def brelse(self, buffer):
# Todo: wakeup all processes (event: waiting for any buffer to become free;
self.eventBus.wake(EventBus.EVENT_WAIT_ANY_BUFFER)
# Todo: wakeup all processes (event: waiting for this buffer to become free;
self.eventBus.wake(EventBus.EVENT_WAIT_SPECIFIC_BUFFER(buffer))
# raise processor execution level to block interrupts;
if buffer.isDataValid() and not buffer.isOld():
# enqueue buffer at end of free list;
self.bufferCache.freeList.push(buffer)
else:
# enqueue buffer at beginning of free list;
self.bufferCache.freeList.unshift(buffer)
# lower processor execution level to allow interrupts;
buffer.unlock()
return buffer
def getblk(self, blockNumber):
"""
getblk algo from textbook
"""
while (True):
if self.bufferCache.hashQueue.has(blockNumber):
buffer = self.bufferCache.hashQueue.get(blockNumber)
if buffer.isLocked():
logger.info(
f'getblk(): accessing |Block:{blockNumber}|, resulted in "Scenario 5"'
)
# logger.info("Scenario 5: Block was found on the hash queue, but its buffer is currently busy.")
# sleep until this buffer becomes free
self.eventBus.sleep(
EventBus.EVENT_WAIT_SPECIFIC_BUFFER(buffer))
self.eventBus.clear(
EventBus.EVENT_WAIT_SPECIFIC_BUFFER(buffer))
continue
# Scenario 1
buffer.lock()
self.bufferCache.freeList.remove(buffer)
logger.info(
f'getblk(): accessing |Block:{blockNumber}|, resulted in "Scenario 1"'
)
# logger.info("Scenario 1: Block is found on its hash queue and its buffer is free.")
return buffer #block found on hashQ
else:
if self.bufferCache.freeList.isEmpty():
logger.info(
f'getblk(): accessing |Block:{blockNumber}|, resulted in "Scenario 4"'
)
# logger.info('Scenario 4: Block could not be found on the hash queue and the free list of buffers is empty.')
# Sleep until any buffer becomes free
self.eventBus.sleep(EventBus.EVENT_WAIT_ANY_BUFFER)
self.eventBus.clear(EventBus.EVENT_WAIT_ANY_BUFFER)
continue
else:
buffer = self.bufferCache.freeList.pop()
# Scenario 3
if buffer.isDelayedWrite():
logger.info(
f'getblk(): accessing |Block:{blockNumber}|, resulted in "Scenario 3"'
)
# write buffer asynchronously to the disk
self.bwrite(buffer, synchronous=False)
continue
buffer.lock()
logger.info(
f'getblk(): accessing |Block:{blockNumber}|, resulted in "Scenario 2"'
)
# logger.info("Scenario 2: Buffer not found on hash queue but a buffer from free list is assigned")
if buffer.blockNumber:
self.bufferCache.hashQueue.remove(buffer)
logger.debug(
f'REMOVE BUFFER{buffer} - UPDATED HASH QUEUE:{self.bufferCache.hashQueue}'
)
buffer.updateBlockNumber(blockNumber)
self.bufferCache.hashQueue.add(buffer)
return buffer # block not in hashQ, taken from freelist
time.sleep(.5)
