Please note that diffs are not public domain; they are subject to the copyright notices on the relevant files. =================================================================== RCS file: /ftp/cvs/cvsroot/src/sys/kern/kern_mutex.c,v rcsdiff: /ftp/cvs/cvsroot/src/sys/kern/kern_mutex.c,v: warning: Unknown phrases like `commitid ...;' are present. retrieving revision 1.17 retrieving revision 1.54 diff -u -p -r1.17 -r1.54 --- src/sys/kern/kern_mutex.c 2007/09/17 21:33:34 1.17 +++ src/sys/kern/kern_mutex.c 2013/04/27 08:12:34 1.54 @@ -1,7 +1,7 @@ -/* $NetBSD: kern_mutex.c,v 1.17 2007/09/17 21:33:34 ad Exp $ */ +/* $NetBSD: kern_mutex.c,v 1.54 2013/04/27 08:12:34 mlelstv Exp $ */ /*- - * Copyright (c) 2002, 2006, 2007 The NetBSD Foundation, Inc. + * Copyright (c) 2002, 2006, 2007, 2008 The NetBSD Foundation, Inc. * All rights reserved. * * This code is derived from software contributed to The NetBSD Foundation @@ -15,13 +15,6 @@ * 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 NetBSD - * Foundation, Inc. and its contributors. - * 4. Neither the name of The NetBSD Foundation 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 NETBSD FOUNDATION, INC. AND CONTRIBUTORS * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED @@ -44,14 +37,13 @@ * Richard McDougall. */ -#include "opt_multiprocessor.h" - #define __MUTEX_PRIVATE #include -__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.17 2007/09/17 21:33:34 ad Exp $"); +__KERNEL_RCSID(0, "$NetBSD: kern_mutex.c,v 1.54 2013/04/27 08:12:34 mlelstv Exp $"); #include +#include #include #include #include @@ -59,10 +51,13 @@ __KERNEL_RCSID(0, "$NetBSD: kern_mutex.c #include #include #include +#include +#include +#include #include -#include +#include /* * When not running a debug kernel, spin mutexes are not much @@ -78,13 +73,13 @@ __KERNEL_RCSID(0, "$NetBSD: kern_mutex.c */ #define MUTEX_WANTLOCK(mtx) \ - LOCKDEBUG_WANTLOCK(MUTEX_GETID(mtx), \ + LOCKDEBUG_WANTLOCK(MUTEX_DEBUG_P(mtx), (mtx), \ (uintptr_t)__builtin_return_address(0), 0) #define MUTEX_LOCKED(mtx) \ - LOCKDEBUG_LOCKED(MUTEX_GETID(mtx), \ + LOCKDEBUG_LOCKED(MUTEX_DEBUG_P(mtx), (mtx), NULL, \ (uintptr_t)__builtin_return_address(0), 0) #define MUTEX_UNLOCKED(mtx) \ - LOCKDEBUG_UNLOCKED(MUTEX_GETID(mtx), \ + LOCKDEBUG_UNLOCKED(MUTEX_DEBUG_P(mtx), (mtx), \ (uintptr_t)__builtin_return_address(0), 0) #define MUTEX_ABORT(mtx, msg) \ mutex_abort(mtx, __func__, msg) @@ -120,17 +115,16 @@ do { \ /* * Spin mutex SPL save / restore. */ -#ifndef MUTEX_COUNT_BIAS -#define MUTEX_COUNT_BIAS 0 -#endif #define MUTEX_SPIN_SPLRAISE(mtx) \ do { \ - struct cpu_info *x__ci = curcpu(); \ + struct cpu_info *x__ci; \ int x__cnt, s; \ - x__cnt = x__ci->ci_mtx_count--; \ s = splraiseipl(mtx->mtx_ipl); \ - if (x__cnt == MUTEX_COUNT_BIAS) \ + x__ci = curcpu(); \ + x__cnt = x__ci->ci_mtx_count--; \ + __insn_barrier(); \ + if (x__cnt == 0) \ x__ci->ci_mtx_oldspl = (s); \ } while (/* CONSTCOND */ 0) @@ -139,7 +133,7 @@ do { \ struct cpu_info *x__ci = curcpu(); \ int s = x__ci->ci_mtx_oldspl; \ __insn_barrier(); \ - if (++(x__ci->ci_mtx_count) == MUTEX_COUNT_BIAS) \ + if (++(x__ci->ci_mtx_count) == 0) \ splx(s); \ } while (/* CONSTCOND */ 0) @@ -154,28 +148,27 @@ do { \ #define MUTEX_OWNER(owner) \ (owner & MUTEX_THREAD) -#define MUTEX_OWNED(owner) \ - (owner != 0) #define MUTEX_HAS_WAITERS(mtx) \ (((int)(mtx)->mtx_owner & MUTEX_BIT_WAITERS) != 0) -#define MUTEX_INITIALIZE_ADAPTIVE(mtx, id) \ +#define MUTEX_INITIALIZE_ADAPTIVE(mtx, dodebug) \ + if (!dodebug) \ + (mtx)->mtx_owner |= MUTEX_BIT_NODEBUG; \ do { \ - (mtx)->mtx_id = (id); \ } while (/* CONSTCOND */ 0); -#define MUTEX_INITIALIZE_SPIN(mtx, id, ipl) \ +#define MUTEX_INITIALIZE_SPIN(mtx, dodebug, ipl) \ do { \ (mtx)->mtx_owner = MUTEX_BIT_SPIN; \ + if (!dodebug) \ + (mtx)->mtx_owner |= MUTEX_BIT_NODEBUG; \ (mtx)->mtx_ipl = makeiplcookie((ipl)); \ - (mtx)->mtx_id = (id); \ __cpu_simple_lock_init(&(mtx)->mtx_lock); \ } while (/* CONSTCOND */ 0) #define MUTEX_DESTROY(mtx) \ do { \ (mtx)->mtx_owner = MUTEX_THREAD; \ - (mtx)->mtx_id = -1; \ } while (/* CONSTCOND */ 0); #define MUTEX_SPIN_P(mtx) \ @@ -183,13 +176,25 @@ do { \ #define MUTEX_ADAPTIVE_P(mtx) \ (((mtx)->mtx_owner & MUTEX_BIT_SPIN) == 0) -#define MUTEX_GETID(mtx) ((mtx)->mtx_id) +#define MUTEX_DEBUG_P(mtx) (((mtx)->mtx_owner & MUTEX_BIT_NODEBUG) == 0) +#if defined(LOCKDEBUG) +#define MUTEX_OWNED(owner) (((owner) & ~MUTEX_BIT_NODEBUG) != 0) +#define MUTEX_INHERITDEBUG(new, old) (new) |= (old) & MUTEX_BIT_NODEBUG +#else /* defined(LOCKDEBUG) */ +#define MUTEX_OWNED(owner) ((owner) != 0) +#define MUTEX_INHERITDEBUG(new, old) /* nothing */ +#endif /* defined(LOCKDEBUG) */ static inline int MUTEX_ACQUIRE(kmutex_t *mtx, uintptr_t curthread) { int rv; - rv = MUTEX_CAS(&mtx->mtx_owner, 0UL, curthread); + uintptr_t old = 0; + uintptr_t new = curthread; + + MUTEX_INHERITDEBUG(old, mtx->mtx_owner); + MUTEX_INHERITDEBUG(new, old); + rv = MUTEX_CAS(&mtx->mtx_owner, old, new); MUTEX_RECEIVE(mtx); return rv; } @@ -206,8 +211,12 @@ MUTEX_SET_WAITERS(kmutex_t *mtx, uintptr static inline void MUTEX_RELEASE(kmutex_t *mtx) { + uintptr_t new; + MUTEX_GIVE(mtx); - mtx->mtx_owner = 0; + new = 0; + MUTEX_INHERITDEBUG(new, mtx->mtx_owner); + mtx->mtx_owner = new; } static inline void @@ -236,20 +245,18 @@ __strong_alias(mutex_spin_enter,mutex_ve __strong_alias(mutex_spin_exit,mutex_vector_exit); #endif -void mutex_abort(kmutex_t *, const char *, const char *); -void mutex_dump(volatile void *); -int mutex_onproc(uintptr_t, struct cpu_info **); -static struct lwp *mutex_owner(wchan_t); +static void mutex_abort(kmutex_t *, const char *, const char *); +static void mutex_dump(volatile void *); lockops_t mutex_spin_lockops = { "Mutex", - 0, + LOCKOPS_SPIN, mutex_dump }; lockops_t mutex_adaptive_lockops = { "Mutex", - 1, + LOCKOPS_SLEEP, mutex_dump }; @@ -258,7 +265,7 @@ syncobj_t mutex_syncobj = { turnstile_unsleep, turnstile_changepri, sleepq_lendpri, - mutex_owner, + (void *)mutex_owner, }; /* @@ -283,17 +290,12 @@ mutex_dump(volatile void *cookie) * generates a lot of machine code in the DIAGNOSTIC case, so * we ask the compiler to not inline it. */ - -#if __GNUC_PREREQ__(3, 0) -__attribute ((noinline)) __attribute ((noreturn)) -#endif -void +void __noinline mutex_abort(kmutex_t *mtx, const char *func, const char *msg) { - LOCKDEBUG_ABORT(MUTEX_GETID(mtx), mtx, (MUTEX_SPIN_P(mtx) ? + LOCKDEBUG_ABORT(mtx, (MUTEX_SPIN_P(mtx) ? &mutex_spin_lockops : &mutex_adaptive_lockops), func, msg); - /* NOTREACHED */ } /* @@ -308,17 +310,23 @@ mutex_abort(kmutex_t *mtx, const char *f void mutex_init(kmutex_t *mtx, kmutex_type_t type, int ipl) { - u_int id; + bool dodebug; memset(mtx, 0, sizeof(*mtx)); switch (type) { case MUTEX_ADAPTIVE: - case MUTEX_DEFAULT: KASSERT(ipl == IPL_NONE); break; + case MUTEX_DEFAULT: case MUTEX_DRIVER: - type = (ipl == IPL_NONE ? MUTEX_ADAPTIVE : MUTEX_SPIN); + if (ipl == IPL_NONE || ipl == IPL_SOFTCLOCK || + ipl == IPL_SOFTBIO || ipl == IPL_SOFTNET || + ipl == IPL_SOFTSERIAL) { + type = MUTEX_ADAPTIVE; + } else { + type = MUTEX_SPIN; + } break; default: break; @@ -326,17 +334,19 @@ mutex_init(kmutex_t *mtx, kmutex_type_t switch (type) { case MUTEX_NODEBUG: - id = LOCKDEBUG_ALLOC(mtx, NULL); - MUTEX_INITIALIZE_SPIN(mtx, id, ipl); + dodebug = LOCKDEBUG_ALLOC(mtx, NULL, + (uintptr_t)__builtin_return_address(0)); + MUTEX_INITIALIZE_SPIN(mtx, dodebug, ipl); break; case MUTEX_ADAPTIVE: - case MUTEX_DEFAULT: - id = LOCKDEBUG_ALLOC(mtx, &mutex_adaptive_lockops); - MUTEX_INITIALIZE_ADAPTIVE(mtx, id); + dodebug = LOCKDEBUG_ALLOC(mtx, &mutex_adaptive_lockops, + (uintptr_t)__builtin_return_address(0)); + MUTEX_INITIALIZE_ADAPTIVE(mtx, dodebug); break; case MUTEX_SPIN: - id = LOCKDEBUG_ALLOC(mtx, &mutex_spin_lockops); - MUTEX_INITIALIZE_SPIN(mtx, id, ipl); + dodebug = LOCKDEBUG_ALLOC(mtx, &mutex_spin_lockops, + (uintptr_t)__builtin_return_address(0)); + MUTEX_INITIALIZE_SPIN(mtx, dodebug, ipl); break; default: panic("mutex_init: impossible type"); @@ -360,55 +370,51 @@ mutex_destroy(kmutex_t *mtx) MUTEX_ASSERT(mtx, !__SIMPLELOCK_LOCKED_P(&mtx->mtx_lock)); } - LOCKDEBUG_FREE(mtx, MUTEX_GETID(mtx)); + LOCKDEBUG_FREE(MUTEX_DEBUG_P(mtx), mtx); MUTEX_DESTROY(mtx); } +#ifdef MULTIPROCESSOR /* - * mutex_onproc: + * mutex_oncpu: * * Return true if an adaptive mutex owner is running on a CPU in the * system. If the target is waiting on the kernel big lock, then we * must release it. This is necessary to avoid deadlock. - * - * Note that we can't use the mutex owner field as an LWP pointer. We - * don't have full control over the timing of our execution, and so the - * pointer could be completely invalid by the time we dereference it. */ -#ifdef MULTIPROCESSOR -int -mutex_onproc(uintptr_t owner, struct cpu_info **cip) +static bool +mutex_oncpu(uintptr_t owner) { - CPU_INFO_ITERATOR cii; struct cpu_info *ci; - struct lwp *l; + lwp_t *l; - if (!MUTEX_OWNED(owner)) - return 0; - l = (struct lwp *)MUTEX_OWNER(owner); + KASSERT(kpreempt_disabled()); - /* See if the target is running on a CPU somewhere. */ - if ((ci = *cip) != NULL && ci->ci_curlwp == l) - goto run; - for (CPU_INFO_FOREACH(cii, ci)) - if (ci->ci_curlwp == l) - goto run; + if (!MUTEX_OWNED(owner)) { + return false; + } - /* No: it may be safe to block now. */ - *cip = NULL; - return 0; + /* + * See lwp_dtor() why dereference of the LWP pointer is safe. + * We must have kernel preemption disabled for that. + */ + l = (lwp_t *)MUTEX_OWNER(owner); + ci = l->l_cpu; + + if (ci && ci->ci_curlwp == l) { + /* Target is running; do we need to block? */ + return (ci->ci_biglock_wanted != l); + } - run: - /* Target is running; do we need to block? */ - *cip = ci; - return ci->ci_biglock_wanted != l; + /* Not running. It may be safe to block now. */ + return false; } #endif /* MULTIPROCESSOR */ /* * mutex_vector_enter: * - * Support routine for mutex_enter() that must handles all cases. In + * Support routine for mutex_enter() that must handle all cases. In * the LOCKDEBUG case, mutex_enter() is always aliased here, even if * fast-path stubs are available. If an mutex_spin_enter() stub is * not available, then it is also aliased directly here. @@ -419,7 +425,6 @@ mutex_vector_enter(kmutex_t *mtx) uintptr_t owner, curthread; turnstile_t *ts; #ifdef MULTIPROCESSOR - struct cpu_info *ci = NULL; u_int count; #endif LOCKSTAT_COUNTER(spincnt); @@ -484,16 +489,9 @@ mutex_vector_enter(kmutex_t *mtx) MUTEX_ASSERT(mtx, curthread != 0); MUTEX_WANTLOCK(mtx); -#ifdef LOCKDEBUG if (panicstr == NULL) { - simple_lock_only_held(NULL, "mutex_enter"); -#ifdef MULTIPROCESSOR LOCKDEBUG_BARRIER(&kernel_lock, 1); -#else - LOCKDEBUG_BARRIER(NULL, 1); -#endif } -#endif LOCKSTAT_ENTER(lsflag); @@ -502,8 +500,8 @@ mutex_vector_enter(kmutex_t *mtx) * determine that the owner is not running on a processor, * then we stop spinning, and sleep instead. */ - for (;;) { - owner = mtx->mtx_owner; + KPREEMPT_DISABLE(curlwp); + for (owner = mtx->mtx_owner;;) { if (!MUTEX_OWNED(owner)) { /* * Mutex owner clear could mean two things: @@ -516,29 +514,31 @@ mutex_vector_enter(kmutex_t *mtx) */ if (MUTEX_ACQUIRE(mtx, curthread)) break; + owner = mtx->mtx_owner; continue; } - - if (panicstr != NULL) + if (__predict_false(panicstr != NULL)) { + kpreempt_enable(); return; - if (MUTEX_OWNER(owner) == curthread) + } + if (__predict_false(MUTEX_OWNER(owner) == curthread)) { MUTEX_ABORT(mtx, "locking against myself"); - + } #ifdef MULTIPROCESSOR /* * Check to see if the owner is running on a processor. * If so, then we should just spin, as the owner will * likely release the lock very soon. */ - if (mutex_onproc(owner, &ci)) { + if (mutex_oncpu(owner)) { LOCKSTAT_START_TIMER(lsflag, spintime); count = SPINLOCK_BACKOFF_MIN; - for (;;) { - owner = mtx->mtx_owner; - if (!mutex_onproc(owner, &ci)) - break; + do { + KPREEMPT_ENABLE(curlwp); SPINLOCK_BACKOFF(count); - } + KPREEMPT_DISABLE(curlwp); + owner = mtx->mtx_owner; + } while (mutex_oncpu(owner)); LOCKSTAT_STOP_TIMER(lsflag, spintime); LOCKSTAT_COUNT(spincnt, 1); if (!MUTEX_OWNED(owner)) @@ -555,6 +555,7 @@ mutex_vector_enter(kmutex_t *mtx) */ if (!MUTEX_SET_WAITERS(mtx, owner)) { turnstile_exit(mtx); + owner = mtx->mtx_owner; continue; } @@ -577,7 +578,7 @@ mutex_vector_enter(kmutex_t *mtx) * .. clear lock word, waiters * return success * - * There is a another race that can occur: a third CPU could + * There is another race that can occur: a third CPU could * acquire the mutex as soon as it is released. Since * adaptive mutexes are primarily spin mutexes, this is not * something that we need to worry about too much. What we @@ -592,7 +593,7 @@ mutex_vector_enter(kmutex_t *mtx) * or preempted). * * o At any given time, MUTEX_SET_WAITERS() can only ever - * be in progress on one CPU in the system - guarenteed + * be in progress on one CPU in the system - guaranteed * by the turnstile chain lock. * * o No other operations other than MUTEX_SET_WAITERS() @@ -622,23 +623,23 @@ mutex_vector_enter(kmutex_t *mtx) * waiters field) and check the lock holder's status again. * Some of the possible outcomes (not an exhaustive list): * - * 1. The onproc check returns true: the holding LWP is + * 1. The on-CPU check returns true: the holding LWP is * running again. The lock may be released soon and * we should spin. Importantly, we can't trust the * value of the waiters flag. * - * 2. The onproc check returns false: the holding LWP is - * not running. We now have the oppertunity to check + * 2. The on-CPU check returns false: the holding LWP is + * not running. We now have the opportunity to check * if mutex_exit() has blatted the modifications made * by MUTEX_SET_WAITERS(). * - * 3. The onproc check returns false: the holding LWP may + * 3. The on-CPU check returns false: the holding LWP may * or may not be running. It has context switched at * some point during our check. Again, we have the * chance to see if the waiters bit is still set or * has been overwritten. * - * 4. The onproc check returns false: the holding LWP is + * 4. The on-CPU check returns false: the holding LWP is * running on a CPU, but wants the big lock. It's OK * to check the waiters field in this case. * @@ -652,9 +653,10 @@ mutex_vector_enter(kmutex_t *mtx) * If the waiters bit is not set it's unsafe to go asleep, * as we might never be awoken. */ - if ((mb_read(), mutex_onproc(owner, &ci)) || - (mb_read(), !MUTEX_HAS_WAITERS(mtx))) { + if ((membar_consumer(), mutex_oncpu(owner)) || + (membar_consumer(), !MUTEX_HAS_WAITERS(mtx))) { turnstile_exit(mtx); + owner = mtx->mtx_owner; continue; } #endif /* MULTIPROCESSOR */ @@ -665,7 +667,10 @@ mutex_vector_enter(kmutex_t *mtx) LOCKSTAT_STOP_TIMER(lsflag, slptime); LOCKSTAT_COUNT(slpcnt, 1); + + owner = mtx->mtx_owner; } + KPREEMPT_ENABLE(curlwp); LOCKSTAT_EVENT(lsflag, mtx, LB_ADAPTIVE_MUTEX | LB_SLEEP1, slpcnt, slptime); @@ -690,8 +695,11 @@ mutex_vector_exit(kmutex_t *mtx) if (MUTEX_SPIN_P(mtx)) { #ifdef FULL - if (!__SIMPLELOCK_LOCKED_P(&mtx->mtx_lock)) + if (__predict_false(!__SIMPLELOCK_LOCKED_P(&mtx->mtx_lock))) { + if (panicstr != NULL) + return; MUTEX_ABORT(mtx, "exiting unheld spin mutex"); + } MUTEX_UNLOCKED(mtx); __cpu_simple_unlock(&mtx->mtx_lock); #endif @@ -778,6 +786,8 @@ int mutex_owned(kmutex_t *mtx) { + if (mtx == NULL) + return 0; if (MUTEX_ADAPTIVE_P(mtx)) return MUTEX_OWNER(mtx->mtx_owner) == (uintptr_t)curlwp; #ifdef FULL @@ -793,10 +803,9 @@ mutex_owned(kmutex_t *mtx) * Return the current owner of an adaptive mutex. Used for * priority inheritance. */ -static struct lwp * -mutex_owner(wchan_t obj) +lwp_t * +mutex_owner(kmutex_t *mtx) { - kmutex_t *mtx = (void *)(uintptr_t)obj; /* discard qualifiers */ MUTEX_ASSERT(mtx, MUTEX_ADAPTIVE_P(mtx)); return (struct lwp *)MUTEX_OWNER(mtx->mtx_owner);