1.1 --- /dev/null Thu Jan 01 00:00:00 1970 +0000
1.2 +++ b/xpcom/threads/ThreadStackHelper.cpp Wed Dec 31 06:09:35 2014 +0100
1.3 @@ -0,0 +1,238 @@
1.4 +/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
1.5 +/* This Source Code Form is subject to the terms of the Mozilla Public
1.6 + * License, v. 2.0. If a copy of the MPL was not distributed with this
1.7 + * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
1.8 +
1.9 +#include "ThreadStackHelper.h"
1.10 +#include "MainThreadUtils.h"
1.11 +
1.12 +#include "mozilla/Assertions.h"
1.13 +#include "mozilla/Move.h"
1.14 +
1.15 +#ifdef XP_LINUX
1.16 +#include <unistd.h>
1.17 +#include <sys/syscall.h>
1.18 +#endif
1.19 +
1.20 +#ifdef ANDROID
1.21 +#ifndef SYS_gettid
1.22 +#define SYS_gettid __NR_gettid
1.23 +#endif
1.24 +#ifndef SYS_tgkill
1.25 +#define SYS_tgkill __NR_tgkill
1.26 +#endif
1.27 +#endif
1.28 +
1.29 +namespace mozilla {
1.30 +
1.31 +void
1.32 +ThreadStackHelper::Startup()
1.33 +{
1.34 +#if defined(XP_LINUX)
1.35 + MOZ_ASSERT(NS_IsMainThread());
1.36 + if (!sInitialized) {
1.37 + MOZ_ALWAYS_TRUE(!::sem_init(&sSem, 0, 0));
1.38 + }
1.39 + sInitialized++;
1.40 +#endif
1.41 +}
1.42 +
1.43 +void
1.44 +ThreadStackHelper::Shutdown()
1.45 +{
1.46 +#if defined(XP_LINUX)
1.47 + MOZ_ASSERT(NS_IsMainThread());
1.48 + if (sInitialized == 1) {
1.49 + MOZ_ALWAYS_TRUE(!::sem_destroy(&sSem));
1.50 + }
1.51 + sInitialized--;
1.52 +#endif
1.53 +}
1.54 +
1.55 +ThreadStackHelper::ThreadStackHelper()
1.56 + :
1.57 +#ifdef MOZ_ENABLE_PROFILER_SPS
1.58 + mPseudoStack(mozilla_get_pseudo_stack()),
1.59 +#endif
1.60 + mStackBuffer()
1.61 + , mMaxStackSize(mStackBuffer.capacity())
1.62 +{
1.63 +#if defined(XP_LINUX)
1.64 + mThreadID = ::syscall(SYS_gettid);
1.65 +#elif defined(XP_WIN)
1.66 + mInitialized = !!::DuplicateHandle(
1.67 + ::GetCurrentProcess(), ::GetCurrentThread(),
1.68 + ::GetCurrentProcess(), &mThreadID,
1.69 + THREAD_SUSPEND_RESUME, FALSE, 0);
1.70 + MOZ_ASSERT(mInitialized);
1.71 +#elif defined(XP_MACOSX)
1.72 + mThreadID = mach_thread_self();
1.73 +#endif
1.74 +}
1.75 +
1.76 +ThreadStackHelper::~ThreadStackHelper()
1.77 +{
1.78 +#if defined(XP_WIN)
1.79 + if (mInitialized) {
1.80 + MOZ_ALWAYS_TRUE(!!::CloseHandle(mThreadID));
1.81 + }
1.82 +#endif
1.83 +}
1.84 +
1.85 +#if defined(XP_LINUX) && defined(__arm__)
1.86 +// Some (old) Linux kernels on ARM have a bug where a signal handler
1.87 +// can be called without clearing the IT bits in CPSR first. The result
1.88 +// is that the first few instructions of the handler could be skipped,
1.89 +// ultimately resulting in crashes. To workaround this bug, the handler
1.90 +// on ARM is a trampoline that starts with enough NOP instructions, so
1.91 +// that even if the IT bits are not cleared, only the NOP instructions
1.92 +// will be skipped over.
1.93 +
1.94 +template <void (*H)(int, siginfo_t*, void*)>
1.95 +__attribute__((naked)) void
1.96 +SignalTrampoline(int aSignal, siginfo_t* aInfo, void* aContext)
1.97 +{
1.98 + asm volatile (
1.99 + "nop; nop; nop; nop"
1.100 + : : : "memory");
1.101 +
1.102 + // Because the assembler may generate additional insturctions below, we
1.103 + // need to ensure NOPs are inserted first by separating them out above.
1.104 +
1.105 + asm volatile (
1.106 + "bx %0"
1.107 + :
1.108 + : "r"(H), "l"(aSignal), "l"(aInfo), "l"(aContext)
1.109 + : "memory");
1.110 +}
1.111 +#endif // XP_LINUX && __arm__
1.112 +
1.113 +void
1.114 +ThreadStackHelper::GetStack(Stack& aStack)
1.115 +{
1.116 + // Always run PrepareStackBuffer first to clear aStack
1.117 + if (!PrepareStackBuffer(aStack)) {
1.118 + // Skip and return empty aStack
1.119 + return;
1.120 + }
1.121 +
1.122 +#if defined(XP_LINUX)
1.123 + if (profiler_is_active()) {
1.124 + // Profiler can interfere with our Linux signal handling
1.125 + return;
1.126 + }
1.127 + if (!sInitialized) {
1.128 + MOZ_ASSERT(false);
1.129 + return;
1.130 + }
1.131 + sCurrent = this;
1.132 + struct sigaction sigact = {};
1.133 +#ifdef __arm__
1.134 + sigact.sa_sigaction = SignalTrampoline<SigAction>;
1.135 +#else
1.136 + sigact.sa_sigaction = SigAction;
1.137 +#endif
1.138 + sigemptyset(&sigact.sa_mask);
1.139 + sigact.sa_flags = SA_SIGINFO | SA_RESTART;
1.140 + if (::sigaction(SIGPROF, &sigact, &sOldSigAction)) {
1.141 + MOZ_ASSERT(false);
1.142 + return;
1.143 + }
1.144 + MOZ_ALWAYS_TRUE(!::syscall(SYS_tgkill, getpid(), mThreadID, SIGPROF));
1.145 + MOZ_ALWAYS_TRUE(!::sem_wait(&sSem));
1.146 +
1.147 +#elif defined(XP_WIN)
1.148 + if (!mInitialized) {
1.149 + MOZ_ASSERT(false);
1.150 + return;
1.151 + }
1.152 + if (::SuspendThread(mThreadID) == DWORD(-1)) {
1.153 + MOZ_ASSERT(false);
1.154 + return;
1.155 + }
1.156 + FillStackBuffer();
1.157 + MOZ_ALWAYS_TRUE(::ResumeThread(mThreadID) != DWORD(-1));
1.158 +
1.159 +#elif defined(XP_MACOSX)
1.160 + if (::thread_suspend(mThreadID) != KERN_SUCCESS) {
1.161 + MOZ_ASSERT(false);
1.162 + return;
1.163 + }
1.164 + FillStackBuffer();
1.165 + MOZ_ALWAYS_TRUE(::thread_resume(mThreadID) == KERN_SUCCESS);
1.166 +
1.167 +#endif
1.168 + aStack = Move(mStackBuffer);
1.169 +}
1.170 +
1.171 +#ifdef XP_LINUX
1.172 +
1.173 +int ThreadStackHelper::sInitialized;
1.174 +sem_t ThreadStackHelper::sSem;
1.175 +struct sigaction ThreadStackHelper::sOldSigAction;
1.176 +ThreadStackHelper* ThreadStackHelper::sCurrent;
1.177 +
1.178 +void
1.179 +ThreadStackHelper::SigAction(int aSignal, siginfo_t* aInfo, void* aContext)
1.180 +{
1.181 + ::sigaction(SIGPROF, &sOldSigAction, nullptr);
1.182 + sCurrent->FillStackBuffer();
1.183 + sCurrent = nullptr;
1.184 + ::sem_post(&sSem);
1.185 +}
1.186 +
1.187 +#endif // XP_LINUX
1.188 +
1.189 +bool
1.190 +ThreadStackHelper::PrepareStackBuffer(Stack& aStack) {
1.191 + // Return false to skip getting the stack and return an empty stack
1.192 + aStack.clear();
1.193 +#ifdef MOZ_ENABLE_PROFILER_SPS
1.194 + /* Normally, provided the profiler is enabled, it would be an error if we
1.195 + don't have a pseudostack here (the thread probably forgot to call
1.196 + profiler_register_thread). However, on B2G, profiling secondary threads
1.197 + may be disabled despite profiler being enabled. This is by-design and
1.198 + is not an error. */
1.199 +#ifdef MOZ_WIDGET_GONK
1.200 + if (!mPseudoStack) {
1.201 + return false;
1.202 + }
1.203 +#endif
1.204 + MOZ_ASSERT(mPseudoStack);
1.205 + mStackBuffer.clear();
1.206 + MOZ_ALWAYS_TRUE(mStackBuffer.reserve(mMaxStackSize));
1.207 + return true;
1.208 +#else
1.209 + return false;
1.210 +#endif
1.211 +}
1.212 +
1.213 +void
1.214 +ThreadStackHelper::FillStackBuffer() {
1.215 +#ifdef MOZ_ENABLE_PROFILER_SPS
1.216 + size_t reservedSize = mMaxStackSize;
1.217 +
1.218 + // Go from front to back
1.219 + const volatile StackEntry* entry = mPseudoStack->mStack;
1.220 + const volatile StackEntry* end = entry + mPseudoStack->stackSize();
1.221 + // Deduplicate identical, consecutive frames
1.222 + const char* prevLabel = nullptr;
1.223 + for (; reservedSize-- && entry != end; entry++) {
1.224 + /* We only accept non-copy labels, because
1.225 + we are unable to actually copy labels here */
1.226 + if (entry->isCopyLabel()) {
1.227 + continue;
1.228 + }
1.229 + const char* const label = entry->label();
1.230 + if (label == prevLabel) {
1.231 + continue;
1.232 + }
1.233 + mStackBuffer.infallibleAppend(label);
1.234 + prevLabel = label;
1.235 + }
1.236 + // If we exited early due to buffer size, expand the buffer for next time
1.237 + mMaxStackSize += (end - entry);
1.238 +#endif
1.239 +}
1.240 +
1.241 +} // namespace mozilla
