/* Copyright (c) 2009, Google Inc.
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*
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* 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 registered threads in the program are profiled.
* (Note: if using linux 2.4 or earlier, you must use the Thread class, in
* google3/thread, to ensure all threads 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 ITIMER_PROF timer and the
* SIGPROF signal.
*/
#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"
/* All this code should be usable from within C apps. */
#ifdef __cplusplus
extern "C" {
#endif
/* 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);
#ifdef __cplusplus
} /* extern "C" */
#endif
#endif /* BASE_PROFILE_HANDLER_H_ */