GPU Display: Fix race condition

davidrohr · davidrohr · commit b8b824ce09d7 · 2024-11-14T12:07:02.000+01:00
diff --git a/GPU/GPUTracking/display/render/GPUDisplayDraw.cxx b/GPU/GPUTracking/display/render/GPUDisplayDraw.cxx
@@ -27,6 +27,7 @@
 #include "GPUTPCGMPropagator.h"
 #include "GPUTPCMCInfo.h"
 #include "GPUParam.inc"
+#include "GPUCommonMath.h"
 
 #include <type_traits>
 
@@ -66,8 +67,12 @@ inline void GPUDisplay::insertVertexList(int32_t iSlice, size_t first, size_t la
 inline void GPUDisplay::drawPointLinestrip(int32_t iSlice, int32_t cid, int32_t id, int32_t id_limit)
 {
   mVertexBuffer[iSlice].emplace_back(mGlobalPos[cid].x, mGlobalPos[cid].y * mYFactor, mCfgH.projectXY ? 0 : mGlobalPos[cid].z);
-  if (mGlobalPos[cid].w < id_limit) {
-    mGlobalPos[cid].w = id;
+  float curVal;
+  while ((curVal = mGlobalPos[cid].w) < id_limit) {
+    if (GPUCommonMath::AtomicCAS(&mGlobalPos[cid].w, curVal, (float)id)) {
+      break;
+    }
+    curVal = mGlobalPos[cid].w;
   }
 }
 

Original file line number	Diff line number	Diff line change
`@@ -27,6 +27,7 @@`
`27`	`27`	`#include "GPUTPCGMPropagator.h"`
`28`	`28`	`#include "GPUTPCMCInfo.h"`
`29`	`29`	`#include "GPUParam.inc"`
	`30`	`+#include "GPUCommonMath.h"`
`30`	`31`
`31`	`32`	`#include <type_traits>`
`32`	`33`
`@@ -66,8 +67,12 @@ inline void GPUDisplay::insertVertexList(int32_t iSlice, size_t first, size_t la`
`66`	`67`	`inline void GPUDisplay::drawPointLinestrip(int32_t iSlice, int32_t cid, int32_t id, int32_t id_limit)`
`67`	`68`	`{`
`68`	`69`	`mVertexBuffer[iSlice].emplace_back(mGlobalPos[cid].x, mGlobalPos[cid].y * mYFactor, mCfgH.projectXY ? 0 : mGlobalPos[cid].z);`
`69`		`- if (mGlobalPos[cid].w < id_limit) {`
`70`		`- mGlobalPos[cid].w = id;`
	`70`	`+ float curVal;`
	`71`	`+ while ((curVal = mGlobalPos[cid].w) < id_limit) {`
	`72`	`+ if (GPUCommonMath::AtomicCAS(&mGlobalPos[cid].w, curVal, (float)id)) {`
	`73`	`+ break;`
	`74`	`+ }`
	`75`	`+ curVal = mGlobalPos[cid].w;`
`71`	`76`	`}`
`72`	`77`	`}`
`73`	`78`