src/system/kernel/fs/Vnode.cpp

   1 /*
   2  * Copyright 2009-2011, Ingo Weinhold, ingo_weinhold@gmx.de.
   3  * Distributed under the terms of the MIT License.
   4  */
   5
   6
   7 #include "Vnode.h"
   8
   9 #include <util/AutoLock.h>
  10
  11
  12 vnode::Bucket vnode::sBuckets[kBucketCount];
  13
  14
  15 vnode::Bucket::Bucket()
  16 {
  17         mutex_init(&lock, "vnode bucket");
  18 }
  19
  20
  21 /*static*/ void
  22 vnode::StaticInit()
  23 {
  24         for (uint32 i = 0; i < kBucketCount; i++)
  25                 new(&sBuckets[i]) Bucket;
  26 }
  27
  28
  29 void
  30 vnode::_WaitForLock()
  31 {
  32         LockWaiter waiter;
  33         waiter.thread = thread_get_current_thread();
  34         waiter.vnode = this;
  35
  36         Bucket& bucket = _Bucket();
  37         MutexLocker bucketLocker(bucket.lock);
  38
  39         if ((atomic_or(&fFlags, kFlagsWaitingLocker)
  40                         & (kFlagsLocked | kFlagsWaitingLocker)) == 0) {
  41                 // The lock holder dropped it in the meantime and no-one else was faster
  42                 // than us, so it's ours now. Just mark the node locked and clear the
  43                 // waiting flag again.
  44                 atomic_or(&fFlags, kFlagsLocked);
  45                 atomic_and(&fFlags, ~kFlagsWaitingLocker);
  46                 return;
  47         }
  48
  49         // prepare for waiting
  50         bucket.waiters.Add(&waiter);
  51         thread_prepare_to_block(waiter.thread, 0, THREAD_BLOCK_TYPE_OTHER,
  52                 "vnode lock");
  53
  54         // start waiting
  55         bucketLocker.Unlock();
  56         thread_block();
  57 }
  58
  59
  60 void
  61 vnode::_WakeUpLocker()
  62 {
  63         Bucket& bucket = _Bucket();
  64         MutexLocker bucketLocker(bucket.lock);
  65
  66         // mark the node locked again
  67         atomic_or(&fFlags, kFlagsLocked);
  68
  69         // get the first waiter from the list
  70         LockWaiter* waiter = NULL;
  71         bool onlyWaiter = true;
  72         for (LockWaiterList::Iterator it = bucket.waiters.GetIterator();
  73                         LockWaiter* someWaiter = it.Next();) {
  74                 if (someWaiter->vnode == this) {
  75                         if (waiter != NULL) {
  76                                 onlyWaiter = false;
  77                                 break;
  78                         }
  79                         waiter = someWaiter;
  80                         it.Remove();
  81                 }
  82         }
  83
  84         ASSERT(waiter != NULL);
  85
  86         // if that's the only waiter, clear the flag
  87         if (onlyWaiter)
  88                 atomic_and(&fFlags, ~kFlagsWaitingLocker);
  89
  90         // and wake it up
  91         thread_unblock(waiter->thread, B_OK);
  92 }