1 files changed, 594 insertions, 0 deletions

diff --git a/sys/kern/kern_lock.c b/sys/kern/kern_lock.c
new file mode 100644
index 0000000..5189bb7
--- /dev/null
+++ b/sys/kern/kern_lock.c
@@ -0,0 +1,594 @@
+/* 
+ * Copyright (c) 1995
+ *	The Regents of the University of California.  All rights reserved.
+ *
+ * Copyright (C) 1997
+ *	John S. Dyson.  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
+ * $FreeBSD$
+ */
+
+#include <sys/param.h>
+#include <sys/proc.h>
+#include <sys/kernel.h>
+#include <sys/ktr.h>
+#include <sys/lock.h>
+#include <sys/malloc.h>
+#include <sys/mutex.h>
+#include <sys/systm.h>
+
+/*
+ * Locking primitives implementation.
+ * Locks provide shared/exclusive sychronization.
+ */
+
+#define LOCK_WAIT_TIME 100
+#define LOCK_SAMPLE_WAIT 7
+
+#if defined(DIAGNOSTIC)
+#define LOCK_INLINE
+#else
+#define LOCK_INLINE __inline
+#endif
+
+#define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \
+	LK_SHARE_NONZERO | LK_WAIT_NONZERO)
+
+/*
+ * Mutex array variables.  Rather than each lockmgr lock having its own mutex,
+ * share a fixed (at boot time) number of mutexes across all lockmgr locks in
+ * order to keep sizeof(struct lock) down.
+ */
+int lock_mtx_valid;
+static struct mtx lock_mtx;
+
+static int acquire(struct lock *lkp, int extflags, int wanted);
+static int apause(struct lock *lkp, int flags);
+static int acquiredrain(struct lock *lkp, int extflags) ;
+
+static void
+lockmgr_init(void *dummy __unused)
+{
+	/*
+	 * Initialize the lockmgr protection mutex if it hasn't already been
+	 * done.  Unless something changes about kernel startup order, VM
+	 * initialization will always cause this mutex to already be
+	 * initialized in a call to lockinit().
+	 */
+	if (lock_mtx_valid == 0) {
+		mtx_init(&lock_mtx, "lockmgr", NULL, MTX_DEF);
+		lock_mtx_valid = 1;
+	}
+}
+SYSINIT(lmgrinit, SI_SUB_LOCK, SI_ORDER_FIRST, lockmgr_init, NULL)
+
+static LOCK_INLINE void
+sharelock(struct lock *lkp, int incr) {
+	lkp->lk_flags |= LK_SHARE_NONZERO;
+	lkp->lk_sharecount += incr;
+}
+
+static LOCK_INLINE void
+shareunlock(struct lock *lkp, int decr) {
+
+	KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr"));
+
+	if (lkp->lk_sharecount == decr) {
+		lkp->lk_flags &= ~LK_SHARE_NONZERO;
+		if (lkp->lk_flags & (LK_WANT_UPGRADE | LK_WANT_EXCL)) {
+			wakeup(lkp);
+		}
+		lkp->lk_sharecount = 0;
+	} else {
+		lkp->lk_sharecount -= decr;
+	}
+}
+
+/*
+ * This is the waitloop optimization.
+ */
+static int
+apause(struct lock *lkp, int flags)
+{
+#ifdef SMP
+	int i, lock_wait;
+#endif
+
+	if ((lkp->lk_flags & flags) == 0)
+		return 0;
+#ifdef SMP
+	for (lock_wait = LOCK_WAIT_TIME; lock_wait > 0; lock_wait--) {
+		mtx_unlock(lkp->lk_interlock);
+		for (i = LOCK_SAMPLE_WAIT; i > 0; i--)
+			if ((lkp->lk_flags & flags) == 0)
+				break;
+		mtx_lock(lkp->lk_interlock);
+		if ((lkp->lk_flags & flags) == 0)
+			return 0;
+	}
+#endif
+	return 1;
+}
+
+static int
+acquire(struct lock *lkp, int extflags, int wanted) {
+	int s, error;
+
+	CTR3(KTR_LOCKMGR,
+	    "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x\n",
+	    lkp, extflags, wanted);
+
+	if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) {
+		return EBUSY;
+	}
+
+	if (((lkp->lk_flags | extflags) & LK_NOPAUSE) == 0) {
+		error = apause(lkp, wanted);
+		if (error == 0)
+			return 0;
+	}
+
+	s = splhigh();
+	while ((lkp->lk_flags & wanted) != 0) {
+		lkp->lk_flags |= LK_WAIT_NONZERO;
+		lkp->lk_waitcount++;
+		error = msleep(lkp, lkp->lk_interlock, lkp->lk_prio,
+		    lkp->lk_wmesg, 
+		    ((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
+		if (lkp->lk_waitcount == 1) {
+			lkp->lk_flags &= ~LK_WAIT_NONZERO;
+			lkp->lk_waitcount = 0;
+		} else {
+			lkp->lk_waitcount--;
+		}
+		if (error) {
+			splx(s);
+			return error;
+		}
+		if (extflags & LK_SLEEPFAIL) {
+			splx(s);
+			return ENOLCK;
+		}
+	}
+	splx(s);
+	return 0;
+}
+
+/*
+ * 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
+#ifndef	DEBUG_LOCKS
+lockmgr(lkp, flags, interlkp, td)
+#else
+debuglockmgr(lkp, flags, interlkp, td, name, file, line)
+#endif
+	struct lock *lkp;
+	u_int flags;
+	struct mtx *interlkp;
+	struct thread *td;
+#ifdef	DEBUG_LOCKS
+	const char *name;	/* Name of lock function */
+	const char *file;	/* Name of file call is from */
+	int line;		/* Line number in file */
+#endif
+{
+	int error;
+	pid_t pid;
+	int extflags, lockflags;
+
+	CTR5(KTR_LOCKMGR,
+	    "lockmgr(): lkp == %p (lk_wmesg == \"%s\"), flags == 0x%x, "
+	    "interlkp == %p, td == %p", lkp, lkp->lk_wmesg, flags, interlkp, td);
+
+	error = 0;
+	if (td == NULL)
+		pid = LK_KERNPROC;
+	else
+		pid = td->td_proc->p_pid;
+
+	mtx_lock(lkp->lk_interlock);
+	if (flags & LK_INTERLOCK) {
+		mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED);
+		mtx_unlock(interlkp);
+	}
+
+	if (panicstr != NULL) {
+		mtx_unlock(lkp->lk_interlock);
+		return (0);
+	}
+
+	extflags = (flags | lkp->lk_flags) & LK_EXTFLG_MASK;
+
+	switch (flags & LK_TYPE_MASK) {
+
+	case LK_SHARED:
+		/*
+		 * If we are not the exclusive lock holder, we have to block
+		 * while there is an exclusive lock holder or while an
+		 * exclusive lock request or upgrade request is in progress.
+		 *
+		 * However, if TDF_DEADLKTREAT is set, we override exclusive
+		 * lock requests or upgrade requests ( but not the exclusive
+		 * lock itself ).
+		 */
+		if (lkp->lk_lockholder != pid) {
+			lockflags = LK_HAVE_EXCL;
+			mtx_lock_spin(&sched_lock);
+			if (td != NULL && !(td->td_flags & TDF_DEADLKTREAT))
+				lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE;
+			mtx_unlock_spin(&sched_lock);
+			error = acquire(lkp, extflags, lockflags);
+			if (error)
+				break;
+			sharelock(lkp, 1);
+#if defined(DEBUG_LOCKS)
+			lkp->lk_slockholder = pid;
+			lkp->lk_sfilename = file;
+			lkp->lk_slineno = line;
+			lkp->lk_slockername = name;
+#endif
+			break;
+		}
+		/*
+		 * We hold an exclusive lock, so downgrade it to shared.
+		 * An alternative would be to fail with EDEADLK.
+		 */
+		sharelock(lkp, 1);
+		/* fall into downgrade */
+
+	case LK_DOWNGRADE:
+		KASSERT(lkp->lk_lockholder == pid && lkp->lk_exclusivecount != 0,
+			("lockmgr: not holding exclusive lock "
+			"(owner pid (%d) != pid (%d), exlcnt (%d) != 0",
+			lkp->lk_lockholder, pid, lkp->lk_exclusivecount));
+		sharelock(lkp, 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) {
+			shareunlock(lkp, 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");
+		shareunlock(lkp, 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;
+			error = acquire(lkp, extflags, LK_SHARE_NONZERO);
+			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;
+#if defined(DEBUG_LOCKS)
+			lkp->lk_filename = file;
+			lkp->lk_lineno = line;
+			lkp->lk_lockername = name;
+#endif
+			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_flags & (LK_SHARE_NONZERO|LK_WAIT_NONZERO)) ==
+			LK_WAIT_NONZERO)
+			wakeup((void *)lkp);
+		/* fall into exclusive request */
+
+	case LK_EXCLUSIVE:
+		if (lkp->lk_lockholder == pid && pid != LK_KERNPROC) {
+			/*
+			 *	Recursive lock.
+			 */
+			if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0)
+				panic("lockmgr: locking against myself");
+			if ((extflags & LK_CANRECURSE) != 0) {
+				lkp->lk_exclusivecount++;
+				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 | LK_SHARE_NONZERO))) {
+			error = EBUSY;
+			break;
+		}
+		/*
+		 * Try to acquire the want_exclusive flag.
+		 */
+		error = acquire(lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL));
+		if (error)
+			break;
+		lkp->lk_flags |= LK_WANT_EXCL;
+		/*
+		 * Wait for shared locks and upgrades to finish.
+		 */
+		error = acquire(lkp, extflags, LK_WANT_UPGRADE | LK_SHARE_NONZERO);
+		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;
+#if defined(DEBUG_LOCKS)
+			lkp->lk_filename = file;
+			lkp->lk_lineno = line;
+			lkp->lk_lockername = name;
+#endif
+		break;
+
+	case LK_RELEASE:
+		if (lkp->lk_exclusivecount != 0) {
+			if (lkp->lk_lockholder != pid &&
+			    lkp->lk_lockholder != LK_KERNPROC) {
+				panic("lockmgr: pid %d, not %s %d unlocking",
+				    pid, "exclusive lock holder",
+				    lkp->lk_lockholder);
+			}
+			if (lkp->lk_exclusivecount == 1) {
+				lkp->lk_flags &= ~LK_HAVE_EXCL;
+				lkp->lk_lockholder = LK_NOPROC;
+				lkp->lk_exclusivecount = 0;
+			} else {
+				lkp->lk_exclusivecount--;
+			}
+		} else if (lkp->lk_flags & LK_SHARE_NONZERO)
+			shareunlock(lkp, 1);
+		if (lkp->lk_flags & LK_WAIT_NONZERO)
+			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");
+
+		error = acquiredrain(lkp, extflags);
+		if (error)
+			break;
+		lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL;
+		lkp->lk_lockholder = pid;
+		lkp->lk_exclusivecount = 1;
+#if defined(DEBUG_LOCKS)
+			lkp->lk_filename = file;
+			lkp->lk_lineno = line;
+			lkp->lk_lockername = name;
+#endif
+		break;
+
+	default:
+		mtx_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 |
+		LK_SHARE_NONZERO | LK_WAIT_NONZERO)) == 0) {
+		lkp->lk_flags &= ~LK_WAITDRAIN;
+		wakeup((void *)&lkp->lk_flags);
+	}
+	mtx_unlock(lkp->lk_interlock);
+	return (error);
+}
+
+static int
+acquiredrain(struct lock *lkp, int extflags) {
+	int error;
+
+	if ((extflags & LK_NOWAIT) && (lkp->lk_flags & LK_ALL)) {
+		return EBUSY;
+	}
+
+	error = apause(lkp, LK_ALL);
+	if (error == 0)
+		return 0;
+
+	while (lkp->lk_flags & LK_ALL) {
+		lkp->lk_flags |= LK_WAITDRAIN;
+		error = msleep(&lkp->lk_flags, lkp->lk_interlock, lkp->lk_prio,
+			lkp->lk_wmesg, 
+			((extflags & LK_TIMELOCK) ? lkp->lk_timo : 0));
+		if (error)
+			return error;
+		if (extflags & LK_SLEEPFAIL) {
+			return ENOLCK;
+		}
+	}
+	return 0;
+}
+
+/*
+ * Initialize a lock; required before use.
+ */
+void
+lockinit(lkp, prio, wmesg, timo, flags)
+	struct lock *lkp;
+	int prio;
+	const char *wmesg;
+	int timo;
+	int flags;
+{
+	CTR5(KTR_LOCKMGR, "lockinit(): lkp == %p, prio == %d, wmesg == \"%s\", "
+	    "timo == %d, flags = 0x%x\n", lkp, prio, wmesg, timo, flags);
+
+	if (lock_mtx_valid == 0) {
+		mtx_init(&lock_mtx, "lockmgr", NULL, MTX_DEF);
+		lock_mtx_valid = 1;
+	}
+	/*
+	 * XXX cleanup - make sure mtxpool is always initialized before
+	 * this is ever called.
+	 */
+	if (mtx_pool_valid) {
+		mtx_lock(&lock_mtx);
+		lkp->lk_interlock = mtx_pool_alloc();
+		mtx_unlock(&lock_mtx);
+	} else {
+		lkp->lk_interlock = &lock_mtx;
+	}
+	lkp->lk_flags = (flags & LK_EXTFLG_MASK);
+	lkp->lk_sharecount = 0;
+	lkp->lk_waitcount = 0;
+	lkp->lk_exclusivecount = 0;
+	lkp->lk_prio = prio;
+	lkp->lk_wmesg = wmesg;
+	lkp->lk_timo = timo;
+	lkp->lk_lockholder = LK_NOPROC;
+}
+
+/*
+ * Destroy a lock.
+ */
+void
+lockdestroy(lkp)
+	struct lock *lkp;
+{
+	CTR2(KTR_LOCKMGR, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")",
+	    lkp, lkp->lk_wmesg);
+}
+
+/*
+ * Determine the status of a lock.
+ */
+int
+lockstatus(lkp, td)
+	struct lock *lkp;
+	struct thread *td;
+{
+	int lock_type = 0;
+
+	mtx_lock(lkp->lk_interlock);
+	if (lkp->lk_exclusivecount != 0) {
+		if (td == NULL || lkp->lk_lockholder == td->td_proc->p_pid)
+			lock_type = LK_EXCLUSIVE;
+		else
+			lock_type = LK_EXCLOTHER;
+	} else if (lkp->lk_sharecount != 0)
+		lock_type = LK_SHARED;
+	mtx_unlock(lkp->lk_interlock);
+	return (lock_type);
+}
+
+/*
+ * Determine the number of holders of a lock.
+ */
+int
+lockcount(lkp)
+	struct lock *lkp;
+{
+	int count;
+
+	mtx_lock(lkp->lk_interlock);
+	count = lkp->lk_exclusivecount + lkp->lk_sharecount;
+	mtx_unlock(lkp->lk_interlock);
+	return (count);
+}
+
+/*
+ * Print out information about state of a lock. Used by VOP_PRINT
+ * routines to display status 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);
+}