pthread_create.cpp revision 4b4a8824289c48c823cd38bc63289d121aae3d67
1/* 2 * Copyright (C) 2008 The Android Open Source Project 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * * Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * * Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in 12 * the documentation and/or other materials provided with the 13 * distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS 16 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT 17 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS 18 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE 19 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, 20 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, 21 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS 22 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED 23 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, 24 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT 25 * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 26 * SUCH DAMAGE. 27 */ 28 29#include <pthread.h> 30 31#include <errno.h> 32#include <sys/mman.h> 33 34#include "pthread_internal.h" 35 36#include "private/bionic_ssp.h" 37#include "private/bionic_tls.h" 38#include "private/debug_format.h" 39#include "private/logd.h" 40#include "private/thread_private.h" 41#include "private/ErrnoRestorer.h" 42#include "private/ScopedPthreadMutexLocker.h" 43 44extern "C" int __pthread_clone(int (*fn)(void*), void* child_stack, int flags, void* arg); 45 46#ifdef __i386__ 47#define ATTRIBUTES __attribute__((noinline)) __attribute__((fastcall)) 48#else 49#define ATTRIBUTES __attribute__((noinline)) 50#endif 51 52extern "C" void ATTRIBUTES _thread_created_hook(pid_t thread_id); 53 54static const int kPthreadInitFailed = 1; 55 56static pthread_mutex_t gPthreadStackCreationLock = PTHREAD_MUTEX_INITIALIZER; 57 58static pthread_mutex_t gDebuggerNotificationLock = PTHREAD_MUTEX_INITIALIZER; 59 60void __init_tls(void** tls, void* thread) { 61 ((pthread_internal_t*) thread)->tls = tls; 62 63 // Zero-initialize all the slots. 64 for (size_t i = 0; i < BIONIC_TLS_SLOTS; ++i) { 65 tls[i] = NULL; 66 } 67 68 // Slot 0 must point to itself. The x86 Linux kernel reads the TLS from %fs:0. 69 tls[TLS_SLOT_SELF] = tls; 70 tls[TLS_SLOT_THREAD_ID] = thread; 71 // GCC looks in the TLS for the stack guard on x86, so copy it there from our global. 72 tls[TLS_SLOT_STACK_GUARD] = (void*) __stack_chk_guard; 73 74 __set_tls((void*) tls); 75} 76 77// This trampoline is called from the assembly _pthread_clone() function. 78extern "C" void __thread_entry(int (*func)(void*), void *arg, void **tls) { 79 // Wait for our creating thread to release us. This lets it have time to 80 // notify gdb about this thread before we start doing anything. 81 // This also provides the memory barrier needed to ensure that all memory 82 // accesses previously made by the creating thread are visible to us. 83 pthread_mutex_t* start_mutex = (pthread_mutex_t*) &tls[TLS_SLOT_SELF]; 84 pthread_mutex_lock(start_mutex); 85 pthread_mutex_destroy(start_mutex); 86 87 pthread_internal_t* thread = (pthread_internal_t*) tls[TLS_SLOT_THREAD_ID]; 88 __init_tls(tls, thread); 89 90 if ((thread->internal_flags & kPthreadInitFailed) != 0) { 91 pthread_exit(NULL); 92 } 93 94 int result = func(arg); 95 pthread_exit((void*) result); 96} 97 98__LIBC_ABI_PRIVATE__ 99int _init_thread(pthread_internal_t* thread, pid_t kernel_id, bool add_to_thread_list) { 100 int error = 0; 101 102 thread->kernel_id = kernel_id; 103 104 // Set the scheduling policy/priority of the thread. 105 if (thread->attr.sched_policy != SCHED_NORMAL) { 106 struct sched_param param; 107 param.sched_priority = thread->attr.sched_priority; 108 if (sched_setscheduler(kernel_id, thread->attr.sched_policy, ¶m) == -1) { 109 // For backwards compatibility reasons, we just warn about failures here. 110 // error = errno; 111 const char* msg = "pthread_create sched_setscheduler call failed: %s\n"; 112 __libc_format_log(ANDROID_LOG_WARN, "libc", msg, strerror(errno)); 113 } 114 } 115 116 pthread_cond_init(&thread->join_cond, NULL); 117 thread->join_count = 0; 118 thread->cleanup_stack = NULL; 119 120 if (add_to_thread_list) { 121 _pthread_internal_add(thread); 122 } 123 124 return error; 125} 126 127static void* __create_thread_stack(size_t stack_size, size_t guard_size) { 128 ScopedPthreadMutexLocker lock(&gPthreadStackCreationLock); 129 130 // Create a new private anonymous map. 131 int prot = PROT_READ | PROT_WRITE; 132 int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE; 133 void* stack = mmap(NULL, stack_size, prot, flags, -1, 0); 134 if (stack == MAP_FAILED) { 135 return NULL; 136 } 137 138 // Set the guard region at the end of the stack to PROT_NONE. 139 if (mprotect(stack, guard_size, PROT_NONE) == -1) { 140 munmap(stack, stack_size); 141 return NULL; 142 } 143 144 return stack; 145} 146 147int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, 148 void* (*start_routine)(void*), void* arg) { 149 ErrnoRestorer errno_restorer; 150 151 // Inform the rest of the C library that at least one thread 152 // was created. This will enforce certain functions to acquire/release 153 // locks (e.g. atexit()) to protect shared global structures. 154 // This works because pthread_create() is not called by the C library 155 // initialization routine that sets up the main thread's data structures. 156 __isthreaded = 1; 157 158 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(calloc(sizeof(*thread), 1)); 159 if (thread == NULL) { 160 return EAGAIN; 161 } 162 thread->allocated_on_heap = true; 163 164 if (attr == NULL) { 165 pthread_attr_init(&thread->attr); 166 } else { 167 thread->attr = *attr; 168 attr = NULL; // Prevent misuse below. 169 } 170 171 // Make sure the stack size is PAGE_SIZE aligned. 172 size_t stack_size = (thread->attr.stack_size + (PAGE_SIZE-1)) & ~(PAGE_SIZE-1); 173 174 if (thread->attr.stack_base == NULL) { 175 // The caller didn't provide a stack, so allocate one. 176 thread->attr.stack_base = __create_thread_stack(stack_size, thread->attr.guard_size); 177 if (thread->attr.stack_base == NULL) { 178 free(thread); 179 return EAGAIN; 180 } 181 } else { 182 // The caller did provide a stack, so remember we're not supposed to free it. 183 thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_STACK; 184 } 185 186 // Make room for TLS. 187 void** tls = (void**)((uint8_t*)(thread->attr.stack_base) + stack_size - BIONIC_TLS_SLOTS * sizeof(void*)); 188 189 // Create a mutex for the thread in TLS_SLOT_SELF to wait on once it starts so we can keep 190 // it from doing anything until after we notify the debugger about it 191 // 192 // This also provides the memory barrier we need to ensure that all 193 // memory accesses previously performed by this thread are visible to 194 // the new thread. 195 pthread_mutex_t* start_mutex = (pthread_mutex_t*) &tls[TLS_SLOT_SELF]; 196 pthread_mutex_init(start_mutex, NULL); 197 ScopedPthreadMutexLocker start_locker(start_mutex); 198 199 tls[TLS_SLOT_THREAD_ID] = thread; 200 201 int flags = CLONE_FILES | CLONE_FS | CLONE_VM | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM | CLONE_DETACHED; 202 int tid = __pthread_clone((int(*)(void*))start_routine, tls, flags, arg); 203 204 if (tid < 0) { 205 int clone_errno = errno; 206 if ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_STACK) == 0) { 207 munmap(thread->attr.stack_base, stack_size); 208 } 209 free(thread); 210 return clone_errno; 211 } 212 213 int init_errno = _init_thread(thread, tid, true); 214 if (init_errno != 0) { 215 // Mark the thread detached and let its __thread_entry run to 216 // completion. (It'll just exit immediately, cleaning up its resources.) 217 thread->internal_flags |= kPthreadInitFailed; 218 thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED; 219 return init_errno; 220 } 221 222 // Notify any debuggers about the new thread. 223 { 224 ScopedPthreadMutexLocker debugger_locker(&gDebuggerNotificationLock); 225 _thread_created_hook(tid); 226 } 227 228 // Publish the pthread_t and let the thread run. 229 *thread_out = (pthread_t) thread; 230 231 return 0; 232} 233