patch-2.4.27 linux-2.4.27/fs/xfs/linux-2.4/mrlock.c

• Lines: 275
• Date: 2004-08-07 16:26:06.063404673 -0700
• Orig file: linux-2.4.26/fs/xfs/linux-2.4/mrlock.c
• Orig date: 1969-12-31 16:00:00.000000000 -0800

diff -urN linux-2.4.26/fs/xfs/linux-2.4/mrlock.c linux-2.4.27/fs/xfs/linux-2.4/mrlock.c
@@ -0,0 +1,274 @@
+/*
+ * Copyright (c) 2000-2003 Silicon Graphics, Inc.  All Rights Reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it would be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
+ *
+ * Further, this software is distributed without any warranty that it is
+ * free of the rightful claim of any third person regarding infringement
+ * or the like.  Any license provided herein, whether implied or
+ * otherwise, applies only to this software file.  Patent licenses, if
+ * any, provided herein do not apply to combinations of this program with
+ * other software, or any other product whatsoever.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program; if not, write the Free Software Foundation, Inc., 59
+ * Temple Place - Suite 330, Boston MA 02111-1307, USA.
+ *
+ * Contact information: Silicon Graphics, Inc., 1600 Amphitheatre Pkwy,
+ * Mountain View, CA  94043, or:
+ *
+ * http://www.sgi.com
+ *
+ * For further information regarding this notice, see:
+ *
+ * http://oss.sgi.com/projects/GenInfo/SGIGPLNoticeExplan/
+ */
+
+#include <linux/time.h>
+#include <linux/sched.h>
+#include <asm/system.h>
+#include <linux/interrupt.h>
+#include <asm/current.h>
+
+#include "mrlock.h"
+
+
+#if USE_RW_WAIT_QUEUE_SPINLOCK
+# define wq_write_lock	write_lock
+#else
+# define wq_write_lock	spin_lock
+#endif
+
+/*
+ * We don't seem to need lock_type (only one supported), name, or
+ * sequence. But, XFS will pass it so let's leave them here for now.
+ */
+/* ARGSUSED */
+void
+mrlock_init(mrlock_t *mrp, int lock_type, char *name, long sequence)
+{
+	mrp->mr_count = 0;
+	mrp->mr_reads_waiting = 0;
+	mrp->mr_writes_waiting = 0;
+	init_waitqueue_head(&mrp->mr_readerq);
+	init_waitqueue_head(&mrp->mr_writerq);
+	mrp->mr_lock = SPIN_LOCK_UNLOCKED;
+}
+
+/*
+ * Macros to lock/unlock the mrlock_t.
+ */
+
+#define MRLOCK(m)		spin_lock(&(m)->mr_lock);
+#define MRUNLOCK(m)		spin_unlock(&(m)->mr_lock);
+
+
+/*
+ * lock_wait should never be called in an interrupt thread.
+ *
+ * mrlocks can sleep (i.e. call schedule) and so they can't ever
+ * be called from an interrupt thread.
+ *
+ * threads that wake-up should also never be invoked from interrupt threads.
+ *
+ * But, waitqueue_lock is locked from interrupt threads - and we are
+ * called with interrupts disabled, so it is all OK.
+ */
+
+/* ARGSUSED */
+void
+lock_wait(wait_queue_head_t *q, spinlock_t *lock, int rw)
+{
+	DECLARE_WAITQUEUE( wait, current );
+
+	__set_current_state(TASK_UNINTERRUPTIBLE);
+
+	wq_write_lock(&q->lock);
+	if (rw) {
+		__add_wait_queue_tail(q, &wait);
+	} else {
+		__add_wait_queue(q, &wait);
+	}
+
+	wq_write_unlock(&q->lock);
+	spin_unlock(lock);
+
+	schedule();
+
+	wq_write_lock(&q->lock);
+	__remove_wait_queue(q, &wait);
+	wq_write_unlock(&q->lock);
+
+	spin_lock(lock);
+
+	/* return with lock held */
+}
+
+/* ARGSUSED */
+void
+mrfree(mrlock_t *mrp)
+{
+}
+
+/* ARGSUSED */
+void
+mrlock(mrlock_t *mrp, int type, int flags)
+{
+	if (type == MR_ACCESS)
+		mraccess(mrp);
+	else
+		mrupdate(mrp);
+}
+
+/* ARGSUSED */
+void
+mraccessf(mrlock_t *mrp, int flags)
+{
+	MRLOCK(mrp);
+	if(mrp->mr_writes_waiting > 0) {
+		mrp->mr_reads_waiting++;
+		lock_wait(&mrp->mr_readerq, &mrp->mr_lock, 0);
+		mrp->mr_reads_waiting--;
+	}
+	while (mrp->mr_count < 0) {
+		mrp->mr_reads_waiting++;
+		lock_wait(&mrp->mr_readerq, &mrp->mr_lock, 0);
+		mrp->mr_reads_waiting--;
+	}
+	mrp->mr_count++;
+	MRUNLOCK(mrp);
+}
+
+/* ARGSUSED */
+void
+mrupdatef(mrlock_t *mrp, int flags)
+{
+	MRLOCK(mrp);
+	while(mrp->mr_count) {
+		mrp->mr_writes_waiting++;
+		lock_wait(&mrp->mr_writerq, &mrp->mr_lock, 1);
+		mrp->mr_writes_waiting--;
+	}
+
+	mrp->mr_count = -1; /* writer on it */
+	MRUNLOCK(mrp);
+}
+
+int
+mrtryaccess(mrlock_t *mrp)
+{
+	MRLOCK(mrp);
+	/*
+	 * If anyone is waiting for update access or the lock is held for update
+	 * fail the request.
+	 */
+	if(mrp->mr_writes_waiting > 0 || mrp->mr_count < 0) {
+		MRUNLOCK(mrp);
+		return 0;
+	}
+	mrp->mr_count++;
+	MRUNLOCK(mrp);
+	return 1;
+}
+
+int
+mrtrypromote(mrlock_t *mrp)
+{
+	MRLOCK(mrp);
+
+	if(mrp->mr_count == 1) { /* We are the only thread with the lock */
+		mrp->mr_count = -1; /* writer on it */
+		MRUNLOCK(mrp);
+		return 1;
+	}
+
+	MRUNLOCK(mrp);
+	return 0;
+}
+
+int
+mrtryupdate(mrlock_t *mrp)
+{
+	MRLOCK(mrp);
+
+	if(mrp->mr_count) {
+		MRUNLOCK(mrp);
+		return 0;
+	}
+
+	mrp->mr_count = -1; /* writer on it */
+	MRUNLOCK(mrp);
+	return 1;
+}
+
+static __inline__ void mrwake(mrlock_t *mrp)
+{
+	/*
+	 * First, if the count is now 0, we need to wake-up anyone waiting.
+	 */
+	if (!mrp->mr_count) {
+		if (mrp->mr_writes_waiting) {	/* Wake-up first writer waiting */
+			wake_up(&mrp->mr_writerq);
+		} else if (mrp->mr_reads_waiting) {	/* Wakeup any readers waiting */
+			wake_up(&mrp->mr_readerq);
+		}
+	}
+}
+
+void
+mraccunlock(mrlock_t *mrp)
+{
+	MRLOCK(mrp);
+	mrp->mr_count--;
+	mrwake(mrp);
+	MRUNLOCK(mrp);
+}
+
+void
+mrunlock(mrlock_t *mrp)
+{
+	MRLOCK(mrp);
+	if (mrp->mr_count < 0) {
+		mrp->mr_count = 0;
+	} else {
+		mrp->mr_count--;
+	}
+	mrwake(mrp);
+	MRUNLOCK(mrp);
+}
+
+int
+ismrlocked(mrlock_t *mrp, int type)	/* No need to lock since info can change */
+{
+	if (type == MR_ACCESS)
+		return (mrp->mr_count > 0); /* Read lock */
+	else if (type == MR_UPDATE)
+		return (mrp->mr_count < 0); /* Write lock */
+	else if (type == (MR_UPDATE | MR_ACCESS))
+		return (mrp->mr_count);	/* Any type of lock held */
+	else /* Any waiters */
+		return (mrp->mr_reads_waiting | mrp->mr_writes_waiting);
+}
+
+/*
+ * Demote from update to access. We better be the only thread with the
+ * lock in update mode so it should be easy to set to 1.
+ * Wake-up any readers waiting.
+ */
+
+void
+mrdemote(mrlock_t *mrp)
+{
+	MRLOCK(mrp);
+	mrp->mr_count = 1;
+	if (mrp->mr_reads_waiting) {	/* Wakeup all readers waiting */
+		wake_up(&mrp->mr_readerq);
+	}
+	MRUNLOCK(mrp);
+}