st/wgl: add some mutex checking code

This would have caught the locking bug that was fixed in the earlier
"st/wgl: fix locking issue in stw_st_framebuffer_present_locked()"
patch.

v2: minor coding style changes by Brian.

Reviewed-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Charmaine Lee <charmainel@vmware.com>

1 files changed, 26 insertions, 0 deletions

diff --git a/src/gallium/state_trackers/wgl/stw_st.c b/src/gallium/state_trackers/wgl/stw_st.c
index ecf4cfc..78586db 100644
--- a/src/gallium/state_trackers/wgl/stw_st.c
+++ b/src/gallium/state_trackers/wgl/stw_st.c
@@ -52,6 +52,28 @@ stw_st_framebuffer(struct st_framebuffer_iface *stfb)
    return (struct stw_st_framebuffer *) stfb;
 }
 
+
+/**
+ * Is the given mutex held by the calling thread?
+ */
+static bool
+own_mutex(const CRITICAL_SECTION *cs)
+{
+   // We can't compare OwningThread with our thread handle/id (see
+   // http://stackoverflow.com/a/12675635 ) but we can compare with the
+   // OwningThread member of a critical section we know we own.
+   CRITICAL_SECTION dummy;
+   InitializeCriticalSection(&dummy);
+   EnterCriticalSection(&dummy);
+   if (0)
+      _debug_printf("%p %p\n", cs->OwningThread, dummy.OwningThread);
+   bool ret = cs->OwningThread == dummy.OwningThread;
+   LeaveCriticalSection(&dummy);
+   DeleteCriticalSection(&dummy);
+   return ret;
+}
+
+
 /**
  * Remove outdated textures and create the requested ones.
  */
@@ -165,6 +187,8 @@ stw_st_framebuffer_present_locked(HDC hdc,
    struct stw_st_framebuffer *stwfb = stw_st_framebuffer(stfb);
    struct pipe_resource *resource;
 
+   assert(own_mutex(&stwfb->fb->mutex));
+
    resource = stwfb->textures[statt];
    if (resource) {
       stw_framebuffer_present_locked(hdc, stwfb->fb, resource);
@@ -173,6 +197,8 @@ stw_st_framebuffer_present_locked(HDC hdc,
       stw_framebuffer_unlock(stwfb->fb);
    }
 
+   assert(!own_mutex(&stwfb->fb->mutex));
+
    return TRUE;
 }