1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 245 246 247 248 249 250 251 252 253 254 255 256 257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503
|
/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
/* vim: set ts=8 sts=2 et sw=2 tw=80: */
// Copyright (c) 2006-2011 The Chromium Authors. All rights reserved.
//
// Redistribution and use in source and binary forms, with or without
// modification, are permitted provided that the following conditions
// are met:
// * Redistributions of source code must retain the above copyright
// notice, this list of conditions and the following disclaimer.
// * Redistributions in binary form must reproduce the above copyright
// notice, this list of conditions and the following disclaimer in
// the documentation and/or other materials provided with the
// distribution.
// * Neither the name of Google, Inc. nor the names of its contributors
// may be used to endorse or promote products derived from this
// software without specific prior written permission.
//
// THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
// "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
// LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
// FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
// COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
// INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
// BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
// OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
// AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
// OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
// OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
// SUCH DAMAGE.
// This file is used for both Linux and Android.
#include <stdio.h>
#include <math.h>
#include <pthread.h>
#include <semaphore.h>
#include <signal.h>
#include <sys/time.h>
#include <sys/resource.h>
#include <sys/syscall.h>
#include <sys/types.h>
#include <stdlib.h>
#include <sched.h>
#include <ucontext.h>
// Ubuntu Dapper requires memory pages to be marked as
// executable. Otherwise, OS raises an exception when executing code
// in that page.
#include <sys/types.h> // mmap & munmap
#include <sys/mman.h> // mmap & munmap
#include <sys/stat.h> // open
#include <fcntl.h> // open
#include <unistd.h> // sysconf
#include <semaphore.h>
#ifdef __GLIBC__
#include <execinfo.h> // backtrace, backtrace_symbols
#endif // def __GLIBC__
#include <strings.h> // index
#include <errno.h>
#include <stdarg.h>
#include "prenv.h"
#include "mozilla/PodOperations.h"
#include "mozilla/DebugOnly.h"
#include <string.h>
#include <list>
using namespace mozilla;
/* static */ int Thread::GetCurrentId() { return gettid(); }
void* GetStackTop(void* aGuess) { return aGuess; }
static void PopulateRegsFromContext(Registers& aRegs, ucontext_t* aContext) {
aRegs.mContext = aContext;
mcontext_t& mcontext = aContext->uc_mcontext;
// Extracting the sample from the context is extremely machine dependent.
#if defined(GP_ARCH_x86)
aRegs.mPC = reinterpret_cast<Address>(mcontext.gregs[REG_EIP]);
aRegs.mSP = reinterpret_cast<Address>(mcontext.gregs[REG_ESP]);
aRegs.mFP = reinterpret_cast<Address>(mcontext.gregs[REG_EBP]);
aRegs.mLR = 0;
#elif defined(GP_ARCH_amd64)
aRegs.mPC = reinterpret_cast<Address>(mcontext.gregs[REG_RIP]);
aRegs.mSP = reinterpret_cast<Address>(mcontext.gregs[REG_RSP]);
aRegs.mFP = reinterpret_cast<Address>(mcontext.gregs[REG_RBP]);
aRegs.mLR = 0;
#elif defined(GP_ARCH_arm)
aRegs.mPC = reinterpret_cast<Address>(mcontext.arm_pc);
aRegs.mSP = reinterpret_cast<Address>(mcontext.arm_sp);
aRegs.mFP = reinterpret_cast<Address>(mcontext.arm_fp);
aRegs.mLR = reinterpret_cast<Address>(mcontext.arm_lr);
#elif defined(GP_ARCH_aarch64)
aRegs.mPC = reinterpret_cast<Address>(mcontext.pc);
aRegs.mSP = reinterpret_cast<Address>(mcontext.sp);
aRegs.mFP = reinterpret_cast<Address>(mcontext.regs[29]);
aRegs.mLR = reinterpret_cast<Address>(mcontext.regs[30]);
#elif defined(GP_ARCH_mips64)
aRegs.mPC = reinterpret_cast<Address>(mcontext.pc);
aRegs.mSP = reinterpret_cast<Address>(mcontext.gregs[29]);
aRegs.mFP = reinterpret_cast<Address>(mcontext.gregs[30]);
#else
#error "bad platform"
#endif
}
#if defined(GP_OS_android)
#define SYS_tgkill __NR_tgkill
#endif
int tgkill(pid_t tgid, pid_t tid, int signalno) {
return syscall(SYS_tgkill, tgid, tid, signalno);
}
class PlatformData {
public:
explicit PlatformData(int aThreadId) { MOZ_COUNT_CTOR(PlatformData); }
~PlatformData() { MOZ_COUNT_DTOR(PlatformData); }
};
////////////////////////////////////////////////////////////////////////
// BEGIN Sampler target specifics
// The only way to reliably interrupt a Linux thread and inspect its register
// and stack state is by sending a signal to it, and doing the work inside the
// signal handler. But we don't want to run much code inside the signal
// handler, since POSIX severely restricts what we can do in signal handlers.
// So we use a system of semaphores to suspend the thread and allow the
// sampler thread to do all the work of unwinding and copying out whatever
// data it wants.
//
// A four-message protocol is used to reliably suspend and later resume the
// thread to be sampled (the samplee):
//
// Sampler (signal sender) thread Samplee (thread to be sampled)
//
// Prepare the SigHandlerCoordinator
// and point sSigHandlerCoordinator at it
//
// send SIGPROF to samplee ------- MSG 1 ----> (enter signal handler)
// wait(mMessage2) Copy register state
// into sSigHandlerCoordinator
// <------ MSG 2 ----- post(mMessage2)
// Samplee is now suspended. wait(mMessage3)
// Examine its stack/register
// state at leisure
//
// Release samplee:
// post(mMessage3) ------- MSG 3 ----->
// wait(mMessage4) Samplee now resumes. Tell
// the sampler that we are done.
// <------ MSG 4 ------ post(mMessage4)
// Now we know the samplee's signal (leave signal handler)
// handler has finished using
// sSigHandlerCoordinator. We can
// safely reuse it for some other thread.
//
// A type used to coordinate between the sampler (signal sending) thread and
// the thread currently being sampled (the samplee, which receives the
// signals).
//
// The first message is sent using a SIGPROF signal delivery. The subsequent
// three are sent using sem_wait/sem_post pairs. They are named accordingly
// in the following struct.
struct SigHandlerCoordinator {
SigHandlerCoordinator() {
PodZero(&mUContext);
int r = sem_init(&mMessage2, /* pshared */ 0, 0);
r |= sem_init(&mMessage3, /* pshared */ 0, 0);
r |= sem_init(&mMessage4, /* pshared */ 0, 0);
MOZ_ASSERT(r == 0);
}
~SigHandlerCoordinator() {
int r = sem_destroy(&mMessage2);
r |= sem_destroy(&mMessage3);
r |= sem_destroy(&mMessage4);
MOZ_ASSERT(r == 0);
}
sem_t mMessage2; // To sampler: "context is in sSigHandlerCoordinator"
sem_t mMessage3; // To samplee: "resume"
sem_t mMessage4; // To sampler: "finished with sSigHandlerCoordinator"
ucontext_t mUContext; // Context at signal
};
struct SigHandlerCoordinator* Sampler::sSigHandlerCoordinator = nullptr;
static void SigprofHandler(int aSignal, siginfo_t* aInfo, void* aContext) {
// Avoid TSan warning about clobbering errno.
int savedErrno = errno;
MOZ_ASSERT(aSignal == SIGPROF);
MOZ_ASSERT(Sampler::sSigHandlerCoordinator);
// By sending us this signal, the sampler thread has sent us message 1 in
// the comment above, with the meaning "|sSigHandlerCoordinator| is ready
// for use, please copy your register context into it."
Sampler::sSigHandlerCoordinator->mUContext =
*static_cast<ucontext_t*>(aContext);
// Send message 2: tell the sampler thread that the context has been copied
// into |sSigHandlerCoordinator->mUContext|. sem_post can never fail by
// being interrupted by a signal, so there's no loop around this call.
int r = sem_post(&Sampler::sSigHandlerCoordinator->mMessage2);
MOZ_ASSERT(r == 0);
// At this point, the sampler thread assumes we are suspended, so we must
// not touch any global state here.
// Wait for message 3: the sampler thread tells us to resume.
while (true) {
r = sem_wait(&Sampler::sSigHandlerCoordinator->mMessage3);
if (r == -1 && errno == EINTR) {
// Interrupted by a signal. Try again.
continue;
}
// We don't expect any other kind of failure
MOZ_ASSERT(r == 0);
break;
}
// Send message 4: tell the sampler thread that we are finished accessing
// |sSigHandlerCoordinator|. After this point it is not safe to touch
// |sSigHandlerCoordinator|.
r = sem_post(&Sampler::sSigHandlerCoordinator->mMessage4);
MOZ_ASSERT(r == 0);
errno = savedErrno;
}
Sampler::Sampler(PSLockRef aLock)
: mMyPid(getpid())
// We don't know what the sampler thread's ID will be until it runs, so
// set mSamplerTid to a dummy value and fill it in for real in
// SuspendAndSampleAndResumeThread().
,
mSamplerTid(-1) {
#if defined(USE_EHABI_STACKWALK)
mozilla::EHABIStackWalkInit();
#endif
// NOTE: We don't initialize LUL here, instead initializing it in
// SamplerThread's constructor. This is because with the
// profiler_suspend_and_sample_thread entry point, we want to be able to
// sample without waiting for LUL to be initialized.
// Request profiling signals.
struct sigaction sa;
sa.sa_sigaction = SigprofHandler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART | SA_SIGINFO;
if (sigaction(SIGPROF, &sa, &mOldSigprofHandler) != 0) {
MOZ_CRASH("Error installing SIGPROF handler in the profiler");
}
}
void Sampler::Disable(PSLockRef aLock) {
// Restore old signal handler. This is global state so it's important that
// we do it now, while gPSMutex is locked.
sigaction(SIGPROF, &mOldSigprofHandler, 0);
}
template <typename Func>
void Sampler::SuspendAndSampleAndResumeThread(
PSLockRef aLock, const RegisteredThread& aRegisteredThread,
const Func& aProcessRegs) {
// Only one sampler thread can be sampling at once. So we expect to have
// complete control over |sSigHandlerCoordinator|.
MOZ_ASSERT(!sSigHandlerCoordinator);
if (mSamplerTid == -1) {
mSamplerTid = gettid();
}
int sampleeTid = aRegisteredThread.Info()->ThreadId();
MOZ_RELEASE_ASSERT(sampleeTid != mSamplerTid);
//----------------------------------------------------------------//
// Suspend the samplee thread and get its context.
SigHandlerCoordinator coord; // on sampler thread's stack
sSigHandlerCoordinator = &coord;
// Send message 1 to the samplee (the thread to be sampled), by
// signalling at it.
int r = tgkill(mMyPid, sampleeTid, SIGPROF);
MOZ_ASSERT(r == 0);
// Wait for message 2 from the samplee, indicating that the context
// is available and that the thread is suspended.
while (true) {
r = sem_wait(&sSigHandlerCoordinator->mMessage2);
if (r == -1 && errno == EINTR) {
// Interrupted by a signal. Try again.
continue;
}
// We don't expect any other kind of failure.
MOZ_ASSERT(r == 0);
break;
}
//----------------------------------------------------------------//
// Sample the target thread.
// WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
//
// The profiler's "critical section" begins here. In the critical section,
// we must not do any dynamic memory allocation, nor try to acquire any lock
// or any other unshareable resource. This is because the thread to be
// sampled has been suspended at some entirely arbitrary point, and we have
// no idea which unsharable resources (locks, essentially) it holds. So any
// attempt to acquire any lock, including the implied locks used by the
// malloc implementation, risks deadlock. This includes TimeStamp::Now(),
// which gets a lock on Windows.
// The samplee thread is now frozen and sSigHandlerCoordinator->mUContext is
// valid. We can poke around in it and unwind its stack as we like.
// Extract the current register values.
Registers regs;
PopulateRegsFromContext(regs, &sSigHandlerCoordinator->mUContext);
aProcessRegs(regs);
//----------------------------------------------------------------//
// Resume the target thread.
// Send message 3 to the samplee, which tells it to resume.
r = sem_post(&sSigHandlerCoordinator->mMessage3);
MOZ_ASSERT(r == 0);
// Wait for message 4 from the samplee, which tells us that it has
// finished with |sSigHandlerCoordinator|.
while (true) {
r = sem_wait(&sSigHandlerCoordinator->mMessage4);
if (r == -1 && errno == EINTR) {
continue;
}
MOZ_ASSERT(r == 0);
break;
}
// The profiler's critical section ends here. After this point, none of the
// critical section limitations documented above apply.
//
// WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
// This isn't strictly necessary, but doing so does help pick up anomalies
// in which the signal handler is running when it shouldn't be.
sSigHandlerCoordinator = nullptr;
}
// END Sampler target specifics
////////////////////////////////////////////////////////////////////////
////////////////////////////////////////////////////////////////////////
// BEGIN SamplerThread target specifics
static void* ThreadEntry(void* aArg) {
auto thread = static_cast<SamplerThread*>(aArg);
thread->Run();
return nullptr;
}
SamplerThread::SamplerThread(PSLockRef aLock, uint32_t aActivityGeneration,
double aIntervalMilliseconds)
: Sampler(aLock),
mActivityGeneration(aActivityGeneration),
mIntervalMicroseconds(
std::max(1, int(floor(aIntervalMilliseconds * 1000 + 0.5)))) {
#if defined(USE_LUL_STACKWALK)
lul::LUL* lul = CorePS::Lul(aLock);
if (!lul) {
CorePS::SetLul(aLock, MakeUnique<lul::LUL>(logging_sink_for_LUL));
// Read all the unwind info currently available.
lul = CorePS::Lul(aLock);
read_procmaps(lul);
// Switch into unwind mode. After this point, we can't add or remove any
// unwind info to/from this LUL instance. The only thing we can do with
// it is Unwind() calls.
lul->EnableUnwinding();
// Has a test been requested?
if (PR_GetEnv("MOZ_PROFILER_LUL_TEST")) {
int nTests = 0, nTestsPassed = 0;
RunLulUnitTests(&nTests, &nTestsPassed, lul);
}
}
#endif
// Start the sampling thread. It repeatedly sends a SIGPROF signal. Sending
// the signal ourselves instead of relying on itimer provides much better
// accuracy.
if (pthread_create(&mThread, nullptr, ThreadEntry, this) != 0) {
MOZ_CRASH("pthread_create failed");
}
}
SamplerThread::~SamplerThread() { pthread_join(mThread, nullptr); }
void SamplerThread::SleepMicro(uint32_t aMicroseconds) {
if (aMicroseconds >= 1000000) {
// Use usleep for larger intervals, because the nanosleep
// code below only supports intervals < 1 second.
MOZ_ALWAYS_TRUE(!::usleep(aMicroseconds));
return;
}
struct timespec ts;
ts.tv_sec = 0;
ts.tv_nsec = aMicroseconds * 1000UL;
int rv = ::nanosleep(&ts, &ts);
while (rv != 0 && errno == EINTR) {
// Keep waiting in case of interrupt.
// nanosleep puts the remaining time back into ts.
rv = ::nanosleep(&ts, &ts);
}
MOZ_ASSERT(!rv, "nanosleep call failed");
}
void SamplerThread::Stop(PSLockRef aLock) {
// Restore old signal handler. This is global state so it's important that
// we do it now, while gPSMutex is locked. It's safe to do this now even
// though this SamplerThread is still alive, because the next time the main
// loop of Run() iterates it won't get past the mActivityGeneration check,
// and so won't send any signals.
Sampler::Disable(aLock);
}
// END SamplerThread target specifics
////////////////////////////////////////////////////////////////////////
#if defined(GP_OS_linux)
// We use pthread_atfork() to temporarily disable signal delivery during any
// fork() call. Without that, fork() can be repeatedly interrupted by signal
// delivery, requiring it to be repeatedly restarted, which can lead to *long*
// delays. See bug 837390.
//
// We provide no paf_child() function to run in the child after forking. This
// is fine because we always immediately exec() after fork(), and exec()
// clobbers all process state. (At one point we did have a paf_child()
// function, but it caused problems related to locking gPSMutex. See bug
// 1348374.)
//
// Unfortunately all this is only doable on non-Android because Bionic doesn't
// have pthread_atfork.
// In the parent, before the fork, record IsPaused, and then pause.
static void paf_prepare() {
MOZ_RELEASE_ASSERT(CorePS::Exists());
PSAutoLock lock(gPSMutex);
if (ActivePS::Exists(lock)) {
ActivePS::SetWasPaused(lock, ActivePS::IsPaused(lock));
ActivePS::SetIsPaused(lock, true);
}
}
// In the parent, after the fork, return IsPaused to the pre-fork state.
static void paf_parent() {
MOZ_RELEASE_ASSERT(CorePS::Exists());
PSAutoLock lock(gPSMutex);
if (ActivePS::Exists(lock)) {
ActivePS::SetIsPaused(lock, ActivePS::WasPaused(lock));
ActivePS::SetWasPaused(lock, false);
}
}
static void PlatformInit(PSLockRef aLock) {
// Set up the fork handlers.
pthread_atfork(paf_prepare, paf_parent, nullptr);
}
#else
static void PlatformInit(PSLockRef aLock) {}
#endif
#if defined(HAVE_NATIVE_UNWIND)
// Context used by synchronous samples. It's safe to have a single one because
// only one synchronous sample can be taken at a time (due to
// profiler_get_backtrace()'s PSAutoLock).
ucontext_t sSyncUContext;
void Registers::SyncPopulate() {
if (!getcontext(&sSyncUContext)) {
PopulateRegsFromContext(*this, &sSyncUContext);
}
}
#endif
|