radeon: Add protection against recursive DRM locking.

Reference counting protects DRM lock call from recursive locking that would
cause hang. Code also adds optional debugging output for recursive call that
is compiled only if NDEBUG is not defined.

This code is not 100% thread safe because mesa doesn't include increment and
test atomic operation. There is built-in gcc functions but they are only
available from gcc 4.2.

4 files changed, 64 insertions, 3 deletions

diff --git a/src/mesa/drivers/dri/radeon/radeon_common_context.c b/src/mesa/drivers/dri/radeon/radeon_common_context.c
index 5e744f9deb..d68aa2bd62 100644
--- a/src/mesa/drivers/dri/radeon/radeon_common_context.c
+++ b/src/mesa/drivers/dri/radeon/radeon_common_context.c
@@ -211,6 +211,7 @@ GLboolean radeonInitContext(radeonContextPtr radeon,
 	radeon->dri.screen = sPriv;
 	radeon->dri.hwContext = driContextPriv->hHWContext;
 	radeon->dri.hwLock = &sPriv->pSAREA->lock;
+	radeon->dri.hwLockCount = 0;
 	radeon->dri.fd = sPriv->fd;
 	radeon->dri.drmMinor = sPriv->drm_version.minor;
 
diff --git a/src/mesa/drivers/dri/radeon/radeon_common_context.h b/src/mesa/drivers/dri/radeon/radeon_common_context.h
index d7e94a6894..f8e1a25c9f 100644
--- a/src/mesa/drivers/dri/radeon/radeon_common_context.h
+++ b/src/mesa/drivers/dri/radeon/radeon_common_context.h
@@ -365,6 +365,7 @@ struct radeon_dri_mirror {
 
 	drm_context_t hwContext;
 	drm_hw_lock_t *hwLock;
+	int hwLockCount;
 	int fd;
 	int drmMinor;
 };
diff --git a/src/mesa/drivers/dri/radeon/radeon_lock.c b/src/mesa/drivers/dri/radeon/radeon_lock.c
index 2f0ed1cfce..6294b7e42b 100644
--- a/src/mesa/drivers/dri/radeon/radeon_lock.c
+++ b/src/mesa/drivers/dri/radeon/radeon_lock.c
@@ -86,8 +86,34 @@ void radeonGetLock(radeonContextPtr rmesa, GLuint flags)
 
 	rmesa->vtbl.get_lock(rmesa);
 }
-
-void radeon_lock_hardware(radeonContextPtr radeon)
+#ifndef NDEBUG
+struct lock_debug {
+	const char* function;
+	const char* file;
+	int line;
+};
+
+static struct lock_debug ldebug = {0};
+#endif
+
+#if 0
+/** TODO: use atomic operations for reference counting **/
+/** gcc 4.2 has builtin functios for this **/
+#define ATOMIC_INC_AND_FETCH(atomic) __sync_add_and_fetch(&atomic, 1)
+#define ATOMIC_DEC_AND_FETCH(atomic) __sync_sub_and_fetch(&atomic, 1)
+#else
+#define ATOMIC_INC_AND_FETCH(atomic) (++atomic)
+#define ATOMIC_DEC_AND_FETCH(atomic) (--atomic)
+#endif
+
+
+void radeon_lock_hardware(radeonContextPtr radeon
+#ifndef NDEBUG
+		,const char* function
+		,const char* file
+		,const int line
+#endif
+		)
 {
 	char ret = 0;
 	struct radeon_framebuffer *rfb = NULL;
@@ -102,16 +128,39 @@ void radeon_lock_hardware(radeonContextPtr radeon)
 	}
 
 	if (!radeon->radeonScreen->driScreen->dri2.enabled) {
+		if (ATOMIC_INC_AND_FETCH(radeon->dri.hwLockCount) > 1)
+		{
+#ifndef NDEBUG
+			if ( RADEON_DEBUG & DEBUG_SANITY )
+				fprintf(stderr, "*** %d times of recursive call to %s ***\n"
+						"Original call was from %s (file: %s line: %d)\n"
+						"Now call is coming from %s (file: %s line: %d)\n"
+						, radeon->dri.hwLockCount, __FUNCTION__
+						, ldebug.function, ldebug.file, ldebug.line
+						, function, file, line
+					   );
+#endif
+			return;
+		}
 		DRM_CAS(radeon->dri.hwLock, radeon->dri.hwContext,
 			 (DRM_LOCK_HELD | radeon->dri.hwContext), ret );
 		if (ret)
 			radeonGetLock(radeon, 0);
+#ifndef NDEBUG
+		ldebug.function = function;
+		ldebug.file = file;
+		ldebug.line = line;
+#endif
 	}
 }
 
 void radeon_unlock_hardware(radeonContextPtr radeon)
 {
 	if (!radeon->radeonScreen->driScreen->dri2.enabled) {
+		if (ATOMIC_DEC_AND_FETCH(radeon->dri.hwLockCount) > 0)
+		{
+			return;
+		}
 		DRM_UNLOCK( radeon->dri.fd,
 			    radeon->dri.hwLock,
 			    radeon->dri.hwContext );
diff --git a/src/mesa/drivers/dri/radeon/radeon_lock.h b/src/mesa/drivers/dri/radeon/radeon_lock.h
index 2817709eed..da5a5b4371 100644
--- a/src/mesa/drivers/dri/radeon/radeon_lock.h
+++ b/src/mesa/drivers/dri/radeon/radeon_lock.h
@@ -48,12 +48,22 @@ WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
 
 extern void radeonGetLock(radeonContextPtr rmesa, GLuint flags);
 
-void radeon_lock_hardware(radeonContextPtr rmesa);
+void radeon_lock_hardware(radeonContextPtr rmesa
+#ifndef NDEBUG
+		,const char* function
+		,const char* file
+		,const int line
+#endif
+		);
 void radeon_unlock_hardware(radeonContextPtr rmesa);
 
 /* Lock the hardware and validate our state.
  */
+#ifdef NDEBUG
 #define LOCK_HARDWARE( rmesa )	radeon_lock_hardware(rmesa)
+#else
+#define LOCK_HARDWARE( rmesa )	radeon_lock_hardware(rmesa, __FUNCTION__, __FILE__, __LINE__)
+#endif
 #define UNLOCK_HARDWARE( rmesa )  radeon_unlock_hardware(rmesa)
 
 #endif