--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/nspr/pr/src/threads/prcmon.c	Mon Jul 28 10:47:06 2014 +0200
@@ -0,0 +1,431 @@
+/* -*- Mode: C++; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "primpl.h"
+
+#include <stdlib.h>
+#include <stddef.h>
+
+/* Lock used to lock the monitor cache */
+#ifdef _PR_NO_PREEMPT
+#define _PR_NEW_LOCK_MCACHE()
+#define _PR_DESTROY_LOCK_MCACHE()
+#define _PR_LOCK_MCACHE()
+#define _PR_UNLOCK_MCACHE()
+#else
+#ifdef _PR_LOCAL_THREADS_ONLY
+#define _PR_NEW_LOCK_MCACHE()
+#define _PR_DESTROY_LOCK_MCACHE()
+#define _PR_LOCK_MCACHE() { PRIntn _is; _PR_INTSOFF(_is)
+#define _PR_UNLOCK_MCACHE() _PR_INTSON(_is); }
+#else
+PRLock *_pr_mcacheLock;
+#define _PR_NEW_LOCK_MCACHE() (_pr_mcacheLock = PR_NewLock())
+#define _PR_DESTROY_LOCK_MCACHE()               \
+    PR_BEGIN_MACRO                              \
+        if (_pr_mcacheLock) {                   \
+            PR_DestroyLock(_pr_mcacheLock);     \
+            _pr_mcacheLock = NULL;              \
+        }                                       \
+    PR_END_MACRO
+#define _PR_LOCK_MCACHE() PR_Lock(_pr_mcacheLock)
+#define _PR_UNLOCK_MCACHE() PR_Unlock(_pr_mcacheLock)
+#endif
+#endif
+
+/************************************************************************/
+
+typedef struct MonitorCacheEntryStr MonitorCacheEntry;
+
+struct MonitorCacheEntryStr {
+    MonitorCacheEntry*  next;
+    void*               address;
+    PRMonitor*          mon;
+    long                cacheEntryCount;
+};
+
+/*
+** An array of MonitorCacheEntry's, plus a pointer to link these
+** arrays together.
+*/
+
+typedef struct MonitorCacheEntryBlockStr MonitorCacheEntryBlock;
+
+struct MonitorCacheEntryBlockStr {
+    MonitorCacheEntryBlock* next;
+    MonitorCacheEntry entries[1];
+};
+
+static PRUint32 hash_mask;
+static PRUintn num_hash_buckets;
+static PRUintn num_hash_buckets_log2;
+static MonitorCacheEntry **hash_buckets;
+static MonitorCacheEntry *free_entries;
+static PRUintn num_free_entries;
+static PRBool expanding;
+static MonitorCacheEntryBlock *mcache_blocks;
+
+static void (*OnMonitorRecycle)(void *address);
+
+#define HASH(address)                               \
+    ((PRUint32) ( ((PRUptrdiff)(address) >> 2) ^    \
+                  ((PRUptrdiff)(address) >> 10) )   \
+     & hash_mask)
+
+/*
+** Expand the monitor cache. This grows the hash buckets and allocates a
+** new chunk of cache entries and throws them on the free list. We keep
+** as many hash buckets as there are entries.
+**
+** Because we call malloc and malloc may need the monitor cache, we must
+** ensure that there are several free monitor cache entries available for
+** malloc to get. FREE_THRESHOLD is used to prevent monitor cache
+** starvation during monitor cache expansion.
+*/
+
+#define FREE_THRESHOLD  5
+
+static PRStatus ExpandMonitorCache(PRUintn new_size_log2)
+{
+    MonitorCacheEntry **old_hash_buckets, *p;
+    PRUintn i, entries, old_num_hash_buckets, added;
+    MonitorCacheEntry **new_hash_buckets;
+    MonitorCacheEntryBlock *new_block;
+
+    entries = 1L << new_size_log2;
+
+    /*
+    ** Expand the monitor-cache-entry free list
+    */
+    new_block = (MonitorCacheEntryBlock*)
+        PR_CALLOC(sizeof(MonitorCacheEntryBlock)
+        + (entries - 1) * sizeof(MonitorCacheEntry));
+    if (NULL == new_block) return PR_FAILURE;
+
+    /*
+    ** Allocate system monitors for the new monitor cache entries. If we
+    ** run out of system monitors, break out of the loop.
+    */
+    for (i = 0, p = new_block->entries; i < entries; i++, p++) {
+        p->mon = PR_NewMonitor();
+        if (!p->mon)
+            break;
+    }
+    added = i;
+    if (added != entries) {
+        MonitorCacheEntryBlock *realloc_block;
+
+        if (added == 0) {
+            /* Totally out of system monitors. Lossage abounds */
+            PR_DELETE(new_block);
+            return PR_FAILURE;
+        }
+
+        /*
+        ** We were able to allocate some of the system monitors. Use
+        ** realloc to shrink down the new_block memory. If that fails,
+        ** carry on with the too-large new_block.
+        */
+        realloc_block = (MonitorCacheEntryBlock*)
+            PR_REALLOC(new_block, sizeof(MonitorCacheEntryBlock)
+            + (added - 1) * sizeof(MonitorCacheEntry));
+        if (realloc_block)
+            new_block = realloc_block;
+    }
+
+    /*
+    ** Now that we have allocated all of the system monitors, build up
+    ** the new free list. We can just update the free_list because we own
+    ** the mcache-lock and we aren't calling anyone who might want to use
+    ** it.
+    */
+    for (i = 0, p = new_block->entries; i < added - 1; i++, p++)
+        p->next = p + 1;
+    p->next = free_entries;
+    free_entries = new_block->entries;
+    num_free_entries += added;
+    new_block->next = mcache_blocks;
+    mcache_blocks = new_block;
+
+    /* Try to expand the hash table */
+    new_hash_buckets = (MonitorCacheEntry**)
+        PR_CALLOC(entries * sizeof(MonitorCacheEntry*));
+    if (NULL == new_hash_buckets) {
+        /*
+        ** Partial lossage. In this situation we don't get any more hash
+        ** buckets, which just means that the table lookups will take
+        ** longer. This is bad, but not fatal
+        */
+        PR_LOG(_pr_cmon_lm, PR_LOG_WARNING,
+               ("unable to grow monitor cache hash buckets"));
+        return PR_SUCCESS;
+    }
+
+    /*
+    ** Compute new hash mask value. This value is used to mask an address
+    ** until it's bits are in the right spot for indexing into the hash
+    ** table.
+    */
+    hash_mask = entries - 1;
+
+    /*
+    ** Expand the hash table. We have to rehash everything in the old
+    ** table into the new table.
+    */
+    old_hash_buckets = hash_buckets;
+    old_num_hash_buckets = num_hash_buckets;
+    for (i = 0; i < old_num_hash_buckets; i++) {
+        p = old_hash_buckets[i];
+        while (p) {
+            MonitorCacheEntry *next = p->next;
+
+            /* Hash based on new table size, and then put p in the new table */
+            PRUintn hash = HASH(p->address);
+            p->next = new_hash_buckets[hash];
+            new_hash_buckets[hash] = p;
+
+            p = next;
+        }
+    }
+
+    /*
+    ** Switch over to new hash table and THEN call free of the old
+    ** table. Since free might re-enter _pr_mcache_lock, things would
+    ** break terribly if it used the old hash table.
+    */
+    hash_buckets = new_hash_buckets;
+    num_hash_buckets = entries;
+    num_hash_buckets_log2 = new_size_log2;
+    PR_DELETE(old_hash_buckets);
+
+    PR_LOG(_pr_cmon_lm, PR_LOG_NOTICE,
+           ("expanded monitor cache to %d (buckets %d)",
+            num_free_entries, entries));
+
+    return PR_SUCCESS;
+}  /* ExpandMonitorCache */
+
+/*
+** Lookup a monitor cache entry by address. Return a pointer to the
+** pointer to the monitor cache entry on success, null on failure.
+*/
+static MonitorCacheEntry **LookupMonitorCacheEntry(void *address)
+{
+    PRUintn hash;
+    MonitorCacheEntry **pp, *p;
+
+    hash = HASH(address);
+    pp = hash_buckets + hash;
+    while ((p = *pp) != 0) {
+        if (p->address == address) {
+            if (p->cacheEntryCount > 0)
+                return pp;
+            return NULL;
+        }
+        pp = &p->next;
+    }
+    return NULL;
+}
+
+/*
+** Try to create a new cached monitor. If it's already in the cache,
+** great - return it. Otherwise get a new free cache entry and set it
+** up. If the cache free space is getting low, expand the cache.
+*/
+static PRMonitor *CreateMonitor(void *address)
+{
+    PRUintn hash;
+    MonitorCacheEntry **pp, *p;
+
+    hash = HASH(address);
+    pp = hash_buckets + hash;
+    while ((p = *pp) != 0) {
+        if (p->address == address) goto gotit;
+
+        pp = &p->next;
+    }
+
+    /* Expand the monitor cache if we have run out of free slots in the table */
+    if (num_free_entries < FREE_THRESHOLD) {
+        /* Expand monitor cache */
+
+        /*
+        ** This function is called with the lock held. So what's the 'expanding'
+        ** boolean all about? Seems a bit redundant.
+        */
+        if (!expanding) {
+            PRStatus rv;
+
+            expanding = PR_TRUE;
+            rv = ExpandMonitorCache(num_hash_buckets_log2 + 1);
+            expanding = PR_FALSE;
+            if (PR_FAILURE == rv)  return NULL;
+
+            /* redo the hash because it'll be different now */
+            hash = HASH(address);
+        } else {
+            /*
+            ** We are in process of expanding and we need a cache
+            ** monitor.  Make sure we have enough!
+            */
+            PR_ASSERT(num_free_entries > 0);
+        }
+    }
+
+    /* Make a new monitor */
+    p = free_entries;
+    free_entries = p->next;
+    num_free_entries--;
+    if (OnMonitorRecycle && p->address)
+        OnMonitorRecycle(p->address);
+    p->address = address;
+    p->next = hash_buckets[hash];
+    hash_buckets[hash] = p;
+    PR_ASSERT(p->cacheEntryCount == 0);
+
+  gotit:
+    p->cacheEntryCount++;
+    return p->mon;
+}
+
+/*
+** Initialize the monitor cache
+*/
+void _PR_InitCMon(void)
+{
+    _PR_NEW_LOCK_MCACHE();
+    ExpandMonitorCache(3);
+}
+
+/*
+** Destroy the monitor cache
+*/
+void _PR_CleanupCMon(void)
+{
+    _PR_DESTROY_LOCK_MCACHE();
+
+    while (free_entries) {
+        PR_DestroyMonitor(free_entries->mon);
+        free_entries = free_entries->next;
+    }
+    num_free_entries = 0;
+
+    while (mcache_blocks) {
+        MonitorCacheEntryBlock *block;
+
+        block = mcache_blocks;
+        mcache_blocks = block->next;
+        PR_DELETE(block);
+    }
+
+    PR_DELETE(hash_buckets);
+    hash_mask = 0;
+    num_hash_buckets = 0;
+    num_hash_buckets_log2 = 0;
+
+    expanding = PR_FALSE;
+    OnMonitorRecycle = NULL;
+}
+
+/*
+** Create monitor for address. Don't enter the monitor while we have the
+** mcache locked because we might block!
+*/
+PR_IMPLEMENT(PRMonitor*) PR_CEnterMonitor(void *address)
+{
+    PRMonitor *mon;
+
+    if (!_pr_initialized) _PR_ImplicitInitialization();
+
+    _PR_LOCK_MCACHE();
+    mon = CreateMonitor(address);
+    _PR_UNLOCK_MCACHE();
+
+    if (!mon) return NULL;
+
+    PR_EnterMonitor(mon);
+    return mon;
+}
+
+PR_IMPLEMENT(PRStatus) PR_CExitMonitor(void *address)
+{
+    MonitorCacheEntry **pp, *p;
+    PRStatus status = PR_SUCCESS;
+
+    _PR_LOCK_MCACHE();
+    pp = LookupMonitorCacheEntry(address);
+    if (pp != NULL) {
+        p = *pp;
+        if (--p->cacheEntryCount == 0) {
+            /*
+            ** Nobody is using the system monitor. Put it on the cached free
+            ** list. We are safe from somebody trying to use it because we
+            ** have the mcache locked.
+            */
+            p->address = 0;             /* defensive move */
+            *pp = p->next;              /* unlink from hash_buckets */
+            p->next = free_entries;     /* link into free list */
+            free_entries = p;
+            num_free_entries++;         /* count it as free */
+        }
+        status = PR_ExitMonitor(p->mon);
+    } else {
+        status = PR_FAILURE;
+    }
+    _PR_UNLOCK_MCACHE();
+
+    return status;
+}
+
+PR_IMPLEMENT(PRStatus) PR_CWait(void *address, PRIntervalTime ticks)
+{
+    MonitorCacheEntry **pp;
+    PRMonitor *mon;
+
+    _PR_LOCK_MCACHE();
+    pp = LookupMonitorCacheEntry(address);
+    mon = pp ? ((*pp)->mon) : NULL;
+    _PR_UNLOCK_MCACHE();
+
+    if (mon == NULL)
+        return PR_FAILURE;
+    return PR_Wait(mon, ticks);
+}
+
+PR_IMPLEMENT(PRStatus) PR_CNotify(void *address)
+{
+    MonitorCacheEntry **pp;
+    PRMonitor *mon;
+
+    _PR_LOCK_MCACHE();
+    pp = LookupMonitorCacheEntry(address);
+    mon = pp ? ((*pp)->mon) : NULL;
+    _PR_UNLOCK_MCACHE();
+
+    if (mon == NULL)
+        return PR_FAILURE;
+    return PR_Notify(mon);
+}
+
+PR_IMPLEMENT(PRStatus) PR_CNotifyAll(void *address)
+{
+    MonitorCacheEntry **pp;
+    PRMonitor *mon;
+
+    _PR_LOCK_MCACHE();
+    pp = LookupMonitorCacheEntry(address);
+    mon = pp ? ((*pp)->mon) : NULL;
+    _PR_UNLOCK_MCACHE();
+
+    if (mon == NULL)
+        return PR_FAILURE;
+    return PR_NotifyAll(mon);
+}
+
+PR_IMPLEMENT(void)
+PR_CSetOnMonitorRecycle(void (*callback)(void *address))
+{
+    OnMonitorRecycle = callback;
+}