[sanitizer] Fix StackDepotPrintAll

[vitalybuka]

Summary

unlock corrupted backets by using s set by loop to nullptr.
Also StackDepot supports iterating without locking.

[dvyukov]

LGTM with a nit

compiler-rt/lib/sanitizer_common/sanitizer_stackdepotbase.h

183

Strictly speaking this must be memory_order_consume if we remove the lock.

[vitalybuka]

consume

compiler-rt/lib/sanitizer_common/sanitizer_stackdepotbase.h

for (int i = 0; i < kTabSize; ++i) {
     unlock(p, (Node *)(s & ~1UL));
   }
 }
 
 template <class Node, int kReservedBits, int kTabSizeLog>
 void StackDepotBase<Node, kReservedBits, kTabSizeLog>::PrintAll() {
   for (int i = 0; i < kTabSize; ++i) {
     atomic_uintptr_t *p = &tab[i];
-    lock(p);
-    uptr v = atomic_load(p, memory_order_relaxed);
+    uptr v = atomic_load(p, memory_order_consume);
     Node *s = (Node *)(v & ~1UL);
     for (; s; s = s->link) {
       Printf("Stack for id %u:\n", s->id);
       s->load().Print();
     }
-    unlock(p, s);
   }
 }
 
 } // namespace __sanitizer
 
 #endif // SANITIZER_STACKDEPOTBASE_H

compiler-rt/lib/sanitizer_common/tests/sanitizer_stackdepot_test.cpp

TEST(SanitizerCommon, Maybe_StackDepotPrint) {
   EXPECT_NE(i1, i2);
   EXPECT_EXIT((StackDepotPrintAll(), exit(0)), ::testing::ExitedWithCode(0),
               "Stack for id .*#0 0x1.*#1 0x2.*#2 0x3.*#3 0x4.*#4 0x7.*");
   EXPECT_EXIT(
       (StackDepotPrintAll(), exit(0)), ::testing::ExitedWithCode(0),
       "Stack for id .*#0 0x1.*#1 0x2.*#2 0x3.*#3 0x4.*#4 0x8.*#5 0x9.*");
 }
 
+TEST(SanitizerCommon, StackDepotPrintNoLock) {
+  u32 n = 2000;
+  for (u32 i = 1; i < n; ++i) {
+    uptr array[] = {0x111, 0x222, i, 0x444, 0x777};
+    StackTrace s(array, ARRAY_SIZE(array));
+    CHECK_EQ(i, StackDepotPut(s));
+  }
+  StackDepotPrintAll();
+  for (u32 i = 1; i < n; ++i) {
+    uptr array[] = {0x111, 0x222, i, 0x444, 0x777};
+    StackTrace s(array, ARRAY_SIZE(array));
+    CHECK_EQ(i, StackDepotPut(s));
+  }
+}
+
 TEST(SanitizerCommon, StackDepotReverseMap) {
   uptr array1[] = {1, 2, 3, 4, 5};
   uptr array2[] = {7, 1, 3, 0};
   uptr array3[] = {10, 2, 5, 3};
   uptr array4[] = {1, 3, 2, 5};
   u32 ids[4] = {0};
   StackTrace s1(array1, ARRAY_SIZE(array1));
   StackTrace s2(array2, ARRAY_SIZE(array2));