VFS Lite2 Changes

1 files changed, 537 insertions, 0 deletions

diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c
new file mode 100644
index 00000000000..c6793d24f58
--- /dev/null
+++ b/sys/kern/kern_lock.c
@@ -0,0 +1,537 @@
+/* 
+ * Copyright (c) 1995
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * This code contains ideas from software contributed to Berkeley by
+ * Avadis Tevanian, Jr., Michael Wayne Young, and the Mach Operating
+ * System project at Carnegie-Mellon University.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *	This product includes software developed by the University of
+ *	California, Berkeley and its contributors.
+ * 4. Neither the name of the University nor the names of its contributors
+ *    may be used to endorse or promote products derived from this software
+ *    without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
+ * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+ * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+ * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
+ * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+ * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+ * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+ * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+ * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+ * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ *
+ *	@(#)kern_lock.c	8.18 (Berkeley) 5/21/95
+ */
+
+#include <sys/param.h>
+#include <sys/proc.h>
+#include <sys/lock.h>
+#include <sys/systm.h>
+
+#include <machine/cpu.h>
+
+void record_stacktrace __P((int *, int));
+void playback_stacktrace __P((int *, int));
+
+/*
+ * Locking primitives implementation.
+ * Locks provide shared/exclusive sychronization.
+ */
+
+#ifdef DEBUG
+#define COUNT(p, x) if (p) (p)->p_locks += (x)
+#else
+#define COUNT(p, x)
+#endif
+
+#if NCPUS > 1
+
+/*
+ * For multiprocessor system, try spin lock first.
+ *
+ * This should be inline expanded below, but we cannot have #if
+ * inside a multiline define.
+ */
+int lock_wait_time = 100;
+#define PAUSE(lkp, wanted)						\
+		if (lock_wait_time > 0) {				\
+			int i;						\
+									\
+			simple_unlock(&lkp->lk_interlock);		\
+			for (i = lock_wait_time; i > 0; i--)		\
+				if (!(wanted))				\
+					break;				\
+			simple_lock(&lkp->lk_interlock);		\
+		}							\
+		if (!(wanted))						\
+			break;
+
+#else /* NCPUS == 1 */
+
+/*
+ * It is an error to spin on a uniprocessor as nothing will ever cause
+ * the simple lock to clear while we are executing.
+ */
+#define PAUSE(lkp, wanted)
+
+#endif /* NCPUS == 1 */
+
+/*
+ * Acquire a resource.
+ */
+#define ACQUIRE(lkp, error, extflags, wanted)				\
+	PAUSE(lkp, wanted);						\
+	for (error = 0; wanted; ) {					\
+		(lkp)->lk_waitcount++;					\
+		simple_unlock(&(lkp)->lk_interlock);			\
+		error = tsleep((void *)lkp, (lkp)->lk_prio,		\
+		    (lkp)->lk_wmesg, (lkp)->lk_timo);			\
+		simple_lock(&(lkp)->lk_interlock);			\
+		(lkp)->lk_waitcount--;					\
+		if (error)						\
+			break;						\
+		if ((extflags) & LK_SLEEPFAIL) {			\
+			error = ENOLCK;					\
+			break;						\
+		}							\
+	}
+
+/*
+ * Initialize a lock; required before use.
+ */
+void
+lockinit(lkp, prio, wmesg, timo, flags)
+	struct lock *lkp;
+	int prio;
+	char *wmesg;
+	int timo;
+	int flags;
+{
+
+	bzero(lkp, sizeof(struct lock));
+	simple_lock_init(&lkp->lk_interlock);
+	lkp->lk_flags = flags & LK_EXTFLG_MASK;
+	lkp->lk_prio = prio;
+	lkp->lk_timo = timo;
+	lkp->lk_wmesg = wmesg;
+	lkp->lk_lockholder = LK_NOPROC;
+}
+
+/*
+ * Determine the status of a lock.
+ */
+int
+lockstatus(lkp)
+	struct lock *lkp;
+{
+	int lock_type = 0;
+
+	simple_lock(&lkp->lk_interlock);
+	if (lkp->lk_exclusivecount != 0)
+		lock_type = LK_EXCLUSIVE;
+	else if (lkp->lk_sharecount != 0)
+		lock_type = LK_SHARED;
+	simple_unlock(&lkp->lk_interlock);
+	return (lock_type);
+}
+
+/*
+ * Set, change, or release a lock.
+ *
+ * Shared requests increment the shared count. Exclusive requests set the
+ * LK_WANT_EXCL flag (preventing further shared locks), and wait for already
+ * accepted shared locks and shared-to-exclusive upgrades to go away.
+ */
+int
+lockmgr(lkp, flags, interlkp, p)
+	__volatile struct lock *lkp;
+	u_int flags;
+	struct simplelock *interlkp;
+	struct proc *p;
+{
+	int error;
+	pid_t pid;
+	int extflags;
+
+	error = 0;
+	if (p)
+		pid = p->p_pid;
+	else
+		pid = LK_KERNPROC;
+	simple_lock(&lkp->lk_interlock);
+	if (flags & LK_INTERLOCK)
+		simple_unlock(interlkp);
+	extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
+#ifdef DIAGNOSTIC
+	/*
+	 * Once a lock has drained, the LK_DRAINING flag is set and an
+	 * exclusive lock is returned. The only valid operation thereafter
+	 * is a single release of that exclusive lock. This final release
+	 * clears the LK_DRAINING flag and sets the LK_DRAINED flag. Any
+	 * further requests of any sort will result in a panic. The bits
+	 * selected for these two flags are chosen so that they will be set
+	 * in memory that is freed (freed memory is filled with 0xdeadbeef).
+	 * The final release is permitted to give a new lease on life to
+	 * the lock by specifying LK_REENABLE.
+	 */
+	if (lkp->lk_flags & (LK_DRAINING|LK_DRAINED)) {
+		if (lkp->lk_flags & LK_DRAINED)
+			panic("lockmgr: using decommissioned lock");
+		if ((flags & LK_TYPE_MASK) != LK_RELEASE ||
+		    lkp->lk_lockholder != pid)
+			panic("lockmgr: non-release on draining lock: %d\n",
+			    flags & LK_TYPE_MASK);
+		lkp->lk_flags &= ~LK_DRAINING;
+		if ((flags & LK_REENABLE) == 0)
+			lkp->lk_flags |= LK_DRAINED;
+	}
+#endif DIAGNOSTIC
+
+	switch (flags & LK_TYPE_MASK) {
+
+	case LK_SHARED:
+		if (lkp->lk_lockholder != pid) {
+			/*
+			 * If just polling, check to see if we will block.
+			 */
+			if ((extflags & LK_NOWAIT) && (lkp->lk_flags &
+			    (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE))) {
+				error = EBUSY;
+				break;
+			}
+			/*
+			 * Wait for exclusive locks and upgrades to clear.
+			 */
+			ACQUIRE(lkp, error, extflags, lkp->lk_flags &
+			    (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE));
+			if (error)
+				break;
+			lkp->lk_sharecount++;
+			COUNT(p, 1);
+			break;
+		}
+		/*
+		 * We hold an exclusive lock, so downgrade it to shared.
+		 * An alternative would be to fail with EDEADLK.
+		 */
+		lkp->lk_sharecount++;
+		COUNT(p, 1);
+		/* fall into downgrade */
+
+	case LK_DOWNGRADE:
+		if (lkp->lk_lockholder != pid || lkp->lk_exclusivecount == 0)
+			panic("lockmgr: not holding exclusive lock");
+		lkp->lk_sharecount += lkp->lk_exclusivecount;
+		lkp->lk_exclusivecount = 0;
+		lkp->lk_flags &= ~LK_HAVE_EXCL;
+		lkp->lk_lockholder = LK_NOPROC;
+		if (lkp->lk_waitcount)
+			wakeup((void *)lkp);
+		break;
+
+	case LK_EXCLUPGRADE:
+		/*
+		 * If another process is ahead of us to get an upgrade,
+		 * then we want to fail rather than have an intervening
+		 * exclusive access.
+		 */
+		if (lkp->lk_flags & LK_WANT_UPGRADE) {
+			lkp->lk_sharecount--;
+			COUNT(p, -1);
+			error = EBUSY;
+			break;
+		}
+		/* fall into normal upgrade */
+
+	case LK_UPGRADE:
+		/*
+		 * Upgrade a shared lock to an exclusive one. If another
+		 * shared lock has already requested an upgrade to an
+		 * exclusive lock, our shared lock is released and an
+		 * exclusive lock is requested (which will be granted
+		 * after the upgrade). If we return an error, the file
+		 * will always be unlocked.
+		 */
+		if (lkp->lk_lockholder == pid || lkp->lk_sharecount <= 0)
+			panic("lockmgr: upgrade exclusive lock");
+		lkp->lk_sharecount--;
+		COUNT(p, -1);
+		/*
+		 * If we are just polling, check to see if we will block.
+		 */
+		if ((extflags & LK_NOWAIT) &&
+		    ((lkp->lk_flags & LK_WANT_UPGRADE) ||
+		     lkp->lk_sharecount > 1)) {
+			error = EBUSY;
+			break;
+		}
+		if ((lkp->lk_flags & LK_WANT_UPGRADE) == 0) {
+			/*
+			 * We are first shared lock to request an upgrade, so
+			 * request upgrade and wait for the shared count to
+			 * drop to zero, then take exclusive lock.
+			 */
+			lkp->lk_flags |= LK_WANT_UPGRADE;
+			ACQUIRE(lkp, error, extflags, lkp->lk_sharecount);
+			lkp->lk_flags &= ~LK_WANT_UPGRADE;
+			if (error)
+				break;
+			lkp->lk_flags |= LK_HAVE_EXCL;
+			lkp->lk_lockholder = pid;
+			if (lkp->lk_exclusivecount != 0)
+				panic("lockmgr: non-zero exclusive count");
+			lkp->lk_exclusivecount = 1;
+			COUNT(p, 1);
+			break;
+		}
+		/*
+		 * Someone else has requested upgrade. Release our shared
+		 * lock, awaken upgrade requestor if we are the last shared
+		 * lock, then request an exclusive lock.
+		 */
+		if (lkp->lk_sharecount == 0 && lkp->lk_waitcount)
+			wakeup((void *)lkp);
+		/* fall into exclusive request */
+
+	case LK_EXCLUSIVE:
+		if (lkp->lk_lockholder == pid && pid != LK_KERNPROC) {
+			/*
+			 *	Recursive lock.
+			 */
+			if ((extflags & LK_CANRECURSE) == 0)
+				panic("lockmgr: locking against myself");
+			lkp->lk_exclusivecount++;
+			COUNT(p, 1);
+			break;
+		}
+		/*
+		 * If we are just polling, check to see if we will sleep.
+		 */
+		if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
+		     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
+		     lkp->lk_sharecount != 0)) {
+			error = EBUSY;
+			break;
+		}
+		/*
+		 * Try to acquire the want_exclusive flag.
+		 */
+		ACQUIRE(lkp, error, extflags, lkp->lk_flags &
+		    (LK_HAVE_EXCL | LK_WANT_EXCL));
+		if (error)
+			break;
+		lkp->lk_flags |= LK_WANT_EXCL;
+		/*
+		 * Wait for shared locks and upgrades to finish.
+		 */
+		ACQUIRE(lkp, error, extflags, lkp->lk_sharecount != 0 ||
+		       (lkp->lk_flags & LK_WANT_UPGRADE));
+		lkp->lk_flags &= ~LK_WANT_EXCL;
+		if (error)
+			break;
+		lkp->lk_flags |= LK_HAVE_EXCL;
+		lkp->lk_lockholder = pid;
+		if (lkp->lk_exclusivecount != 0)
+			panic("lockmgr: non-zero exclusive count");
+		lkp->lk_exclusivecount = 1;
+		COUNT(p, 1);
+		break;
+
+	case LK_RELEASE:
+		if (lkp->lk_exclusivecount != 0) {
+			if (pid != lkp->lk_lockholder)
+				panic("lockmgr: pid %d, not %s %d unlocking",
+				    pid, "exclusive lock holder",
+				    lkp->lk_lockholder);
+			lkp->lk_exclusivecount--;
+			COUNT(p, -1);
+			if (lkp->lk_exclusivecount == 0) {
+				lkp->lk_flags &= ~LK_HAVE_EXCL;
+				lkp->lk_lockholder = LK_NOPROC;
+			}
+		} else if (lkp->lk_sharecount != 0) {
+			lkp->lk_sharecount--;
+			COUNT(p, -1);
+		}
+		if (lkp->lk_waitcount)
+			wakeup((void *)lkp);
+		break;
+
+	case LK_DRAIN:
+		/*
+		 * Check that we do not already hold the lock, as it can 
+		 * never drain if we do. Unfortunately, we have no way to
+		 * check for holding a shared lock, but at least we can
+		 * check for an exclusive one.
+		 */
+		if (lkp->lk_lockholder == pid)
+			panic("lockmgr: draining against myself");
+		/*
+		 * If we are just polling, check to see if we will sleep.
+		 */
+		if ((extflags & LK_NOWAIT) && ((lkp->lk_flags &
+		     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
+		     lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0)) {
+			error = EBUSY;
+			break;
+		}
+		PAUSE(lkp, ((lkp->lk_flags &
+		     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
+		     lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0));
+		for (error = 0; ((lkp->lk_flags &
+		     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) ||
+		     lkp->lk_sharecount != 0 || lkp->lk_waitcount != 0); ) {
+			lkp->lk_flags |= LK_WAITDRAIN;
+			simple_unlock(&lkp->lk_interlock);
+			if ((error = tsleep((void *)&lkp->lk_flags, lkp->lk_prio,
+			    lkp->lk_wmesg, lkp->lk_timo)) != 0)
+				return (error);
+			if ((extflags) & LK_SLEEPFAIL)
+				return (ENOLCK);
+			simple_lock(&lkp->lk_interlock);
+		}
+		lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
+		lkp->lk_lockholder = pid;
+		lkp->lk_exclusivecount = 1;
+		COUNT(p, 1);
+		break;
+
+	default:
+		simple_unlock(&lkp->lk_interlock);
+		panic("lockmgr: unknown locktype request %d",
+		    flags & LK_TYPE_MASK);
+		/* NOTREACHED */
+	}
+	if ((lkp->lk_flags & LK_WAITDRAIN) && ((lkp->lk_flags &
+	     (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE)) == 0 &&
+	     lkp->lk_sharecount == 0 && lkp->lk_waitcount == 0)) {
+		lkp->lk_flags &= ~LK_WAITDRAIN;
+		wakeup((void *)&lkp->lk_flags);
+	}
+	simple_unlock(&lkp->lk_interlock);
+	return (error);
+}
+
+/*
+ * Print out information about state of a lock. Used by VOP_PRINT
+ * routines to display ststus about contained locks.
+ */
+void
+lockmgr_printinfo(lkp)
+	struct lock *lkp;
+{
+
+	if (lkp->lk_sharecount)
+		printf(" lock type %s: SHARED (count %d)", lkp->lk_wmesg,
+		    lkp->lk_sharecount);
+	else if (lkp->lk_flags & LK_HAVE_EXCL)
+		printf(" lock type %s: EXCL (count %d) by pid %d",
+		    lkp->lk_wmesg, lkp->lk_exclusivecount, lkp->lk_lockholder);
+	if (lkp->lk_waitcount > 0)
+		printf(" with %d pending", lkp->lk_waitcount);
+}
+
+#if defined(DEBUG) && NCPUS == 1
+#include <sys/kernel.h>
+#include <vm/vm.h>
+#include <sys/sysctl.h>
+int lockpausetime = 0;
+struct ctldebug debug2 = { "lockpausetime", &lockpausetime };
+int simplelockrecurse;
+/*
+ * Simple lock functions so that the debugger can see from whence
+ * they are being called.
+ */
+void
+simple_lock_init(alp)
+	struct simplelock *alp;
+{
+
+	alp->lock_data = 0;
+}
+
+void
+_simple_lock(alp, id, l)
+	__volatile struct simplelock *alp;
+	const char *id;
+	int l;
+{
+
+	if (simplelockrecurse)
+		return;
+	if (alp->lock_data == 1) {
+		if (lockpausetime == -1)
+			panic("%s:%d: simple_lock: lock held", id, l);
+		printf("%s:%d: simple_lock: lock held\n", id, l);
+		if (lockpausetime == 1) {
+			BACKTRACE(curproc);
+		} else if (lockpausetime > 1) {
+			printf("%s:%d: simple_lock: lock held...", id, l);
+			tsleep(&lockpausetime, PCATCH | PPAUSE, "slock",
+			    lockpausetime * hz);
+			printf(" continuing\n");
+		}
+	}
+	alp->lock_data = 1;
+	if (curproc)
+		curproc->p_simple_locks++;
+}
+
+int
+_simple_lock_try(alp, id, l)
+	__volatile struct simplelock *alp;
+	const char *id;
+	int l;
+{
+
+	if (alp->lock_data)
+		return (0);
+	if (simplelockrecurse)
+		return (1);
+	alp->lock_data = 1;
+	if (curproc)
+		curproc->p_simple_locks++;
+	return (1);
+}
+
+void
+_simple_unlock(alp, id, l)
+	__volatile struct simplelock *alp;
+	const char *id;
+	int l;
+{
+
+	if (simplelockrecurse)
+		return;
+	if (alp->lock_data == 0) {
+		if (lockpausetime == -1)
+			panic("%s:%d: simple_unlock: lock not held", id, l);
+		printf("%s:%d: simple_unlock: lock not held\n", id, l);
+		if (lockpausetime == 1) {
+			BACKTRACE(curproc);
+		} else if (lockpausetime > 1) {
+			printf("%s:%d: simple_unlock: lock not held...", id, l);
+			tsleep(&lockpausetime, PCATCH | PPAUSE, "sunlock",
+			    lockpausetime * hz);
+			printf(" continuing\n");
+		}
+	}
+	alp->lock_data = 0;
+	if (curproc)
+		curproc->p_simple_locks--;
+}
+#endif /* DEBUG && NCPUS == 1 */