From c77e482b60bea40a422691b16af02a429d9c2edc Mon Sep 17 00:00:00 2001 From: Aaron Plattner Date: Mon, 3 Aug 2015 21:15:15 -0700 Subject: [PATCH] compositor: Fix GL_EXT_x11_sync_object race condition The compositor maintains a ring of shared fences with the X server in order to properly synchronize rendering between the X server and the compositor's GPU channel. When all of the fences have been used, the compositor needs to reset one so that it can be reused. It does this by first waiting on the CPU for the fence to become triggered, and then sending a request to the X server to reset the fence. If the compositor's GPU channel is busy processing other work (e.g. the desktop switcher animation), then the X server may process the reset request before the GPU has consumed the fence. This causes the GPU channel to hang. Fix the problem by having the compositor's GPU channel trigger its own fence after waiting for the X server's fence. Wait for that fence on the CPU before sending the reset request to the X server. This ensures that the GPU has consumed the X11 fence before the server resets it. Signed-off-by: Aaron Plattner https://bugzilla.gnome.org/show_bug.cgi?id=728464 --- src/compositor/meta-sync-ring.c | 25 +++++++++++++++++++------ 1 file changed, 19 insertions(+), 6 deletions(-) diff --git a/src/compositor/meta-sync-ring.c b/src/compositor/meta-sync-ring.c index 4ee61f851..44b1c41d7 100644 --- a/src/compositor/meta-sync-ring.c +++ b/src/compositor/meta-sync-ring.c @@ -73,7 +73,8 @@ typedef struct Display *xdisplay; XSyncFence xfence; - GLsync glsync; + GLsync gl_x11_sync; + GLsync gpu_fence; XSyncCounter xcounter; XSyncAlarm xalarm; @@ -118,6 +119,8 @@ static void (*meta_gl_wait_sync) (GLsync sync, static GLsync (*meta_gl_import_sync) (GLenum external_sync_type, GLintptr external_sync, GLbitfield flags); +static GLsync (*meta_gl_fence_sync) (GLenum condition, + GLbitfield flags); static MetaSyncRing * meta_sync_ring_get (void) @@ -224,6 +227,8 @@ load_required_symbols (void) goto out; if (!load_gl_symbol ("glImportSyncEXT", (void **) &meta_gl_import_sync)) goto out; + if (!load_gl_symbol ("glFenceSync", (void **) &meta_gl_fence_sync)) + goto out; success = TRUE; out: @@ -238,7 +243,8 @@ meta_sync_insert (MetaSync *self) XSyncTriggerFence (self->xdisplay, self->xfence); XFlush (self->xdisplay); - meta_gl_wait_sync (self->glsync, 0, GL_TIMEOUT_IGNORED); + meta_gl_wait_sync (self->gl_x11_sync, 0, GL_TIMEOUT_IGNORED); + self->gpu_fence = meta_gl_fence_sync (GL_SYNC_GPU_COMMANDS_COMPLETE, 0); self->state = META_SYNC_STATE_WAITING; } @@ -255,9 +261,13 @@ meta_sync_check_update_finished (MetaSync *self, status = GL_ALREADY_SIGNALED; break; case META_SYNC_STATE_WAITING: - status = meta_gl_client_wait_sync (self->glsync, 0, timeout); + status = meta_gl_client_wait_sync (self->gpu_fence, 0, timeout); if (status == GL_ALREADY_SIGNALED || status == GL_CONDITION_SATISFIED) - self->state = META_SYNC_STATE_DONE; + { + self->state = META_SYNC_STATE_DONE; + meta_gl_delete_sync (self->gpu_fence); + self->gpu_fence = 0; + } break; default: break; @@ -312,7 +322,8 @@ meta_sync_new (Display *xdisplay) self->xdisplay = xdisplay; self->xfence = XSyncCreateFence (xdisplay, DefaultRootWindow (xdisplay), FALSE); - self->glsync = meta_gl_import_sync (GL_SYNC_X11_FENCE_EXT, self->xfence, 0); + self->gl_x11_sync = meta_gl_import_sync (GL_SYNC_X11_FENCE_EXT, self->xfence, 0); + self->gpu_fence = 0; self->xcounter = XSyncCreateCounter (xdisplay, SYNC_VALUE_ZERO); @@ -365,6 +376,8 @@ meta_sync_free (MetaSync *self) switch (self->state) { case META_SYNC_STATE_WAITING: + meta_gl_delete_sync (self->gpu_fence); + break; case META_SYNC_STATE_DONE: /* nothing to do */ break; @@ -383,7 +396,7 @@ meta_sync_free (MetaSync *self) break; } - meta_gl_delete_sync (self->glsync); + meta_gl_delete_sync (self->gl_x11_sync); XSyncDestroyFence (self->xdisplay, self->xfence); XSyncDestroyCounter (self->xdisplay, self->xcounter); XSyncDestroyAlarm (self->xdisplay, self->xalarm);