/*- * 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 */ #include <sys/cdefs.h> __FBSDID("$FreeBSD$"); #include "opt_ddb.h" #include "opt_global.h" #include <sys/param.h> #include <sys/kdb.h> #include <sys/kernel.h> #include <sys/ktr.h> #include <sys/lock.h> #include <sys/lockmgr.h> #include <sys/mutex.h> #include <sys/proc.h> #include <sys/systm.h> #include <sys/lock_profile.h> #ifdef DEBUG_LOCKS #include <sys/stack.h> #endif #ifdef DDB #include <ddb/ddb.h> static void db_show_lockmgr(struct lock_object *lock); #endif static void lock_lockmgr(struct lock_object *lock, int how); static int unlock_lockmgr(struct lock_object *lock); struct lock_class lock_class_lockmgr = { .lc_name = "lockmgr", .lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE, #ifdef DDB .lc_ddb_show = db_show_lockmgr, #endif .lc_lock = lock_lockmgr, .lc_unlock = unlock_lockmgr, }; /* * Locking primitives implementation. * Locks provide shared/exclusive sychronization. */ void lock_lockmgr(struct lock_object *lock, int how) { panic("lockmgr locks do not support sleep interlocking"); } int unlock_lockmgr(struct lock_object *lock) { panic("lockmgr locks do not support sleep interlocking"); } #define COUNT(td, x) if ((td)) (td)->td_locks += (x) #define LK_ALL (LK_HAVE_EXCL | LK_WANT_EXCL | LK_WANT_UPGRADE | \ LK_SHARE_NONZERO | LK_WAIT_NONZERO) static int acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime); static int acquiredrain(struct lock *lkp, int extflags) ; static __inline void sharelock(struct thread *td, struct lock *lkp, int incr) { lkp->lk_flags |= LK_SHARE_NONZERO; lkp->lk_sharecount += incr; COUNT(td, incr); } static __inline void shareunlock(struct thread *td, struct lock *lkp, int decr) { KASSERT(lkp->lk_sharecount >= decr, ("shareunlock: count < decr")); COUNT(td, -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; } } static int acquire(struct lock **lkpp, int extflags, int wanted, int *contested, uint64_t *waittime) { struct lock *lkp = *lkpp; int error; CTR3(KTR_LOCK, "acquire(): lkp == %p, extflags == 0x%x, wanted == 0x%x", lkp, extflags, wanted); if ((extflags & LK_NOWAIT) && (lkp->lk_flags & wanted)) return EBUSY; error = 0; if ((lkp->lk_flags & wanted) != 0) lock_profile_obtain_lock_failed(&lkp->lk_object, contested, waittime); while ((lkp->lk_flags & wanted) != 0) { CTR2(KTR_LOCK, "acquire(): lkp == %p, lk_flags == 0x%x sleeping", lkp, lkp->lk_flags); 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)); lkp->lk_waitcount--; if (lkp->lk_waitcount == 0) lkp->lk_flags &= ~LK_WAIT_NONZERO; if (error) break; if (extflags & LK_SLEEPFAIL) { error = ENOLCK; break; } if (lkp->lk_newlock != NULL) { mtx_lock(lkp->lk_newlock->lk_interlock); mtx_unlock(lkp->lk_interlock); if (lkp->lk_waitcount == 0) wakeup((void *)(&lkp->lk_newlock)); *lkpp = lkp = lkp->lk_newlock; } } mtx_assert(lkp->lk_interlock, MA_OWNED); return (error); } /* * 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(struct lock *lkp, u_int flags, struct mtx *interlkp, struct thread *td, char *file, int line) { int error; struct thread *thr; int extflags, lockflags; int contested = 0; uint64_t waitstart = 0; error = 0; if (td == NULL) thr = LK_KERNPROC; else thr = td; if ((flags & LK_INTERNAL) == 0) mtx_lock(lkp->lk_interlock); CTR6(KTR_LOCK, "lockmgr(): lkp == %p (lk_wmesg == \"%s\"), owner == %p, exclusivecount == %d, flags == 0x%x, " "td == %p", lkp, lkp->lk_wmesg, lkp->lk_lockholder, lkp->lk_exclusivecount, flags, td); #ifdef DEBUG_LOCKS { struct stack stack; /* XXX */ stack_save(&stack); CTRSTACK(KTR_LOCK, &stack, 0, 1); } #endif if (flags & LK_INTERLOCK) { mtx_assert(interlkp, MA_OWNED | MA_NOTRECURSED); mtx_unlock(interlkp); } if ((flags & (LK_NOWAIT|LK_RELEASE)) == 0) WITNESS_WARN(WARN_GIANTOK | WARN_SLEEPOK, &lkp->lk_interlock->lock_object, "Acquiring lockmgr lock \"%s\"", lkp->lk_wmesg); if (panicstr != NULL) { mtx_unlock(lkp->lk_interlock); return (0); } if ((lkp->lk_flags & LK_NOSHARE) && (flags & LK_TYPE_MASK) == LK_SHARED) { flags &= ~LK_TYPE_MASK; flags |= LK_EXCLUSIVE; } 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 TDP_DEADLKTREAT is set, we override exclusive * lock requests or upgrade requests ( but not the exclusive * lock itself ). */ if (lkp->lk_lockholder != thr) { lockflags = LK_HAVE_EXCL; if (td != NULL && !(td->td_pflags & TDP_DEADLKTREAT)) lockflags |= LK_WANT_EXCL | LK_WANT_UPGRADE; error = acquire(&lkp, extflags, lockflags, &contested, &waitstart); if (error) break; sharelock(td, lkp, 1); if (lkp->lk_sharecount == 1) lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); #if defined(DEBUG_LOCKS) stack_save(&lkp->lk_stack); #endif break; } /* * We hold an exclusive lock, so downgrade it to shared. * An alternative would be to fail with EDEADLK. */ sharelock(td, lkp, 1); if (lkp->lk_sharecount == 1) lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); /* FALLTHROUGH downgrade */ case LK_DOWNGRADE: KASSERT(lkp->lk_lockholder == thr && lkp->lk_exclusivecount != 0, ("lockmgr: not holding exclusive lock " "(owner thread (%p) != thread (%p), exlcnt (%d) != 0", lkp->lk_lockholder, thr, lkp->lk_exclusivecount)); sharelock(td, lkp, lkp->lk_exclusivecount); COUNT(td, -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(td, lkp, 1); error = EBUSY; break; } /* FALLTHROUGH 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 == thr) panic("lockmgr: upgrade exclusive lock"); if (lkp->lk_sharecount <= 0) panic("lockmgr: upgrade without shared"); shareunlock(td, lkp, 1); if (lkp->lk_sharecount == 0) lock_profile_release_lock(&lkp->lk_object); /* * 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, &contested, &waitstart); lkp->lk_flags &= ~LK_WANT_UPGRADE; if (error) { if ((lkp->lk_flags & ( LK_WANT_EXCL | LK_WAIT_NONZERO)) == (LK_WANT_EXCL | LK_WAIT_NONZERO)) wakeup((void *)lkp); break; } if (lkp->lk_exclusivecount != 0) panic("lockmgr: non-zero exclusive count"); lkp->lk_flags |= LK_HAVE_EXCL; lkp->lk_lockholder = thr; lkp->lk_exclusivecount = 1; COUNT(td, 1); lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); #if defined(DEBUG_LOCKS) stack_save(&lkp->lk_stack); #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); /* FALLTHROUGH exclusive request */ case LK_EXCLUSIVE: if (lkp->lk_lockholder == thr && thr != LK_KERNPROC) { /* * Recursive lock. */ if ((extflags & (LK_NOWAIT | LK_CANRECURSE)) == 0) panic("lockmgr: locking against myself"); if ((extflags & LK_CANRECURSE) != 0) { lkp->lk_exclusivecount++; COUNT(td, 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 | LK_SHARE_NONZERO))) { error = EBUSY; break; } /* * Try to acquire the want_exclusive flag. */ error = acquire(&lkp, extflags, (LK_HAVE_EXCL | LK_WANT_EXCL), &contested, &waitstart); if (error) break; lkp->lk_flags |= LK_WANT_EXCL; /* * Wait for shared locks and upgrades to finish. */ error = acquire(&lkp, extflags, LK_HAVE_EXCL | LK_WANT_UPGRADE | LK_SHARE_NONZERO, &contested, &waitstart); lkp->lk_flags &= ~LK_WANT_EXCL; if (error) { if (lkp->lk_flags & LK_WAIT_NONZERO) wakeup((void *)lkp); break; } lkp->lk_flags |= LK_HAVE_EXCL; lkp->lk_lockholder = thr; if (lkp->lk_exclusivecount != 0) panic("lockmgr: non-zero exclusive count"); lkp->lk_exclusivecount = 1; COUNT(td, 1); lock_profile_obtain_lock_success(&lkp->lk_object, contested, waitstart, file, line); #if defined(DEBUG_LOCKS) stack_save(&lkp->lk_stack); #endif break; case LK_RELEASE: if (lkp->lk_exclusivecount != 0) { if (lkp->lk_lockholder != thr && lkp->lk_lockholder != LK_KERNPROC) { panic("lockmgr: thread %p, not %s %p unlocking", thr, "exclusive lock holder", lkp->lk_lockholder); } if (lkp->lk_lockholder != LK_KERNPROC) COUNT(td, -1); if (lkp->lk_exclusivecount == 1) { lkp->lk_flags &= ~LK_HAVE_EXCL; lkp->lk_lockholder = LK_NOPROC; lkp->lk_exclusivecount = 0; lock_profile_release_lock(&lkp->lk_object); } else { lkp->lk_exclusivecount--; } } else if (lkp->lk_flags & LK_SHARE_NONZERO) shareunlock(td, lkp, 1); else { printf("lockmgr: thread %p unlocking unheld lock\n", thr); kdb_backtrace(); } 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 == thr) panic("lockmgr: draining against myself"); error = acquiredrain(lkp, extflags); if (error) break; lkp->lk_flags |= LK_DRAINING | LK_HAVE_EXCL; lkp->lk_lockholder = thr; lkp->lk_exclusivecount = 1; COUNT(td, 1); #if defined(DEBUG_LOCKS) stack_save(&lkp->lk_stack); #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; } 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; } /* * Transfer any waiting processes from one lock to another. */ void transferlockers(from, to) struct lock *from; struct lock *to; { KASSERT(from != to, ("lock transfer to self")); KASSERT((from->lk_flags&LK_WAITDRAIN) == 0, ("transfer draining lock")); mtx_lock(from->lk_interlock); if (from->lk_waitcount == 0) { mtx_unlock(from->lk_interlock); return; } from->lk_newlock = to; wakeup((void *)from); msleep(&from->lk_newlock, from->lk_interlock, from->lk_prio, "lkxfer", 0); from->lk_newlock = NULL; from->lk_flags &= ~(LK_WANT_EXCL | LK_WANT_UPGRADE); KASSERT(from->lk_waitcount == 0, ("active lock")); mtx_unlock(from->lk_interlock); } /* * 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_LOCK, "lockinit(): lkp == %p, prio == %d, wmesg == \"%s\", " "timo == %d, flags = 0x%x\n", lkp, prio, wmesg, timo, flags); lkp->lk_interlock = mtx_pool_alloc(mtxpool_lockbuilder); 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_timo = timo; lkp->lk_lockholder = LK_NOPROC; lkp->lk_newlock = NULL; #ifdef DEBUG_LOCKS stack_zero(&lkp->lk_stack); #endif lock_init(&lkp->lk_object, &lock_class_lockmgr, wmesg, NULL, LO_RECURSABLE | LO_SLEEPABLE | LO_UPGRADABLE); } /* * Destroy a lock. */ void lockdestroy(lkp) struct lock *lkp; { CTR2(KTR_LOCK, "lockdestroy(): lkp == %p (lk_wmesg == \"%s\")", lkp, lkp->lk_wmesg); lock_destroy(&lkp->lk_object); } /* * Determine the status of a lock. */ int lockstatus(lkp, td) struct lock *lkp; struct thread *td; { int lock_type = 0; int interlocked; if (!kdb_active) { interlocked = 1; mtx_lock(lkp->lk_interlock); } else interlocked = 0; if (lkp->lk_exclusivecount != 0) { if (td == NULL || lkp->lk_lockholder == td) lock_type = LK_EXCLUSIVE; else lock_type = LK_EXCLOTHER; } else if (lkp->lk_sharecount != 0) lock_type = LK_SHARED; if (interlocked) 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); } /* * Determine the number of waiters on a lock. */ int lockwaiters(lkp) struct lock *lkp; { int count; mtx_lock(lkp->lk_interlock); count = lkp->lk_waitcount; 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 thread %p (pid %d)", lkp->lk_wmesg, lkp->lk_exclusivecount, lkp->lk_lockholder, lkp->lk_lockholder->td_proc->p_pid); if (lkp->lk_waitcount > 0) printf(" with %d pending", lkp->lk_waitcount); #ifdef DEBUG_LOCKS stack_print(&lkp->lk_stack); #endif } #ifdef DDB /* * Check to see if a thread that is blocked on a sleep queue is actually * blocked on a 'struct lock'. If so, output some details and return true. * If the lock has an exclusive owner, return that in *ownerp. */ int lockmgr_chain(struct thread *td, struct thread **ownerp) { struct lock *lkp; lkp = td->td_wchan; /* Simple test to see if wchan points to a lockmgr lock. */ if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr && lkp->lk_wmesg == td->td_wmesg) goto ok; /* * If this thread is doing a DRAIN, then it would be asleep on * &lkp->lk_flags rather than lkp. */ lkp = (struct lock *)((char *)td->td_wchan - offsetof(struct lock, lk_flags)); if (LOCK_CLASS(&lkp->lk_object) == &lock_class_lockmgr && lkp->lk_wmesg == td->td_wmesg && (lkp->lk_flags & LK_WAITDRAIN)) goto ok; /* Doen't seem to be a lockmgr lock. */ return (0); ok: /* Ok, we think we have a lockmgr lock, so output some details. */ db_printf("blocked on lk \"%s\" ", lkp->lk_wmesg); if (lkp->lk_sharecount) { db_printf("SHARED (count %d)\n", lkp->lk_sharecount); *ownerp = NULL; } else { db_printf("EXCL (count %d)\n", lkp->lk_exclusivecount); *ownerp = lkp->lk_lockholder; } return (1); } void db_show_lockmgr(struct lock_object *lock) { struct thread *td; struct lock *lkp; lkp = (struct lock *)lock; db_printf(" lock type: %s\n", lkp->lk_wmesg); db_printf(" state: "); if (lkp->lk_sharecount) db_printf("SHARED (count %d)\n", lkp->lk_sharecount); else if (lkp->lk_flags & LK_HAVE_EXCL) { td = lkp->lk_lockholder; db_printf("EXCL (count %d) %p ", lkp->lk_exclusivecount, td); db_printf("(tid %d, pid %d, \"%s\")\n", td->td_tid, td->td_proc->p_pid, td->td_proc->p_comm); } else db_printf("UNLOCKED\n"); if (lkp->lk_waitcount > 0) db_printf(" waiters: %d\n", lkp->lk_waitcount); } #endif