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Merge pull request #4392 from zeromus/master

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rthreads work from desmume
This commit is contained in:
Alcaro 2017-02-05 02:12:31 +01:00 committed by GitHub
commit 7d30b475ba
1 changed files with 276 additions and 34 deletions
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310
libretro-common/rthreads/rthreads.c
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@ -41,6 +41,7 @@
#define _WIN32_WINNT 0x0500 /*_WIN32_WINNT_WIN2K */
#endif
#include <windows.h>
#include <mmsystem.h>
#endif
#elif defined(GEKKO)
#include "gx_pthread.h"
@ -81,16 +82,45 @@ struct sthread
struct slock
{
#ifdef USE_WIN32_THREADS
HANDLE lock;
CRITICAL_SECTION lock;
#else
pthread_mutex_t lock;
#endif
};
#ifdef USE_WIN32_THREADS
/* The syntax we'll use is mind-bending unless we use a struct. Plus, we might want to store more info later */
/* This will be used as a linked list immplementing a queue of waiting threads */
struct QueueEntry
{
struct QueueEntry *next;
};
#endif
struct scond
{
#ifdef USE_WIN32_THREADS
/* With this implementation of scond, we don't have any way of waking (or even identifying) specific threads */
/* But we need to wake them in the order indicated by the queue. */
/* This potato token will get get passed around every waiter. The bearer can test whether he's next, and hold onto the potato if he is. */
/* When he's done he can then put it back into play to progress the queue further */
HANDLE hot_potato;
/* The primary signalled event. Hot potatoes are passed until this is set. */
HANDLE event;
/* the head of the queue; NULL if queue is empty */
struct QueueEntry *head;
/* equivalent to the queue length */
int waiters;
/* how many waiters in the queue have been conceptually wakened by signals (even if we haven't managed to actually wake them yet) */
int wakens;
/* used to control access to this scond, in case the user fails */
CRITICAL_SECTION cs;
#else
pthread_cond_t cond;
#endif
@ -167,7 +197,7 @@ error:
* @thread : pointer to thread object
*
* Detach a thread. When a detached thread terminates, its
* resource sare automatically released back to the system
* resources are automatically released back to the system
* without the need for another thread to join with the
* terminated thread.
*
@ -214,6 +244,9 @@ void sthread_join(sthread_t *thread)
*/
bool sthread_isself(sthread_t *thread)
{
/* This thread can't possibly be a null thread */
if (!thread) return false;
#ifdef USE_WIN32_THREADS
return GetCurrentThread() == thread->thread;
#else
@ -231,23 +264,25 @@ bool sthread_isself(sthread_t *thread)
**/
slock_t *slock_new(void)
{
bool mutex_created = false;
slock_t *lock = (slock_t*)calloc(1, sizeof(*lock));
if (!lock)
return NULL;
#ifdef USE_WIN32_THREADS
lock->lock = CreateMutex(NULL, FALSE, NULL);
if (!lock->lock)
goto error;
InitializeCriticalSection(&lock->lock);
mutex_created = true;
#else
if ((pthread_mutex_init(&lock->lock, NULL) < 0))
goto error;
mutex_created = (pthread_mutex_init(&lock->lock, NULL) == 0);
#endif
if (!mutex_created)
goto error;
return lock;
error:
slock_free(lock);
free(lock);
return NULL;
}
@ -263,7 +298,7 @@ void slock_free(slock_t *lock)
return;
#ifdef USE_WIN32_THREADS
CloseHandle(lock->lock);
DeleteCriticalSection(&lock->lock);
#else
pthread_mutex_destroy(&lock->lock);
#endif
@ -283,7 +318,7 @@ void slock_lock(slock_t *lock)
if (!lock)
return;
#ifdef USE_WIN32_THREADS
WaitForSingleObject(lock->lock, INFINITE);
EnterCriticalSection(&lock->lock);
#else
pthread_mutex_lock(&lock->lock);
#endif
@ -300,7 +335,7 @@ void slock_unlock(slock_t *lock)
if (!lock)
return;
#ifdef USE_WIN32_THREADS
ReleaseMutex(lock->lock);
LeaveCriticalSection(&lock->lock);
#else
pthread_mutex_unlock(&lock->lock);
#endif
@ -317,21 +352,40 @@ void slock_unlock(slock_t *lock)
**/
scond_t *scond_new(void)
{
bool event_created = false;
scond_t *cond = (scond_t*)calloc(1, sizeof(*cond));
if (!cond)
return NULL;
#ifdef USE_WIN32_THREADS
cond->event = CreateEvent(NULL, FALSE, FALSE, NULL);
event_created = !!cond->event;
#else
event_created = (pthread_cond_init(&cond->cond, NULL) == 0);
#endif
if (!event_created)
/* This is very complex because recreating condition variable semantics with win32 parts is not easy */
/* The main problem is that a condition variable can't be used to "pre-wake" a thread (it will get wakened only after it's waited) */
/* whereas a win32 event can pre-wake a thread (the event will be set in advance, so a 'waiter' won't even have to wait on it) */
/* Keep in mind a condition variable can apparently pre-wake a thread, insofar as spurious wakeups are always possible, */
/* but nobody will be expecting this and it does not need to be simulated. */
/* Moreover, we won't be doing this, because it counts as a spurious wakeup -- someone else with a genuine claim must get wakened, in any case. */
/* Therefore we choose to wake only one of the correct waiting threads. */
/* So at the very least, we need to do something clever. But there's bigger problems. */
/* We don't even have a straightforward way in win32 to satisfy pthread_cond_wait's atomicity requirement. The bulk of this algorithm is solving that. */
/* Note: We might could simplify this using vista+ condition variables, but we wanted an XP compatible solution. */
cond->event = CreateEvent(NULL, FALSE, FALSE, NULL);
if (!cond->event) goto error;
cond->hot_potato = CreateEvent(NULL, FALSE, FALSE, NULL);
if (!cond->hot_potato)
{
CloseHandle(cond->event);
goto error;
}
InitializeCriticalSection(&cond->cs);
cond->waiters = cond->wakens = 0;
cond->head = NULL;
#else
if(pthread_cond_init(&cond->cond, NULL) != 0)
goto error;
#endif
return cond;
@ -353,12 +407,163 @@ void scond_free(scond_t *cond)
#ifdef USE_WIN32_THREADS
CloseHandle(cond->event);
CloseHandle(cond->hot_potato);
DeleteCriticalSection(&cond->cs);
#else
pthread_cond_destroy(&cond->cond);
#endif
free(cond);
}
#ifdef USE_WIN32_THREADS
static bool _scond_wait_win32(scond_t *cond, slock_t *lock, DWORD dwMilliseconds)
{
static bool beginPeriod = false;
struct QueueEntry myentry;
struct QueueEntry **ptr;
DWORD tsBegin;
DWORD dwFinalTimeout = dwMilliseconds; /* Careful! in case we begin in the head, we don't do the hot potato stuff, so this timeout needs presetting */
DWORD waitResult;
/* Reminder: `lock` is held before this is called. */
/* however, someone else may have called scond_signal without the lock. soo... */
EnterCriticalSection(&cond->cs);
/* since this library is meant for realtime game software I have no problem setting this to 1 and forgetting about it. */
if(!beginPeriod)
{
beginPeriod = true;
timeBeginPeriod(1);
}
/* Now we can take a good timestamp for use in faking the timeout ourselves. */
/* But don't bother unless we need to (to save a little time) */
if(dwMilliseconds != INFINITE)
tsBegin = timeGetTime();
/* add ourselves to a queue of waiting threads */
ptr = &cond->head;
while(*ptr) /* walk to the end of the linked list */
ptr = &((*ptr)->next);
*ptr = &myentry;
myentry.next = NULL;
cond->waiters++;
/* now the conceptual lock release and condition block are supposed to be atomic. */
/* we can't do that in windows, but we can simulate the effects by using the queue, by the following analysis: */
/* What happens if they aren't atomic? */
/* 1. a signaller can rush in and signal, expecting a waiter to get it; but the waiter wouldn't, because he isn't blocked yet */
/* solution: win32 events make this easy. the event will sit there enabled */
/* 2. a signaller can rush in and signal, and then turn right around and wait */
/* solution: the signaller will get queued behind the waiter, who's enqueued before he releases the mutex */
/* It's my turn if I'm the head of the queue. Check to see if it's my turn. */
while (cond->head != &myentry)
{
/* It isn't my turn: */
DWORD timeout = INFINITE;
/* As long as someone is even going to be able to wake up when they receive the potato, keep it going round */
if (cond->wakens > 0)
SetEvent(cond->hot_potato);
/* Assess the remaining timeout time */
if(dwMilliseconds != INFINITE)
{
DWORD now = timeGetTime();
DWORD elapsed = now - tsBegin;
if(elapsed > dwMilliseconds)
{
/* Try one last time with a zero timeout (keeps the code simpler) */
elapsed = dwMilliseconds;
}
timeout = dwMilliseconds - elapsed;
}
/* Let someone else go */
LeaveCriticalSection(&lock->lock);
LeaveCriticalSection(&cond->cs);
/* Wait a while to catch the hot potato.. someone else should get a chance to go */
/* After all, it isn't my turn (and it must be someone else's) */
Sleep(0);
waitResult = WaitForSingleObject(cond->hot_potato, timeout);
/* I should come out of here with the main lock taken */
EnterCriticalSection(&lock->lock);
EnterCriticalSection(&cond->cs);
if(waitResult == WAIT_TIMEOUT)
{
/* Out of time! Now, let's think about this. I do have the potato now--maybe it's my turn, and I have the event? */
/* If that's the case, I could proceed right now without aborting due to timeout. */
/* However.. I DID wait a real long time. The caller was willing to wait that long. */
/* I choose to give him one last chance with a zero timeout in the next step */
if(cond->head == &myentry)
{
dwFinalTimeout = 0;
break;
}
else
{
/* It's not our turn and we're out of time. Give up. */
/* Remove ourself from the queue and bail. */
struct QueueEntry* curr = cond->head;
while(curr->next != &myentry) curr = curr->next;
curr->next = myentry.next;
cond->waiters--;
LeaveCriticalSection(&cond->cs);
return false;
}
}
}
/* It's my turn now -- and I hold the potato */
/* I still have the main lock, in any case */
/* I need to release it so that someone can set the event */
LeaveCriticalSection(&lock->lock);
LeaveCriticalSection(&cond->cs);
/* Wait for someone to actually signal this condition */
/* We're the only waiter waiting on the event right now -- everyone else is waiting on something different */
waitResult = WaitForSingleObject(cond->event, dwFinalTimeout);
/* Take the main lock so we can do work. Nobody else waits on this lock for very long, so even though it's GO TIME we won't have to wait long */
EnterCriticalSection(&lock->lock);
EnterCriticalSection(&cond->cs);
/* Remove ourselves from the queue */
cond->head = myentry.next;
cond->waiters--;
if(waitResult == WAIT_TIMEOUT)
{
/* Oops! ran out of time in the final wait. Just bail. */
LeaveCriticalSection(&cond->cs);
return false;
}
/* If any other wakenings are pending, go ahead and set it up */
/* There may actually be no waiters. That's OK. The first waiter will come in, find it's his turn, and immediately get the signaled event */
cond->wakens--;
if (cond->wakens > 0)
{
SetEvent(cond->event);
/* Progress the queue: Put the hot potato back into play. It'll be tossed around until next in line gets it */
SetEvent(cond->hot_potato);
}
LeaveCriticalSection(&cond->cs);
return true;
}
#endif
/**
* scond_wait:
* @cond : pointer to condition variable object
@ -369,10 +574,7 @@ void scond_free(scond_t *cond)
void scond_wait(scond_t *cond, slock_t *lock)
{
#ifdef USE_WIN32_THREADS
WaitForSingleObject(cond->event, 0);
SignalObjectAndWait(lock->lock, cond->event, INFINITE, FALSE);
slock_lock(lock);
_scond_wait_win32(cond, lock, INFINITE);
#else
pthread_cond_wait(&cond->cond, &lock->lock);
#endif
@ -388,9 +590,17 @@ void scond_wait(scond_t *cond, slock_t *lock)
int scond_broadcast(scond_t *cond)
{
#ifdef USE_WIN32_THREADS
/* FIXME _- check how this function should differ
* from scond_signal implementation. */
SetEvent(cond->event);
/* remember: we currently have mutex */
if(cond->waiters == 0) return 0;
/* awaken everything which is currently queued up */
if(cond->wakens == 0) SetEvent(cond->event);
cond->wakens = cond->waiters;
/* Since there is now at least one pending waken, the potato must be in play */
SetEvent(cond->hot_potato);
return 0;
#else
return pthread_cond_broadcast(&cond->cond);
@ -407,7 +617,33 @@ int scond_broadcast(scond_t *cond)
void scond_signal(scond_t *cond)
{
#ifdef USE_WIN32_THREADS
SetEvent(cond->event);
/* Unfortunately, pthread_cond_signal does not require that the lock be held in advance */
/* To avoid stomping on the condvar from other threads, we need to control access to it with this */
EnterCriticalSection(&cond->cs);
/* remember: we currently have mutex */
if(cond->waiters == 0)
{
LeaveCriticalSection(&cond->cs);
return;
}
/* wake up the next thing in the queue */
if(cond->wakens == 0) SetEvent(cond->event);
cond->wakens++;
/* The data structure is done being modified.. I think we can leave the CS now. */
/* This would prevent some other thread from receiving the hot potato and then
/* immediately stalling for the critical section. */
/* But remember, we were trying to replicate a semantic where this entire scond_signal call
/* was controlled (by the user) by a lock. */
/* So in case there's trouble with this, we can move it after SetEvent() */
LeaveCriticalSection(&cond->cs);
/* Since there is now at least one pending waken, the potato must be in play */
SetEvent(cond->hot_potato);
#else
pthread_cond_signal(&cond->cond);
#endif
@ -428,14 +664,20 @@ void scond_signal(scond_t *cond)
bool scond_wait_timeout(scond_t *cond, slock_t *lock, int64_t timeout_us)
{
#ifdef USE_WIN32_THREADS
DWORD ret;
WaitForSingleObject(cond->event, 0);
ret = SignalObjectAndWait(lock->lock, cond->event,
(DWORD)(timeout_us) / 1000, FALSE);
slock_lock(lock);
return ret == WAIT_OBJECT_0;
/* How to convert a us timeout to ms? */
/* Someone asking for a 0 timeout clearly wants immediate timeout. */
/* Someone asking for a 1 timeout clearly wants an actual timeout of the minimum length */
/* Someone asking for 1000 or 1001 timeout shouldn't accidentally get 2ms. */
DWORD dwMilliseconds = timeout_us/1000;
if(timeout_us == 0) {
/* The implementation of a 0 timeout here with pthreads is sketchy. */
/* It isn't clear what happens if pthread_cond_timedwait is called with NOW. */
/* Moreover, it is possible that this thread gets pre-empted after the clock_gettime but before the pthread_cond_timedwait. */
/* In order to help smoke out problems caused by this strange usage, let's treat a 0 timeout as always timing out. */
return false;
}
else if(timeout_us < 1000) dwMilliseconds = 1;
return _scond_wait_win32(cond,lock,dwMilliseconds);
#else
int ret;
int64_t seconds, remainder;