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freebsd-dev/lib/libthr/thread/thr_umtx.h
Konstantin Belousov 2a339d9e3d Add implementation of robust mutexes, hopefully close enough to the 
intention of the POSIX IEEE Std 1003.1TM-2008/Cor 1-2013.

A robust mutex is guaranteed to be cleared by the system upon either
thread or process owner termination while the mutex is held.  The next
mutex locker is then notified about inconsistent mutex state and can
execute (or abandon) corrective actions.

The patch mostly consists of small changes here and there, adding
neccessary checks for the inconsistent and abandoned conditions into
existing paths.  Additionally, the thread exit handler was extended to
iterate over the userspace-maintained list of owned robust mutexes,
unlocking and marking as terminated each of them.

The list of owned robust mutexes cannot be maintained atomically
synchronous with the mutex lock state (it is possible in kernel, but
is too expensive).  Instead, for the duration of lock or unlock
operation, the current mutex is remembered in a special slot that is
also checked by the kernel at thread termination.

Kernel must be aware about the per-thread location of the heads of
robust mutex lists and the current active mutex slot.  When a thread
touches a robust mutex for the first time, a new umtx op syscall is
issued which informs about location of lists heads.

The umtx sleep queues for PP and PI mutexes are split between
non-robust and robust.

Somewhat unrelated changes in the patch:
1. Style.
2. The fix for proper tdfind() call use in umtxq_sleep_pi() for shared
   pi mutexes.
3. Removal of the userspace struct pthread_mutex m_owner field.
4. The sysctl kern.ipc.umtx_vnode_persistent is added, which controls
   the lifetime of the shared mutex associated with a vnode' page.

Reviewed by:	jilles (previous version, supposedly the objection was fixed)
Discussed with:	brooks, Martin Simmons <martin@lispworks.com> (some aspects)
Tested by:	pho
Sponsored by:	The FreeBSD Foundation
2016-05-17 09:56:22 +00:00

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/*-
* Copyright (c) 2005 David Xu <davidxu@freebsd.org>
* All rights reserved.
*
* 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.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR 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 AUTHOR 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.
*
* $FreeBSD$
*/
#ifndef _THR_FBSD_UMTX_H_
#define _THR_FBSD_UMTX_H_
#include <strings.h>
#include <sys/umtx.h>
#ifdef __LP64__
#define DEFAULT_UMUTEX {0,0,{0,0},0,{0,0}}
#else
#define DEFAULT_UMUTEX {0,0,{0,0},0,0,{0,0}}
#endif
#define DEFAULT_URWLOCK {0,0,0,0,{0,0,0,0}}
int _umtx_op_err(void *, int op, u_long, void *, void *) __hidden;
int __thr_umutex_lock(struct umutex *mtx, uint32_t id) __hidden;
int __thr_umutex_lock_spin(struct umutex *mtx, uint32_t id) __hidden;
int __thr_umutex_timedlock(struct umutex *mtx, uint32_t id,
const struct timespec *timeout) __hidden;
int __thr_umutex_unlock(struct umutex *mtx, uint32_t id) __hidden;
int __thr_umutex_trylock(struct umutex *mtx) __hidden;
int __thr_umutex_set_ceiling(struct umutex *mtx, uint32_t ceiling,
uint32_t *oldceiling) __hidden;
void _thr_umutex_init(struct umutex *mtx) __hidden;
void _thr_urwlock_init(struct urwlock *rwl) __hidden;
int _thr_umtx_wait(volatile long *mtx, long exp,
const struct timespec *timeout) __hidden;
int _thr_umtx_wait_uint(volatile u_int *mtx, u_int exp,
const struct timespec *timeout, int shared) __hidden;
int _thr_umtx_timedwait_uint(volatile u_int *mtx, u_int exp, int clockid,
const struct timespec *timeout, int shared) __hidden;
int _thr_umtx_wake(volatile void *mtx, int count, int shared) __hidden;
int _thr_ucond_wait(struct ucond *cv, struct umutex *m,
const struct timespec *timeout, int flags) __hidden;
void _thr_ucond_init(struct ucond *cv) __hidden;
int _thr_ucond_signal(struct ucond *cv) __hidden;
int _thr_ucond_broadcast(struct ucond *cv) __hidden;
int __thr_rwlock_rdlock(struct urwlock *rwlock, int flags,
const struct timespec *tsp) __hidden;
int __thr_rwlock_wrlock(struct urwlock *rwlock,
const struct timespec *tsp) __hidden;
int __thr_rwlock_unlock(struct urwlock *rwlock) __hidden;
/* Internal used only */
void _thr_rwl_rdlock(struct urwlock *rwlock) __hidden;
void _thr_rwl_wrlock(struct urwlock *rwlock) __hidden;
void _thr_rwl_unlock(struct urwlock *rwlock) __hidden;
static inline int
_thr_umutex_trylock(struct umutex *mtx, uint32_t id)
{
if (atomic_cmpset_acq_32(&mtx->m_owner, UMUTEX_UNOWNED, id))
return (0);
if (__predict_false((uint32_t)mtx->m_owner == UMUTEX_RB_OWNERDEAD) &&
atomic_cmpset_acq_32(&mtx->m_owner, UMUTEX_RB_OWNERDEAD,
id | UMUTEX_CONTESTED))
return (EOWNERDEAD);
if (__predict_false((uint32_t)mtx->m_owner == UMUTEX_RB_NOTRECOV))
return (ENOTRECOVERABLE);
if ((mtx->m_flags & UMUTEX_PRIO_PROTECT) == 0)
return (EBUSY);
return (__thr_umutex_trylock(mtx));
}
static inline int
_thr_umutex_trylock2(struct umutex *mtx, uint32_t id)
{
if (atomic_cmpset_acq_32(&mtx->m_owner, UMUTEX_UNOWNED, id) != 0)
return (0);
if ((uint32_t)mtx->m_owner == UMUTEX_CONTESTED &&
__predict_true((mtx->m_flags & (UMUTEX_PRIO_PROTECT |
UMUTEX_PRIO_INHERIT)) == 0) &&
atomic_cmpset_acq_32(&mtx->m_owner, UMUTEX_CONTESTED,
id | UMUTEX_CONTESTED))
return (0);
if (__predict_false((uint32_t)mtx->m_owner == UMUTEX_RB_OWNERDEAD) &&
atomic_cmpset_acq_32(&mtx->m_owner, UMUTEX_RB_OWNERDEAD,
id | UMUTEX_CONTESTED))
return (EOWNERDEAD);
if (__predict_false((uint32_t)mtx->m_owner == UMUTEX_RB_NOTRECOV))
return (ENOTRECOVERABLE);
return (EBUSY);
}
static inline int
_thr_umutex_lock(struct umutex *mtx, uint32_t id)
{
if (_thr_umutex_trylock2(mtx, id) == 0)
return (0);
return (__thr_umutex_lock(mtx, id));
}
static inline int
_thr_umutex_lock_spin(struct umutex *mtx, uint32_t id)
{
if (_thr_umutex_trylock2(mtx, id) == 0)
return (0);
return (__thr_umutex_lock_spin(mtx, id));
}
static inline int
_thr_umutex_timedlock(struct umutex *mtx, uint32_t id,
const struct timespec *timeout)
{
if (_thr_umutex_trylock2(mtx, id) == 0)
return (0);
return (__thr_umutex_timedlock(mtx, id, timeout));
}
static inline int
_thr_umutex_unlock2(struct umutex *mtx, uint32_t id, int *defer)
{
uint32_t flags, owner;
bool noncst;
flags = mtx->m_flags;
noncst = (flags & UMUTEX_NONCONSISTENT) != 0;
if ((flags & (UMUTEX_PRIO_PROTECT | UMUTEX_PRIO_INHERIT)) != 0) {
if (atomic_cmpset_rel_32(&mtx->m_owner, id, noncst ?
UMUTEX_RB_NOTRECOV : UMUTEX_UNOWNED))
return (0);
return (__thr_umutex_unlock(mtx, id));
}
do {
owner = mtx->m_owner;
if (__predict_false((owner & ~UMUTEX_CONTESTED) != id))
return (EPERM);
} while (__predict_false(!atomic_cmpset_rel_32(&mtx->m_owner, owner,
noncst ? UMUTEX_RB_NOTRECOV : UMUTEX_UNOWNED)));
if ((owner & UMUTEX_CONTESTED) != 0) {
if (defer == NULL || noncst)
(void)_umtx_op_err(mtx, UMTX_OP_MUTEX_WAKE2,
flags, 0, 0);
else
*defer = 1;
}
return (0);
}
static inline int
_thr_umutex_unlock(struct umutex *mtx, uint32_t id)
{
return (_thr_umutex_unlock2(mtx, id, NULL));
}
static inline int
_thr_rwlock_tryrdlock(struct urwlock *rwlock, int flags)
{
int32_t state, wrflags;
if ((flags & URWLOCK_PREFER_READER) != 0 ||
(rwlock->rw_flags & URWLOCK_PREFER_READER) != 0)
wrflags = URWLOCK_WRITE_OWNER;
else
wrflags = URWLOCK_WRITE_OWNER | URWLOCK_WRITE_WAITERS;
state = rwlock->rw_state;
while (!(state & wrflags)) {
if (__predict_false(URWLOCK_READER_COUNT(state) ==
URWLOCK_MAX_READERS))
return (EAGAIN);
if (atomic_cmpset_acq_32(&rwlock->rw_state, state, state + 1))
return (0);
state = rwlock->rw_state;
}
return (EBUSY);
}
static inline int
_thr_rwlock_trywrlock(struct urwlock *rwlock)
{
int32_t state;
state = rwlock->rw_state;
while ((state & URWLOCK_WRITE_OWNER) == 0 &&
URWLOCK_READER_COUNT(state) == 0) {
if (atomic_cmpset_acq_32(&rwlock->rw_state, state,
state | URWLOCK_WRITE_OWNER))
return (0);
state = rwlock->rw_state;
}
return (EBUSY);
}
static inline int
_thr_rwlock_rdlock(struct urwlock *rwlock, int flags, struct timespec *tsp)
{
if (_thr_rwlock_tryrdlock(rwlock, flags) == 0)
return (0);
return (__thr_rwlock_rdlock(rwlock, flags, tsp));
}
static inline int
_thr_rwlock_wrlock(struct urwlock *rwlock, struct timespec *tsp)
{
if (_thr_rwlock_trywrlock(rwlock) == 0)
return (0);
return (__thr_rwlock_wrlock(rwlock, tsp));
}
static inline int
_thr_rwlock_unlock(struct urwlock *rwlock)
{
int32_t state;
state = rwlock->rw_state;
if ((state & URWLOCK_WRITE_OWNER) != 0) {
if (atomic_cmpset_rel_32(&rwlock->rw_state,
URWLOCK_WRITE_OWNER, 0))
return (0);
} else {
for (;;) {
if (__predict_false(URWLOCK_READER_COUNT(state) == 0))
return (EPERM);
if (!((state & (URWLOCK_WRITE_WAITERS |
URWLOCK_READ_WAITERS)) != 0 &&
URWLOCK_READER_COUNT(state) == 1)) {
if (atomic_cmpset_rel_32(&rwlock->rw_state,
state, state - 1))
return (0);
state = rwlock->rw_state;
} else {
break;
}
}
}
return (__thr_rwlock_unlock(rwlock));
}
#endif
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