence_funcs(&llvmpipe->pipe);
+#endif
+
 #ifdef USE_GLOBAL_LLVM_CONTEXT
    llvmpipe->context.ref = LLVMGetGlobalContext();
    llvmpipe->context.owned = false;

src/gallium/drivers/llvmpipe/lp_fence.c

@@ -28,12 +28,60 @@
 
 #include "pipe/p_screen.h"
 #include "util/u_memory.h"
+#include "util/os_file.h"
 #include "lp_debug.h"
 #include "lp_fence.h"
+#include "lp_screen.h"
+#include "lp_texture.h"
+#include "lp_flush.h"
+#include "lp_context.h"
 
 
 #include "util/timespec.h"
 
+#ifdef HAVE_LIBDRM
+#include <xf86drm.h>
+#include <drm-uapi/dma-buf.h>
+#include <poll.h>
+#include "util/libsync.h"
+#include "util/list.h"
+#endif
+
+static unsigned fence_id = 0;
+
+#ifdef HAVE_LIBDRM
+static int sync_fd_wait(int fd, uint64_t timeout)
+{
+   struct pollfd fds = {0};
+   int ret;
+   struct timespec poll_start, poll_end, timeout_ts, diff;
+   timespec_from_nsec(&timeout_ts, timeout);
+
+   fds.fd = fd;
+   fds.events = POLLIN;
+
+   do {
+      clock_gettime(CLOCK_MONOTONIC, &poll_start);
+      ret = ppoll(&fds, 1, &timeout_ts, NULL);
+      clock_gettime(CLOCK_MONOTONIC, &poll_end);
+      if (ret > 0) {
+         if (fds.revents & (POLLERR | POLLNVAL)) {
+            errno = EINVAL;
+            return -1;
+         }
+         return 0;
+      } else if (ret == 0) {
+         errno = ETIME;
+         return -1;
+      }
+
+      timespec_sub(&diff, &poll_end, &poll_start);
+      timespec_sub_saturate(&timeout_ts, &timeout_ts, &diff);
+   } while (ret == -1 && (errno == EINTR || errno == EAGAIN));
+
+   return ret;
+}
+#endif
 
 /**
  * Create a new fence object.
@@ -47,13 +95,13 @@
 struct lp_fence *
 lp_fence_create(unsigned rank)
 {
-   static unsigned fence_id = 0;
    struct lp_fence *fence = CALLOC_STRUCT(lp_fence);
 
    if (!fence)
       return NULL;
 
    pipe_reference_init(&fence->reference, 1);
+   fence->type = LP_FENCE_TYPE_SW;
 
    (void) mtx_init(&fence->mutex, mtx_plain);
    cnd_init(&fence->signalled);
@@ -61,13 +109,16 @@ lp_fence_create(unsigned rank)
    fence->id = p_atomic_inc_return(&fence_id) - 1;
    fence->rank = rank;
 
+#ifdef HAVE_LIBDRM
+   fence->sync_fd = -1;
+#endif
+
    if (LP_DEBUG & DEBUG_FENCE)
       debug_printf("%s %d\n", __func__, fence->id);
 
    return fence;
 }
 
-
 /** Destroy a fence.  Called when refcount hits zero. */
 void
 lp_fence_destroy(struct lp_fence *fence)
@@ -75,8 +126,16 @@ lp_fence_destroy(struct lp_fence *fence)
    if (LP_DEBUG & DEBUG_FENCE)
       debug_printf("%s %d\n", __func__, fence->id);
 
+   if (fence->type == LP_FENCE_TYPE_SW) {
       mtx_destroy(&fence->mutex);
       cnd_destroy(&fence->signalled);
+   }
+#ifdef HAVE_LIBDRM
+   else {
+      close(fence->sync_fd);
+   }
+#endif
+
    FREE(fence);
 }
 
@@ -91,6 +150,7 @@ lp_fence_signal(struct lp_fence *fence)
    if (LP_DEBUG & DEBUG_FENCE)
       debug_printf("%s %d\n", __func__, fence->id);
 
+   if (fence->type == LP_FENCE_TYPE_SW) {
       mtx_lock(&fence->mutex);
 
       fence->count++;
@@ -105,13 +165,27 @@ lp_fence_signal(struct lp_fence *fence)
       cnd_broadcast(&fence->signalled);
 
       mtx_unlock(&fence->mutex);
+   }
+
+   /* sync fd fence we create ourselves are always signalled so
+    * we don't need an else clause
+    */
 }
 
 
 bool
 lp_fence_signalled(struct lp_fence *f)
 {
+   if (f->type == LP_FENCE_TYPE_SW)
       return f->count == f->rank;
+#ifdef HAVE_LIBDRM
+   else {
+      return sync_wait(f->sync_fd, 0) == 0;
+   }
+#endif
+
+   unreachable("Fence is an unknown type");
+   return false;
 }
 
 
@@ -121,12 +195,20 @@ lp_fence_wait(struct lp_fence *f)
    if (LP_DEBUG & DEBUG_FENCE)
       debug_printf("%s %d\n", __func__, f->id);
 
+   if (f->type == LP_FENCE_TYPE_SW) {
       mtx_lock(&f->mutex);
       assert(f->issued);
       while (f->count < f->rank) {
          cnd_wait(&f->signalled, &f->mutex);
       }
       mtx_unlock(&f->mutex);
+   }
+#ifdef HAVE_LIBDRM
+   else {
+      assert(f->sync_fd != -1);
+      sync_wait(f->sync_fd, -1);
+   }
+#endif
 }
 
 
@@ -142,6 +224,7 @@ lp_fence_timedwait(struct lp_fence *f, uint64_t timeout)
    if (LP_DEBUG & DEBUG_FENCE)
       debug_printf("%s %d\n", __func__, f->id);
 
+   if (f->type == LP_FENCE_TYPE_SW) {
       mtx_lock(&f->mutex);
       assert(f->issued);
       while (f->count < f->rank) {
@@ -156,6 +239,118 @@ lp_fence_timedwait(struct lp_fence *f, uint64_t timeout)
 
       const bool result = (f->count >= f->rank);
       mtx_unlock(&f->mutex);
-
       return result;
+   }
+#ifdef HAVE_LIBDRM
+   else {
+      assert(f->sync_fd != -1);
+      return sync_fd_wait(f->sync_fd, timeout) == 0;
+   }
+#endif
+
+   unreachable("Fence is an unknown type");
+   return false;
 }
+
+#ifdef HAVE_LIBDRM
+static int
+lp_fence_get_fd(struct pipe_screen *pscreen,
+                struct pipe_fence_handle *fence)
+{
+   struct llvmpipe_screen *screen = llvmpipe_screen(pscreen);
+   struct lp_fence *lp_fence = (struct lp_fence *)fence;
+
+   /* It's not ideal, but since we cannot properly support sync files
+    * from userspace, what we will do instead is wait for llvmpipe to
+    * finish rendering, and then export the sync file. If its not a
+    * sync file we imported we can just export a dummy one that is always
+    * signalled since llvmpipe should have now finished all its work.
+    */
+   list_for_each_entry(struct llvmpipe_context, ctx, &screen->ctx_list, list) {
+      llvmpipe_finish((struct pipe_context *)ctx, __func__);
+   }
+
+   if (lp_fence && lp_fence->sync_fd != -1) {
+      return os_dupfd_cloexec(lp_fence->sync_fd);
+   } else if (screen->dummy_sync_fd != -1) {
+      return os_dupfd_cloexec(screen->dummy_sync_fd);
+   }
+
+   return -1;
+}
+
+static void
+lp_create_fence_fd(struct pipe_context *pipe,
+                   struct pipe_fence_handle **fence,
+                   int fd,
+                   enum pipe_fd_type type)
+{
+   /* Only sync fd are supported */
+   if (type != PIPE_FD_TYPE_NATIVE_SYNC)
+      goto fail;
+
+   struct lp_fence *f = CALLOC_STRUCT(lp_fence);
+
+   if (!fence)
+      goto fail;
+
+   pipe_reference_init(&f->reference, 1);
+   f->type = LP_FENCE_TYPE_SYNC_FD;
+   f->id = p_atomic_inc_return(&fence_id) - 1;
+   f->sync_fd = os_dupfd_cloexec(fd);
+   f->issued = true;
+
+   *fence = (struct pipe_fence_handle*)f;
+   return;
+fail:
+   *fence = NULL;
+   return;
+}
+
+void
+llvmpipe_init_screen_fence_funcs(struct pipe_screen *pscreen)
+{
+   struct llvmpipe_screen *screen = llvmpipe_screen(pscreen);
+   screen->dummy_sync_fd = -1;
+
+   /* Try to create dummy dmabuf, and only set functions if we were able to */
+   int fd;
+   screen->dummy_dmabuf =
+      (struct llvmpipe_memory_allocation*)pscreen->allocate_memory_fd(
+            pscreen, 1, &fd, true);
+
+   /* We don't need this fd handle and API always creates it */
+   if (fd != -1)
+      close(fd);
+
+   if (screen->dummy_dmabuf) {
+      struct dma_buf_export_sync_file export = {
+         .flags = DMA_BUF_SYNC_RW,
+         .fd = -1,
+      };
+
+      if (drmIoctl(screen->dummy_dmabuf->dmabuf_fd,
+                   DMA_BUF_IOCTL_EXPORT_SYNC_FILE,
+                   &export))
+         goto fail;
+
+      screen->dummy_sync_fd = export.fd;
+   }
+
+   pscreen->fence_get_fd = lp_fence_get_fd;
+   return;
+fail:
+   if (screen->dummy_dmabuf) {
+      pscreen->free_memory_fd(
+            pscreen, (struct pipe_memory_allocation*)screen->dummy_dmabuf);
+      screen->dummy_dmabuf = NULL;
+   }
+   return;
+}
+
+void
+llvmpipe_init_fence_funcs(struct pipe_context *pipe)
+{
+   pipe->create_fence_fd = lp_create_fence_fd;
+}
+#endif

src/gallium/drivers/llvmpipe/lp_fence.h

@@ -37,10 +37,17 @@
 
 struct pipe_screen;
 
+enum lp_fence_type
+{
+   LP_FENCE_TYPE_SW,
+   LP_FENCE_TYPE_SYNC_FD,
+};
+
 
 struct lp_fence
 {
    struct pipe_reference reference;
+   enum lp_fence_type type;
    unsigned id;
 
    mtx_t mutex;
@@ -49,6 +56,8 @@ struct lp_fence
    bool issued;
    unsigned rank;
    unsigned count;
+
+   int sync_fd;
 };
 
 
@@ -94,5 +103,12 @@ lp_fence_issued(const struct lp_fence *fence)
    return fence->issued;
 }
 
+#ifdef HAVE_LIBDRM
+void
+llvmpipe_init_screen_fence_funcs(struct pipe_screen *pscreen);
+
+void
+llvmpipe_init_fence_funcs(struct pipe_context *pipe);
+#endif
 
 #endif /* LP_FENCE_H */

src/gallium/drivers/llvmpipe/lp_screen.c

@@ -134,6 +134,8 @@ llvmpipe_get_param(struct pipe_screen *screen, enum pipe_cap param)
          return DRM_PRIME_CAP_IMPORT | DRM_PRIME_CAP_EXPORT;
       else
          return DRM_PRIME_CAP_IMPORT;
+   case PIPE_CAP_NATIVE_FENCE_FD:
+      return lscreen->dummy_sync_fd != -1;
 #endif
    case PIPE_CAP_NPOT_TEXTURES:
    case PIPE_CAP_MIXED_FRAMEBUFFER_SIZES:
@@ -1175,6 +1177,7 @@ llvmpipe_create_screen(struct sw_winsys *winsys)
 
 #ifdef HAVE_LINUX_UDMABUF_H
    screen->udmabuf_fd = open("/dev/udmabuf", O_RDWR);
+   llvmpipe_init_screen_fence_funcs(&screen->base);
 #endif
 
    uint64_t alignment;

src/gallium/drivers/llvmpipe/lp_screen.h

@@ -85,6 +85,9 @@ struct llvmpipe_screen
    uint64_t mem_file_size;
    struct util_vma_heap mem_heap;
 #endif
+
+   struct llvmpipe_memory_allocation *dummy_dmabuf;
+   int dummy_sync_fd;
 };
 
 

src/gallium/drivers/llvmpipe/lp_texture.h

@@ -51,7 +51,6 @@ enum llvmpipe_memory_fd_type
    LLVMPIPE_MEMORY_FD_TYPE_DMA_BUF,
 };
 
-
 struct pipe_context;
 struct pipe_screen;
 struct llvmpipe_context;