Index: compiler-rt/include/sanitizer/coverage_interface.h
===================================================================
--- compiler-rt/include/sanitizer/coverage_interface.h
+++ compiler-rt/include/sanitizer/coverage_interface.h
@@ -22,8 +22,11 @@
   // Record and dump coverage info.
   void __sanitizer_cov_dump();
 
-  //  Dump collected coverage info. Sorts pcs by module into individual
-  //  .sancov files.
+  // Clear collected coverage info.
+  void __sanitizer_cov_reset();
+
+  // Dump collected coverage info. Sorts pcs by module into individual .sancov
+  // files.
   void __sanitizer_dump_coverage(const uintptr_t *pcs, uintptr_t len);
 
 #ifdef __cplusplus
Index: compiler-rt/lib/sanitizer_common/sanitizer_coverage_interface.inc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_coverage_interface.inc
+++ compiler-rt/lib/sanitizer_common/sanitizer_coverage_interface.inc
@@ -9,6 +9,7 @@
 // Sanitizer Coverage interface list.
 //===----------------------------------------------------------------------===//
 INTERFACE_FUNCTION(__sanitizer_cov_dump)
+INTERFACE_FUNCTION(__sanitizer_cov_reset)
 INTERFACE_FUNCTION(__sanitizer_dump_coverage)
 INTERFACE_FUNCTION(__sanitizer_dump_trace_pc_guard_coverage)
 INTERFACE_WEAK_FUNCTION(__sancov_default_options)
Index: compiler-rt/lib/sanitizer_common/sanitizer_coverage_libcdep_new.cc
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_coverage_libcdep_new.cc
+++ compiler-rt/lib/sanitizer_common/sanitizer_coverage_libcdep_new.cc
@@ -111,6 +111,7 @@
     initialized = true;
     InitializeSancovFlags();
 
+    SpinMutexLock l(&pc_vector_mtx);
     pc_vector.Initialize(0);
   }
 
@@ -119,26 +120,36 @@
     CHECK(!*start);
     CHECK_NE(start, end);
 
+    SpinMutexLock l(&pc_vector_mtx);
     u32 i = pc_vector.size();
     for (u32* p = start; p < end; p++) *p = ++i;
     pc_vector.resize(i);
   }
 
   void TracePcGuard(u32* guard, uptr pc) {
-    atomic_uint32_t* guard_ptr = reinterpret_cast<atomic_uint32_t*>(guard);
-    u32 idx = atomic_exchange(guard_ptr, 0, memory_order_relaxed);
+    u32 idx = *guard;
     if (!idx) return;
     // we start indices from 1.
-    pc_vector[idx - 1] = pc;
+    atomic_uintptr_t* pc_ptr =
+        reinterpret_cast<atomic_uintptr_t*>(&pc_vector[idx - 1]);
+    if (atomic_load(pc_ptr, memory_order_relaxed) == 0)
+      atomic_store(pc_ptr, pc, memory_order_relaxed);
+  }
+
+  void Reset() {
+    SpinMutexLock l(&pc_vector_mtx);
+    internal_memset(&pc_vector[0], 0, sizeof(pc_vector[0]) * pc_vector.size());
   }
 
   void Dump() {
     if (!initialized || !common_flags()->coverage) return;
+    SpinMutexLock l(&pc_vector_mtx);
     __sanitizer_dump_coverage(pc_vector.data(), pc_vector.size());
   }
 
  private:
   bool initialized;
+  StaticSpinMutex pc_vector_mtx;
   InternalMmapVectorNoCtor<uptr> pc_vector;
 };
 
@@ -181,6 +192,9 @@
 SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov_dump() {
   __sanitizer_dump_trace_pc_guard_coverage();
 }
+SANITIZER_INTERFACE_ATTRIBUTE void __sanitizer_cov_reset() {
+  __sancov::pc_guard_controller.Reset();
+}
 // Default empty implementations (weak). Users should redefine them.
 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp, void) {}
 SANITIZER_INTERFACE_WEAK_DEF(void, __sanitizer_cov_trace_cmp1, void) {}
Index: compiler-rt/test/asan/TestCases/Posix/coverage-reset.cc
===================================================================
--- /dev/null
+++ compiler-rt/test/asan/TestCases/Posix/coverage-reset.cc
@@ -0,0 +1,65 @@
+// RUN: %clangxx_asan -fsanitize-coverage=func,trace-pc-guard -DSHARED %s -shared -o %dynamiclib -fPIC %ld_flags_rpath_so
+// RUN: %clangxx_asan -fsanitize-coverage=func,trace-pc-guard %s %ld_flags_rpath_exe -o %t
+// RUN: rm -rf %T/coverage-reset && mkdir -p %T/coverage-reset && cd %T/coverage-reset
+// RUN: %env_asan_opts=coverage=1:verbosity=1 %run %t 2>&1 | FileCheck %s
+//
+// UNSUPPORTED: ios
+
+#include <stdio.h>
+
+#include <sanitizer/coverage_interface.h>
+
+#ifdef SHARED
+void bar1() { printf("bar1\n"); }
+void bar2() { printf("bar2\n"); }
+#else
+__attribute__((noinline)) void foo1() { printf("foo1\n"); }
+__attribute__((noinline)) void foo2() { printf("foo2\n"); }
+void bar1();
+void bar2();
+
+int main(int argc, char **argv) {
+  fprintf(stderr, "RESET");
+  __sanitizer_cov_reset();
+  foo1();
+  foo2();
+  bar1();
+  bar2();
+  __sanitizer_cov_dump();
+// CHECK: RESET
+// CHECK: SanitizerCoverage: ./coverage-reset.cc{{.*}}.sancov: 2 PCs written
+// CHECK: SanitizerCoverage: ./libcoverage-reset.cc{{.*}}.sancov: 2 PCs written
+
+  fprintf(stderr, "RESET");
+  __sanitizer_cov_reset();
+  foo1();
+  bar1();
+  __sanitizer_cov_dump();
+// CHECK: RESET
+// CHECK: SanitizerCoverage: ./coverage-reset.cc{{.*}}.sancov: 1 PCs written
+// CHECK: SanitizerCoverage: ./libcoverage-reset.cc{{.*}}.sancov: 1 PCs written
+
+  fprintf(stderr, "RESET");
+  __sanitizer_cov_reset();
+  foo1();
+  foo2();
+  __sanitizer_cov_dump();
+// CHECK: RESET
+// CHECK: SanitizerCoverage: ./coverage-reset.cc{{.*}}.sancov: 2 PCs written
+
+  fprintf(stderr, "RESET");
+  __sanitizer_cov_reset();
+  bar1();
+  bar2();
+  __sanitizer_cov_dump();
+// CHECK: RESET
+// CHECK: SanitizerCoverage: ./libcoverage-reset.cc{{.*}}.sancov: 2 PCs written
+
+  fprintf(stderr, "RESET");
+  __sanitizer_cov_reset();
+// CHECK: RESET
+
+  bar2();
+// CHECK: SanitizerCoverage: ./libcoverage-reset.cc{{.*}}.sancov: 1 PCs written
+}
+#endif