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* If BFS's Journal::_WriteTransactionToLog() noticed there wasn't enough free 

space left for the new log entry, it did call cache_sync_transaction(), and
  then just assumed the space would be ready. But since the transaction could
  have been written before that call by the block writer, and since the
  _TransactionWritten() hook is now called asynchronously,
  cache_sync_transaction() actually has to flush all pending TRANSACTION_WRITTEN
  notifications before returning to the caller.
* To implement this, block_cache now publishs a condition variable, and
  wait_for_notifications() adds a fake notification that signals that one.
  Since the notifications are handled in FIFO order, this guarantees that
  the previous TRANSACTION_WRITTEN hook is done.
* notify_transaction_listeners() could accidently delete notifications that
  still had pending signals. Now, it will defer the deletion to the notification
  thread instead in that case. This should fix bug #2008.


git-svn-id: file:///srv/svn/repos/haiku/haiku/trunk@24792 a95241bf-73f2-0310-859d-f6bbb57e9c96
This commit is contained in:
Axel Dörfler 2008-04-04 14:02:30 +00:00
parent 0bb7a9c0ca
commit 807d3aa8e3
1 changed files with 49 additions and 3 deletions
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52
src/system/kernel/cache/block_cache.cpp vendored
View File

@ -15,6 +15,7 @@
#include <KernelExport.h>
#include <fs_cache.h>
#include <condition_variable.h>
#include <lock.h>
#include <vm_low_memory.h>
#include <slab/Slab.h>
@ -114,6 +115,7 @@ struct block_cache : DoublyLinkedListLinkImpl<block_cache> {
bool read_only;
NotificationList pending_notifications;
ConditionVariable<block_cache> condition_variable;
bool deleting;
block_cache(int fd, off_t numBlocks, size_t blockSize, bool readOnly);
@ -351,7 +353,7 @@ set_notification(cache_transaction *transaction,
cache_notification &notification, int32 events,
transaction_notification_hook hook, void *data)
{
notification.transaction_id = transaction->id;
notification.transaction_id = transaction != NULL ? transaction->id : -1;
notification.events_pending = 0;
notification.events = events;
notification.hook = hook;
@ -414,8 +416,14 @@ notify_transaction_listeners(block_cache *cache, cache_transaction *transaction,
if ((listener->events & event) != 0)
add_notification(cache, listener, event, removeListeners);
else if (removeListeners)
delete listener;
else if (removeListeners) {
// we might need to defer the deletion if its currently in use
MutexLocker locker(sNotificationsLock);
if (listener->events_pending != 0)
listener->delete_after_event = true;
else
delete listener;
}
}
}
@ -552,6 +560,8 @@ block_cache::block_cache(int _fd, off_t numBlocks, size_t blockSize,
sCaches.Add(this);
mutex_unlock(&sCachesLock);
condition_variable.Publish(this, "cache transaction sync");
buffer_cache = create_object_cache_etc("block cache buffers", blockSize,
8, 0, CACHE_LARGE_SLAB, NULL, NULL, NULL, NULL);
if (buffer_cache == NULL)
@ -574,6 +584,7 @@ block_cache::block_cache(int _fd, off_t numBlocks, size_t blockSize,
}
//! Should be called with the cache's lock held.
block_cache::~block_cache()
{
deleting = true;
@ -582,6 +593,8 @@ block_cache::~block_cache()
benaphore_destroy(&lock);
condition_variable.Unpublish();
mutex_lock(&sCachesLock);
sCaches.Remove(this);
mutex_unlock(&sCachesLock);
@ -1340,6 +1353,30 @@ dump_caches(int argc, char **argv)
#endif // DEBUG_BLOCK_CACHE
static void
notify_sync(int32 transactionID, int32 event, void *_cache)
{
block_cache *cache = (block_cache *)_cache;
cache->condition_variable.NotifyOne();
}
static void
wait_for_notifications(block_cache *cache)
{
// add sync notification
cache_notification notification;
set_notification(NULL, notification, TRANSACTION_WRITTEN, notify_sync,
cache);
add_notification(cache, &notification, TRANSACTION_WRITTEN, false);
// wait for condition
ConditionVariableEntry<block_cache> entry;
entry.Wait(cache);
}
static block_cache *
get_next_locked_block_cache(block_cache *last)
{
@ -1417,6 +1454,10 @@ flush_pending_notifications(block_cache *cache)
}
/*! Flushes all pending notifications by calling the appropriate hook
functions.
Must not be called with a cache lock held.
*/
static void
flush_pending_notifications()
{
@ -1644,6 +1685,11 @@ cache_sync_transaction(void *_cache, int32 id)
}
hash_close(cache->transaction_hash, &iterator, false);
locker.Unlock();
wait_for_notifications(cache);
// make sure that all pending TRANSACTION_WRITTEN notifications
// are handled after we return
return B_OK;
}