compiler-rt/test/tsan/Linux/fork_deadlock.cpp

   1 // RUN: %clangxx_tsan -O1 %s -o %t && %env_tsan_opts=atexit_sleep_ms=0 %run %t 2>&1 | FileCheck %s
   2
   3 // This test models what happens on Mac when fork
   4 // calls malloc/free inside of our atfork callbacks.
   5 // and ensures that we don't deadlock on malloc/free calls.
   6
   7 #include "../test.h"
   8 #include "syscall.h"
   9 #include <errno.h>
  10 #include <string.h>
  11 #include <sys/types.h>
  12 #include <sys/wait.h>
  13
  14 // disable_sanitizer_instrumentation on __tsan_test_only_on_fork is not
  15 // transitive, so we must apply it here as well.
  16 // Instrumenting alloc_free_blocks() will result in deadlocks in TSan.
  17 __attribute__((disable_sanitizer_instrumentation)) void alloc_free_blocks() {
  18   // Allocate a bunch of blocks to drain local allocator cache
  19   // and provoke it to lock allocator global mutexes.
  20   const int kBlocks = 1000;
  21   void *blocks[kBlocks];
  22   for (int i = 0; i < kBlocks; i++) {
  23     void *p = malloc(10);
  24     *(volatile char *)p = 0;
  25     blocks[i] = p;
  26   }
  27   for (int i = 0; i < kBlocks; i++)
  28     free(blocks[i]);
  29 }
  30
  31 __attribute__((disable_sanitizer_instrumentation)) extern "C" void
  32 __tsan_test_only_on_fork() {
  33   const char *msg = "__tsan_test_only_on_fork\n";
  34   write(2, msg, strlen(msg));
  35   alloc_free_blocks();
  36 }
  37
  38 static void *background(void *p) {
  39   for (;;)
  40     alloc_free_blocks();
  41   return 0;
  42 }
  43
  44 int main() {
  45   pthread_t th;
  46   pthread_create(&th, 0, background, 0);
  47   pthread_detach(th);
  48   for (int i = 0; i < 10; i++) {
  49     int pid = myfork();
  50     if (pid < 0) {
  51       fprintf(stderr, "failed to fork (%d)\n", errno);
  52       exit(1);
  53     }
  54     if (pid == 0) {
  55       // child
  56       exit(0);
  57     }
  58     // parent
  59     while (wait(0) < 0) {
  60     }
  61   }
  62   fprintf(stderr, "DONE\n");
  63 }
  64
  65 // CHECK: __tsan_test_only_on_fork
  66 // CHECK: DONE