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-rw-r--r--nsprpub/pr/src/threads/prcmon.c449
1 files changed, 449 insertions, 0 deletions
diff --git a/nsprpub/pr/src/threads/prcmon.c b/nsprpub/pr/src/threads/prcmon.c
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+++ b/nsprpub/pr/src/threads/prcmon.c
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+/* -*- 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;
+}