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Reimplemented cEvent using C++11 primitives.

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Fixes #1523.
This commit is contained in:
Mattes D 2014-10-23 11:20:25 +02:00
parent 154c329a25
commit 82472d09ac
2 changed files with 54 additions and 139 deletions
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158
src/OSSupport/Event.cpp
View File

@ -12,68 +12,9 @@
cEvent::cEvent(void)
cEvent::cEvent(void) :
m_ShouldWait(true)
{
#ifdef _WIN32
m_Event = CreateEvent(nullptr, FALSE, FALSE, nullptr);
if (m_Event == nullptr)
{
LOGERROR("cEvent: cannot create event, GLE = %u. Aborting server.", (unsigned)GetLastError());
abort();
}
#else // *nix
m_bIsNamed = false;
m_Event = new sem_t;
if (sem_init(m_Event, 0, 0))
{
// This path is used by MacOS, because it doesn't support unnamed semaphores.
delete m_Event;
m_bIsNamed = true;
AString EventName;
Printf(EventName, "cEvent%p", this);
m_Event = sem_open(EventName.c_str(), O_CREAT, 777, 0);
if (m_Event == SEM_FAILED)
{
AString error = GetOSErrorString(errno);
LOGERROR("cEvent: Cannot create event, err = %s. Aborting server.", error.c_str());
abort();
}
// Unlink the semaphore immediately - it will continue to function but will not pollute the namespace
// We don't store the name, so can't call this in the destructor
if (sem_unlink(EventName.c_str()) != 0)
{
AString error = GetOSErrorString(errno);
LOGWARN("ERROR: Could not unlink cEvent. (%s)", error.c_str());
}
}
#endif // *nix
}
cEvent::~cEvent()
{
#ifdef _WIN32
CloseHandle(m_Event);
#else
if (m_bIsNamed)
{
if (sem_close(m_Event) != 0)
{
AString error = GetOSErrorString(errno);
LOGERROR("ERROR: Could not close cEvent. (%s)", error.c_str());
}
}
else
{
sem_destroy(m_Event);
delete m_Event;
m_Event = nullptr;
}
#endif
}
@ -82,20 +23,12 @@ cEvent::~cEvent()
void cEvent::Wait(void)
{
#ifdef _WIN32
DWORD res = WaitForSingleObject(m_Event, INFINITE);
if (res != WAIT_OBJECT_0)
{
LOGWARN("cEvent: waiting for the event failed: %u, GLE = %u. Continuing, but server may be unstable.", (unsigned)res, (unsigned)GetLastError());
}
#else
int res = sem_wait(m_Event);
if (res != 0)
{
AString error = GetOSErrorString(errno);
LOGWARN("cEvent: waiting for the event failed: %i, err = %s. Continuing, but server may be unstable.", res, error.c_str());
}
#endif
std::unique_lock<std::mutex> Lock(m_Mutex);
while (m_ShouldWait)
{
m_CondVar.wait(Lock);
}
m_ShouldWait = true;
}
@ -104,45 +37,34 @@ void cEvent::Wait(void)
bool cEvent::Wait(int a_TimeoutMSec)
{
#ifdef _WIN32
DWORD res = WaitForSingleObject(m_Event, (DWORD)a_TimeoutMSec);
switch (res)
std::chrono::steady_clock::time_point dst = std::chrono::steady_clock::now() + std::chrono::milliseconds(a_TimeoutMSec);
std::unique_lock<std::mutex> Lock(m_Mutex); // We assume that this lock is acquired without much delay - we are the only user of the mutex
while (m_ShouldWait && (std::chrono::steady_clock::now() < dst))
{
switch (m_CondVar.wait_until(Lock, dst))
{
case WAIT_OBJECT_0: return true; // Regular event signalled
case WAIT_TIMEOUT: return false; // Regular event timeout
default:
case std::cv_status::no_timeout:
{
LOGWARN("cEvent: waiting for the event failed: %u, GLE = %u. Continuing, but server may be unstable.", (unsigned)res, (unsigned)GetLastError());
// The wait was successful, check for spurious wakeup:
if (!m_ShouldWait)
{
m_ShouldWait = true;
return true;
}
// This was a spurious wakeup, wait again:
continue;
}
case std::cv_status::timeout:
{
// The wait timed out, return failure:
return false;
}
}
#else
// Get the current time:
timespec timeout;
if (clock_gettime(CLOCK_REALTIME, &timeout) == -1)
{
LOGWARN("cEvent: Getting current time failed: %i, err = %s. Continuing, but the server may be unstable.", errno, GetOSErrorString(errno).c_str());
return false;
}
} // switch (wait_until())
} // while (m_ShouldWait && not timeout)
// Add the specified timeout:
timeout.tv_sec += a_TimeoutMSec / 1000;
timeout.tv_nsec += (a_TimeoutMSec % 1000) * 1000000; // 1 msec = 1000000 usec
// Wait with timeout:
int res = sem_timedwait(m_Event, &timeout);
switch (res)
{
case 0: return true; // Regular event signalled
case ETIMEDOUT: return false; // Regular even timeout
default:
{
AString error = GetOSErrorString(errno);
LOGWARN("cEvent: waiting for the event failed: %i, err = %s. Continuing, but server may be unstable.", res, error.c_str());
return false;
}
}
#endif
// The wait timed out in the while() condition:
return false;
}
@ -151,19 +73,11 @@ bool cEvent::Wait(int a_TimeoutMSec)
void cEvent::Set(void)
{
#ifdef _WIN32
if (!SetEvent(m_Event))
{
LOGWARN("cEvent: Could not set cEvent: GLE = %u", (unsigned)GetLastError());
}
#else
int res = sem_post(m_Event);
if (res != 0)
{
AString error = GetOSErrorString(errno);
LOGWARN("cEvent: Could not set cEvent: %i, err = %s", res, error.c_str());
}
#endif
{
std::unique_lock<std::mutex> Lock(m_Mutex);
m_ShouldWait = false;
}
m_CondVar.notify_one();
}

35
src/OSSupport/Event.h
View File

@ -1,16 +1,17 @@
// Event.h
// Interfaces to the cEvent object representing an OS-specific synchronization primitive that can be waited-for
// Implemented as an Event on Win and as a 1-semaphore on *nix
// Interfaces to the cEvent object representing a synchronization primitive that can be waited-for
// Implemented using C++11 condition variable and mutex
#pragma once
#ifndef CEVENT_H_INCLUDED
#define CEVENT_H_INCLUDED
#include <mutex>
#include <condition_variable>
@ -20,9 +21,13 @@ class cEvent
{
public:
cEvent(void);
~cEvent();
/** Waits until the event has been set.
If the event has been set before it has been waited for, Wait() returns immediately. */
void Wait(void);
/** Sets the event - releases one thread that has been waiting in Wait().
If there was no thread waiting, the next call to Wait() will not block. */
void Set (void);
/** Waits for the event until either it is signalled, or the (relative) timeout is passed.
@ -31,21 +36,17 @@ public:
private:
#ifdef _WIN32
HANDLE m_Event;
#else
sem_t * m_Event;
bool m_bIsNamed;
#endif
/** Used for checking for spurious wakeups. */
bool m_ShouldWait;
/** Mutex protecting m_ShouldWait from multithreaded access. */
std::mutex m_Mutex;
/** The condition variable used as the Event. */
std::condition_variable m_CondVar;
} ;
#endif // CEVENT_H_INCLUDED