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- // -*- Mode: C++; c-basic-offset: 2; indent-tabs-mode: nil -*-
- /* Copyright (c) 2009, Google Inc.
- * 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.
- *
- * ---
- * Author: Nabeel Mian
- *
- * This module manages the cpu profile timers and the associated interrupt
- * handler. When enabled, all threads in the program are profiled.
- *
- * Any component interested in receiving a profile timer interrupt can do so by
- * registering a callback. All registered callbacks must be async-signal-safe.
- *
- * Note: This module requires the sole ownership of the configured timer and
- * signal. The timer defaults to ITIMER_PROF, can be changed to ITIMER_REAL by
- * the environment variable CPUPROFILE_REALTIME, or is changed to a POSIX timer
- * with CPUPROFILE_PER_THREAD_TIMERS. The signal defaults to SIGPROF/SIGALRM to
- * match the choice of timer and can be set to an arbitrary value using
- * CPUPROFILE_TIMER_SIGNAL with CPUPROFILE_PER_THREAD_TIMERS.
- */
- #ifndef BASE_PROFILE_HANDLER_H_
- #define BASE_PROFILE_HANDLER_H_
- #include "config.h"
- #include <signal.h>
- #ifdef COMPILER_MSVC
- #include "conflict-signal.h"
- #endif
- #include "base/basictypes.h"
- /* Forward declaration. */
- struct ProfileHandlerToken;
- /*
- * Callback function to be used with ProfilefHandlerRegisterCallback. This
- * function will be called in the context of SIGPROF signal handler and must
- * be async-signal-safe. The first three arguments are the values provided by
- * the SIGPROF signal handler. We use void* to avoid using ucontext_t on
- * non-POSIX systems.
- *
- * Requirements:
- * - Callback must be async-signal-safe.
- * - None of the functions in ProfileHandler are async-signal-safe. Therefore,
- * callback function *must* not call any of the ProfileHandler functions.
- * - Callback is not required to be re-entrant. At most one instance of
- * callback can run at a time.
- *
- * Notes:
- * - The SIGPROF signal handler saves and restores errno, so the callback
- * doesn't need to.
- * - Callback code *must* not acquire lock(s) to serialize access to data shared
- * with the code outside the signal handler (callback must be
- * async-signal-safe). If such a serialization is needed, follow the model
- * used by profiler.cc:
- *
- * When code other than the signal handler modifies the shared data it must:
- * - Acquire lock.
- * - Unregister the callback with the ProfileHandler.
- * - Modify shared data.
- * - Re-register the callback.
- * - Release lock.
- * and the callback code gets a lockless, read-write access to the data.
- */
- typedef void (*ProfileHandlerCallback)(int sig, siginfo_t* sig_info,
- void* ucontext, void* callback_arg);
- /*
- * Registers a new thread with profile handler and should be called only once
- * per thread. The main thread is registered at program startup. This routine
- * is called by the Thread module in google3/thread whenever a new thread is
- * created. This function is not async-signal-safe.
- */
- void ProfileHandlerRegisterThread();
- /*
- * Registers a callback routine. This callback function will be called in the
- * context of SIGPROF handler, so must be async-signal-safe. The returned token
- * is to be used when unregistering this callback via
- * ProfileHandlerUnregisterCallback. Registering the first callback enables
- * the SIGPROF signal handler. Caller must not free the returned token. This
- * function is not async-signal-safe.
- */
- ProfileHandlerToken* ProfileHandlerRegisterCallback(
- ProfileHandlerCallback callback, void* callback_arg);
- /*
- * Unregisters a previously registered callback. Expects the token returned
- * by the corresponding ProfileHandlerRegisterCallback and asserts that the
- * passed token is valid. Unregistering the last callback disables the SIGPROF
- * signal handler. It waits for the currently running callback to
- * complete before returning. This function is not async-signal-safe.
- */
- void ProfileHandlerUnregisterCallback(ProfileHandlerToken* token);
- /*
- * FOR TESTING ONLY
- * Unregisters all the callbacks, stops the timers (if shared) and disables the
- * SIGPROF handler. All the threads, including the main thread, need to be
- * re-registered after this call. This function is not async-signal-safe.
- */
- void ProfileHandlerReset();
- /*
- * Stores profile handler's current state. This function is not
- * async-signal-safe.
- */
- struct ProfileHandlerState {
- int32 frequency; /* Profiling frequency */
- int32 callback_count; /* Number of callbacks registered */
- int64 interrupts; /* Number of interrupts received */
- bool allowed; /* Profiling is allowed */
- };
- void ProfileHandlerGetState(struct ProfileHandlerState* state);
- #endif /* BASE_PROFILE_HANDLER_H_ */
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