Mutex.cpp   [plain text]

//===-- Mutex.cpp -----------------------------------------------*- C++ -*-===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#include "lldb/Host/Mutex.h"
#include "lldb/Host/Host.h"

#include <string.h>
#include <stdio.h>
#include <unistd.h>

#if 0
// This logging is way too verbose to enable even for a log channel. 
// This logging can be enabled by changing the "#if 0", but should be
// reverted prior to checking in.
#include <cstdio>
#define DEBUG_LOG(fmt, ...) printf(fmt, ## __VA_ARGS__)
#else
#define DEBUG_LOG(fmt, ...)
#endif

// Enable extra mutex error checking
#ifdef LLDB_CONFIGURATION_DEBUG
#define ENABLE_MUTEX_ERROR_CHECKING 1
#endif

#if ENABLE_MUTEX_ERROR_CHECKING
#include <set>

enum MutexAction
{
    eMutexActionInitialized,
    eMutexActionDestroyed,
    eMutexActionAssertInitialized
};

static bool
error_check_mutex (pthread_mutex_t *m, MutexAction action)
{
    typedef std::set<pthread_mutex_t *> mutex_set;
    static pthread_mutex_t g_mutex_set_mutex = PTHREAD_MUTEX_INITIALIZER;
    static mutex_set g_initialized_mutex_set;
    static mutex_set g_destroyed_mutex_set;

    bool success = true;
    int err;
    // Manually call lock so we don't to any of this error checking
    err = ::pthread_mutex_lock (&g_mutex_set_mutex);
    assert(err == 0);
    switch (action)
    {
        case eMutexActionInitialized:
            // Make sure this isn't already in our initialized mutex set...
            assert (g_initialized_mutex_set.find(m) == g_initialized_mutex_set.end());
            // Remove this from the destroyed set in case it was ever in there
            g_destroyed_mutex_set.erase(m);
            // Add the mutex to the initialized set
            g_initialized_mutex_set.insert(m);
            break;
            
        case eMutexActionDestroyed:
            // Make sure this isn't already in our destroyed mutex set...
            assert (g_destroyed_mutex_set.find(m) == g_destroyed_mutex_set.end());
            // Remove this from the initialized so we can put it into the destroyed set
            g_initialized_mutex_set.erase(m);
            // Add the mutex to the destroyed set
            g_destroyed_mutex_set.insert(m);
            break;
        case eMutexActionAssertInitialized:
            // This function will return true if "m" is in the initialized mutex set
            success = g_initialized_mutex_set.find(m) != g_initialized_mutex_set.end();
            assert (success);
            break;
    }
    // Manually call unlock so we don't to any of this error checking
    err = ::pthread_mutex_unlock (&g_mutex_set_mutex);
    assert(err == 0);
    return success;
}

#endif

using namespace lldb_private;

//----------------------------------------------------------------------
// Default constructor.
//
// This will create a scoped mutex locking object that doesn't have
// a mutex to lock. One will need to be provided using the Reset()
// method.
//----------------------------------------------------------------------
Mutex::Locker::Locker () :
    m_mutex_ptr(NULL)
{
}

//----------------------------------------------------------------------
// Constructor with a Mutex object.
//
// This will create a scoped mutex locking object that extracts the
// mutex owned by "m" and locks it.
//----------------------------------------------------------------------
Mutex::Locker::Locker (Mutex& m) :
    m_mutex_ptr(NULL)
{
    Lock (m);
}

//----------------------------------------------------------------------
// Constructor with a Mutex object pointer.
//
// This will create a scoped mutex locking object that extracts the
// mutex owned by "m" and locks it.
//----------------------------------------------------------------------
Mutex::Locker::Locker (Mutex* m) :
    m_mutex_ptr(NULL)
{
    if (m)
        Lock (m);
}

//----------------------------------------------------------------------
// Destructor
//
// Unlocks any owned mutex object (if it is valid).
//----------------------------------------------------------------------
Mutex::Locker::~Locker ()
{
    Unlock();
}

//----------------------------------------------------------------------
// Unlock the current mutex in this object (if this owns a valid
// mutex) and lock the new "mutex" object if it is non-NULL.
//----------------------------------------------------------------------
void
Mutex::Locker::Lock (Mutex &mutex)
{
    // We already have this mutex locked or both are NULL...
    if (m_mutex_ptr == &mutex)
        return;

    Unlock ();

    m_mutex_ptr = &mutex;
    m_mutex_ptr->Lock();
}

void
Mutex::Locker::Unlock ()
{
    if (m_mutex_ptr)
    {
        m_mutex_ptr->Unlock ();
        m_mutex_ptr = NULL;
    }
}

bool
Mutex::Locker::TryLock (Mutex &mutex, const char *failure_message)
{
    // We already have this mutex locked!
    if (m_mutex_ptr == &mutex)
        return true;

    Unlock ();

    if (mutex.TryLock(failure_message) == 0)
        m_mutex_ptr = &mutex;

    return m_mutex_ptr != NULL;
}

//----------------------------------------------------------------------
// Default constructor.
//
// Creates a pthread mutex with no attributes.
//----------------------------------------------------------------------
Mutex::Mutex () :
    m_mutex()
{
    int err;
    err = ::pthread_mutex_init (&m_mutex, NULL);
#if ENABLE_MUTEX_ERROR_CHECKING
    if (err == 0)
        error_check_mutex (&m_mutex, eMutexActionInitialized);
#endif
    assert(err == 0);
}

//----------------------------------------------------------------------
// Default constructor.
//
// Creates a pthread mutex with "type" as the mutex type.
//----------------------------------------------------------------------
Mutex::Mutex (Mutex::Type type) :
    m_mutex()
{
    int err;
    ::pthread_mutexattr_t attr;
    err = ::pthread_mutexattr_init (&attr);
    assert(err == 0);
    switch (type)
    {
    case eMutexTypeNormal:
#if ENABLE_MUTEX_ERROR_CHECKING
        err = ::pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_ERRORCHECK);
#else
        err = ::pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_NORMAL);
#endif
        break;

    case eMutexTypeRecursive:
        err = ::pthread_mutexattr_settype (&attr, PTHREAD_MUTEX_RECURSIVE);
        break;

    default:
        err = -1;
        break;
    }
    assert(err == 0);
    err = ::pthread_mutex_init (&m_mutex, &attr);
#if ENABLE_MUTEX_ERROR_CHECKING
    if (err == 0)
        error_check_mutex (&m_mutex, eMutexActionInitialized);
#endif
    assert(err == 0);
    err = ::pthread_mutexattr_destroy (&attr);
    assert(err == 0);
}

//----------------------------------------------------------------------
// Destructor.
//
// Destroys the mutex owned by this object.
//----------------------------------------------------------------------
Mutex::~Mutex()
{
    int err;
    err = ::pthread_mutex_destroy (&m_mutex);
#if ENABLE_MUTEX_ERROR_CHECKING
    if (err == 0)
        error_check_mutex (&m_mutex, eMutexActionDestroyed);
    else
    {
        Host::SetCrashDescriptionWithFormat ("%s error: pthread_mutex_destroy() => err = %i (%s)", __PRETTY_FUNCTION__, err, strerror(err));
        assert(err == 0);
    }
    memset (&m_mutex, '\xba', sizeof(m_mutex));
#endif
}

//----------------------------------------------------------------------
// Mutex get accessor.
//----------------------------------------------------------------------
pthread_mutex_t *
Mutex::GetMutex()
{
    return &m_mutex;
}

//----------------------------------------------------------------------
// Locks the mutex owned by this object, if the mutex is already
// locked, the calling thread will block until the mutex becomes
// available.
//
// RETURNS
//  The error code from the pthread_mutex_lock() function call.
//----------------------------------------------------------------------
int
Mutex::Lock()
{
    DEBUG_LOG ("[%4.4" PRIx64 "/%4.4" PRIx64 "] pthread_mutex_lock (%p)...\n", Host::GetCurrentProcessID(), Host::GetCurrentThreadID(), &m_mutex);

#if ENABLE_MUTEX_ERROR_CHECKING
    error_check_mutex (&m_mutex, eMutexActionAssertInitialized);
#endif

    int err = ::pthread_mutex_lock (&m_mutex);
    

#if ENABLE_MUTEX_ERROR_CHECKING
    if (err)
    {
        Host::SetCrashDescriptionWithFormat ("%s error: pthread_mutex_lock(%p) => err = %i (%s)", __PRETTY_FUNCTION__, &m_mutex, err, strerror(err));
        assert(err == 0);
    }
#endif
    DEBUG_LOG ("[%4.4" PRIx64 "/%4.4" PRIx64 "] pthread_mutex_lock (%p) => %i\n", Host::GetCurrentProcessID(), Host::GetCurrentThreadID(), &m_mutex, err);
    return err;
}

//----------------------------------------------------------------------
// Attempts to lock the mutex owned by this object without blocking.
// If the mutex is already locked, TryLock() will not block waiting
// for the mutex, but will return an error condition.
//
// RETURNS
//  The error code from the pthread_mutex_trylock() function call.
//----------------------------------------------------------------------
int
Mutex::TryLock(const char *failure_message)
{
#if ENABLE_MUTEX_ERROR_CHECKING
    error_check_mutex (&m_mutex, eMutexActionAssertInitialized);
#endif

    int err = ::pthread_mutex_trylock (&m_mutex);
    DEBUG_LOG ("[%4.4" PRIx64 "/%4.4" PRIx64 "] pthread_mutex_trylock (%p) => %i\n", Host::GetCurrentProcessID(), Host::GetCurrentThreadID(), &m_mutex, err);
    return err;
}

//----------------------------------------------------------------------
// If the current thread holds the lock on the owned mutex, then
// Unlock() will unlock the mutex. Calling Unlock() on this object
// that the calling thread does not hold will result in undefined
// behavior.
//
// RETURNS
//  The error code from the pthread_mutex_unlock() function call.
//----------------------------------------------------------------------
int
Mutex::Unlock()
{
#if ENABLE_MUTEX_ERROR_CHECKING
    error_check_mutex (&m_mutex, eMutexActionAssertInitialized);
#endif

    int err = ::pthread_mutex_unlock (&m_mutex);

#if ENABLE_MUTEX_ERROR_CHECKING
    if (err)
    {
        Host::SetCrashDescriptionWithFormat ("%s error: pthread_mutex_unlock(%p) => err = %i (%s)", __PRETTY_FUNCTION__, &m_mutex, err, strerror(err));
        assert(err == 0);
    }
#endif
    DEBUG_LOG ("[%4.4" PRIx64 "/%4.4" PRIx64 "] pthread_mutex_unlock (%p) => %i\n", Host::GetCurrentProcessID(), Host::GetCurrentThreadID(), &m_mutex, err);
    return err;
}

#ifdef LLDB_CONFIGURATION_DEBUG
int
TrackingMutex::Unlock ()
{
    if (!m_failure_message.empty())
        Host::SetCrashDescriptionWithFormat ("Unlocking lock (on thread %p) that thread: %p failed to get: %s",
                                             pthread_self(),
                                             m_thread_that_tried,
                                             m_failure_message.c_str());
    assert (m_failure_message.empty());
    return Mutex::Unlock();
}
#endif