1 files changed, 332 insertions, 0 deletions
diff --git a/pr/src/md/os2/os2cv.c b/pr/src/md/os2/os2cv.c
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--- /dev/null
+++ b/pr/src/md/os2/os2cv.c
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+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/*
+ * The contents of this file are subject to the Netscape Public License
+ * Version 1.0 (the "NPL"); you may not use this file except in
+ * compliance with the NPL.  You may obtain a copy of the NPL at
+ * http://www.mozilla.org/NPL/
+ * 
+ * Software distributed under the NPL is distributed on an "AS IS" basis,
+ * WITHOUT WARRANTY OF ANY KIND, either express or implied. See the NPL
+ * for the specific language governing rights and limitations under the
+ * NPL.
+ * 
+ * The Initial Developer of this code under the NPL is Netscape
+ * Communications Corporation.  Portions created by Netscape are
+ * Copyright (C) 1998 Netscape Communications Corporation.  All Rights
+ * Reserved.
+ */
+
+/*
+ *  os2cv.c -- OS/2 Machine-Dependent Code for Condition Variables
+ *
+ *  We implement our own condition variable wait queue.  Each thread
+ *  has a semaphore object (thread->md.blocked_sema) to block on while
+ *  waiting on a condition variable.
+ *
+ *  We use a deferred condition notify algorithm.  When PR_NotifyCondVar
+ *  or PR_NotifyAllCondVar is called, the condition notifies are simply
+ *  recorded in the _MDLock structure.  We defer the condition notifies
+ *  until right after we unlock the lock.  This way the awakened threads
+ *  have a better chance to reaquire the lock.
+ */
+ 
+#include "primpl.h"
+
+/*
+ * AddThreadToCVWaitQueueInternal --
+ *
+ * Add the thread to the end of the condition variable's wait queue.
+ * The CV's lock must be locked when this function is called.
+ */
+
+static void
+AddThreadToCVWaitQueueInternal(PRThread *thred, struct _MDCVar *cv)
+{
+    PR_ASSERT((cv->waitTail != NULL && cv->waitHead != NULL)
+            || (cv->waitTail == NULL && cv->waitHead == NULL));
+    cv->nwait += 1;
+    thred->md.inCVWaitQueue = PR_TRUE;
+    thred->md.next = NULL;
+    thred->md.prev = cv->waitTail;
+    if (cv->waitHead == NULL) {
+        cv->waitHead = thred;
+    } else {
+        cv->waitTail->md.next = thred;
+    }
+    cv->waitTail = thred;
+}
+
+/*
+ * md_UnlockAndPostNotifies --
+ *
+ * Unlock the lock, and then do the deferred condition notifies.
+ * If waitThred and waitCV are not NULL, waitThred is added to
+ * the wait queue of waitCV before the lock is unlocked.
+ *
+ * This function is called by _PR_MD_WAIT_CV and _PR_MD_UNLOCK,
+ * the two places where a lock is unlocked.
+ */
+static void
+md_UnlockAndPostNotifies(
+    _MDLock *lock,
+    PRThread *waitThred,
+    _MDCVar *waitCV)
+{
+    PRIntn index;
+    _MDNotified post;
+    _MDNotified *notified, *prev = NULL;
+
+    /*
+     * Time to actually notify any conditions that were affected
+     * while the lock was held.  Get a copy of the list that's in
+     * the lock structure and then zero the original.  If it's
+     * linked to other such structures, we own that storage.
+     */
+    post = lock->notified;  /* a safe copy; we own the lock */
+
+#if defined(DEBUG)
+    memset(&lock->notified, 0, sizeof(_MDNotified));  /* reset */
+#else
+    lock->notified.length = 0;  /* these are really sufficient */
+    lock->notified.link = NULL;
+#endif
+
+    /* 
+     * Figure out how many threads we need to wake up.
+     */
+    notified = &post;  /* this is where we start */
+    do {
+        for (index = 0; index < notified->length; ++index) {
+            _MDCVar *cv = notified->cv[index].cv;
+            PRThread *thred;
+            int i;
+            
+            /* Fast special case: no waiting threads */
+            if (cv->waitHead == NULL) {
+                notified->cv[index].notifyHead = NULL;
+                continue;
+            }
+
+            /* General case */
+            if (-1 == notified->cv[index].times) {
+                /* broadcast */
+                thred = cv->waitHead;
+                while (thred != NULL) {
+                    thred->md.inCVWaitQueue = PR_FALSE;
+                    thred = thred->md.next;
+                }
+                notified->cv[index].notifyHead = cv->waitHead;
+                cv->waitHead = cv->waitTail = NULL;
+                cv->nwait = 0;
+            } else {
+                thred = cv->waitHead;
+                i = notified->cv[index].times;
+                while (thred != NULL && i > 0) {
+                    thred->md.inCVWaitQueue = PR_FALSE;
+                    thred = thred->md.next;
+                    i--;
+                }
+                notified->cv[index].notifyHead = cv->waitHead;
+                cv->waitHead = thred;
+                if (cv->waitHead == NULL) {
+                    cv->waitTail = NULL;
+                } else {
+                    if (cv->waitHead->md.prev != NULL) {
+                        cv->waitHead->md.prev->md.next = NULL;
+                        cv->waitHead->md.prev = NULL;
+                    }
+                }
+                cv->nwait -= notified->cv[index].times - i;
+            }
+        }
+        notified = notified->link;
+    } while (NULL != notified);
+
+    if (waitThred) {
+        AddThreadToCVWaitQueueInternal(waitThred, waitCV);
+    }
+
+    /* Release the lock before notifying */
+        LeaveCriticalSection(&lock->mutex);
+
+    notified = &post;  /* this is where we start */
+    do {
+        for (index = 0; index < notified->length; ++index) {
+            PRThread *thred;
+            PRThread *next;
+
+            thred = notified->cv[index].notifyHead;
+            while (thred != NULL) {
+                BOOL rv;
+
+                next = thred->md.next;
+                thred->md.prev = thred->md.next = NULL;
+                rv = DosPostEventSem(thred->md.blocked_sema.sem);
+                PR_ASSERT(rv == NO_ERROR);
+                thred = next;
+            }
+        }
+        prev = notified;
+        notified = notified->link;
+        if (&post != prev) PR_DELETE(prev);
+    } while (NULL != notified);
+}
+
+/*
+ * Notifies just get posted to the protecting mutex.  The
+ * actual notification is done when the lock is released so that
+ * MP systems don't contend for a lock that they can't have.
+ */
+static void md_PostNotifyToCvar(_MDCVar *cvar, _MDLock *lock,
+        PRBool broadcast)
+{
+    PRIntn index = 0;
+    _MDNotified *notified = &lock->notified;
+
+    while (1) {
+        for (index = 0; index < notified->length; ++index) {
+            if (notified->cv[index].cv == cvar) {
+                if (broadcast) {
+                    notified->cv[index].times = -1;
+                } else if (-1 != notified->cv[index].times) {
+                    notified->cv[index].times += 1;
+                }
+                return;
+            }
+        }
+        /* if not full, enter new CV in this array */
+        if (notified->length < _MD_CV_NOTIFIED_LENGTH) break;
+
+        /* if there's no link, create an empty array and link it */
+        if (NULL == notified->link) {
+            notified->link = PR_NEWZAP(_MDNotified);
+        }
+
+        notified = notified->link;
+    }
+
+    /* A brand new entry in the array */
+    notified->cv[index].times = (broadcast) ? -1 : 1;
+    notified->cv[index].cv = cvar;
+    notified->length += 1;
+}
+
+/*
+ * _PR_MD_NEW_CV() -- Creating new condition variable
+ * ... Solaris uses cond_init() in similar function.
+ *
+ * returns: -1 on failure
+ *          0 when it succeeds.
+ *
+ */
+PR_IMPLEMENT(PRInt32) 
+_PR_MD_NEW_CV(_MDCVar *cv)
+{
+    cv->magic = _MD_MAGIC_CV;
+    /*
+     * The waitHead, waitTail, and nwait fields are zeroed
+     * when the PRCondVar structure is created.
+     */
+    return 0;
+} 
+
+PR_IMPLEMENT(void) _PR_MD_FREE_CV(_MDCVar *cv)
+{
+    cv->magic = (PRUint32)-1;
+    return;
+}
+
+/*
+ *  _PR_MD_WAIT_CV() -- Wait on condition variable
+ */
+PR_IMPLEMENT(void) 
+_PR_MD_WAIT_CV(_MDCVar *cv, _MDLock *lock, PRIntervalTime timeout )
+{
+    PRThread *thred = _PR_MD_CURRENT_THREAD();
+    ULONG rv, count;
+    ULONG msecs = (timeout == PR_INTERVAL_NO_TIMEOUT) ?
+            SEM_INDEFINITE_WAIT : PR_IntervalToMilliseconds(timeout);
+
+    /*
+     * If we have pending notifies, post them now.
+     */
+    if (0 != lock->notified.length) {
+        md_UnlockAndPostNotifies(lock, thred, cv);
+    } else {
+        AddThreadToCVWaitQueueInternal(thred, cv);
+        LeaveCriticalSection(&lock->mutex); 
+    }
+
+    /* Wait for notification or timeout; don't really care which */
+    rv = DosWaitEventSem(thred->md.blocked_sema.sem, msecs);
+    DosResetEventSem(thred->md.blocked_sema.sem, &count);
+
+    EnterCriticalSection(&(lock->mutex));
+
+    PR_ASSERT(rv == NO_ERROR || rv == ERROR_TIMEOUT);
+
+    if(rv == ERROR_TIMEOUT)
+    {
+       if (thred->md.inCVWaitQueue) {
+           PR_ASSERT((cv->waitTail != NULL && cv->waitHead != NULL)
+                   || (cv->waitTail == NULL && cv->waitHead == NULL));
+           cv->nwait -= 1;
+           thred->md.inCVWaitQueue = PR_FALSE;
+           if (cv->waitHead == thred) {
+               cv->waitHead = thred->md.next;
+               if (cv->waitHead == NULL) {
+                   cv->waitTail = NULL;
+               } else {
+                   cv->waitHead->md.prev = NULL;
+               }
+           } else {
+               PR_ASSERT(thred->md.prev != NULL);
+               thred->md.prev->md.next = thred->md.next;
+               if (thred->md.next != NULL) {
+                   thred->md.next->md.prev = thred->md.prev;
+               } else {
+                   PR_ASSERT(cv->waitTail == thred);
+                   cv->waitTail = thred->md.prev;
+               }
+           }
+           thred->md.next = thred->md.prev = NULL;
+       } else {
+           /*
+            * This thread must have been notified, but the
+            * SemRelease call happens after SemRequest
+            * times out.  Wait on the semaphore again to make it
+            * non-signaled.  We assume this wait won't take long.
+            */
+           rv = DosWaitEventSem(thred->md.blocked_sema.sem, SEM_INDEFINITE_WAIT);
+           DosResetEventSem(thred->md.blocked_sema.sem, &count);
+           PR_ASSERT(rv == NO_ERROR);
+       }
+    }
+    PR_ASSERT(thred->md.inCVWaitQueue == PR_FALSE);
+    return;
+} /* --- end _PR_MD_WAIT_CV() --- */
+
+PR_IMPLEMENT(void)
+_PR_MD_NOTIFY_CV(_MDCVar *cv, _MDLock *lock)
+{
+    md_PostNotifyToCvar(cv, lock, PR_FALSE);
+    return;
+}
+
+PR_IMPLEMENT(void)
+_PR_MD_NOTIFYALL_CV(_MDCVar *cv, _MDLock *lock)
+{
+    md_PostNotifyToCvar(cv, lock, PR_TRUE);
+    return;
+}
+
+PR_IMPLEMENT(void)
+_PR_MD_UNLOCK(_MDLock *lock)
+{
+    if (0 != lock->notified.length) {
+        md_UnlockAndPostNotifies(lock, NULL, NULL);
+    } else {
+        LeaveCriticalSection(&lock->mutex);
+    }
+    return;
+}