[Intel-gfx] [PATCH 2/2] intel: Use atomic refcounters

Chris Wilson chris at chris-wilson.co.uk
Fri Oct 2 05:31:35 CEST 2009


As the target architecture for Intel GPUs is the x86, we can presume to
have reasonable compiler support for Intel atomic intrinsics, i.e. gcc,
and so use those in preference to pulling in a complicated mess of
fragile assembly.

Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
---
 configure.ac                    |   17 +++++
 libdrm/intel/Makefile.am        |    1 +
 libdrm/intel/intel_bufmgr_gem.c |  136 +++++++++++++++++++-------------------
 3 files changed, 86 insertions(+), 68 deletions(-)

diff --git a/configure.ac b/configure.ac
index d707052..2852962 100644
--- a/configure.ac
+++ b/configure.ac
@@ -146,6 +146,23 @@ if test "x$HAVE_LIBUDEV" = xyes; then
 fi
 AM_CONDITIONAL(HAVE_LIBUDEV, [test "x$HAVE_LIBUDEV" = xyes])
 
+# Check for atomic intrinsics
+AC_CACHE_CHECK([for native atomic primitives], drm_cv_atomic_primitives,
+[
+	drm_cv_atomic_primitives="none"
+
+	AC_TRY_LINK([
+int atomic_add(int i) { return __sync_fetch_and_add (&i, 1); }
+int atomic_cmpxchg(int i, int j, int k) { return __sync_val_compare_and_swap (&i, j, k); }
+], [],
+	  drm_cv_atomic_primitives="Intel"
+	  )
+])
+if test "x$drm_cv_atomic_primitives" = xIntel; then
+	AC_DEFINE(HAVE_INTEL_ATOMIC_PRIMITIVES, 1,
+		  [Enable if your compiler supports the Intel __sync_* atomic primitives])
+fi
+
 AC_SUBST(WARN_CFLAGS)
 AC_OUTPUT([
 	Makefile
diff --git a/libdrm/intel/Makefile.am b/libdrm/intel/Makefile.am
index e68a3b4..28f8952 100644
--- a/libdrm/intel/Makefile.am
+++ b/libdrm/intel/Makefile.am
@@ -35,6 +35,7 @@ libdrm_intel_la_LDFLAGS = -version-number 1:0:0 -no-undefined
 libdrm_intel_la_LIBADD = ../libdrm.la @PTHREADSTUBS_LIBS@ @CLOCK_LIB@
 
 libdrm_intel_la_SOURCES = \
+	intel_atomic.h \
 	intel_bufmgr.c \
 	intel_bufmgr_priv.h \
 	intel_bufmgr_fake.c \
diff --git a/libdrm/intel/intel_bufmgr_gem.c b/libdrm/intel/intel_bufmgr_gem.c
index 6125f6b..73325ca 100644
--- a/libdrm/intel/intel_bufmgr_gem.c
+++ b/libdrm/intel/intel_bufmgr_gem.c
@@ -53,6 +53,7 @@
 
 #include "errno.h"
 #include "libdrm_lists.h"
+#include "intel_atomic.h"
 #include "intel_bufmgr.h"
 #include "intel_bufmgr_priv.h"
 #include "intel_chipset.h"
@@ -102,7 +103,7 @@ typedef struct _drm_intel_bufmgr_gem {
 struct _drm_intel_bo_gem {
     drm_intel_bo bo;
 
-    int refcount;
+    atomic_t refcount;
     /** Boolean whether the mmap ioctl has been called for this buffer yet. */
     uint32_t gem_handle;
     const char *name;
@@ -172,8 +173,6 @@ struct _drm_intel_bo_gem {
     int reloc_tree_fences;
 };
 
-static void drm_intel_gem_bo_reference_locked(drm_intel_bo *bo);
-
 static unsigned int
 drm_intel_gem_estimate_batch_space(drm_intel_bo **bo_array, int count);
 
@@ -189,6 +188,9 @@ drm_intel_gem_bo_set_tiling(drm_intel_bo *bo, uint32_t *tiling_mode,
 			    uint32_t stride);
 
 static void
+drm_intel_gem_bo_unreference_locked(drm_intel_bo *bo);
+
+static void
 drm_intel_gem_bo_unreference(drm_intel_bo *bo);
 
 static void
@@ -237,6 +239,15 @@ static void drm_intel_gem_dump_validation_list(drm_intel_bufmgr_gem *bufmgr_gem)
     }
 }
 
+static void
+drm_intel_gem_bo_reference(drm_intel_bo *bo)
+{
+    drm_intel_bo_gem *bo_gem = (drm_intel_bo_gem *)bo;
+
+    assert(atomic_read(&bo_gem->refcount) > 0);
+    atomic_inc(&bo_gem->refcount);
+}
+
 /**
  * Adds the given buffer to the list of buffers to be validated (moved into the
  * appropriate memory type) with the next batch submission.
@@ -280,7 +291,7 @@ drm_intel_add_validate_buffer(drm_intel_bo *bo)
     bufmgr_gem->exec_objects[index].alignment = 0;
     bufmgr_gem->exec_objects[index].offset = 0;
     bufmgr_gem->exec_bos[index] = bo;
-    drm_intel_gem_bo_reference_locked(bo);
+    drm_intel_gem_bo_reference(bo);
     bufmgr_gem->exec_count++;
 }
 
@@ -436,7 +447,7 @@ retry:
     }
 
     bo_gem->name = name;
-    bo_gem->refcount = 1;
+    atomic_set(&bo_gem->refcount, 1);
     bo_gem->validate_index = -1;
     bo_gem->reloc_tree_size = bo_gem->bo.size;
     bo_gem->reloc_tree_fences = 0;
@@ -499,7 +510,7 @@ drm_intel_bo_gem_create_from_name(drm_intel_bufmgr *bufmgr, const char *name,
     bo_gem->bo.virtual = NULL;
     bo_gem->bo.bufmgr = bufmgr;
     bo_gem->name = name;
-    bo_gem->refcount = 1;
+    atomic_set (&bo_gem->refcount, 1);
     bo_gem->validate_index = -1;
     bo_gem->gem_handle = open_arg.handle;
     bo_gem->global_name = handle;
@@ -525,27 +536,6 @@ drm_intel_bo_gem_create_from_name(drm_intel_bufmgr *bufmgr, const char *name,
 }
 
 static void
-drm_intel_gem_bo_reference(drm_intel_bo *bo)
-{
-    drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *)bo->bufmgr;
-    drm_intel_bo_gem *bo_gem = (drm_intel_bo_gem *)bo;
-
-    assert(bo_gem->refcount > 0);
-    pthread_mutex_lock(&bufmgr_gem->lock);
-    bo_gem->refcount++;
-    pthread_mutex_unlock(&bufmgr_gem->lock);
-}
-
-static void
-drm_intel_gem_bo_reference_locked(drm_intel_bo *bo)
-{
-    drm_intel_bo_gem *bo_gem = (drm_intel_bo_gem *)bo;
-
-    assert(bo_gem->refcount > 0);
-    bo_gem->refcount++;
-}
-
-static void
 drm_intel_gem_bo_free(drm_intel_bo *bo)
 {
     drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *)bo->bufmgr;
@@ -594,64 +584,74 @@ drm_intel_gem_cleanup_bo_cache(drm_intel_bufmgr_gem *bufmgr_gem, time_t time)
 }
 
 static void
-drm_intel_gem_bo_unreference_locked(drm_intel_bo *bo)
+drm_intel_gem_bo_unreference_final(drm_intel_bo *bo)
 {
     drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *)bo->bufmgr;
     drm_intel_bo_gem *bo_gem = (drm_intel_bo_gem *)bo;
+    struct drm_intel_gem_bo_bucket *bucket;
+    uint32_t tiling_mode;
 
-    assert(bo_gem->refcount > 0);
-    if (--bo_gem->refcount == 0) {
-	struct drm_intel_gem_bo_bucket *bucket;
-	uint32_t tiling_mode;
-
-	if (bo_gem->relocs != NULL) {
-	    int i;
+    if (bo_gem->relocs != NULL) {
+	int i;
 
-	    /* Unreference all the target buffers */
-	    for (i = 0; i < bo_gem->reloc_count; i++)
-		 drm_intel_gem_bo_unreference_locked(bo_gem->reloc_target_bo[i]);
-	    free(bo_gem->reloc_target_bo);
-	    free(bo_gem->relocs);
-	}
+	/* Unreference all the target buffers */
+	for (i = 0; i < bo_gem->reloc_count; i++)
+	     drm_intel_gem_bo_unreference_locked(bo_gem->reloc_target_bo[i]);
+	free(bo_gem->reloc_target_bo);
+	free(bo_gem->relocs);
+    }
 
-	DBG("bo_unreference final: %d (%s)\n",
-	    bo_gem->gem_handle, bo_gem->name);
+    DBG("bo_unreference final: %d (%s)\n",
+	bo_gem->gem_handle, bo_gem->name);
 
-	bucket = drm_intel_gem_bo_bucket_for_size(bufmgr_gem, bo->size);
-	/* Put the buffer into our internal cache for reuse if we can. */
-	tiling_mode = I915_TILING_NONE;
-	if (bufmgr_gem->bo_reuse && bo_gem->reusable && bucket != NULL &&
-	    drm_intel_gem_bo_set_tiling(bo, &tiling_mode, 0) == 0)
-	{
-	    struct timespec time;
+    bucket = drm_intel_gem_bo_bucket_for_size(bufmgr_gem, bo->size);
+    /* Put the buffer into our internal cache for reuse if we can. */
+    tiling_mode = I915_TILING_NONE;
+    if (bufmgr_gem->bo_reuse && bo_gem->reusable && bucket != NULL &&
+	drm_intel_gem_bo_set_tiling(bo, &tiling_mode, 0) == 0)
+    {
+	struct timespec time;
 
-	    clock_gettime(CLOCK_MONOTONIC, &time);
-	    bo_gem->free_time = time.tv_sec;
+	clock_gettime(CLOCK_MONOTONIC, &time);
+	bo_gem->free_time = time.tv_sec;
 
-	    bo_gem->name = NULL;
-	    bo_gem->validate_index = -1;
-	    bo_gem->relocs = NULL;
-	    bo_gem->reloc_target_bo = NULL;
-	    bo_gem->reloc_count = 0;
+	bo_gem->name = NULL;
+	bo_gem->validate_index = -1;
+	bo_gem->relocs = NULL;
+	bo_gem->reloc_target_bo = NULL;
+	bo_gem->reloc_count = 0;
 
-	    DRMLISTADDTAIL(&bo_gem->head, &bucket->head);
+	DRMLISTADDTAIL(&bo_gem->head, &bucket->head);
 
-	    drm_intel_gem_bo_madvise(bufmgr_gem, bo_gem, I915_MADV_DONTNEED);
-	    drm_intel_gem_cleanup_bo_cache(bufmgr_gem, time.tv_sec);
-	} else {
-	    drm_intel_gem_bo_free(bo);
-	}
+	drm_intel_gem_bo_madvise(bufmgr_gem, bo_gem, I915_MADV_DONTNEED);
+	drm_intel_gem_cleanup_bo_cache(bufmgr_gem, time.tv_sec);
+    } else {
+	drm_intel_gem_bo_free(bo);
     }
 }
 
 static void
+drm_intel_gem_bo_unreference_locked(drm_intel_bo *bo)
+{
+    drm_intel_bo_gem *bo_gem = (drm_intel_bo_gem *)bo;
+
+    assert(atomic_read(&bo_gem->refcount) > 0);
+    if (atomic_dec_and_test (&bo_gem->refcount))
+	drm_intel_gem_bo_unreference_final(bo);
+}
+
+static void
 drm_intel_gem_bo_unreference(drm_intel_bo *bo)
 {
-    drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *)bo->bufmgr;
+    drm_intel_bo_gem *bo_gem = (drm_intel_bo_gem *)bo;
 
-    pthread_mutex_lock(&bufmgr_gem->lock);
-    drm_intel_gem_bo_unreference_locked(bo);
-    pthread_mutex_unlock(&bufmgr_gem->lock);
+    assert(atomic_read(&bo_gem->refcount) > 0);
+    if (atomic_dec_and_test (&bo_gem->refcount)) {
+	drm_intel_bufmgr_gem *bufmgr_gem = (drm_intel_bufmgr_gem *)bo->bufmgr;
+	pthread_mutex_lock(&bufmgr_gem->lock);
+	drm_intel_gem_bo_unreference_final(bo);
+	pthread_mutex_unlock(&bufmgr_gem->lock);
+    }
 }
 
 static int
@@ -1018,7 +1018,7 @@ drm_intel_gem_bo_emit_reloc(drm_intel_bo *bo, uint32_t offset,
     bo_gem->relocs[bo_gem->reloc_count].presumed_offset = target_bo->offset;
 
     bo_gem->reloc_target_bo[bo_gem->reloc_count] = target_bo;
-    drm_intel_gem_bo_reference_locked(target_bo);
+    drm_intel_gem_bo_reference(target_bo);
 
     bo_gem->reloc_count++;
 
-- 
1.6.4.3




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