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Merge pull request #29535 from vrabaud/persistence

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Fix benign TSAN warning in TRUCO
This commit is contained in:
Abhishek Gola
2026-07-31 16:43:12 +05:30
committed by GitHub
parent 9548c7ea4e 3924183f42
commit 32dcb2ea6c
1 changed files with 47 additions and 18 deletions
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65
modules/imgproc/src/contours_truco.cpp
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@@ -2,10 +2,36 @@
#include "precomp.hpp"
#include "contours_common.hpp"
#include "opencv2/core/hal/intrin.hpp"
#include <map>
#include <atomic>
namespace{
// Atomic operations to avoid data race between findStartContourPoint and
// traceExternalContourMock. The race is benign functionally because threads
// only modify FOREGROUND (255) to VISITED_OUTER_RIGHT (100) or VISITED_ (200),
// all of which are NON-ZERO. findStartContourPoint only cares if a pixel is
// zero or non-zero, so its termination conditions are unchanged. However,
// concurrent read/write of different values is legally UB in C++ and triggers
// TSAN.
inline uchar atomicLoad(const uchar* ptr) {
#ifdef CV_THREAD_SANITIZER
if constexpr (sizeof(std::atomic<uchar>) == sizeof(uchar)) {
return reinterpret_cast<const std::atomic<uchar>*>(ptr)->load(std::memory_order_relaxed);
}
#endif
return *ptr;
}
inline void atomicStore(uchar* ptr, uchar val) {
#ifdef CV_THREAD_SANITIZER
if constexpr (sizeof(std::atomic<uchar>) == sizeof(uchar)) {
reinterpret_cast<std::atomic<uchar>*>(ptr)->store(val, std::memory_order_relaxed);
return;
}
#endif
*ptr = val;
}
// Tunable block size. 1024 points = 8KB (Fits easily in L1 Cache)
template <size_t BLOCK_SIZE = 2048>
class TRUCOPagedContour {
@@ -186,10 +212,10 @@ public:
int idx = search_idx + n;
// Use offset cache
uchar* neighbor = curr_ptr + offsets_[idx];
if (*neighbor == BACKGROUND) continue;
if (atomicLoad(neighbor) == BACKGROUND) continue;
dir = idx & 7;
if (((search_idx <= 1) || (dir <= search_idx - 2)) && (curr_x!=c && curr_y!=r))//do nt apply to first pixel in the way back
*curr_ptr = VISITED_OUTER_RIGHT;
atomicStore(curr_ptr, VISITED_OUTER_RIGHT);
// --- EXECUTE MOVE ---
curr_y += dy_[dir];
curr_x += dx_[dir];
@@ -238,7 +264,7 @@ public:
for ( n = 0; n < 8; ++n)
{
int idx = search_idx + n;
if ( *(curr_ptr + offsets_[idx]) == BACKGROUND) continue;
if (atomicLoad(curr_ptr + offsets_[idx]) == BACKGROUND) continue;
if(curr_x+ dx_[ idx & 7]!=c+1 || curr_y+ dy_[ idx & 7]!=r-1) return false;
break;
}
@@ -254,7 +280,7 @@ public:
int idx = search_idx + n;
// Use offset cache
uchar* neighbor = curr_ptr + offsets_[idx];
if (*neighbor == BACKGROUND) continue;
if (atomicLoad(neighbor) == BACKGROUND) continue;
dir = idx & 7;
// --- EXECUTE MOVE ---
@@ -268,11 +294,11 @@ public:
}
if ((search_idx <= 1) || (dir <= search_idx - 2))
{
*curr_ptr = VISITED_OUTER_RIGHT;
atomicStore(curr_ptr, VISITED_OUTER_RIGHT);
}
else if (*curr_ptr == FOREGROUND)
else if (atomicLoad(curr_ptr) == FOREGROUND)
{
*curr_ptr = VISITED_;
atomicStore(curr_ptr, VISITED_);
}
// Short-circuit Jacob's Check
@@ -291,7 +317,7 @@ public:
}
if (is_first_move) {
if(dir==-1){//single pixel
*curr_ptr = VISITED_OUTER_RIGHT;
atomicStore(curr_ptr, VISITED_OUTER_RIGHT);
break;//not moved
}
start_dir = dir;
@@ -328,7 +354,7 @@ public:
if ((c = findStartContourPoint(row_ptr, cols, c)) == cols) break;
// 2. CHECK: Only process if actually FOREGROUND (redundancy check)
if (row_ptr[c] == FOREGROUND && r<rowRange.end )
if (atomicLoad(&row_ptr[c]) == FOREGROUND && r<rowRange.end)
{
if( traceContour(&buffer,r,c,row_ptr,rowRange,true)){
// Post-processing
@@ -345,7 +371,7 @@ public:
}
}
}
else if( row_ptr[c] == FOREGROUND && r==rowRange.end ){//extra step to mark east pixels only so that internal contours can be correctly extracted in this line
else if (atomicLoad(&row_ptr[c]) == FOREGROUND && r==rowRange.end){//extra step to mark east pixels only so that internal contours can be correctly extracted in this line
traceExternalContourMock(r,c,row_ptr,rowRange);
}
@@ -353,7 +379,7 @@ public:
c = findEndContourPoint(row_ptr, cols, c + 1);
if(c>=cols)break;//end of row
//internal contour
if(row_ptr[c-1]>VISITED_OUTER_RIGHT && r>rowRange.start){//inner contours of first line are handled by the thread above
if (atomicLoad(&row_ptr[c - 1]) > VISITED_OUTER_RIGHT && r>rowRange.start){//inner contours of first line are handled by the thread above
if(traceContour(&buffer,r,c-1,row_ptr,rowRange,false)){
// Post-processing
@@ -376,7 +402,7 @@ public:
static inline int findStartContourPoint(uchar* src_data, int width, int j)
{
#if (CV_SIMD || CV_SIMD_SCALABLE)
#if (CV_SIMD || CV_SIMD_SCALABLE) && !defined(CV_THREAD_SANITIZER)
cv::v_uint8 v_zero = cv::vx_setzero_u8();
for (; j <= width - cv::VTraits<cv::v_uint8>::vlanes(); j += cv::VTraits<cv::v_uint8>::vlanes())
{
@@ -388,14 +414,16 @@ public:
}
}
#endif
for (; j < width && !src_data[j]; ++j)
;
for (; j < width; ++j) {
if (atomicLoad(&src_data[j])) break;
}
return j;
}
inline static int findEndContourPoint(uchar* src_data,int width, int j)
{
#if (CV_SIMD || CV_SIMD_SCALABLE)
#if (CV_SIMD || CV_SIMD_SCALABLE) && !defined(CV_THREAD_SANITIZER)
if (j < width && !src_data[j])
{
return j;
@@ -414,8 +442,9 @@ public:
}
}
#endif
for (; j < width && src_data[j]; ++j)
;
for (; j < width; ++j) {
if (atomicLoad(&src_data[j]) == 0) break;
}
return j;
}