pthread_create.cpp revision 40eabe24e4e3ae8ebe437f1f4e43cf39cbba2e9e
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(void* (*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(pthread_internal_t* thread) { 61 // Zero-initialize all the slots. 62 for (size_t i = 0; i < BIONIC_TLS_SLOTS; ++i) { 63 thread->tls[i] = NULL; 64 } 65 66 // Slot 0 must point to itself. The x86 Linux kernel reads the TLS from %fs:0. 67 thread->tls[TLS_SLOT_SELF] = thread->tls; 68 thread->tls[TLS_SLOT_THREAD_ID] = thread; 69 // GCC looks in the TLS for the stack guard on x86, so copy it there from our global. 70 thread->tls[TLS_SLOT_STACK_GUARD] = (void*) __stack_chk_guard; 71 72 __set_tls(thread->tls); 73} 74 75// This trampoline is called from the assembly _pthread_clone() function. 76extern "C" void __thread_entry(void* (*func)(void*), void* arg, void** tls) { 77 // Wait for our creating thread to release us. This lets it have time to 78 // notify gdb about this thread before we start doing anything. 79 // This also provides the memory barrier needed to ensure that all memory 80 // accesses previously made by the creating thread are visible to us. 81 pthread_mutex_t* start_mutex = (pthread_mutex_t*) &tls[TLS_SLOT_SELF]; 82 pthread_mutex_lock(start_mutex); 83 pthread_mutex_destroy(start_mutex); 84 85 pthread_internal_t* thread = (pthread_internal_t*) tls[TLS_SLOT_THREAD_ID]; 86 thread->tls = tls; 87 __init_tls(thread); 88 89 if ((thread->internal_flags & kPthreadInitFailed) != 0) { 90 pthread_exit(NULL); 91 } 92 93 void* result = func(arg); 94 pthread_exit(result); 95} 96 97__LIBC_ABI_PRIVATE__ 98int _init_thread(pthread_internal_t* thread, bool add_to_thread_list) { 99 int error = 0; 100 101 // Set the scheduling policy/priority of the thread. 102 if (thread->attr.sched_policy != SCHED_NORMAL) { 103 struct sched_param param; 104 param.sched_priority = thread->attr.sched_priority; 105 if (sched_setscheduler(thread->tid, thread->attr.sched_policy, ¶m) == -1) { 106 // For backwards compatibility reasons, we just warn about failures here. 107 // error = errno; 108 const char* msg = "pthread_create sched_setscheduler call failed: %s\n"; 109 __libc_format_log(ANDROID_LOG_WARN, "libc", msg, strerror(errno)); 110 } 111 } 112 113 pthread_cond_init(&thread->join_cond, NULL); 114 thread->join_count = 0; 115 thread->cleanup_stack = NULL; 116 117 if (add_to_thread_list) { 118 _pthread_internal_add(thread); 119 } 120 121 return error; 122} 123 124static void* __create_thread_stack(size_t stack_size, size_t guard_size) { 125 ScopedPthreadMutexLocker lock(&gPthreadStackCreationLock); 126 127 // Create a new private anonymous map. 128 int prot = PROT_READ | PROT_WRITE; 129 int flags = MAP_PRIVATE | MAP_ANONYMOUS | MAP_NORESERVE; 130 void* stack = mmap(NULL, stack_size, prot, flags, -1, 0); 131 if (stack == MAP_FAILED) { 132 return NULL; 133 } 134 135 // Set the guard region at the end of the stack to PROT_NONE. 136 if (mprotect(stack, guard_size, PROT_NONE) == -1) { 137 munmap(stack, stack_size); 138 return NULL; 139 } 140 141 return stack; 142} 143 144int pthread_create(pthread_t* thread_out, pthread_attr_t const* attr, 145 void* (*start_routine)(void*), void* arg) { 146 ErrnoRestorer errno_restorer; 147 148 // Inform the rest of the C library that at least one thread 149 // was created. This will enforce certain functions to acquire/release 150 // locks (e.g. atexit()) to protect shared global structures. 151 // This works because pthread_create() is not called by the C library 152 // initialization routine that sets up the main thread's data structures. 153 __isthreaded = 1; 154 155 pthread_internal_t* thread = reinterpret_cast<pthread_internal_t*>(calloc(sizeof(*thread), 1)); 156 if (thread == NULL) { 157 return EAGAIN; 158 } 159 thread->allocated_on_heap = true; 160 161 if (attr == NULL) { 162 pthread_attr_init(&thread->attr); 163 } else { 164 thread->attr = *attr; 165 attr = NULL; // Prevent misuse below. 166 } 167 168 // Make sure the stack size is PAGE_SIZE aligned. 169 size_t stack_size = (thread->attr.stack_size + (PAGE_SIZE-1)) & ~(PAGE_SIZE-1); 170 171 if (thread->attr.stack_base == NULL) { 172 // The caller didn't provide a stack, so allocate one. 173 thread->attr.stack_base = __create_thread_stack(stack_size, thread->attr.guard_size); 174 if (thread->attr.stack_base == NULL) { 175 free(thread); 176 return EAGAIN; 177 } 178 } else { 179 // The caller did provide a stack, so remember we're not supposed to free it. 180 thread->attr.flags |= PTHREAD_ATTR_FLAG_USER_STACK; 181 } 182 183 // Make room for TLS. 184 void** tls = (void**)((uint8_t*)(thread->attr.stack_base) + stack_size - BIONIC_TLS_SLOTS * sizeof(void*)); 185 186 // Create a mutex for the thread in TLS_SLOT_SELF to wait on once it starts so we can keep 187 // it from doing anything until after we notify the debugger about it 188 // 189 // This also provides the memory barrier we need to ensure that all 190 // memory accesses previously performed by this thread are visible to 191 // the new thread. 192 pthread_mutex_t* start_mutex = (pthread_mutex_t*) &tls[TLS_SLOT_SELF]; 193 pthread_mutex_init(start_mutex, NULL); 194 ScopedPthreadMutexLocker start_locker(start_mutex); 195 196 tls[TLS_SLOT_THREAD_ID] = thread; 197 198 int flags = CLONE_FILES | CLONE_FS | CLONE_VM | CLONE_SIGHAND | CLONE_THREAD | CLONE_SYSVSEM; 199 200 int tid = __pthread_clone(start_routine, tls, flags, arg); 201 if (tid < 0) { 202 int clone_errno = errno; 203 if ((thread->attr.flags & PTHREAD_ATTR_FLAG_USER_STACK) == 0) { 204 munmap(thread->attr.stack_base, stack_size); 205 } 206 free(thread); 207 return clone_errno; 208 } 209 210 thread->tid = tid; 211 212 int init_errno = _init_thread(thread, true); 213 if (init_errno != 0) { 214 // Mark the thread detached and let its __thread_entry run to 215 // completion. (It'll just exit immediately, cleaning up its resources.) 216 thread->internal_flags |= kPthreadInitFailed; 217 thread->attr.flags |= PTHREAD_ATTR_FLAG_DETACHED; 218 return init_errno; 219 } 220 221 // Notify any debuggers about the new thread. 222 { 223 ScopedPthreadMutexLocker debugger_locker(&gDebuggerNotificationLock); 224 _thread_created_hook(thread->tid); 225 } 226 227 // Publish the pthread_t and let the thread run. 228 *thread_out = (pthread_t) thread; 229 230 return 0; 231} 232