1 //===-- main.cpp ------------------------------------------------*- C++ -*-===// 2 // 3 // The LLVM Compiler Infrastructure 4 // 5 // This file is distributed under the University of Illinois Open Source 6 // License. See LICENSE.TXT for details. 7 // 8 //===----------------------------------------------------------------------===// 9 10 // This test is intended to create a situation in which one thread will exit 11 // while a breakpoint is being handled in another thread. This may not always 12 // happen because it's possible that the exiting thread will exit before the 13 // breakpoint is hit. The test case should be flexible enough to treat that 14 // as success. 15 16 #include <pthread.h> 17 #include <unistd.h> 18 #include <atomic> 19 20 volatile int g_test = 0; 21 22 // Note that although hogging the CPU while waiting for a variable to change 23 // would be terrible in production code, it's great for testing since it 24 // avoids a lot of messy context switching to get multiple threads synchronized. 25 #define do_nothing() 26 27 #define pseudo_barrier_wait(bar) \ 28 --bar; \ 29 while (bar > 0) \ 30 do_nothing(); 31 32 #define pseudo_barrier_init(bar, count) (bar = count) 33 34 // A barrier to synchronize all the threads except the one that will exit. 35 std::atomic_int g_barrier1; 36 37 // A barrier to synchronize all the threads including the one that will exit. 38 std::atomic_int g_barrier2; 39 40 // A barrier to keep the first group of threads from exiting until after the 41 // breakpoint has been passed. 42 std::atomic_int g_barrier3; 43 44 void * 45 break_thread_func (void *input) 46 { 47 // Wait until the entire first group of threads is running 48 pseudo_barrier_wait(g_barrier1); 49 50 // Wait for the exiting thread to start 51 pseudo_barrier_wait(g_barrier2); 52 53 // Do something 54 g_test++; // Set breakpoint here 55 56 // Synchronize after the breakpoint 57 pseudo_barrier_wait(g_barrier3); 58 59 // Return 60 return NULL; 61 } 62 63 void * 64 wait_thread_func (void *input) 65 { 66 // Wait until the entire first group of threads is running 67 pseudo_barrier_wait(g_barrier1); 68 69 // Wait for the exiting thread to start 70 pseudo_barrier_wait(g_barrier2); 71 72 // Wait until the breakpoint has been passed 73 pseudo_barrier_wait(g_barrier3); 74 75 // Return 76 return NULL; 77 } 78 79 void * 80 exit_thread_func (void *input) 81 { 82 // Sync up with the rest of the threads. 83 pseudo_barrier_wait(g_barrier2); 84 85 // Try to make sure this thread doesn't exit until the breakpoint is hit. 86 usleep(1); 87 88 // Return 89 return NULL; 90 } 91 92 int main () 93 { 94 pthread_t thread_1; 95 pthread_t thread_2; 96 pthread_t thread_3; 97 pthread_t thread_4; 98 pthread_t thread_5; 99 100 // The first barrier waits for the non-exiting threads to start. 101 // This thread will also participate in that barrier. 102 // The idea here is to guarantee that the exiting thread will be 103 // last in the internal list maintained by the debugger. 104 pseudo_barrier_init(g_barrier1, 5); 105 106 // The second break synchronyizes thread exection with the breakpoint. 107 pseudo_barrier_init(g_barrier2, 5); 108 109 // The third barrier keeps the waiting threads around until the breakpoint 110 // has been passed. 111 pseudo_barrier_init(g_barrier3, 4); 112 113 // Create a thread to hit the breakpoint 114 pthread_create (&thread_1, NULL, break_thread_func, NULL); 115 116 // Create more threads to slow the debugger down during processing. 117 pthread_create (&thread_2, NULL, wait_thread_func, NULL); 118 pthread_create (&thread_3, NULL, wait_thread_func, NULL); 119 pthread_create (&thread_4, NULL, wait_thread_func, NULL); 120 121 // Wait for all these threads to get started. 122 pseudo_barrier_wait(g_barrier1); 123 124 // Create a thread to exit during the breakpoint 125 pthread_create (&thread_5, NULL, exit_thread_func, NULL); 126 127 // Wait for the threads to finish 128 pthread_join(thread_5, NULL); 129 pthread_join(thread_4, NULL); 130 pthread_join(thread_3, NULL); 131 pthread_join(thread_2, NULL); 132 pthread_join(thread_1, NULL); 133 134 return 0; 135 } 136
