diff options
Diffstat (limited to 'pthreads/ptw32_MCS_lock.c')
| -rw-r--r-- | pthreads/ptw32_MCS_lock.c | 473 |
1 files changed, 263 insertions, 210 deletions
diff --git a/pthreads/ptw32_MCS_lock.c b/pthreads/ptw32_MCS_lock.c index 1a143ea14..270c31e9c 100644 --- a/pthreads/ptw32_MCS_lock.c +++ b/pthreads/ptw32_MCS_lock.c @@ -1,210 +1,263 @@ -/* - * ptw32_MCS_lock.c - * - * Description: - * This translation unit implements queue-based locks. - * - * -------------------------------------------------------------------------- - * - * Pthreads-win32 - POSIX Threads Library for Win32 - * Copyright(C) 1998 John E. Bossom - * Copyright(C) 1999,2005 Pthreads-win32 contributors - * - * Contact Email: rpj@callisto.canberra.edu.au - * - * The current list of contributors is contained - * in the file CONTRIBUTORS included with the source - * code distribution. The list can also be seen at the - * following World Wide Web location: - * http://sources.redhat.com/pthreads-win32/contributors.html - * - * This library is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public - * License as published by the Free Software Foundation; either - * version 2 of the License, or (at your option) any later version. - * - * This library is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this library in the file COPYING.LIB; - * if not, write to the Free Software Foundation, Inc., - * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA - */ - -/* - * About MCS locks: - * - * MCS locks are queue-based locks, where the queue nodes are local to the - * thread. The 'lock' is nothing more than a global pointer that points to - * the last node in the queue, or is NULL if the queue is empty. - * - * Originally designed for use as spin locks requiring no kernel resources - * for synchronisation or blocking, the implementation below has adapted - * the MCS spin lock for use as a general mutex that will suspend threads - * when there is lock contention. - * - * Because the queue nodes are thread-local, most of the memory read/write - * operations required to add or remove nodes from the queue do not trigger - * cache-coherence updates. - * - * Like 'named' mutexes, MCS locks consume system resources transiently - - * they are able to acquire and free resources automatically - but MCS - * locks do not require any unique 'name' to identify the lock to all - * threads using it. - * - * Usage of MCS locks: - * - * - you need a global ptw32_mcs_lock_t instance initialised to 0 or NULL. - * - you need a local thread-scope ptw32_mcs_local_node_t instance, which - * may serve several different locks but you need at least one node for - * every lock held concurrently by a thread. - * - * E.g.: - * - * ptw32_mcs_lock_t lock1 = 0; - * ptw32_mcs_lock_t lock2 = 0; - * - * void *mythread(void *arg) - * { - * ptw32_mcs_local_node_t node; - * - * ptw32_mcs_acquire (&lock1, &node); - * ptw32_mcs_release (&node); - * - * ptw32_mcs_acquire (&lock2, &node); - * ptw32_mcs_release (&node); - * { - * ptw32_mcs_local_node_t nodex; - * - * ptw32_mcs_acquire (&lock1, &node); - * ptw32_mcs_acquire (&lock2, &nodex); - * - * ptw32_mcs_release (&nodex); - * ptw32_mcs_release (&node); - * } - * return (void *)0; - * } - */ - -#include "implement.h" -#include "pthread.h" - -/* - * ptw32_mcs_flag_set -- notify another thread about an event. - * - * Set event if an event handle has been stored in the flag, and - * set flag to -1 otherwise. Note that -1 cannot be a valid handle value. - */ -INLINE void -ptw32_mcs_flag_set (LONG * flag) -{ - HANDLE e = (HANDLE)PTW32_INTERLOCKED_COMPARE_EXCHANGE( - (PTW32_INTERLOCKED_LPLONG)flag, - (PTW32_INTERLOCKED_LONG)-1, - (PTW32_INTERLOCKED_LONG)0); - if ((HANDLE)0 != e) - { - /* another thread has already stored an event handle in the flag */ - SetEvent(e); - } -} - -/* - * ptw32_mcs_flag_set -- wait for notification from another. - * - * Store an event handle in the flag and wait on it if the flag has not been - * set, and proceed without creating an event otherwise. - */ -INLINE void -ptw32_mcs_flag_wait (LONG * flag) -{ - if (0 == InterlockedExchangeAdd((LPLONG)flag, 0)) /* MBR fence */ - { - /* the flag is not set. create event. */ - - HANDLE e = CreateEvent(NULL, PTW32_FALSE, PTW32_FALSE, NULL); - - if (0 == PTW32_INTERLOCKED_COMPARE_EXCHANGE( - (PTW32_INTERLOCKED_LPLONG)flag, - (PTW32_INTERLOCKED_LONG)e, - (PTW32_INTERLOCKED_LONG)0)) - { - /* stored handle in the flag. wait on it now. */ - WaitForSingleObject(e, INFINITE); - } - - CloseHandle(e); - } -} - -/* - * ptw32_mcs_lock_acquire -- acquire an MCS lock. - * - * See: - * J. M. Mellor-Crummey and M. L. Scott. - * Algorithms for Scalable Synchronization on Shared-Memory Multiprocessors. - * ACM Transactions on Computer Systems, 9(1):21-65, Feb. 1991. - */ -INLINE void -ptw32_mcs_lock_acquire (ptw32_mcs_lock_t * lock, ptw32_mcs_local_node_t * node) -{ - ptw32_mcs_local_node_t *pred; - - node->lock = lock; - node->nextFlag = 0; - node->readyFlag = 0; - node->next = 0; /* initially, no successor */ - - /* queue for the lock */ - pred = (ptw32_mcs_local_node_t *)PTW32_INTERLOCKED_EXCHANGE((LPLONG)lock, - (LONG)node); - - if (0 != pred) - { - /* the lock was not free. link behind predecessor. */ - pred->next = node; - ptw32_mcs_flag_set(&pred->nextFlag); - ptw32_mcs_flag_wait(&node->readyFlag); - } -} - -/* - * ptw32_mcs_lock_release -- release an MCS lock. - * - * See: - * J. M. Mellor-Crummey and M. L. Scott. - * Algorithms for Scalable Synchronization on Shared-Memory Multiprocessors. - * ACM Transactions on Computer Systems, 9(1):21-65, Feb. 1991. - */ -INLINE void -ptw32_mcs_lock_release (ptw32_mcs_local_node_t * node) -{ - ptw32_mcs_lock_t *lock = node->lock; - ptw32_mcs_local_node_t *next = (ptw32_mcs_local_node_t *) - InterlockedExchangeAdd((LPLONG)&node->next, 0); /* MBR fence */ - - if (0 == next) - { - /* no known successor */ - - if (node == (ptw32_mcs_local_node_t *) - PTW32_INTERLOCKED_COMPARE_EXCHANGE((PTW32_INTERLOCKED_LPLONG)lock, - (PTW32_INTERLOCKED_LONG)0, - (PTW32_INTERLOCKED_LONG)node)) - { - /* no successor, lock is free now */ - return; - } - - /* wait for successor */ - ptw32_mcs_flag_wait(&node->nextFlag); - next = (ptw32_mcs_local_node_t *) - InterlockedExchangeAdd((LPLONG)&node->next, 0); /* MBR fence */ - } - - /* pass the lock */ - ptw32_mcs_flag_set(&next->readyFlag); -} +/*
+ * ptw32_MCS_lock.c
+ *
+ * Description:
+ * This translation unit implements queue-based locks.
+ *
+ * --------------------------------------------------------------------------
+ *
+ * Pthreads-win32 - POSIX Threads Library for Win32
+ * Copyright(C) 1998 John E. Bossom
+ * Copyright(C) 1999,2005 Pthreads-win32 contributors
+ *
+ * Contact Email: rpj@callisto.canberra.edu.au
+ *
+ * The current list of contributors is contained
+ * in the file CONTRIBUTORS included with the source
+ * code distribution. The list can also be seen at the
+ * following World Wide Web location:
+ * http://sources.redhat.com/pthreads-win32/contributors.html
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library in the file COPYING.LIB;
+ * if not, write to the Free Software Foundation, Inc.,
+ * 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA
+ */
+
+/*
+ * About MCS locks:
+ *
+ * MCS locks are queue-based locks, where the queue nodes are local to the
+ * thread. The 'lock' is nothing more than a global pointer that points to
+ * the last node in the queue, or is NULL if the queue is empty.
+ *
+ * Originally designed for use as spin locks requiring no kernel resources
+ * for synchronisation or blocking, the implementation below has adapted
+ * the MCS spin lock for use as a general mutex that will suspend threads
+ * when there is lock contention.
+ *
+ * Because the queue nodes are thread-local, most of the memory read/write
+ * operations required to add or remove nodes from the queue do not trigger
+ * cache-coherence updates.
+ *
+ * Like 'named' mutexes, MCS locks consume system resources transiently -
+ * they are able to acquire and free resources automatically - but MCS
+ * locks do not require any unique 'name' to identify the lock to all
+ * threads using it.
+ *
+ * Usage of MCS locks:
+ *
+ * - you need a global ptw32_mcs_lock_t instance initialised to 0 or NULL.
+ * - you need a local thread-scope ptw32_mcs_local_node_t instance, which
+ * may serve several different locks but you need at least one node for
+ * every lock held concurrently by a thread.
+ *
+ * E.g.:
+ *
+ * ptw32_mcs_lock_t lock1 = 0;
+ * ptw32_mcs_lock_t lock2 = 0;
+ *
+ * void *mythread(void *arg)
+ * {
+ * ptw32_mcs_local_node_t node;
+ *
+ * ptw32_mcs_acquire (&lock1, &node);
+ * ptw32_mcs_release (&node);
+ *
+ * ptw32_mcs_acquire (&lock2, &node);
+ * ptw32_mcs_release (&node);
+ * {
+ * ptw32_mcs_local_node_t nodex;
+ *
+ * ptw32_mcs_acquire (&lock1, &node);
+ * ptw32_mcs_acquire (&lock2, &nodex);
+ *
+ * ptw32_mcs_release (&nodex);
+ * ptw32_mcs_release (&node);
+ * }
+ * return (void *)0;
+ * }
+ */
+
+#include "implement.h"
+#include "pthread.h"
+
+/*
+ * ptw32_mcs_flag_set -- notify another thread about an event.
+ *
+ * Set event if an event handle has been stored in the flag, and
+ * set flag to -1 otherwise. Note that -1 cannot be a valid handle value.
+ */
+INLINE void
+ptw32_mcs_flag_set (LONG * flag)
+{
+ HANDLE e = (HANDLE)PTW32_INTERLOCKED_COMPARE_EXCHANGE(
+ (PTW32_INTERLOCKED_LPLONG)flag,
+ (PTW32_INTERLOCKED_LONG)-1,
+ (PTW32_INTERLOCKED_LONG)0);
+ if ((HANDLE)0 != e)
+ {
+ /* another thread has already stored an event handle in the flag */
+ SetEvent(e);
+ }
+}
+
+/*
+ * ptw32_mcs_flag_set -- wait for notification from another.
+ *
+ * Store an event handle in the flag and wait on it if the flag has not been
+ * set, and proceed without creating an event otherwise.
+ */
+INLINE void
+ptw32_mcs_flag_wait (LONG * flag)
+{
+ if (0 == InterlockedExchangeAdd((LPLONG)flag, 0)) /* MBR fence */
+ {
+ /* the flag is not set. create event. */
+
+ HANDLE e = CreateEvent(NULL, PTW32_FALSE, PTW32_FALSE, NULL);
+
+ if (0 == PTW32_INTERLOCKED_COMPARE_EXCHANGE(
+ (PTW32_INTERLOCKED_LPLONG)flag,
+ (PTW32_INTERLOCKED_LONG)e,
+ (PTW32_INTERLOCKED_LONG)0))
+ {
+ /* stored handle in the flag. wait on it now. */
+ WaitForSingleObject(e, INFINITE);
+ }
+
+ CloseHandle(e);
+ }
+}
+
+/*
+ * ptw32_mcs_lock_acquire -- acquire an MCS lock.
+ *
+ * See:
+ * J. M. Mellor-Crummey and M. L. Scott.
+ * Algorithms for Scalable Synchronization on Shared-Memory Multiprocessors.
+ * ACM Transactions on Computer Systems, 9(1):21-65, Feb. 1991.
+ */
+INLINE void
+ptw32_mcs_lock_acquire (ptw32_mcs_lock_t * lock, ptw32_mcs_local_node_t * node)
+{
+ ptw32_mcs_local_node_t *pred;
+
+ node->lock = lock;
+ node->nextFlag = 0;
+ node->readyFlag = 0;
+ node->next = 0; /* initially, no successor */
+
+ /* queue for the lock */
+ pred = (ptw32_mcs_local_node_t *)PTW32_INTERLOCKED_EXCHANGE((PTW32_INTERLOCKED_LPLONG)lock,
+ (PTW32_INTERLOCKED_LONG)node);
+
+ if (0 != pred)
+ {
+ /* the lock was not free. link behind predecessor. */
+ pred->next = node;
+ ptw32_mcs_flag_set(&pred->nextFlag);
+ ptw32_mcs_flag_wait(&node->readyFlag);
+ }
+}
+
+/*
+ * ptw32_mcs_lock_release -- release an MCS lock.
+ *
+ * See:
+ * J. M. Mellor-Crummey and M. L. Scott.
+ * Algorithms for Scalable Synchronization on Shared-Memory Multiprocessors.
+ * ACM Transactions on Computer Systems, 9(1):21-65, Feb. 1991.
+ */
+INLINE void
+ptw32_mcs_lock_release (ptw32_mcs_local_node_t * node)
+{
+ ptw32_mcs_lock_t *lock = node->lock;
+ ptw32_mcs_local_node_t *next = (ptw32_mcs_local_node_t *)
+ InterlockedExchangeAdd((LPLONG)&node->next,
+ (LONG)0); /* MBR fence */
+
+ if (0 == next)
+ {
+ /* no known successor */
+
+ if (node == (ptw32_mcs_local_node_t *)
+ PTW32_INTERLOCKED_COMPARE_EXCHANGE((PTW32_INTERLOCKED_LPLONG)lock,
+ (PTW32_INTERLOCKED_LONG)0,
+ (PTW32_INTERLOCKED_LONG)node))
+ {
+ /* no successor, lock is free now */
+ return;
+ }
+
+ /* wait for successor */
+ ptw32_mcs_flag_wait(&node->nextFlag);
+ next = (ptw32_mcs_local_node_t *)
+ InterlockedExchangeAdd((LPLONG)&node->next, 0); /* MBR fence */
+ }
+
+ /* pass the lock */
+ ptw32_mcs_flag_set(&next->readyFlag);
+}
+
+/*
+ * ptw32_mcs_lock_try_acquire
+ */
+INLINE int
+ptw32_mcs_lock_try_acquire (ptw32_mcs_lock_t * lock, ptw32_mcs_local_node_t * node)
+{
+ node->lock = lock;
+ node->nextFlag = 0;
+ node->readyFlag = 0;
+ node->next = 0; /* initially, no successor */
+
+ return ((PTW32_INTERLOCKED_LPLONG)PTW32_INTERLOCKED_COMPARE_EXCHANGE(
+ (PTW32_INTERLOCKED_LPLONG)lock,
+ (PTW32_INTERLOCKED_LONG)node,
+ (PTW32_INTERLOCKED_LONG)0)
+ == (PTW32_INTERLOCKED_LPLONG)0) ? 0 : EBUSY;
+}
+
+/*
+ * ptw32_mcs_node_substitute -- move an MCS lock local node, usually from thread
+ * space to, for example, global space so that another thread can release
+ * the lock on behalf of the current lock owner.
+ *
+ * Example: used in pthread_barrier_wait where we want the last thread out of
+ * the barrier to release the lock owned by the last thread to enter the barrier
+ * (the one that releases all threads but not necessarily the last to leave).
+ *
+ * Should only be called by the thread that has the lock.
+ */
+INLINE void
+ptw32_mcs_node_substitute (ptw32_mcs_local_node_t * new_node, ptw32_mcs_local_node_t * old_node)
+{
+ new_node->lock = old_node->lock;
+ new_node->nextFlag = 0; /* Not needed - used only in initial Acquire */
+ new_node->readyFlag = 0; /* Not needed - we were waiting on this */
+ new_node->next = 0;
+
+ if ((ptw32_mcs_local_node_t *)PTW32_INTERLOCKED_COMPARE_EXCHANGE((PTW32_INTERLOCKED_LPLONG)new_node->lock,
+ (PTW32_INTERLOCKED_LONG)new_node,
+ (PTW32_INTERLOCKED_LONG)old_node) != old_node)
+ {
+ /*
+ * A successor has queued after us, so wait for them to link to us
+ */
+ while (old_node->next == 0)
+ {
+ Sleep(0);
+ }
+ new_node->next = old_node->next;
+ }
+}
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