xref: /freebsd/sys/kern/kern_sx.c (revision f9721b43ed506f2ab7b1a60c6b92a9e4a360c6aa)
19454b2d8SWarner Losh /*-
24e7f640dSJohn Baldwin  * Copyright (c) 2007 Attilio Rao <attilio@freebsd.org>
34e7f640dSJohn Baldwin  * Copyright (c) 2001 Jason Evans <jasone@freebsd.org>
44e7f640dSJohn Baldwin  * All rights reserved.
56281b30aSJason Evans  *
66281b30aSJason Evans  * Redistribution and use in source and binary forms, with or without
76281b30aSJason Evans  * modification, are permitted provided that the following conditions
86281b30aSJason Evans  * are met:
96281b30aSJason Evans  * 1. Redistributions of source code must retain the above copyright
106281b30aSJason Evans  *    notice(s), this list of conditions and the following disclaimer as
116281b30aSJason Evans  *    the first lines of this file unmodified other than the possible
126281b30aSJason Evans  *    addition of one or more copyright notices.
136281b30aSJason Evans  * 2. Redistributions in binary form must reproduce the above copyright
146281b30aSJason Evans  *    notice(s), this list of conditions and the following disclaimer in the
156281b30aSJason Evans  *    documentation and/or other materials provided with the distribution.
166281b30aSJason Evans  *
176281b30aSJason Evans  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDER(S) ``AS IS'' AND ANY
186281b30aSJason Evans  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
196281b30aSJason Evans  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
206281b30aSJason Evans  * DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT HOLDER(S) BE LIABLE FOR ANY
216281b30aSJason Evans  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
226281b30aSJason Evans  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
236281b30aSJason Evans  * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
246281b30aSJason Evans  * CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
256281b30aSJason Evans  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
266281b30aSJason Evans  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
276281b30aSJason Evans  * DAMAGE.
286281b30aSJason Evans  */
296281b30aSJason Evans 
306281b30aSJason Evans /*
314e7f640dSJohn Baldwin  * Shared/exclusive locks.  This implementation attempts to ensure
324e7f640dSJohn Baldwin  * deterministic lock granting behavior, so that slocks and xlocks are
334e7f640dSJohn Baldwin  * interleaved.
346281b30aSJason Evans  *
356281b30aSJason Evans  * Priority propagation will not generally raise the priority of lock holders,
366281b30aSJason Evans  * so should not be relied upon in combination with sx locks.
376281b30aSJason Evans  */
386281b30aSJason Evans 
394e7f640dSJohn Baldwin #include "opt_adaptive_sx.h"
404e7f640dSJohn Baldwin #include "opt_ddb.h"
414e7f640dSJohn Baldwin 
42677b542eSDavid E. O'Brien #include <sys/cdefs.h>
43677b542eSDavid E. O'Brien __FBSDID("$FreeBSD$");
44677b542eSDavid E. O'Brien 
456281b30aSJason Evans #include <sys/param.h>
466281b30aSJason Evans #include <sys/ktr.h>
4719284646SJohn Baldwin #include <sys/lock.h>
486281b30aSJason Evans #include <sys/mutex.h>
49d272fe53SJohn Baldwin #include <sys/proc.h>
504e7f640dSJohn Baldwin #include <sys/sleepqueue.h>
516281b30aSJason Evans #include <sys/sx.h>
524e7f640dSJohn Baldwin #include <sys/systm.h>
534e7f640dSJohn Baldwin 
544e7f640dSJohn Baldwin #ifdef ADAPTIVE_SX
554e7f640dSJohn Baldwin #include <machine/cpu.h>
564e7f640dSJohn Baldwin #endif
576281b30aSJason Evans 
58462a7addSJohn Baldwin #ifdef DDB
59d272fe53SJohn Baldwin #include <ddb/ddb.h>
604e7f640dSJohn Baldwin #endif
61d272fe53SJohn Baldwin 
624e7f640dSJohn Baldwin #if !defined(SMP) && defined(ADAPTIVE_SX)
634e7f640dSJohn Baldwin #error "You must have SMP to enable the ADAPTIVE_SX option"
644e7f640dSJohn Baldwin #endif
654e7f640dSJohn Baldwin 
66c1a6d9faSAttilio Rao CTASSERT(((SX_ADAPTIVESPIN | SX_RECURSE) & LO_CLASSFLAGS) ==
67c1a6d9faSAttilio Rao     (SX_ADAPTIVESPIN | SX_RECURSE));
68c1a6d9faSAttilio Rao 
694e7f640dSJohn Baldwin /* Handy macros for sleep queues. */
704e7f640dSJohn Baldwin #define	SQ_EXCLUSIVE_QUEUE	0
714e7f640dSJohn Baldwin #define	SQ_SHARED_QUEUE		1
724e7f640dSJohn Baldwin 
734e7f640dSJohn Baldwin /*
744e7f640dSJohn Baldwin  * Variations on DROP_GIANT()/PICKUP_GIANT() for use in this file.  We
754e7f640dSJohn Baldwin  * drop Giant anytime we have to sleep or if we adaptively spin.
764e7f640dSJohn Baldwin  */
774e7f640dSJohn Baldwin #define	GIANT_DECLARE							\
784e7f640dSJohn Baldwin 	int _giantcnt = 0;						\
794e7f640dSJohn Baldwin 	WITNESS_SAVE_DECL(Giant)					\
804e7f640dSJohn Baldwin 
814e7f640dSJohn Baldwin #define	GIANT_SAVE() do {						\
824e7f640dSJohn Baldwin 	if (mtx_owned(&Giant)) {					\
834e7f640dSJohn Baldwin 		WITNESS_SAVE(&Giant.lock_object, Giant);		\
844e7f640dSJohn Baldwin 		while (mtx_owned(&Giant)) {				\
854e7f640dSJohn Baldwin 			_giantcnt++;					\
864e7f640dSJohn Baldwin 			mtx_unlock(&Giant);				\
874e7f640dSJohn Baldwin 		}							\
884e7f640dSJohn Baldwin 	}								\
894e7f640dSJohn Baldwin } while (0)
904e7f640dSJohn Baldwin 
914e7f640dSJohn Baldwin #define GIANT_RESTORE() do {						\
924e7f640dSJohn Baldwin 	if (_giantcnt > 0) {						\
934e7f640dSJohn Baldwin 		mtx_assert(&Giant, MA_NOTOWNED);			\
944e7f640dSJohn Baldwin 		while (_giantcnt--)					\
954e7f640dSJohn Baldwin 			mtx_lock(&Giant);				\
964e7f640dSJohn Baldwin 		WITNESS_RESTORE(&Giant.lock_object, Giant);		\
974e7f640dSJohn Baldwin 	}								\
984e7f640dSJohn Baldwin } while (0)
994e7f640dSJohn Baldwin 
1004e7f640dSJohn Baldwin /*
101da7d0d1eSJohn Baldwin  * Returns true if an exclusive lock is recursed.  It assumes
102da7d0d1eSJohn Baldwin  * curthread currently has an exclusive lock.
1034e7f640dSJohn Baldwin  */
1044e7f640dSJohn Baldwin #define	sx_recursed(sx)		((sx)->sx_recurse != 0)
1054e7f640dSJohn Baldwin 
106f9721b43SAttilio Rao static void	assert_sx(struct lock_object *lock, int what);
1074e7f640dSJohn Baldwin #ifdef DDB
108d272fe53SJohn Baldwin static void	db_show_sx(struct lock_object *lock);
109d272fe53SJohn Baldwin #endif
1106e21afd4SJohn Baldwin static void	lock_sx(struct lock_object *lock, int how);
1116e21afd4SJohn Baldwin static int	unlock_sx(struct lock_object *lock);
112d272fe53SJohn Baldwin 
11319284646SJohn Baldwin struct lock_class lock_class_sx = {
114ae8dde30SJohn Baldwin 	.lc_name = "sx",
115ae8dde30SJohn Baldwin 	.lc_flags = LC_SLEEPLOCK | LC_SLEEPABLE | LC_RECURSABLE | LC_UPGRADABLE,
116f9721b43SAttilio Rao 	.lc_assert = assert_sx,
117d272fe53SJohn Baldwin #ifdef DDB
118ae8dde30SJohn Baldwin 	.lc_ddb_show = db_show_sx,
119d272fe53SJohn Baldwin #endif
1206e21afd4SJohn Baldwin 	.lc_lock = lock_sx,
1216e21afd4SJohn Baldwin 	.lc_unlock = unlock_sx,
12219284646SJohn Baldwin };
12319284646SJohn Baldwin 
124781a35dfSJohn Baldwin #ifndef INVARIANTS
125781a35dfSJohn Baldwin #define	_sx_assert(sx, what, file, line)
126781a35dfSJohn Baldwin #endif
127781a35dfSJohn Baldwin 
1286281b30aSJason Evans void
129f9721b43SAttilio Rao assert_sx(struct lock_object *lock, int what)
130f9721b43SAttilio Rao {
131f9721b43SAttilio Rao 
132f9721b43SAttilio Rao 	sx_assert((struct sx *)lock, what);
133f9721b43SAttilio Rao }
134f9721b43SAttilio Rao 
135f9721b43SAttilio Rao void
1366e21afd4SJohn Baldwin lock_sx(struct lock_object *lock, int how)
1376e21afd4SJohn Baldwin {
1386e21afd4SJohn Baldwin 	struct sx *sx;
1396e21afd4SJohn Baldwin 
1406e21afd4SJohn Baldwin 	sx = (struct sx *)lock;
1416e21afd4SJohn Baldwin 	if (how)
1426e21afd4SJohn Baldwin 		sx_xlock(sx);
1436e21afd4SJohn Baldwin 	else
1446e21afd4SJohn Baldwin 		sx_slock(sx);
1456e21afd4SJohn Baldwin }
1466e21afd4SJohn Baldwin 
1476e21afd4SJohn Baldwin int
1486e21afd4SJohn Baldwin unlock_sx(struct lock_object *lock)
1496e21afd4SJohn Baldwin {
1506e21afd4SJohn Baldwin 	struct sx *sx;
1516e21afd4SJohn Baldwin 
1526e21afd4SJohn Baldwin 	sx = (struct sx *)lock;
1537ec137e5SJohn Baldwin 	sx_assert(sx, SA_LOCKED | SA_NOTRECURSED);
1546e21afd4SJohn Baldwin 	if (sx_xlocked(sx)) {
1556e21afd4SJohn Baldwin 		sx_xunlock(sx);
1566e21afd4SJohn Baldwin 		return (1);
1576e21afd4SJohn Baldwin 	} else {
1586e21afd4SJohn Baldwin 		sx_sunlock(sx);
1596e21afd4SJohn Baldwin 		return (0);
1606e21afd4SJohn Baldwin 	}
1616e21afd4SJohn Baldwin }
1626e21afd4SJohn Baldwin 
1636e21afd4SJohn Baldwin void
164c27b5699SAndrew R. Reiter sx_sysinit(void *arg)
165c27b5699SAndrew R. Reiter {
166c27b5699SAndrew R. Reiter 	struct sx_args *sargs = arg;
167c27b5699SAndrew R. Reiter 
168c27b5699SAndrew R. Reiter 	sx_init(sargs->sa_sx, sargs->sa_desc);
169c27b5699SAndrew R. Reiter }
170c27b5699SAndrew R. Reiter 
171c27b5699SAndrew R. Reiter void
1724e7f640dSJohn Baldwin sx_init_flags(struct sx *sx, const char *description, int opts)
1736281b30aSJason Evans {
1744e7f640dSJohn Baldwin 	int flags;
1756281b30aSJason Evans 
176b0d67325SJohn Baldwin 	MPASS((opts & ~(SX_QUIET | SX_RECURSE | SX_NOWITNESS | SX_DUPOK |
17746a8b9cbSJohn Baldwin 	    SX_NOPROFILE | SX_ADAPTIVESPIN)) == 0);
178b0d67325SJohn Baldwin 
1792c7289cbSAttilio Rao 	flags = LO_RECURSABLE | LO_SLEEPABLE | LO_UPGRADABLE;
1804e7f640dSJohn Baldwin 	if (opts & SX_DUPOK)
1814e7f640dSJohn Baldwin 		flags |= LO_DUPOK;
1824e7f640dSJohn Baldwin 	if (opts & SX_NOPROFILE)
1834e7f640dSJohn Baldwin 		flags |= LO_NOPROFILE;
1844e7f640dSJohn Baldwin 	if (!(opts & SX_NOWITNESS))
1854e7f640dSJohn Baldwin 		flags |= LO_WITNESS;
1864e7f640dSJohn Baldwin 	if (opts & SX_QUIET)
1874e7f640dSJohn Baldwin 		flags |= LO_QUIET;
1884e7f640dSJohn Baldwin 
189b0d67325SJohn Baldwin 	flags |= opts & (SX_ADAPTIVESPIN | SX_RECURSE);
1904e7f640dSJohn Baldwin 	sx->sx_lock = SX_LOCK_UNLOCKED;
1914e7f640dSJohn Baldwin 	sx->sx_recurse = 0;
1924e7f640dSJohn Baldwin 	lock_init(&sx->lock_object, &lock_class_sx, description, NULL, flags);
1936281b30aSJason Evans }
1946281b30aSJason Evans 
1956281b30aSJason Evans void
1966281b30aSJason Evans sx_destroy(struct sx *sx)
1976281b30aSJason Evans {
1986281b30aSJason Evans 
1994e7f640dSJohn Baldwin 	KASSERT(sx->sx_lock == SX_LOCK_UNLOCKED, ("sx lock still held"));
2004e7f640dSJohn Baldwin 	KASSERT(sx->sx_recurse == 0, ("sx lock still recursed"));
2010026c92cSJohn Baldwin 	sx->sx_lock = SX_LOCK_DESTROYED;
202aa89d8cdSJohn Baldwin 	lock_destroy(&sx->lock_object);
2036281b30aSJason Evans }
2046281b30aSJason Evans 
205f9819486SAttilio Rao int
206f9819486SAttilio Rao _sx_slock(struct sx *sx, int opts, const char *file, int line)
2076281b30aSJason Evans {
208f9819486SAttilio Rao 	int error = 0;
2096281b30aSJason Evans 
2104e7f640dSJohn Baldwin 	MPASS(curthread != NULL);
2110026c92cSJohn Baldwin 	KASSERT(sx->sx_lock != SX_LOCK_DESTROYED,
2120026c92cSJohn Baldwin 	    ("sx_slock() of destroyed sx @ %s:%d", file, line));
213aa89d8cdSJohn Baldwin 	WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER, file, line);
214f9819486SAttilio Rao 	error = __sx_slock(sx, opts, file, line);
215f9819486SAttilio Rao 	if (!error) {
216aa89d8cdSJohn Baldwin 		LOCK_LOG_LOCK("SLOCK", &sx->lock_object, 0, 0, file, line);
217aa89d8cdSJohn Baldwin 		WITNESS_LOCK(&sx->lock_object, 0, file, line);
218764e4d54SJohn Baldwin 		curthread->td_locks++;
2196281b30aSJason Evans 	}
2206281b30aSJason Evans 
221f9819486SAttilio Rao 	return (error);
222f9819486SAttilio Rao }
223f9819486SAttilio Rao 
2245f36700aSJohn Baldwin int
2255f36700aSJohn Baldwin _sx_try_slock(struct sx *sx, const char *file, int line)
2265f36700aSJohn Baldwin {
2274e7f640dSJohn Baldwin 	uintptr_t x;
2285f36700aSJohn Baldwin 
229764a938bSPawel Jakub Dawidek 	for (;;) {
2304e7f640dSJohn Baldwin 		x = sx->sx_lock;
2310026c92cSJohn Baldwin 		KASSERT(x != SX_LOCK_DESTROYED,
2320026c92cSJohn Baldwin 		    ("sx_try_slock() of destroyed sx @ %s:%d", file, line));
233764a938bSPawel Jakub Dawidek 		if (!(x & SX_LOCK_SHARED))
234764a938bSPawel Jakub Dawidek 			break;
235764a938bSPawel Jakub Dawidek 		if (atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER)) {
236aa89d8cdSJohn Baldwin 			LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 1, file, line);
237aa89d8cdSJohn Baldwin 			WITNESS_LOCK(&sx->lock_object, LOP_TRYLOCK, file, line);
238764e4d54SJohn Baldwin 			curthread->td_locks++;
2395f36700aSJohn Baldwin 			return (1);
2405f36700aSJohn Baldwin 		}
241764a938bSPawel Jakub Dawidek 	}
2424e7f640dSJohn Baldwin 
2434e7f640dSJohn Baldwin 	LOCK_LOG_TRY("SLOCK", &sx->lock_object, 0, 0, file, line);
2444e7f640dSJohn Baldwin 	return (0);
2455f36700aSJohn Baldwin }
2465f36700aSJohn Baldwin 
247f9819486SAttilio Rao int
248f9819486SAttilio Rao _sx_xlock(struct sx *sx, int opts, const char *file, int line)
2496281b30aSJason Evans {
250f9819486SAttilio Rao 	int error = 0;
2516281b30aSJason Evans 
2524e7f640dSJohn Baldwin 	MPASS(curthread != NULL);
2530026c92cSJohn Baldwin 	KASSERT(sx->sx_lock != SX_LOCK_DESTROYED,
2540026c92cSJohn Baldwin 	    ("sx_xlock() of destroyed sx @ %s:%d", file, line));
255aa89d8cdSJohn Baldwin 	WITNESS_CHECKORDER(&sx->lock_object, LOP_NEWORDER | LOP_EXCLUSIVE, file,
2568d768e76SJohn Baldwin 	    line);
257f9819486SAttilio Rao 	error = __sx_xlock(sx, curthread, opts, file, line);
258f9819486SAttilio Rao 	if (!error) {
259f9819486SAttilio Rao 		LOCK_LOG_LOCK("XLOCK", &sx->lock_object, 0, sx->sx_recurse,
260f9819486SAttilio Rao 		    file, line);
261aa89d8cdSJohn Baldwin 		WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line);
262764e4d54SJohn Baldwin 		curthread->td_locks++;
2636281b30aSJason Evans 	}
2646281b30aSJason Evans 
265f9819486SAttilio Rao 	return (error);
266f9819486SAttilio Rao }
267f9819486SAttilio Rao 
2685f36700aSJohn Baldwin int
2695f36700aSJohn Baldwin _sx_try_xlock(struct sx *sx, const char *file, int line)
2705f36700aSJohn Baldwin {
2714e7f640dSJohn Baldwin 	int rval;
2725f36700aSJohn Baldwin 
2734e7f640dSJohn Baldwin 	MPASS(curthread != NULL);
2740026c92cSJohn Baldwin 	KASSERT(sx->sx_lock != SX_LOCK_DESTROYED,
2750026c92cSJohn Baldwin 	    ("sx_try_xlock() of destroyed sx @ %s:%d", file, line));
2764e7f640dSJohn Baldwin 
277b0d67325SJohn Baldwin 	if (sx_xlocked(sx) && (sx->lock_object.lo_flags & SX_RECURSE) != 0) {
2784e7f640dSJohn Baldwin 		sx->sx_recurse++;
2794e7f640dSJohn Baldwin 		atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED);
2804e7f640dSJohn Baldwin 		rval = 1;
2814e7f640dSJohn Baldwin 	} else
2824e7f640dSJohn Baldwin 		rval = atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED,
2834e7f640dSJohn Baldwin 		    (uintptr_t)curthread);
2844e7f640dSJohn Baldwin 	LOCK_LOG_TRY("XLOCK", &sx->lock_object, 0, rval, file, line);
2854e7f640dSJohn Baldwin 	if (rval) {
2864e7f640dSJohn Baldwin 		WITNESS_LOCK(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK,
2874e7f640dSJohn Baldwin 		    file, line);
288764e4d54SJohn Baldwin 		curthread->td_locks++;
2895f36700aSJohn Baldwin 	}
2904e7f640dSJohn Baldwin 
2914e7f640dSJohn Baldwin 	return (rval);
2925f36700aSJohn Baldwin }
2935f36700aSJohn Baldwin 
2946281b30aSJason Evans void
29519284646SJohn Baldwin _sx_sunlock(struct sx *sx, const char *file, int line)
2966281b30aSJason Evans {
2976281b30aSJason Evans 
2984e7f640dSJohn Baldwin 	MPASS(curthread != NULL);
2990026c92cSJohn Baldwin 	KASSERT(sx->sx_lock != SX_LOCK_DESTROYED,
3000026c92cSJohn Baldwin 	    ("sx_sunlock() of destroyed sx @ %s:%d", file, line));
3017ec137e5SJohn Baldwin 	_sx_assert(sx, SA_SLOCKED, file, line);
302764e4d54SJohn Baldwin 	curthread->td_locks--;
303aa89d8cdSJohn Baldwin 	WITNESS_UNLOCK(&sx->lock_object, 0, file, line);
304aa89d8cdSJohn Baldwin 	LOCK_LOG_LOCK("SUNLOCK", &sx->lock_object, 0, 0, file, line);
305c1a6d9faSAttilio Rao #ifdef LOCK_PROFILING_SHARED
306acf840c4SAttilio Rao 	if (SX_SHARERS(sx->sx_lock) == 1)
307e2bc1066SKip Macy 		lock_profile_release_lock(&sx->lock_object);
308c1a6d9faSAttilio Rao #endif
3094e7f640dSJohn Baldwin 	__sx_sunlock(sx, file, line);
3106281b30aSJason Evans }
3116281b30aSJason Evans 
3126281b30aSJason Evans void
31319284646SJohn Baldwin _sx_xunlock(struct sx *sx, const char *file, int line)
3146281b30aSJason Evans {
3156281b30aSJason Evans 
3164e7f640dSJohn Baldwin 	MPASS(curthread != NULL);
3170026c92cSJohn Baldwin 	KASSERT(sx->sx_lock != SX_LOCK_DESTROYED,
3180026c92cSJohn Baldwin 	    ("sx_xunlock() of destroyed sx @ %s:%d", file, line));
3197ec137e5SJohn Baldwin 	_sx_assert(sx, SA_XLOCKED, file, line);
320764e4d54SJohn Baldwin 	curthread->td_locks--;
321aa89d8cdSJohn Baldwin 	WITNESS_UNLOCK(&sx->lock_object, LOP_EXCLUSIVE, file, line);
3224e7f640dSJohn Baldwin 	LOCK_LOG_LOCK("XUNLOCK", &sx->lock_object, 0, sx->sx_recurse, file,
3234e7f640dSJohn Baldwin 	    line);
324afc0bfbdSKip Macy 	if (!sx_recursed(sx))
325aa89d8cdSJohn Baldwin 		lock_profile_release_lock(&sx->lock_object);
3264e7f640dSJohn Baldwin 	__sx_xunlock(sx, curthread, file, line);
3276281b30aSJason Evans }
328d55229b7SJason Evans 
3294e7f640dSJohn Baldwin /*
3304e7f640dSJohn Baldwin  * Try to do a non-blocking upgrade from a shared lock to an exclusive lock.
3314e7f640dSJohn Baldwin  * This will only succeed if this thread holds a single shared lock.
3324e7f640dSJohn Baldwin  * Return 1 if if the upgrade succeed, 0 otherwise.
3334e7f640dSJohn Baldwin  */
334d55229b7SJason Evans int
335d55229b7SJason Evans _sx_try_upgrade(struct sx *sx, const char *file, int line)
336d55229b7SJason Evans {
3374e7f640dSJohn Baldwin 	uintptr_t x;
3384e7f640dSJohn Baldwin 	int success;
339d55229b7SJason Evans 
3400026c92cSJohn Baldwin 	KASSERT(sx->sx_lock != SX_LOCK_DESTROYED,
3410026c92cSJohn Baldwin 	    ("sx_try_upgrade() of destroyed sx @ %s:%d", file, line));
3427ec137e5SJohn Baldwin 	_sx_assert(sx, SA_SLOCKED, file, line);
343d55229b7SJason Evans 
3444e7f640dSJohn Baldwin 	/*
3454e7f640dSJohn Baldwin 	 * Try to switch from one shared lock to an exclusive lock.  We need
3464e7f640dSJohn Baldwin 	 * to maintain the SX_LOCK_EXCLUSIVE_WAITERS flag if set so that
3474e7f640dSJohn Baldwin 	 * we will wake up the exclusive waiters when we drop the lock.
3484e7f640dSJohn Baldwin 	 */
3494e7f640dSJohn Baldwin 	x = sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS;
3504e7f640dSJohn Baldwin 	success = atomic_cmpset_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) | x,
3514e7f640dSJohn Baldwin 	    (uintptr_t)curthread | x);
3524e7f640dSJohn Baldwin 	LOCK_LOG_TRY("XUPGRADE", &sx->lock_object, 0, success, file, line);
3534e7f640dSJohn Baldwin 	if (success)
354aa89d8cdSJohn Baldwin 		WITNESS_UPGRADE(&sx->lock_object, LOP_EXCLUSIVE | LOP_TRYLOCK,
355b0b7cb50SJohn Baldwin 		    file, line);
3564e7f640dSJohn Baldwin 	return (success);
357d55229b7SJason Evans }
358d55229b7SJason Evans 
3594e7f640dSJohn Baldwin /*
3604e7f640dSJohn Baldwin  * Downgrade an unrecursed exclusive lock into a single shared lock.
3614e7f640dSJohn Baldwin  */
362d55229b7SJason Evans void
363d55229b7SJason Evans _sx_downgrade(struct sx *sx, const char *file, int line)
364d55229b7SJason Evans {
3654e7f640dSJohn Baldwin 	uintptr_t x;
366d55229b7SJason Evans 
3670026c92cSJohn Baldwin 	KASSERT(sx->sx_lock != SX_LOCK_DESTROYED,
3680026c92cSJohn Baldwin 	    ("sx_downgrade() of destroyed sx @ %s:%d", file, line));
3697ec137e5SJohn Baldwin 	_sx_assert(sx, SA_XLOCKED | SA_NOTRECURSED, file, line);
3704e7f640dSJohn Baldwin #ifndef INVARIANTS
3714e7f640dSJohn Baldwin 	if (sx_recursed(sx))
3724e7f640dSJohn Baldwin 		panic("downgrade of a recursed lock");
3734e7f640dSJohn Baldwin #endif
374d55229b7SJason Evans 
375aa89d8cdSJohn Baldwin 	WITNESS_DOWNGRADE(&sx->lock_object, 0, file, line);
376d55229b7SJason Evans 
3774e7f640dSJohn Baldwin 	/*
3784e7f640dSJohn Baldwin 	 * Try to switch from an exclusive lock with no shared waiters
3794e7f640dSJohn Baldwin 	 * to one sharer with no shared waiters.  If there are
3804e7f640dSJohn Baldwin 	 * exclusive waiters, we don't need to lock the sleep queue so
3814e7f640dSJohn Baldwin 	 * long as we preserve the flag.  We do one quick try and if
3824e7f640dSJohn Baldwin 	 * that fails we grab the sleepq lock to keep the flags from
3834e7f640dSJohn Baldwin 	 * changing and do it the slow way.
3844e7f640dSJohn Baldwin 	 *
3854e7f640dSJohn Baldwin 	 * We have to lock the sleep queue if there are shared waiters
3864e7f640dSJohn Baldwin 	 * so we can wake them up.
3874e7f640dSJohn Baldwin 	 */
3884e7f640dSJohn Baldwin 	x = sx->sx_lock;
3894e7f640dSJohn Baldwin 	if (!(x & SX_LOCK_SHARED_WAITERS) &&
3904e7f640dSJohn Baldwin 	    atomic_cmpset_rel_ptr(&sx->sx_lock, x, SX_SHARERS_LOCK(1) |
3914e7f640dSJohn Baldwin 	    (x & SX_LOCK_EXCLUSIVE_WAITERS))) {
3924e7f640dSJohn Baldwin 		LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line);
3934e7f640dSJohn Baldwin 		return;
3944e7f640dSJohn Baldwin 	}
3954e7f640dSJohn Baldwin 
3964e7f640dSJohn Baldwin 	/*
3974e7f640dSJohn Baldwin 	 * Lock the sleep queue so we can read the waiters bits
3984e7f640dSJohn Baldwin 	 * without any races and wakeup any shared waiters.
3994e7f640dSJohn Baldwin 	 */
4004e7f640dSJohn Baldwin 	sleepq_lock(&sx->lock_object);
4014e7f640dSJohn Baldwin 
4024e7f640dSJohn Baldwin 	/*
4034e7f640dSJohn Baldwin 	 * Preserve SX_LOCK_EXCLUSIVE_WAITERS while downgraded to a single
4044e7f640dSJohn Baldwin 	 * shared lock.  If there are any shared waiters, wake them up.
4054e7f640dSJohn Baldwin 	 */
4064e7f640dSJohn Baldwin 	x = sx->sx_lock;
4074e7f640dSJohn Baldwin 	atomic_store_rel_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1) |
4084e7f640dSJohn Baldwin 	    (x & SX_LOCK_EXCLUSIVE_WAITERS));
4094e7f640dSJohn Baldwin 	if (x & SX_LOCK_SHARED_WAITERS)
4104e7f640dSJohn Baldwin 		sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, -1,
4114e7f640dSJohn Baldwin 		    SQ_SHARED_QUEUE);
4124e7f640dSJohn Baldwin 	else
4134e7f640dSJohn Baldwin 		sleepq_release(&sx->lock_object);
414d55229b7SJason Evans 
415aa89d8cdSJohn Baldwin 	LOCK_LOG_LOCK("XDOWNGRADE", &sx->lock_object, 0, 0, file, line);
4164e7f640dSJohn Baldwin }
417d55229b7SJason Evans 
4184e7f640dSJohn Baldwin /*
4194e7f640dSJohn Baldwin  * This function represents the so-called 'hard case' for sx_xlock
4204e7f640dSJohn Baldwin  * operation.  All 'easy case' failures are redirected to this.  Note
4214e7f640dSJohn Baldwin  * that ideally this would be a static function, but it needs to be
4224e7f640dSJohn Baldwin  * accessible from at least sx.h.
4234e7f640dSJohn Baldwin  */
424f9819486SAttilio Rao int
425f9819486SAttilio Rao _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts, const char *file,
426f9819486SAttilio Rao     int line)
4274e7f640dSJohn Baldwin {
4284e7f640dSJohn Baldwin 	GIANT_DECLARE;
4294e7f640dSJohn Baldwin #ifdef ADAPTIVE_SX
4304e7f640dSJohn Baldwin 	volatile struct thread *owner;
4314e7f640dSJohn Baldwin #endif
432c1a6d9faSAttilio Rao 	uint64_t waittime = 0;
4334e7f640dSJohn Baldwin 	uintptr_t x;
434f9819486SAttilio Rao 	int contested = 0, error = 0;
4354e7f640dSJohn Baldwin 
4364e7f640dSJohn Baldwin 	/* If we already hold an exclusive lock, then recurse. */
4374e7f640dSJohn Baldwin 	if (sx_xlocked(sx)) {
438b0d67325SJohn Baldwin 		KASSERT((sx->lock_object.lo_flags & SX_RECURSE) != 0,
439b0d67325SJohn Baldwin 	    ("_sx_xlock_hard: recursed on non-recursive sx %s @ %s:%d\n",
440b0d67325SJohn Baldwin 		    sx->lock_object.lo_name, file, line));
4414e7f640dSJohn Baldwin 		sx->sx_recurse++;
4424e7f640dSJohn Baldwin 		atomic_set_ptr(&sx->sx_lock, SX_LOCK_RECURSED);
4434e7f640dSJohn Baldwin 		if (LOCK_LOG_TEST(&sx->lock_object, 0))
4444e7f640dSJohn Baldwin 			CTR2(KTR_LOCK, "%s: %p recursing", __func__, sx);
445f9819486SAttilio Rao 		return (0);
4464e7f640dSJohn Baldwin 	}
4474e7f640dSJohn Baldwin 
4484e7f640dSJohn Baldwin 	if (LOCK_LOG_TEST(&sx->lock_object, 0))
4494e7f640dSJohn Baldwin 		CTR5(KTR_LOCK, "%s: %s contested (lock=%p) at %s:%d", __func__,
4504e7f640dSJohn Baldwin 		    sx->lock_object.lo_name, (void *)sx->sx_lock, file, line);
4514e7f640dSJohn Baldwin 
4524e7f640dSJohn Baldwin 	while (!atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid)) {
4534e7f640dSJohn Baldwin #ifdef ADAPTIVE_SX
4544e7f640dSJohn Baldwin 		/*
4554e7f640dSJohn Baldwin 		 * If the lock is write locked and the owner is
4564e7f640dSJohn Baldwin 		 * running on another CPU, spin until the owner stops
4574e7f640dSJohn Baldwin 		 * running or the state of the lock changes.
4584e7f640dSJohn Baldwin 		 */
4594e7f640dSJohn Baldwin 		x = sx->sx_lock;
4604e7f640dSJohn Baldwin 		if (!(x & SX_LOCK_SHARED) &&
4614e7f640dSJohn Baldwin 		    (sx->lock_object.lo_flags & SX_ADAPTIVESPIN)) {
4624e7f640dSJohn Baldwin 			x = SX_OWNER(x);
4634e7f640dSJohn Baldwin 			owner = (struct thread *)x;
4644e7f640dSJohn Baldwin 			if (TD_IS_RUNNING(owner)) {
4654e7f640dSJohn Baldwin 				if (LOCK_LOG_TEST(&sx->lock_object, 0))
4664e7f640dSJohn Baldwin 					CTR3(KTR_LOCK,
4674e7f640dSJohn Baldwin 					    "%s: spinning on %p held by %p",
4684e7f640dSJohn Baldwin 					    __func__, sx, owner);
4694e7f640dSJohn Baldwin 				GIANT_SAVE();
470c1a6d9faSAttilio Rao 				lock_profile_obtain_lock_failed(
471c1a6d9faSAttilio Rao 				    &sx->lock_object, &contested, &waittime);
4724e7f640dSJohn Baldwin 				while (SX_OWNER(sx->sx_lock) == x &&
4734e7f640dSJohn Baldwin 				    TD_IS_RUNNING(owner))
4744e7f640dSJohn Baldwin 					cpu_spinwait();
4754e7f640dSJohn Baldwin 				continue;
4764e7f640dSJohn Baldwin 			}
4774e7f640dSJohn Baldwin 		}
4784e7f640dSJohn Baldwin #endif
4794e7f640dSJohn Baldwin 
4804e7f640dSJohn Baldwin 		sleepq_lock(&sx->lock_object);
4814e7f640dSJohn Baldwin 		x = sx->sx_lock;
4824e7f640dSJohn Baldwin 
4834e7f640dSJohn Baldwin 		/*
4844e7f640dSJohn Baldwin 		 * If the lock was released while spinning on the
4854e7f640dSJohn Baldwin 		 * sleep queue chain lock, try again.
4864e7f640dSJohn Baldwin 		 */
4874e7f640dSJohn Baldwin 		if (x == SX_LOCK_UNLOCKED) {
4884e7f640dSJohn Baldwin 			sleepq_release(&sx->lock_object);
4894e7f640dSJohn Baldwin 			continue;
4904e7f640dSJohn Baldwin 		}
4914e7f640dSJohn Baldwin 
4924e7f640dSJohn Baldwin #ifdef ADAPTIVE_SX
4934e7f640dSJohn Baldwin 		/*
4944e7f640dSJohn Baldwin 		 * The current lock owner might have started executing
4954e7f640dSJohn Baldwin 		 * on another CPU (or the lock could have changed
4964e7f640dSJohn Baldwin 		 * owners) while we were waiting on the sleep queue
4974e7f640dSJohn Baldwin 		 * chain lock.  If so, drop the sleep queue lock and try
4984e7f640dSJohn Baldwin 		 * again.
4994e7f640dSJohn Baldwin 		 */
5004e7f640dSJohn Baldwin 		if (!(x & SX_LOCK_SHARED) &&
5014e7f640dSJohn Baldwin 		    (sx->lock_object.lo_flags & SX_ADAPTIVESPIN)) {
5024e7f640dSJohn Baldwin 			owner = (struct thread *)SX_OWNER(x);
5034e7f640dSJohn Baldwin 			if (TD_IS_RUNNING(owner)) {
5044e7f640dSJohn Baldwin 				sleepq_release(&sx->lock_object);
5054e7f640dSJohn Baldwin 				continue;
5064e7f640dSJohn Baldwin 			}
5074e7f640dSJohn Baldwin 		}
5084e7f640dSJohn Baldwin #endif
5094e7f640dSJohn Baldwin 
5104e7f640dSJohn Baldwin 		/*
5114e7f640dSJohn Baldwin 		 * If an exclusive lock was released with both shared
5124e7f640dSJohn Baldwin 		 * and exclusive waiters and a shared waiter hasn't
5134e7f640dSJohn Baldwin 		 * woken up and acquired the lock yet, sx_lock will be
5144e7f640dSJohn Baldwin 		 * set to SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS.
5154e7f640dSJohn Baldwin 		 * If we see that value, try to acquire it once.  Note
5164e7f640dSJohn Baldwin 		 * that we have to preserve SX_LOCK_EXCLUSIVE_WAITERS
5174e7f640dSJohn Baldwin 		 * as there are other exclusive waiters still.  If we
5184e7f640dSJohn Baldwin 		 * fail, restart the loop.
5194e7f640dSJohn Baldwin 		 */
5204e7f640dSJohn Baldwin 		if (x == (SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS)) {
5214e7f640dSJohn Baldwin 			if (atomic_cmpset_acq_ptr(&sx->sx_lock,
5224e7f640dSJohn Baldwin 			    SX_LOCK_UNLOCKED | SX_LOCK_EXCLUSIVE_WAITERS,
5234e7f640dSJohn Baldwin 			    tid | SX_LOCK_EXCLUSIVE_WAITERS)) {
5244e7f640dSJohn Baldwin 				sleepq_release(&sx->lock_object);
5254e7f640dSJohn Baldwin 				CTR2(KTR_LOCK, "%s: %p claimed by new writer",
5264e7f640dSJohn Baldwin 				    __func__, sx);
5274e7f640dSJohn Baldwin 				break;
5284e7f640dSJohn Baldwin 			}
5294e7f640dSJohn Baldwin 			sleepq_release(&sx->lock_object);
5304e7f640dSJohn Baldwin 			continue;
5314e7f640dSJohn Baldwin 		}
5324e7f640dSJohn Baldwin 
5334e7f640dSJohn Baldwin 		/*
5344e7f640dSJohn Baldwin 		 * Try to set the SX_LOCK_EXCLUSIVE_WAITERS.  If we fail,
5354e7f640dSJohn Baldwin 		 * than loop back and retry.
5364e7f640dSJohn Baldwin 		 */
5374e7f640dSJohn Baldwin 		if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) {
5384e7f640dSJohn Baldwin 			if (!atomic_cmpset_ptr(&sx->sx_lock, x,
5394e7f640dSJohn Baldwin 			    x | SX_LOCK_EXCLUSIVE_WAITERS)) {
5404e7f640dSJohn Baldwin 				sleepq_release(&sx->lock_object);
5414e7f640dSJohn Baldwin 				continue;
5424e7f640dSJohn Baldwin 			}
5434e7f640dSJohn Baldwin 			if (LOCK_LOG_TEST(&sx->lock_object, 0))
5444e7f640dSJohn Baldwin 				CTR2(KTR_LOCK, "%s: %p set excl waiters flag",
5454e7f640dSJohn Baldwin 				    __func__, sx);
5464e7f640dSJohn Baldwin 		}
5474e7f640dSJohn Baldwin 
5484e7f640dSJohn Baldwin 		/*
5494e7f640dSJohn Baldwin 		 * Since we have been unable to acquire the exclusive
5504e7f640dSJohn Baldwin 		 * lock and the exclusive waiters flag is set, we have
5514e7f640dSJohn Baldwin 		 * to sleep.
5524e7f640dSJohn Baldwin 		 */
5534e7f640dSJohn Baldwin 		if (LOCK_LOG_TEST(&sx->lock_object, 0))
5544e7f640dSJohn Baldwin 			CTR2(KTR_LOCK, "%s: %p blocking on sleep queue",
5554e7f640dSJohn Baldwin 			    __func__, sx);
5564e7f640dSJohn Baldwin 
5574e7f640dSJohn Baldwin 		GIANT_SAVE();
558c1a6d9faSAttilio Rao 		lock_profile_obtain_lock_failed(&sx->lock_object, &contested,
559c1a6d9faSAttilio Rao 		    &waittime);
5604e7f640dSJohn Baldwin 		sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name,
561f9819486SAttilio Rao 		    SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ?
562f9819486SAttilio Rao 		    SLEEPQ_INTERRUPTIBLE : 0), SQ_EXCLUSIVE_QUEUE);
563f9819486SAttilio Rao 		if (!(opts & SX_INTERRUPTIBLE))
5644e7f640dSJohn Baldwin 			sleepq_wait(&sx->lock_object);
565f9819486SAttilio Rao 		else
566f9819486SAttilio Rao 			error = sleepq_wait_sig(&sx->lock_object);
5674e7f640dSJohn Baldwin 
568f9819486SAttilio Rao 		if (error) {
569f9819486SAttilio Rao 			if (LOCK_LOG_TEST(&sx->lock_object, 0))
570f9819486SAttilio Rao 				CTR2(KTR_LOCK,
571f9819486SAttilio Rao 			"%s: interruptible sleep by %p suspended by signal",
572f9819486SAttilio Rao 				    __func__, sx);
573f9819486SAttilio Rao 			break;
574f9819486SAttilio Rao 		}
5754e7f640dSJohn Baldwin 		if (LOCK_LOG_TEST(&sx->lock_object, 0))
5764e7f640dSJohn Baldwin 			CTR2(KTR_LOCK, "%s: %p resuming from sleep queue",
5774e7f640dSJohn Baldwin 			    __func__, sx);
5784e7f640dSJohn Baldwin 	}
5794e7f640dSJohn Baldwin 
5804e7f640dSJohn Baldwin 	GIANT_RESTORE();
581f9819486SAttilio Rao 	if (!error)
582c1a6d9faSAttilio Rao 		lock_profile_obtain_lock_success(&sx->lock_object, contested,
583c1a6d9faSAttilio Rao 		    waittime, file, line);
584f9819486SAttilio Rao 	return (error);
5854e7f640dSJohn Baldwin }
5864e7f640dSJohn Baldwin 
5874e7f640dSJohn Baldwin /*
5884e7f640dSJohn Baldwin  * This function represents the so-called 'hard case' for sx_xunlock
5894e7f640dSJohn Baldwin  * operation.  All 'easy case' failures are redirected to this.  Note
5904e7f640dSJohn Baldwin  * that ideally this would be a static function, but it needs to be
5914e7f640dSJohn Baldwin  * accessible from at least sx.h.
5924e7f640dSJohn Baldwin  */
5934e7f640dSJohn Baldwin void
5944e7f640dSJohn Baldwin _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int line)
5954e7f640dSJohn Baldwin {
5964e7f640dSJohn Baldwin 	uintptr_t x;
5974e7f640dSJohn Baldwin 	int queue;
5984e7f640dSJohn Baldwin 
5994e7f640dSJohn Baldwin 	MPASS(!(sx->sx_lock & SX_LOCK_SHARED));
6004e7f640dSJohn Baldwin 
6014e7f640dSJohn Baldwin 	/* If the lock is recursed, then unrecurse one level. */
6024e7f640dSJohn Baldwin 	if (sx_xlocked(sx) && sx_recursed(sx)) {
6034e7f640dSJohn Baldwin 		if ((--sx->sx_recurse) == 0)
6044e7f640dSJohn Baldwin 			atomic_clear_ptr(&sx->sx_lock, SX_LOCK_RECURSED);
6054e7f640dSJohn Baldwin 		if (LOCK_LOG_TEST(&sx->lock_object, 0))
6064e7f640dSJohn Baldwin 			CTR2(KTR_LOCK, "%s: %p unrecursing", __func__, sx);
6074e7f640dSJohn Baldwin 		return;
6084e7f640dSJohn Baldwin 	}
6094e7f640dSJohn Baldwin 	MPASS(sx->sx_lock & (SX_LOCK_SHARED_WAITERS |
6104e7f640dSJohn Baldwin 	    SX_LOCK_EXCLUSIVE_WAITERS));
6114e7f640dSJohn Baldwin 	if (LOCK_LOG_TEST(&sx->lock_object, 0))
6124e7f640dSJohn Baldwin 		CTR2(KTR_LOCK, "%s: %p contested", __func__, sx);
6134e7f640dSJohn Baldwin 
6144e7f640dSJohn Baldwin 	sleepq_lock(&sx->lock_object);
6154e7f640dSJohn Baldwin 	x = SX_LOCK_UNLOCKED;
6164e7f640dSJohn Baldwin 
6174e7f640dSJohn Baldwin 	/*
6184e7f640dSJohn Baldwin 	 * The wake up algorithm here is quite simple and probably not
6194e7f640dSJohn Baldwin 	 * ideal.  It gives precedence to shared waiters if they are
6204e7f640dSJohn Baldwin 	 * present.  For this condition, we have to preserve the
6214e7f640dSJohn Baldwin 	 * state of the exclusive waiters flag.
6224e7f640dSJohn Baldwin 	 */
6234e7f640dSJohn Baldwin 	if (sx->sx_lock & SX_LOCK_SHARED_WAITERS) {
6244e7f640dSJohn Baldwin 		queue = SQ_SHARED_QUEUE;
6254e7f640dSJohn Baldwin 		x |= (sx->sx_lock & SX_LOCK_EXCLUSIVE_WAITERS);
6264e7f640dSJohn Baldwin 	} else
6274e7f640dSJohn Baldwin 		queue = SQ_EXCLUSIVE_QUEUE;
6284e7f640dSJohn Baldwin 
6294e7f640dSJohn Baldwin 	/* Wake up all the waiters for the specific queue. */
6304e7f640dSJohn Baldwin 	if (LOCK_LOG_TEST(&sx->lock_object, 0))
6314e7f640dSJohn Baldwin 		CTR3(KTR_LOCK, "%s: %p waking up all threads on %s queue",
6324e7f640dSJohn Baldwin 		    __func__, sx, queue == SQ_SHARED_QUEUE ? "shared" :
6334e7f640dSJohn Baldwin 		    "exclusive");
6344e7f640dSJohn Baldwin 	atomic_store_rel_ptr(&sx->sx_lock, x);
6354e7f640dSJohn Baldwin 	sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, -1, queue);
6364e7f640dSJohn Baldwin }
6374e7f640dSJohn Baldwin 
6384e7f640dSJohn Baldwin /*
6394e7f640dSJohn Baldwin  * This function represents the so-called 'hard case' for sx_slock
6404e7f640dSJohn Baldwin  * operation.  All 'easy case' failures are redirected to this.  Note
6414e7f640dSJohn Baldwin  * that ideally this would be a static function, but it needs to be
6424e7f640dSJohn Baldwin  * accessible from at least sx.h.
6434e7f640dSJohn Baldwin  */
644f9819486SAttilio Rao int
645f9819486SAttilio Rao _sx_slock_hard(struct sx *sx, int opts, const char *file, int line)
6464e7f640dSJohn Baldwin {
6474e7f640dSJohn Baldwin 	GIANT_DECLARE;
6484e7f640dSJohn Baldwin #ifdef ADAPTIVE_SX
6494e7f640dSJohn Baldwin 	volatile struct thread *owner;
6504e7f640dSJohn Baldwin #endif
651c1a6d9faSAttilio Rao #ifdef LOCK_PROFILING_SHARED
652c1a6d9faSAttilio Rao 	uint64_t waittime = 0;
653c1a6d9faSAttilio Rao 	int contested = 0;
654c1a6d9faSAttilio Rao #endif
6554e7f640dSJohn Baldwin 	uintptr_t x;
656c1a6d9faSAttilio Rao 	int error = 0;
657c1a6d9faSAttilio Rao 
6584e7f640dSJohn Baldwin 	/*
6594e7f640dSJohn Baldwin 	 * As with rwlocks, we don't make any attempt to try to block
6604e7f640dSJohn Baldwin 	 * shared locks once there is an exclusive waiter.
6614e7f640dSJohn Baldwin 	 */
6624e7f640dSJohn Baldwin 	for (;;) {
6634e7f640dSJohn Baldwin 		x = sx->sx_lock;
6644e7f640dSJohn Baldwin 
6654e7f640dSJohn Baldwin 		/*
6664e7f640dSJohn Baldwin 		 * If no other thread has an exclusive lock then try to bump up
6674e7f640dSJohn Baldwin 		 * the count of sharers.  Since we have to preserve the state
6684e7f640dSJohn Baldwin 		 * of SX_LOCK_EXCLUSIVE_WAITERS, if we fail to acquire the
6694e7f640dSJohn Baldwin 		 * shared lock loop back and retry.
6704e7f640dSJohn Baldwin 		 */
6714e7f640dSJohn Baldwin 		if (x & SX_LOCK_SHARED) {
6724e7f640dSJohn Baldwin 			MPASS(!(x & SX_LOCK_SHARED_WAITERS));
6734e7f640dSJohn Baldwin 			if (atomic_cmpset_acq_ptr(&sx->sx_lock, x,
6744e7f640dSJohn Baldwin 			    x + SX_ONE_SHARER)) {
675c1a6d9faSAttilio Rao #ifdef LOCK_PROFILING_SHARED
676afc0bfbdSKip Macy 				if (SX_SHARERS(x) == 0)
677afc0bfbdSKip Macy 					lock_profile_obtain_lock_success(
678afc0bfbdSKip Macy 					    &sx->lock_object, contested,
679c1a6d9faSAttilio Rao 					    waittime, file, line);
680c1a6d9faSAttilio Rao #endif
6814e7f640dSJohn Baldwin 				if (LOCK_LOG_TEST(&sx->lock_object, 0))
6824e7f640dSJohn Baldwin 					CTR4(KTR_LOCK,
6834e7f640dSJohn Baldwin 					    "%s: %p succeed %p -> %p", __func__,
6844e7f640dSJohn Baldwin 					    sx, (void *)x,
6854e7f640dSJohn Baldwin 					    (void *)(x + SX_ONE_SHARER));
6864e7f640dSJohn Baldwin 				break;
6874e7f640dSJohn Baldwin 			}
6884e7f640dSJohn Baldwin 			continue;
6894e7f640dSJohn Baldwin 		}
6904e7f640dSJohn Baldwin 
6914e7f640dSJohn Baldwin #ifdef ADAPTIVE_SX
6924e7f640dSJohn Baldwin 		/*
6934e7f640dSJohn Baldwin 		 * If the owner is running on another CPU, spin until
6944e7f640dSJohn Baldwin 		 * the owner stops running or the state of the lock
6954e7f640dSJohn Baldwin 		 * changes.
6964e7f640dSJohn Baldwin 		 */
6974e7f640dSJohn Baldwin 		else if (sx->lock_object.lo_flags & SX_ADAPTIVESPIN) {
6984e7f640dSJohn Baldwin 			x = SX_OWNER(x);
6994e7f640dSJohn Baldwin 			owner = (struct thread *)x;
7004e7f640dSJohn Baldwin 			if (TD_IS_RUNNING(owner)) {
7014e7f640dSJohn Baldwin 				if (LOCK_LOG_TEST(&sx->lock_object, 0))
7024e7f640dSJohn Baldwin 					CTR3(KTR_LOCK,
7034e7f640dSJohn Baldwin 					    "%s: spinning on %p held by %p",
7044e7f640dSJohn Baldwin 					    __func__, sx, owner);
7054e7f640dSJohn Baldwin 				GIANT_SAVE();
706c1a6d9faSAttilio Rao #ifdef LOCK_PROFILING_SHARED
707c1a6d9faSAttilio Rao 				lock_profile_obtain_lock_failed(
708c1a6d9faSAttilio Rao 				    &sx->lock_object, &contested, &waittime);
709c1a6d9faSAttilio Rao #endif
7104e7f640dSJohn Baldwin 				while (SX_OWNER(sx->sx_lock) == x &&
7114e7f640dSJohn Baldwin 				    TD_IS_RUNNING(owner))
7124e7f640dSJohn Baldwin 					cpu_spinwait();
7134e7f640dSJohn Baldwin 				continue;
7144e7f640dSJohn Baldwin 			}
7154e7f640dSJohn Baldwin 		}
7164e7f640dSJohn Baldwin #endif
7174e7f640dSJohn Baldwin 
7184e7f640dSJohn Baldwin 		/*
7194e7f640dSJohn Baldwin 		 * Some other thread already has an exclusive lock, so
7204e7f640dSJohn Baldwin 		 * start the process of blocking.
7214e7f640dSJohn Baldwin 		 */
7224e7f640dSJohn Baldwin 		sleepq_lock(&sx->lock_object);
7234e7f640dSJohn Baldwin 		x = sx->sx_lock;
7244e7f640dSJohn Baldwin 
7254e7f640dSJohn Baldwin 		/*
7264e7f640dSJohn Baldwin 		 * The lock could have been released while we spun.
7274e7f640dSJohn Baldwin 		 * In this case loop back and retry.
7284e7f640dSJohn Baldwin 		 */
7294e7f640dSJohn Baldwin 		if (x & SX_LOCK_SHARED) {
7304e7f640dSJohn Baldwin 			sleepq_release(&sx->lock_object);
7314e7f640dSJohn Baldwin 			continue;
7324e7f640dSJohn Baldwin 		}
7334e7f640dSJohn Baldwin 
7344e7f640dSJohn Baldwin #ifdef ADAPTIVE_SX
7354e7f640dSJohn Baldwin 		/*
7364e7f640dSJohn Baldwin 		 * If the owner is running on another CPU, spin until
7374e7f640dSJohn Baldwin 		 * the owner stops running or the state of the lock
7384e7f640dSJohn Baldwin 		 * changes.
7394e7f640dSJohn Baldwin 		 */
7404e7f640dSJohn Baldwin 		if (!(x & SX_LOCK_SHARED) &&
7414e7f640dSJohn Baldwin 		    (sx->lock_object.lo_flags & SX_ADAPTIVESPIN)) {
7424e7f640dSJohn Baldwin 			owner = (struct thread *)SX_OWNER(x);
7434e7f640dSJohn Baldwin 			if (TD_IS_RUNNING(owner)) {
7444e7f640dSJohn Baldwin 				sleepq_release(&sx->lock_object);
7454e7f640dSJohn Baldwin 				continue;
7464e7f640dSJohn Baldwin 			}
7474e7f640dSJohn Baldwin 		}
7484e7f640dSJohn Baldwin #endif
7494e7f640dSJohn Baldwin 
7504e7f640dSJohn Baldwin 		/*
7514e7f640dSJohn Baldwin 		 * Try to set the SX_LOCK_SHARED_WAITERS flag.  If we
7524e7f640dSJohn Baldwin 		 * fail to set it drop the sleep queue lock and loop
7534e7f640dSJohn Baldwin 		 * back.
7544e7f640dSJohn Baldwin 		 */
7554e7f640dSJohn Baldwin 		if (!(x & SX_LOCK_SHARED_WAITERS)) {
7564e7f640dSJohn Baldwin 			if (!atomic_cmpset_ptr(&sx->sx_lock, x,
7574e7f640dSJohn Baldwin 			    x | SX_LOCK_SHARED_WAITERS)) {
7584e7f640dSJohn Baldwin 				sleepq_release(&sx->lock_object);
7594e7f640dSJohn Baldwin 				continue;
7604e7f640dSJohn Baldwin 			}
7614e7f640dSJohn Baldwin 			if (LOCK_LOG_TEST(&sx->lock_object, 0))
7624e7f640dSJohn Baldwin 				CTR2(KTR_LOCK, "%s: %p set shared waiters flag",
7634e7f640dSJohn Baldwin 				    __func__, sx);
7644e7f640dSJohn Baldwin 		}
7654e7f640dSJohn Baldwin 
7664e7f640dSJohn Baldwin 		/*
7674e7f640dSJohn Baldwin 		 * Since we have been unable to acquire the shared lock,
7684e7f640dSJohn Baldwin 		 * we have to sleep.
7694e7f640dSJohn Baldwin 		 */
7704e7f640dSJohn Baldwin 		if (LOCK_LOG_TEST(&sx->lock_object, 0))
7714e7f640dSJohn Baldwin 			CTR2(KTR_LOCK, "%s: %p blocking on sleep queue",
7724e7f640dSJohn Baldwin 			    __func__, sx);
7734e7f640dSJohn Baldwin 
7744e7f640dSJohn Baldwin 		GIANT_SAVE();
775c1a6d9faSAttilio Rao #ifdef LOCK_PROFILING_SHARED
776c1a6d9faSAttilio Rao 		lock_profile_obtain_lock_failed(&sx->lock_object, &contested,
777c1a6d9faSAttilio Rao 		    &waittime);
778c1a6d9faSAttilio Rao #endif
7794e7f640dSJohn Baldwin 		sleepq_add(&sx->lock_object, NULL, sx->lock_object.lo_name,
780f9819486SAttilio Rao 		    SLEEPQ_SX | ((opts & SX_INTERRUPTIBLE) ?
781f9819486SAttilio Rao 		    SLEEPQ_INTERRUPTIBLE : 0), SQ_SHARED_QUEUE);
782f9819486SAttilio Rao 		if (!(opts & SX_INTERRUPTIBLE))
7834e7f640dSJohn Baldwin 			sleepq_wait(&sx->lock_object);
784f9819486SAttilio Rao 		else
785f9819486SAttilio Rao 			error = sleepq_wait_sig(&sx->lock_object);
7864e7f640dSJohn Baldwin 
787f9819486SAttilio Rao 		if (error) {
788f9819486SAttilio Rao 			if (LOCK_LOG_TEST(&sx->lock_object, 0))
789f9819486SAttilio Rao 				CTR2(KTR_LOCK,
790f9819486SAttilio Rao 			"%s: interruptible sleep by %p suspended by signal",
791f9819486SAttilio Rao 				    __func__, sx);
792f9819486SAttilio Rao 			break;
793f9819486SAttilio Rao 		}
7944e7f640dSJohn Baldwin 		if (LOCK_LOG_TEST(&sx->lock_object, 0))
7954e7f640dSJohn Baldwin 			CTR2(KTR_LOCK, "%s: %p resuming from sleep queue",
7964e7f640dSJohn Baldwin 			    __func__, sx);
7974e7f640dSJohn Baldwin 	}
7984e7f640dSJohn Baldwin 
7994e7f640dSJohn Baldwin 	GIANT_RESTORE();
800f9819486SAttilio Rao 	return (error);
8014e7f640dSJohn Baldwin }
8024e7f640dSJohn Baldwin 
8034e7f640dSJohn Baldwin /*
8044e7f640dSJohn Baldwin  * This function represents the so-called 'hard case' for sx_sunlock
8054e7f640dSJohn Baldwin  * operation.  All 'easy case' failures are redirected to this.  Note
8064e7f640dSJohn Baldwin  * that ideally this would be a static function, but it needs to be
8074e7f640dSJohn Baldwin  * accessible from at least sx.h.
8084e7f640dSJohn Baldwin  */
8094e7f640dSJohn Baldwin void
8104e7f640dSJohn Baldwin _sx_sunlock_hard(struct sx *sx, const char *file, int line)
8114e7f640dSJohn Baldwin {
8124e7f640dSJohn Baldwin 	uintptr_t x;
8134e7f640dSJohn Baldwin 
8144e7f640dSJohn Baldwin 	for (;;) {
8154e7f640dSJohn Baldwin 		x = sx->sx_lock;
8164e7f640dSJohn Baldwin 
8174e7f640dSJohn Baldwin 		/*
8184e7f640dSJohn Baldwin 		 * We should never have sharers while at least one thread
8194e7f640dSJohn Baldwin 		 * holds a shared lock.
8204e7f640dSJohn Baldwin 		 */
8214e7f640dSJohn Baldwin 		KASSERT(!(x & SX_LOCK_SHARED_WAITERS),
8224e7f640dSJohn Baldwin 		    ("%s: waiting sharers", __func__));
8234e7f640dSJohn Baldwin 
8244e7f640dSJohn Baldwin 		/*
8254e7f640dSJohn Baldwin 		 * See if there is more than one shared lock held.  If
8264e7f640dSJohn Baldwin 		 * so, just drop one and return.
8274e7f640dSJohn Baldwin 		 */
8284e7f640dSJohn Baldwin 		if (SX_SHARERS(x) > 1) {
8294e7f640dSJohn Baldwin 			if (atomic_cmpset_ptr(&sx->sx_lock, x,
8304e7f640dSJohn Baldwin 			    x - SX_ONE_SHARER)) {
8314e7f640dSJohn Baldwin 				if (LOCK_LOG_TEST(&sx->lock_object, 0))
8324e7f640dSJohn Baldwin 					CTR4(KTR_LOCK,
8334e7f640dSJohn Baldwin 					    "%s: %p succeeded %p -> %p",
8344e7f640dSJohn Baldwin 					    __func__, sx, (void *)x,
8354e7f640dSJohn Baldwin 					    (void *)(x - SX_ONE_SHARER));
8364e7f640dSJohn Baldwin 				break;
8374e7f640dSJohn Baldwin 			}
8384e7f640dSJohn Baldwin 			continue;
8394e7f640dSJohn Baldwin 		}
8404e7f640dSJohn Baldwin 
8414e7f640dSJohn Baldwin 		/*
8424e7f640dSJohn Baldwin 		 * If there aren't any waiters for an exclusive lock,
8434e7f640dSJohn Baldwin 		 * then try to drop it quickly.
8444e7f640dSJohn Baldwin 		 */
8454e7f640dSJohn Baldwin 		if (!(x & SX_LOCK_EXCLUSIVE_WAITERS)) {
8464e7f640dSJohn Baldwin 			MPASS(x == SX_SHARERS_LOCK(1));
8474e7f640dSJohn Baldwin 			if (atomic_cmpset_ptr(&sx->sx_lock, SX_SHARERS_LOCK(1),
8484e7f640dSJohn Baldwin 			    SX_LOCK_UNLOCKED)) {
8494e7f640dSJohn Baldwin 				if (LOCK_LOG_TEST(&sx->lock_object, 0))
8504e7f640dSJohn Baldwin 					CTR2(KTR_LOCK, "%s: %p last succeeded",
8514e7f640dSJohn Baldwin 					    __func__, sx);
8524e7f640dSJohn Baldwin 				break;
8534e7f640dSJohn Baldwin 			}
8544e7f640dSJohn Baldwin 			continue;
8554e7f640dSJohn Baldwin 		}
8564e7f640dSJohn Baldwin 
8574e7f640dSJohn Baldwin 		/*
8584e7f640dSJohn Baldwin 		 * At this point, there should just be one sharer with
8594e7f640dSJohn Baldwin 		 * exclusive waiters.
8604e7f640dSJohn Baldwin 		 */
8614e7f640dSJohn Baldwin 		MPASS(x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS));
8624e7f640dSJohn Baldwin 
8634e7f640dSJohn Baldwin 		sleepq_lock(&sx->lock_object);
8644e7f640dSJohn Baldwin 
8654e7f640dSJohn Baldwin 		/*
8664e7f640dSJohn Baldwin 		 * Wake up semantic here is quite simple:
8674e7f640dSJohn Baldwin 		 * Just wake up all the exclusive waiters.
8684e7f640dSJohn Baldwin 		 * Note that the state of the lock could have changed,
8694e7f640dSJohn Baldwin 		 * so if it fails loop back and retry.
8704e7f640dSJohn Baldwin 		 */
8714e7f640dSJohn Baldwin 		if (!atomic_cmpset_ptr(&sx->sx_lock,
8724e7f640dSJohn Baldwin 		    SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS,
8734e7f640dSJohn Baldwin 		    SX_LOCK_UNLOCKED)) {
8744e7f640dSJohn Baldwin 			sleepq_release(&sx->lock_object);
8754e7f640dSJohn Baldwin 			continue;
8764e7f640dSJohn Baldwin 		}
8774e7f640dSJohn Baldwin 		if (LOCK_LOG_TEST(&sx->lock_object, 0))
8784e7f640dSJohn Baldwin 			CTR2(KTR_LOCK, "%s: %p waking up all thread on"
8794e7f640dSJohn Baldwin 			    "exclusive queue", __func__, sx);
8804e7f640dSJohn Baldwin 		sleepq_broadcast(&sx->lock_object, SLEEPQ_SX, -1,
8814e7f640dSJohn Baldwin 		    SQ_EXCLUSIVE_QUEUE);
8824e7f640dSJohn Baldwin 		break;
8834e7f640dSJohn Baldwin 	}
884d55229b7SJason Evans }
8854e5e677bSJohn Baldwin 
8864e5e677bSJohn Baldwin #ifdef INVARIANT_SUPPORT
887781a35dfSJohn Baldwin #ifndef INVARIANTS
888781a35dfSJohn Baldwin #undef	_sx_assert
889781a35dfSJohn Baldwin #endif
890781a35dfSJohn Baldwin 
8914e5e677bSJohn Baldwin /*
8924e5e677bSJohn Baldwin  * In the non-WITNESS case, sx_assert() can only detect that at least
8934e5e677bSJohn Baldwin  * *some* thread owns an slock, but it cannot guarantee that *this*
8944e5e677bSJohn Baldwin  * thread owns an slock.
8954e5e677bSJohn Baldwin  */
8964e5e677bSJohn Baldwin void
8974e5e677bSJohn Baldwin _sx_assert(struct sx *sx, int what, const char *file, int line)
8984e5e677bSJohn Baldwin {
8994e7f640dSJohn Baldwin #ifndef WITNESS
9004e7f640dSJohn Baldwin 	int slocked = 0;
9014e7f640dSJohn Baldwin #endif
9024e5e677bSJohn Baldwin 
90303129ba9SJohn Baldwin 	if (panicstr != NULL)
90403129ba9SJohn Baldwin 		return;
9054e5e677bSJohn Baldwin 	switch (what) {
9067ec137e5SJohn Baldwin 	case SA_SLOCKED:
9077ec137e5SJohn Baldwin 	case SA_SLOCKED | SA_NOTRECURSED:
9087ec137e5SJohn Baldwin 	case SA_SLOCKED | SA_RECURSED:
9094e7f640dSJohn Baldwin #ifndef WITNESS
9104e7f640dSJohn Baldwin 		slocked = 1;
9114e7f640dSJohn Baldwin 		/* FALLTHROUGH */
9124e7f640dSJohn Baldwin #endif
9137ec137e5SJohn Baldwin 	case SA_LOCKED:
9147ec137e5SJohn Baldwin 	case SA_LOCKED | SA_NOTRECURSED:
9157ec137e5SJohn Baldwin 	case SA_LOCKED | SA_RECURSED:
9164e5e677bSJohn Baldwin #ifdef WITNESS
917aa89d8cdSJohn Baldwin 		witness_assert(&sx->lock_object, what, file, line);
9184e5e677bSJohn Baldwin #else
9194e7f640dSJohn Baldwin 		/*
9204e7f640dSJohn Baldwin 		 * If some other thread has an exclusive lock or we
9214e7f640dSJohn Baldwin 		 * have one and are asserting a shared lock, fail.
9224e7f640dSJohn Baldwin 		 * Also, if no one has a lock at all, fail.
9234e7f640dSJohn Baldwin 		 */
9244e7f640dSJohn Baldwin 		if (sx->sx_lock == SX_LOCK_UNLOCKED ||
9254e7f640dSJohn Baldwin 		    (!(sx->sx_lock & SX_LOCK_SHARED) && (slocked ||
9264e7f640dSJohn Baldwin 		    sx_xholder(sx) != curthread)))
92703129ba9SJohn Baldwin 			panic("Lock %s not %slocked @ %s:%d\n",
9284e7f640dSJohn Baldwin 			    sx->lock_object.lo_name, slocked ? "share " : "",
9294e7f640dSJohn Baldwin 			    file, line);
9304e7f640dSJohn Baldwin 
9314e7f640dSJohn Baldwin 		if (!(sx->sx_lock & SX_LOCK_SHARED)) {
9324e7f640dSJohn Baldwin 			if (sx_recursed(sx)) {
9337ec137e5SJohn Baldwin 				if (what & SA_NOTRECURSED)
9344e7f640dSJohn Baldwin 					panic("Lock %s recursed @ %s:%d\n",
9354e7f640dSJohn Baldwin 					    sx->lock_object.lo_name, file,
9364e7f640dSJohn Baldwin 					    line);
9377ec137e5SJohn Baldwin 			} else if (what & SA_RECURSED)
9384e7f640dSJohn Baldwin 				panic("Lock %s not recursed @ %s:%d\n",
9394e7f640dSJohn Baldwin 				    sx->lock_object.lo_name, file, line);
9404e7f640dSJohn Baldwin 		}
9414e5e677bSJohn Baldwin #endif
9424e5e677bSJohn Baldwin 		break;
9437ec137e5SJohn Baldwin 	case SA_XLOCKED:
9447ec137e5SJohn Baldwin 	case SA_XLOCKED | SA_NOTRECURSED:
9457ec137e5SJohn Baldwin 	case SA_XLOCKED | SA_RECURSED:
9464e7f640dSJohn Baldwin 		if (sx_xholder(sx) != curthread)
94703129ba9SJohn Baldwin 			panic("Lock %s not exclusively locked @ %s:%d\n",
948aa89d8cdSJohn Baldwin 			    sx->lock_object.lo_name, file, line);
9494e7f640dSJohn Baldwin 		if (sx_recursed(sx)) {
9507ec137e5SJohn Baldwin 			if (what & SA_NOTRECURSED)
9514e7f640dSJohn Baldwin 				panic("Lock %s recursed @ %s:%d\n",
9524e7f640dSJohn Baldwin 				    sx->lock_object.lo_name, file, line);
9537ec137e5SJohn Baldwin 		} else if (what & SA_RECURSED)
9544e7f640dSJohn Baldwin 			panic("Lock %s not recursed @ %s:%d\n",
9554e7f640dSJohn Baldwin 			    sx->lock_object.lo_name, file, line);
9564e5e677bSJohn Baldwin 		break;
9577ec137e5SJohn Baldwin 	case SA_UNLOCKED:
95819b0efd3SPawel Jakub Dawidek #ifdef WITNESS
959aa89d8cdSJohn Baldwin 		witness_assert(&sx->lock_object, what, file, line);
96019b0efd3SPawel Jakub Dawidek #else
961f6739b1dSPawel Jakub Dawidek 		/*
9624e7f640dSJohn Baldwin 		 * If we hold an exclusve lock fail.  We can't
9634e7f640dSJohn Baldwin 		 * reliably check to see if we hold a shared lock or
9644e7f640dSJohn Baldwin 		 * not.
965f6739b1dSPawel Jakub Dawidek 		 */
9664e7f640dSJohn Baldwin 		if (sx_xholder(sx) == curthread)
96703129ba9SJohn Baldwin 			panic("Lock %s exclusively locked @ %s:%d\n",
968aa89d8cdSJohn Baldwin 			    sx->lock_object.lo_name, file, line);
96919b0efd3SPawel Jakub Dawidek #endif
97019b0efd3SPawel Jakub Dawidek 		break;
9714e5e677bSJohn Baldwin 	default:
9724e5e677bSJohn Baldwin 		panic("Unknown sx lock assertion: %d @ %s:%d", what, file,
9734e5e677bSJohn Baldwin 		    line);
9744e5e677bSJohn Baldwin 	}
9754e5e677bSJohn Baldwin }
9764e5e677bSJohn Baldwin #endif	/* INVARIANT_SUPPORT */
977d272fe53SJohn Baldwin 
978d272fe53SJohn Baldwin #ifdef DDB
9794e7f640dSJohn Baldwin static void
980d272fe53SJohn Baldwin db_show_sx(struct lock_object *lock)
981d272fe53SJohn Baldwin {
982d272fe53SJohn Baldwin 	struct thread *td;
983d272fe53SJohn Baldwin 	struct sx *sx;
984d272fe53SJohn Baldwin 
985d272fe53SJohn Baldwin 	sx = (struct sx *)lock;
986d272fe53SJohn Baldwin 
987d272fe53SJohn Baldwin 	db_printf(" state: ");
9884e7f640dSJohn Baldwin 	if (sx->sx_lock == SX_LOCK_UNLOCKED)
9894e7f640dSJohn Baldwin 		db_printf("UNLOCKED\n");
9900026c92cSJohn Baldwin 	else if (sx->sx_lock == SX_LOCK_DESTROYED) {
9910026c92cSJohn Baldwin 		db_printf("DESTROYED\n");
9920026c92cSJohn Baldwin 		return;
9930026c92cSJohn Baldwin 	} else if (sx->sx_lock & SX_LOCK_SHARED)
9944e7f640dSJohn Baldwin 		db_printf("SLOCK: %ju\n", (uintmax_t)SX_SHARERS(sx->sx_lock));
9954e7f640dSJohn Baldwin 	else {
9964e7f640dSJohn Baldwin 		td = sx_xholder(sx);
997d272fe53SJohn Baldwin 		db_printf("XLOCK: %p (tid %d, pid %d, \"%s\")\n", td,
998431f8906SJulian Elischer 		    td->td_tid, td->td_proc->p_pid, td->td_name);
9994e7f640dSJohn Baldwin 		if (sx_recursed(sx))
10004e7f640dSJohn Baldwin 			db_printf(" recursed: %d\n", sx->sx_recurse);
10014e7f640dSJohn Baldwin 	}
10024e7f640dSJohn Baldwin 
10034e7f640dSJohn Baldwin 	db_printf(" waiters: ");
10044e7f640dSJohn Baldwin 	switch(sx->sx_lock &
10054e7f640dSJohn Baldwin 	    (SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)) {
10064e7f640dSJohn Baldwin 	case SX_LOCK_SHARED_WAITERS:
10074e7f640dSJohn Baldwin 		db_printf("shared\n");
10084e7f640dSJohn Baldwin 		break;
10094e7f640dSJohn Baldwin 	case SX_LOCK_EXCLUSIVE_WAITERS:
10104e7f640dSJohn Baldwin 		db_printf("exclusive\n");
10114e7f640dSJohn Baldwin 		break;
10124e7f640dSJohn Baldwin 	case SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS:
10134e7f640dSJohn Baldwin 		db_printf("exclusive and shared\n");
10144e7f640dSJohn Baldwin 		break;
10154e7f640dSJohn Baldwin 	default:
10164e7f640dSJohn Baldwin 		db_printf("none\n");
10174e7f640dSJohn Baldwin 	}
1018d272fe53SJohn Baldwin }
1019462a7addSJohn Baldwin 
1020462a7addSJohn Baldwin /*
1021462a7addSJohn Baldwin  * Check to see if a thread that is blocked on a sleep queue is actually
1022462a7addSJohn Baldwin  * blocked on an sx lock.  If so, output some details and return true.
1023462a7addSJohn Baldwin  * If the lock has an exclusive owner, return that in *ownerp.
1024462a7addSJohn Baldwin  */
1025462a7addSJohn Baldwin int
1026462a7addSJohn Baldwin sx_chain(struct thread *td, struct thread **ownerp)
1027462a7addSJohn Baldwin {
1028462a7addSJohn Baldwin 	struct sx *sx;
1029462a7addSJohn Baldwin 
1030462a7addSJohn Baldwin 	/*
10314e7f640dSJohn Baldwin 	 * Check to see if this thread is blocked on an sx lock.
10324e7f640dSJohn Baldwin 	 * First, we check the lock class.  If that is ok, then we
10334e7f640dSJohn Baldwin 	 * compare the lock name against the wait message.
1034462a7addSJohn Baldwin 	 */
10354e7f640dSJohn Baldwin 	sx = td->td_wchan;
10364e7f640dSJohn Baldwin 	if (LOCK_CLASS(&sx->lock_object) != &lock_class_sx ||
10374e7f640dSJohn Baldwin 	    sx->lock_object.lo_name != td->td_wmesg)
1038462a7addSJohn Baldwin 		return (0);
1039462a7addSJohn Baldwin 
1040462a7addSJohn Baldwin 	/* We think we have an sx lock, so output some details. */
1041462a7addSJohn Baldwin 	db_printf("blocked on sx \"%s\" ", td->td_wmesg);
10424e7f640dSJohn Baldwin 	*ownerp = sx_xholder(sx);
10434e7f640dSJohn Baldwin 	if (sx->sx_lock & SX_LOCK_SHARED)
10444e7f640dSJohn Baldwin 		db_printf("SLOCK (count %ju)\n",
10454e7f640dSJohn Baldwin 		    (uintmax_t)SX_SHARERS(sx->sx_lock));
10464e7f640dSJohn Baldwin 	else
1047462a7addSJohn Baldwin 		db_printf("XLOCK\n");
1048462a7addSJohn Baldwin 	return (1);
1049462a7addSJohn Baldwin }
1050d272fe53SJohn Baldwin #endif
1051