Revert "tsan: add fiber support"

This reverts commit r353817 because we think it broke AARch64 and
PowerPC buildbots.

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@353939 91177308-0d34-0410-b5e6-96231b3b80d8

13 files changed, 2 insertions, 464 deletions

diff --git a/include/sanitizer/tsan_interface.h b/include/sanitizer/tsan_interface.h
index 011b23350..4a98a4e12 100644
--- a/include/sanitizer/tsan_interface.h
+++ b/include/sanitizer/tsan_interface.h
@@ -136,24 +136,6 @@ void __tsan_external_assign_tag(void *addr, void *tag);
 void __tsan_external_read(void *addr, void *caller_pc, void *tag);
 void __tsan_external_write(void *addr, void *caller_pc, void *tag);
 
-// Fiber switching API.
-//   - TSAN context for fiber can be created by __tsan_create_fiber
-//     and freed by __tsan_destroy_fiber.
-//   - TSAN context of current fiber or thread can be obtained
-//     by calling __tsan_get_current_fiber.
-//   - __tsan_switch_to_fiber should be called immediatly before switch
-//     to fiber, such as call of swapcontext.
-//   - Fiber name can be set by __tsan_set_fiber_name.
-void *__tsan_get_current_fiber(void);
-void *__tsan_create_fiber(unsigned flags);
-void __tsan_destroy_fiber(void *fiber);
-void __tsan_switch_to_fiber(void *fiber, unsigned flags);
-void __tsan_set_fiber_name(void *fiber, const char *name);
-
-// Flags for __tsan_switch_to_fiber:
-// Do not establish a happens-before relation between fibers
-const unsigned __tsan_switch_to_fiber_no_sync = 1 << 0;
-
 #ifdef __cplusplus
 }  // extern "C"
 #endif
diff --git a/lib/sanitizer_common/sanitizer_thread_registry.h b/lib/sanitizer_common/sanitizer_thread_registry.h
index 493aa988f..fc38d0f80 100644
--- a/lib/sanitizer_common/sanitizer_thread_registry.h
+++ b/lib/sanitizer_common/sanitizer_thread_registry.h
@@ -31,7 +31,6 @@ enum ThreadStatus {
 enum class ThreadType {
   Regular, // Normal thread
   Worker,  // macOS Grand Central Dispatch (GCD) worker thread
-  Fiber,   // Fiber
 };
 
 // Generic thread context. Specific sanitizer tools may inherit from it.
diff --git a/lib/tsan/rtl/tsan_interceptors.cc b/lib/tsan/rtl/tsan_interceptors.cc
index ef11000c0..b9f245e40 100644
--- a/lib/tsan/rtl/tsan_interceptors.cc
+++ b/lib/tsan/rtl/tsan_interceptors.cc
@@ -554,7 +554,6 @@ static void LongJmp(ThreadState *thr, uptr *env) {
 
 // FIXME: put everything below into a common extern "C" block?
 extern "C" void __tsan_setjmp(uptr sp, uptr mangled_sp) {
-  cur_thread_init();
   SetJmp(cur_thread(), sp, mangled_sp);
 }
 
@@ -943,7 +942,6 @@ extern "C" void *__tsan_thread_start_func(void *arg) {
   void *param = p->param;
   int tid = 0;
   {
-    cur_thread_init();
     ThreadState *thr = cur_thread();
     // Thread-local state is not initialized yet.
     ScopedIgnoreInterceptors ignore;
@@ -1055,9 +1053,6 @@ TSAN_INTERCEPTOR(int, pthread_detach, void *th) {
 TSAN_INTERCEPTOR(void, pthread_exit, void *retval) {
   {
     SCOPED_INTERCEPTOR_RAW(pthread_exit, retval);
-#if !SANITIZER_MAC && !SANITIZER_ANDROID
-    CHECK_EQ(thr, &cur_thread_placeholder);
-#endif
   }
   REAL(pthread_exit)(retval);
 }
@@ -1986,7 +1981,6 @@ static bool is_sync_signal(ThreadSignalContext *sctx, int sig) {
 void ALWAYS_INLINE rtl_generic_sighandler(bool sigact, int sig,
                                           __sanitizer_siginfo *info,
                                           void *ctx) {
-  cur_thread_init();
   ThreadState *thr = cur_thread();
   ThreadSignalContext *sctx = SigCtx(thr);
   if (sig < 0 || sig >= kSigCount) {
diff --git a/lib/tsan/rtl/tsan_interceptors.h b/lib/tsan/rtl/tsan_interceptors.h
index 88d1edd77..29b0f76f9 100644
--- a/lib/tsan/rtl/tsan_interceptors.h
+++ b/lib/tsan/rtl/tsan_interceptors.h
@@ -23,7 +23,6 @@ LibIgnore *libignore();
 
 #if !SANITIZER_GO
 INLINE bool in_symbolizer() {
-  cur_thread_init();
   return UNLIKELY(cur_thread()->in_symbolizer);
 }
 #endif
@@ -31,7 +30,6 @@ INLINE bool in_symbolizer() {
 }  // namespace __tsan
 
 #define SCOPED_INTERCEPTOR_RAW(func, ...) \
-    cur_thread_init(); \
     ThreadState *thr = cur_thread(); \
     const uptr caller_pc = GET_CALLER_PC(); \
     ScopedInterceptor si(thr, #func, caller_pc); \
diff --git a/lib/tsan/rtl/tsan_interface.cc b/lib/tsan/rtl/tsan_interface.cc
index 8101ba193..09a840152 100644
--- a/lib/tsan/rtl/tsan_interface.cc
+++ b/lib/tsan/rtl/tsan_interface.cc
@@ -24,7 +24,6 @@ typedef u32 uint32_t;
 typedef u64 uint64_t;
 
 void __tsan_init() {
-  cur_thread_init();
   Initialize(cur_thread());
 }
 
@@ -124,33 +123,6 @@ void __sanitizer_unaligned_store64(uu64 *addr, u64 v) {
   __tsan_unaligned_write8(addr);
   *addr = v;
 }
-
-#if !SANITIZER_MAC && !SANITIZER_ANDROID
-SANITIZER_INTERFACE_ATTRIBUTE
-void *__tsan_get_current_fiber() {
-  return cur_thread();
-}
-
-SANITIZER_INTERFACE_ATTRIBUTE
-void *__tsan_create_fiber(unsigned flags) {
-  return FiberCreate(cur_thread(), CALLERPC, flags);
-}
-
-SANITIZER_INTERFACE_ATTRIBUTE
-void __tsan_destroy_fiber(void *fiber) {
-  FiberDestroy(cur_thread(), CALLERPC, static_cast<ThreadState *>(fiber));
-}
-
-SANITIZER_INTERFACE_ATTRIBUTE
-void __tsan_switch_to_fiber(void *fiber, unsigned flags) {
-  FiberSwitch(cur_thread(), CALLERPC, static_cast<ThreadState *>(fiber), flags);
-}
-
-SANITIZER_INTERFACE_ATTRIBUTE
-void __tsan_set_fiber_name(void *fiber, const char *name) {
-  ThreadSetName(static_cast<ThreadState *>(fiber), name);
-}
-#endif // !SANITIZER_MAC && !SANITIZER_ANDROID
 }  // extern "C"
 
 void __tsan_acquire(void *addr) {
diff --git a/lib/tsan/rtl/tsan_rtl.h b/lib/tsan/rtl/tsan_rtl.h
index 1804deaf5..37ca731e9 100644
--- a/lib/tsan/rtl/tsan_rtl.h
+++ b/lib/tsan/rtl/tsan_rtl.h
@@ -384,9 +384,6 @@ struct ThreadState {
   // taken by epoch between synchs.
   // This way we can save one load from tls.
   u64 fast_synch_epoch;
-  // Technically `current` should be a separate THREADLOCAL variable;
-  // but it is placed here in order to share cache line with previous fields.
-  ThreadState* current;
   // This is a slow path flag. On fast path, fast_state.GetIgnoreBit() is read.
   // We do not distinguish beteween ignoring reads and writes
   // for better performance.
@@ -465,20 +462,11 @@ struct ThreadState {
 #if SANITIZER_MAC || SANITIZER_ANDROID
 ThreadState *cur_thread();
 void cur_thread_finalize();
-INLINE void cur_thread_init() { }
 #else
 __attribute__((tls_model("initial-exec")))
 extern THREADLOCAL char cur_thread_placeholder[];
 INLINE ThreadState *cur_thread() {
-  return reinterpret_cast<ThreadState *>(cur_thread_placeholder)->current;
-}
-INLINE void cur_thread_init() {
-  ThreadState *thr = reinterpret_cast<ThreadState *>(cur_thread_placeholder);
-  if (UNLIKELY(!thr->current))
-    thr->current = thr;
-}
-INLINE void set_cur_thread(ThreadState *thr) {
-  reinterpret_cast<ThreadState *>(cur_thread_placeholder)->current = thr;
+  return reinterpret_cast<ThreadState *>(&cur_thread_placeholder);
 }
 INLINE void cur_thread_finalize() { }
 #endif  // SANITIZER_MAC || SANITIZER_ANDROID
@@ -880,16 +868,6 @@ uptr ALWAYS_INLINE HeapEnd() {
 }
 #endif
 
-ThreadState *FiberCreate(ThreadState *thr, uptr pc, unsigned flags);
-void FiberDestroy(ThreadState *thr, uptr pc, ThreadState *fiber);
-void FiberSwitch(ThreadState *thr, uptr pc, ThreadState *fiber, unsigned flags);
-
-// These need to match __tsan_switch_to_fiber_* flags defined in
-// tsan_interface.h. See documentation there as well.
-enum FiberSwitchFlags {
-  FiberSwitchFlagNoSync = 1 << 0, // __tsan_switch_to_fiber_no_sync
-};
-
 }  // namespace __tsan
 
 #endif  // TSAN_RTL_H
diff --git a/lib/tsan/rtl/tsan_rtl_thread.cc b/lib/tsan/rtl/tsan_rtl_thread.cc
index 605134894..de429a553 100644
--- a/lib/tsan/rtl/tsan_rtl_thread.cc
+++ b/lib/tsan/rtl/tsan_rtl_thread.cc
@@ -246,8 +246,7 @@ void ThreadStart(ThreadState *thr, int tid, tid_t os_id,
   uptr tls_addr = 0;
   uptr tls_size = 0;
 #if !SANITIZER_GO
-  if (thread_type != ThreadType::Fiber)
-    GetThreadStackAndTls(tid == 0, &stk_addr, &stk_size, &tls_addr, &tls_size);
+  GetThreadStackAndTls(tid == 0, &stk_addr, &stk_size, &tls_addr, &tls_size);
 
   if (tid) {
     if (stk_addr && stk_size)
@@ -405,40 +404,4 @@ void MemoryAccessRange(ThreadState *thr, uptr pc, uptr addr,
   }
 }
 
-#if !SANITIZER_MAC && !SANITIZER_ANDROID && !SANITIZER_GO
-void FiberSwitchImpl(ThreadState *from, ThreadState *to) {
-  Processor *proc = from->proc();
-  ProcUnwire(proc, from);
-  ProcWire(proc, to);
-  set_cur_thread(to);
-}
-
-ThreadState *FiberCreate(ThreadState *thr, uptr pc, unsigned flags) {
-  void *mem = internal_alloc(MBlockThreadContex, sizeof(ThreadState));
-  ThreadState *fiber = static_cast<ThreadState *>(mem);
-  internal_memset(fiber, 0, sizeof(*fiber));
-  int tid = ThreadCreate(thr, pc, 0, true);
-  FiberSwitchImpl(thr, fiber);
-  ThreadStart(fiber, tid, 0, ThreadType::Fiber);
-  FiberSwitchImpl(fiber, thr);
-  return fiber;
-}
-
-void FiberDestroy(ThreadState *thr, uptr pc, ThreadState *fiber) {
-  FiberSwitchImpl(thr, fiber);
-  ThreadFinish(fiber);
-  FiberSwitchImpl(fiber, thr);
-  internal_free(fiber);
-}
-
-void FiberSwitch(ThreadState *thr, uptr pc,
-                 ThreadState *fiber, unsigned flags) {
-  if (!(flags & FiberSwitchFlagNoSync))
-    Release(thr, pc, (uptr)fiber);
-  FiberSwitchImpl(thr, fiber);
-  if (!(flags & FiberSwitchFlagNoSync))
-    Acquire(fiber, pc, (uptr)fiber);
-}
-#endif
-
 }  // namespace __tsan
diff --git a/test/tsan/fiber_asm.cc b/test/tsan/fiber_asm.cc
deleted file mode 100644
index 806c70cce..000000000
--- a/test/tsan/fiber_asm.cc
+++ /dev/null
@@ -1,86 +0,0 @@
-// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
-// REQUIRES: x86_64-target-arch
-// UNSUPPORTED: darwin
-#include "test.h"
-
-struct ucontext {
-  void *sp;
-  void *fiber;
-};
-
-extern "C" {
-  void ucontext_do_switch(void **save, void **load);
-  void ucontext_trampoline();
-}
-
-__asm__(".global ucontext_do_switch\n"
-        "ucontext_do_switch:\n\t"
-        "pushq %rbp\n\t"
-        "pushq %r15\n\t"
-        "pushq %r14\n\t"
-        "pushq %r13\n\t"
-        "pushq %r12\n\t"
-        "pushq %rbx\n\t"
-        "movq %rsp, (%rdi)\n\t"
-        "movq (%rsi), %rsp\n\t"
-        "popq %rbx\n\t"
-        "popq %r12\n\t"
-        "popq %r13\n\t"
-        "popq %r14\n\t"
-        "popq %r15\n\t"
-        "popq %rbp\n\t"
-        "retq");
-
-__asm__(".global ucontext_trampoline\n"
-        "ucontext_trampoline:\n\t"
-        ".cfi_startproc\n\t"
-        ".cfi_undefined rip\n\t"
-        "movq %r12, %rdi\n\t"
-        "jmpq *%rbx\n\t"
-        ".cfi_endproc");
-
-void ucontext_init(ucontext *context, void *stack, unsigned stack_sz,
-                   void (*func)(void*), void *arg) {
-  void **sp = reinterpret_cast<void **>(static_cast<char *>(stack) + stack_sz);
-  *(--sp) = 0;
-  *(--sp) = reinterpret_cast<void *>(ucontext_trampoline);
-  *(--sp) = 0;   // rbp
-  *(--sp) = 0;   // r15
-  *(--sp) = 0;   // r14
-  *(--sp) = 0;   // r13
-  *(--sp) = arg; // r12
-  *(--sp) = reinterpret_cast<void *>(func); // rbx
-  context->sp = sp;
-  context->fiber = __tsan_create_fiber(0);
-}
-
-void ucontext_free(ucontext *context) {
-  __tsan_destroy_fiber(context->fiber);
-}
-
-__attribute__((no_sanitize_thread))
-void ucontext_switch(ucontext *save, ucontext *load) {
-  save->fiber = __tsan_get_current_fiber();
-  __tsan_switch_to_fiber(load->fiber, 0);
-  ucontext_do_switch(&save->sp, &load->sp);
-}
-
-char stack[64 * 1024] __attribute__((aligned(16)));
-
-ucontext uc, orig_uc;
-
-void func(void *arg) {
-  __asm__ __volatile__(".cfi_undefined rip");
-  ucontext_switch(&uc, &orig_uc);
-}
-
-int main() {
-  ucontext_init(&uc, stack, sizeof(stack), func, 0);
-  ucontext_switch(&orig_uc, &uc);
-  ucontext_free(&uc);
-  fprintf(stderr, "PASS\n");
-  return 0;
-}
-
-// CHECK-NOT: WARNING: ThreadSanitizer:
-// CHECK: PASS
diff --git a/test/tsan/fiber_from_thread.cc b/test/tsan/fiber_from_thread.cc
deleted file mode 100644
index d8af1e8e7..000000000
--- a/test/tsan/fiber_from_thread.cc
+++ /dev/null
@@ -1,48 +0,0 @@
-// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
-// UNSUPPORTED: darwin
-#include "test.h"
-#include <ucontext.h>
-
-char stack[64 * 1024] __attribute__((aligned(16)));
-
-ucontext_t uc, orig_uc1, orig_uc2;
-void *fiber, *orig_fiber1, *orig_fiber2;
-
-int var;
-
-void *Thread(void *x) {
-  orig_fiber2 = __tsan_get_current_fiber();
-  swapcontext(&orig_uc2, &orig_uc1);
-  return 0;
-}
-
-void func() {
-  pthread_t t;
-  pthread_create(&t, 0, Thread, 0);
-  pthread_join(t, 0);
-  __tsan_switch_to_fiber(orig_fiber1, 0);
-  swapcontext(&uc, &orig_uc1);
-}
-
-int main() {
-  orig_fiber1 = __tsan_get_current_fiber();
-  fiber = __tsan_create_fiber(0);
-  getcontext(&uc);
-  uc.uc_stack.ss_sp = stack;
-  uc.uc_stack.ss_size = sizeof(stack);
-  uc.uc_link = 0;
-  makecontext(&uc, func, 0);
-  var = 1;
-  __tsan_switch_to_fiber(fiber, 0);
-  swapcontext(&orig_uc1, &uc);
-  var = 2;
-  __tsan_switch_to_fiber(orig_fiber2, 0);
-  swapcontext(&orig_uc1, &orig_uc2);
-  var = 3;
-  __tsan_destroy_fiber(fiber);
-  fprintf(stderr, "PASS\n");
-  return 0;
-}
-
-// CHECK-NOT: WARNING: ThreadSanitizer:
-// CHECK: PASS
diff --git a/test/tsan/fiber_longjmp.cc b/test/tsan/fiber_longjmp.cc
deleted file mode 100644
index 27d776a78..000000000
--- a/test/tsan/fiber_longjmp.cc
+++ /dev/null
@@ -1,80 +0,0 @@
-// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
-// UNSUPPORTED: darwin
-#include "test.h"
-#include <setjmp.h>
-#include <ucontext.h>
-
-char stack[64 * 1024] __attribute__((aligned(16)));
-
-sigjmp_buf jmpbuf, orig_jmpbuf[2];
-void *fiber, *orig_fiber[2];
-
-const unsigned N = 1000;
-
-__attribute__((noinline))
-void switch0() {
-  if (!sigsetjmp(jmpbuf, 0)) {
-    __tsan_switch_to_fiber(orig_fiber[0], 0);
-    siglongjmp(orig_jmpbuf[0], 1);
-  }
-}
-
-void func() {
-  if (!sigsetjmp(jmpbuf, 0)) {
-    __tsan_switch_to_fiber(orig_fiber[0], 0);
-    siglongjmp(orig_jmpbuf[0], 1);
-  }
-  for (;;) {
-    switch0();
-    if (!sigsetjmp(jmpbuf, 0)) {
-      __tsan_switch_to_fiber(orig_fiber[1], 0);
-      siglongjmp(orig_jmpbuf[1], 1);
-    }
-  }
-}
-
-void *Thread(void *x) {
-  orig_fiber[1] = __tsan_get_current_fiber();
-  for (unsigned i = 0; i < N; i++) {
-    barrier_wait(&barrier);
-    if (!sigsetjmp(orig_jmpbuf[1], 0)) {
-      __tsan_switch_to_fiber(fiber, 0);
-      siglongjmp(jmpbuf, 1);
-    }
-    barrier_wait(&barrier);
-  }
-  return 0;
-}
-
-int main() {
-  fiber = __tsan_create_fiber(0);
-  barrier_init(&barrier, 2);
-  pthread_t t;
-  pthread_create(&t, 0, Thread, 0);
-  orig_fiber[0] = __tsan_get_current_fiber();
-  ucontext_t uc, orig_uc;
-  getcontext(&uc);
-  uc.uc_stack.ss_sp = stack;
-  uc.uc_stack.ss_size = sizeof(stack);
-  uc.uc_link = 0;
-  makecontext(&uc, func, 0);
-  if (!sigsetjmp(orig_jmpbuf[0], 0)) {
-    __tsan_switch_to_fiber(fiber, 0);
-    swapcontext(&orig_uc, &uc);
-  }
-  for (unsigned i = 0; i < N; i++) {
-    if (!sigsetjmp(orig_jmpbuf[0], 0)) {
-      __tsan_switch_to_fiber(fiber, 0);
-      siglongjmp(jmpbuf, 1);
-    }
-    barrier_wait(&barrier);
-    barrier_wait(&barrier);
-  }
-  pthread_join(t, 0);
-  __tsan_destroy_fiber(fiber);
-  fprintf(stderr, "PASS\n");
-  return 0;
-}
-
-// CHECK-NOT: WARNING: ThreadSanitizer:
-// CHECK: PASS
diff --git a/test/tsan/fiber_race.cc b/test/tsan/fiber_race.cc
deleted file mode 100644
index 89bcdddd5..000000000
--- a/test/tsan/fiber_race.cc
+++ /dev/null
@@ -1,36 +0,0 @@
-// RUN: %clang_tsan -O1 %s -o %t && %deflake %run %t 2>&1 | FileCheck %s
-// UNSUPPORTED: darwin
-#include "test.h"
-#include <ucontext.h>
-
-char stack[64 * 1024] __attribute__((aligned(16)));
-
-ucontext_t uc, orig_uc;
-void *fiber, *orig_fiber;
-
-int var;
-
-void func() {
-  var = 1;
-  __tsan_switch_to_fiber(orig_fiber, __tsan_switch_to_fiber_no_sync);
-  swapcontext(&uc, &orig_uc);
-}
-
-int main() {
-  orig_fiber = __tsan_get_current_fiber();
-  fiber = __tsan_create_fiber(0);
-  getcontext(&uc);
-  uc.uc_stack.ss_sp = stack;
-  uc.uc_stack.ss_size = sizeof(stack);
-  uc.uc_link = 0;
-  makecontext(&uc, func, 0);
-  var = 2;
-  __tsan_switch_to_fiber(fiber, __tsan_switch_to_fiber_no_sync);
-  swapcontext(&orig_uc, &uc);
-  __tsan_destroy_fiber(fiber);
-  fprintf(stderr, "PASS\n");
-  return 0;
-}
-
-// CHECK: WARNING: ThreadSanitizer: data race
-// CHECK: PASS
diff --git a/test/tsan/fiber_simple.cc b/test/tsan/fiber_simple.cc
deleted file mode 100644
index ce529e729..000000000
--- a/test/tsan/fiber_simple.cc
+++ /dev/null
@@ -1,36 +0,0 @@
-// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
-// UNSUPPORTED: darwin
-#include "test.h"
-#include <ucontext.h>
-
-char stack[64 * 1024] __attribute__((aligned(16)));
-
-ucontext_t uc, orig_uc;
-void *fiber, *orig_fiber;
-
-int var;
-
-void func() {
-  var = 1;
-  __tsan_switch_to_fiber(orig_fiber, 0);
-  swapcontext(&uc, &orig_uc);
-}
-
-int main() {
-  orig_fiber = __tsan_get_current_fiber();
-  fiber = __tsan_create_fiber(0);
-  getcontext(&uc);
-  uc.uc_stack.ss_sp = stack;
-  uc.uc_stack.ss_size = sizeof(stack);
-  uc.uc_link = 0;
-  makecontext(&uc, func, 0);
-  var = 2;
-  __tsan_switch_to_fiber(fiber, 0);
-  swapcontext(&orig_uc, &uc);
-  __tsan_destroy_fiber(fiber);
-  fprintf(stderr, "PASS\n");
-  return 0;
-}
-
-// CHECK-NOT: WARNING: ThreadSanitizer:
-// CHECK: PASS
diff --git a/test/tsan/fiber_two_threads.cc b/test/tsan/fiber_two_threads.cc
deleted file mode 100644
index eaadb65ac..000000000
--- a/test/tsan/fiber_two_threads.cc
+++ /dev/null
@@ -1,62 +0,0 @@
-// RUN: %clang_tsan -O1 %s -o %t && %run %t 2>&1 | FileCheck %s
-// UNSUPPORTED: darwin
-#include "test.h"
-#include <ucontext.h>
-
-char stack[64 * 1024] __attribute__((aligned(16)));
-
-ucontext_t uc, orig_uc[2];
-void *fiber, *orig_fiber[2];
-
-const unsigned N = 1000;
-
-__attribute__((noinline))
-void switch0() {
-  __tsan_switch_to_fiber(orig_fiber[0], 0);
-  swapcontext(&uc, &orig_uc[0]);
-}
-
-void func() {
-  for (;;) {
-    switch0();
-    __tsan_switch_to_fiber(orig_fiber[1], 0);
-    swapcontext(&uc, &orig_uc[1]);
-  }
-}
-
-void *Thread(void *x) {
-  orig_fiber[1] = __tsan_get_current_fiber();
-  for (unsigned i = 0; i < N; i++) {
-    barrier_wait(&barrier);
-    __tsan_switch_to_fiber(fiber, 0);
-    swapcontext(&orig_uc[1], &uc);
-    barrier_wait(&barrier);
-  }
-  return 0;
-}
-
-int main() {
-  fiber = __tsan_create_fiber(0);
-  barrier_init(&barrier, 2);
-  pthread_t t;
-  pthread_create(&t, 0, Thread, 0);
-  orig_fiber[0] = __tsan_get_current_fiber();
-  getcontext(&uc);
-  uc.uc_stack.ss_sp = stack;
-  uc.uc_stack.ss_size = sizeof(stack);
-  uc.uc_link = 0;
-  makecontext(&uc, func, 0);
-  for (unsigned i = 0; i < N; i++) {
-    __tsan_switch_to_fiber(fiber, 0);
-    swapcontext(&orig_uc[0], &uc);
-    barrier_wait(&barrier);
-    barrier_wait(&barrier);
-  }
-  pthread_join(t, 0);
-  __tsan_destroy_fiber(fiber);
-  fprintf(stderr, "PASS\n");
-  return 0;
-}
-
-// CHECK-NOT: WARNING: ThreadSanitizer:
-// CHECK: PASS