/*-
* Copyright (c) 2007 Attilio Rao <attilio@freebsd.org>
* Copyright (c) 2001 Jason Evans <jasone@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(s), this list of conditions and the following disclaimer as
* the first lines of this file unmodified other than the possible
* addition of one or more copyright notices.
* 2. Redistributions in binary form must reproduce the above copyright
* notice(s), 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 COPYRIGHT HOLDER(S) ``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 COPYRIGHT HOLDER(S) 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 _SYS_SX_H_
#define _SYS_SX_H_
#include <sys/_lock.h>
#include <sys/_sx.h>
#ifdef _KERNEL
#include <sys/pcpu.h>
#include <sys/lock_profile.h>
#include <sys/lockstat.h>
#include <machine/atomic.h>
#endif
/*
* In general, the sx locks and rwlocks use very similar algorithms.
* The main difference in the implementations is how threads are
* blocked when a lock is unavailable. For this, sx locks use sleep
* queues which do not support priority propagation, and rwlocks use
* turnstiles which do.
*
* The sx_lock field consists of several fields. The low bit
* indicates if the lock is locked with a shared or exclusive lock. A
* value of 0 indicates an exclusive lock, and a value of 1 indicates
* a shared lock. Bit 1 is a boolean indicating if there are any
* threads waiting for a shared lock. Bit 2 is a boolean indicating
* if there are any threads waiting for an exclusive lock. Bit 3 is a
* boolean indicating if an exclusive lock is recursively held. The
* rest of the variable's definition is dependent on the value of the
* first bit. For an exclusive lock, it is a pointer to the thread
* holding the lock, similar to the mtx_lock field of mutexes. For
* shared locks, it is a count of read locks that are held.
*
* When the lock is not locked by any thread, it is encoded as a
* shared lock with zero waiters.
*/
#define SX_LOCK_SHARED 0x01
#define SX_LOCK_SHARED_WAITERS 0x02
#define SX_LOCK_EXCLUSIVE_WAITERS 0x04
#define SX_LOCK_RECURSED 0x08
#define SX_LOCK_FLAGMASK \
(SX_LOCK_SHARED | SX_LOCK_SHARED_WAITERS | \
SX_LOCK_EXCLUSIVE_WAITERS | SX_LOCK_RECURSED)
#define SX_OWNER(x) ((x) & ~SX_LOCK_FLAGMASK)
#define SX_SHARERS_SHIFT 4
#define SX_SHARERS(x) (SX_OWNER(x) >> SX_SHARERS_SHIFT)
#define SX_SHARERS_LOCK(x) \
((x) << SX_SHARERS_SHIFT | SX_LOCK_SHARED)
#define SX_ONE_SHARER (1 << SX_SHARERS_SHIFT)
#define SX_LOCK_UNLOCKED SX_SHARERS_LOCK(0)
#define SX_LOCK_DESTROYED \
(SX_LOCK_SHARED_WAITERS | SX_LOCK_EXCLUSIVE_WAITERS)
#ifdef _KERNEL
#define sx_recurse lock_object.lo_data
/*
* Function prototipes. Routines that start with an underscore are not part
* of the public interface and are wrappered with a macro.
*/
void sx_sysinit(void *arg);
#define sx_init(sx, desc) sx_init_flags((sx), (desc), 0)
void sx_init_flags(struct sx *sx, const char *description, int opts);
void sx_destroy(struct sx *sx);
int sx_try_slock_(struct sx *sx, const char *file, int line);
int sx_try_xlock_(struct sx *sx, const char *file, int line);
int sx_try_upgrade_(struct sx *sx, const char *file, int line);
void sx_downgrade_(struct sx *sx, const char *file, int line);
int _sx_slock(struct sx *sx, int opts, const char *file, int line);
int _sx_xlock(struct sx *sx, int opts, const char *file, int line);
void _sx_sunlock(struct sx *sx, const char *file, int line);
void _sx_xunlock(struct sx *sx, const char *file, int line);
int _sx_xlock_hard(struct sx *sx, uintptr_t tid, int opts,
const char *file, int line);
int _sx_slock_hard(struct sx *sx, int opts, const char *file, int line);
void _sx_xunlock_hard(struct sx *sx, uintptr_t tid, const char *file, int
line);
void _sx_sunlock_hard(struct sx *sx, const char *file, int line);
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
void _sx_assert(const struct sx *sx, int what, const char *file, int line);
#endif
#ifdef DDB
int sx_chain(struct thread *td, struct thread **ownerp);
#endif
struct sx_args {
struct sx *sa_sx;
const char *sa_desc;
int sa_flags;
};
#define SX_SYSINIT_FLAGS(name, sxa, desc, flags) \
static struct sx_args name##_args = { \
(sxa), \
(desc), \
(flags) \
}; \
SYSINIT(name##_sx_sysinit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
sx_sysinit, &name##_args); \
SYSUNINIT(name##_sx_sysuninit, SI_SUB_LOCK, SI_ORDER_MIDDLE, \
sx_destroy, (sxa))
#define SX_SYSINIT(name, sxa, desc) SX_SYSINIT_FLAGS(name, sxa, desc, 0)
/*
* Full lock operations that are suitable to be inlined in non-debug kernels.
* If the lock can't be acquired or released trivially then the work is
* deferred to 'tougher' functions.
*/
/* Acquire an exclusive lock. */
static __inline int
__sx_xlock(struct sx *sx, struct thread *td, int opts, const char *file,
int line)
{
uintptr_t tid = (uintptr_t)td;
int error = 0;
if (!atomic_cmpset_acq_ptr(&sx->sx_lock, SX_LOCK_UNLOCKED, tid))
error = _sx_xlock_hard(sx, tid, opts, file, line);
else
LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx,
0, 0, file, line, LOCKSTAT_WRITER);
return (error);
}
/* Release an exclusive lock. */
static __inline void
__sx_xunlock(struct sx *sx, struct thread *td, const char *file, int line)
{
uintptr_t tid = (uintptr_t)td;
if (sx->sx_recurse == 0)
LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx,
LOCKSTAT_WRITER);
if (!atomic_cmpset_rel_ptr(&sx->sx_lock, tid, SX_LOCK_UNLOCKED))
_sx_xunlock_hard(sx, tid, file, line);
}
/* Acquire a shared lock. */
static __inline int
__sx_slock(struct sx *sx, int opts, const char *file, int line)
{
uintptr_t x = sx->sx_lock;
int error = 0;
if (!(x & SX_LOCK_SHARED) ||
!atomic_cmpset_acq_ptr(&sx->sx_lock, x, x + SX_ONE_SHARER))
error = _sx_slock_hard(sx, opts, file, line);
else
LOCKSTAT_PROFILE_OBTAIN_RWLOCK_SUCCESS(sx__acquire, sx,
0, 0, file, line, LOCKSTAT_READER);
return (error);
}
/*
* Release a shared lock. We can just drop a single shared lock so
* long as we aren't trying to drop the last shared lock when other
* threads are waiting for an exclusive lock. This takes advantage of
* the fact that an unlocked lock is encoded as a shared lock with a
* count of 0.
*/
static __inline void
__sx_sunlock(struct sx *sx, const char *file, int line)
{
uintptr_t x = sx->sx_lock;
LOCKSTAT_PROFILE_RELEASE_RWLOCK(sx__release, sx, LOCKSTAT_READER);
if (x == (SX_SHARERS_LOCK(1) | SX_LOCK_EXCLUSIVE_WAITERS) ||
!atomic_cmpset_rel_ptr(&sx->sx_lock, x, x - SX_ONE_SHARER))
_sx_sunlock_hard(sx, file, line);
}
/*
* Public interface for lock operations.
*/
#ifndef LOCK_DEBUG
#error "LOCK_DEBUG not defined, include <sys/lock.h> before <sys/sx.h>"
#endif
#if (LOCK_DEBUG > 0) || defined(SX_NOINLINE)
#define sx_xlock_(sx, file, line) \
(void)_sx_xlock((sx), 0, (file), (line))
#define sx_xlock_sig_(sx, file, line) \
_sx_xlock((sx), SX_INTERRUPTIBLE, (file), (line))
#define sx_xunlock_(sx, file, line) \
_sx_xunlock((sx), (file), (line))
#define sx_slock_(sx, file, line) \
(void)_sx_slock((sx), 0, (file), (line))
#define sx_slock_sig_(sx, file, line) \
_sx_slock((sx), SX_INTERRUPTIBLE, (file) , (line))
#define sx_sunlock_(sx, file, line) \
_sx_sunlock((sx), (file), (line))
#else
#define sx_xlock_(sx, file, line) \
(void)__sx_xlock((sx), curthread, 0, (file), (line))
#define sx_xlock_sig_(sx, file, line) \
__sx_xlock((sx), curthread, SX_INTERRUPTIBLE, (file), (line))
#define sx_xunlock_(sx, file, line) \
__sx_xunlock((sx), curthread, (file), (line))
#define sx_slock_(sx, file, line) \
(void)__sx_slock((sx), 0, (file), (line))
#define sx_slock_sig_(sx, file, line) \
__sx_slock((sx), SX_INTERRUPTIBLE, (file), (line))
#define sx_sunlock_(sx, file, line) \
__sx_sunlock((sx), (file), (line))
#endif /* LOCK_DEBUG > 0 || SX_NOINLINE */
#define sx_try_slock(sx) sx_try_slock_((sx), LOCK_FILE, LOCK_LINE)
#define sx_try_xlock(sx) sx_try_xlock_((sx), LOCK_FILE, LOCK_LINE)
#define sx_try_upgrade(sx) sx_try_upgrade_((sx), LOCK_FILE, LOCK_LINE)
#define sx_downgrade(sx) sx_downgrade_((sx), LOCK_FILE, LOCK_LINE)
#ifdef INVARIANTS
#define sx_assert_(sx, what, file, line) \
_sx_assert((sx), (what), (file), (line))
#else
#define sx_assert_(sx, what, file, line) (void)0
#endif
#define sx_xlock(sx) sx_xlock_((sx), LOCK_FILE, LOCK_LINE)
#define sx_xlock_sig(sx) sx_xlock_sig_((sx), LOCK_FILE, LOCK_LINE)
#define sx_xunlock(sx) sx_xunlock_((sx), LOCK_FILE, LOCK_LINE)
#define sx_slock(sx) sx_slock_((sx), LOCK_FILE, LOCK_LINE)
#define sx_slock_sig(sx) sx_slock_sig_((sx), LOCK_FILE, LOCK_LINE)
#define sx_sunlock(sx) sx_sunlock_((sx), LOCK_FILE, LOCK_LINE)
#define sx_assert(sx, what) sx_assert_((sx), (what), __FILE__, __LINE__)
/*
* Return a pointer to the owning thread if the lock is exclusively
* locked.
*/
#define sx_xholder(sx) \
((sx)->sx_lock & SX_LOCK_SHARED ? NULL : \
(struct thread *)SX_OWNER((sx)->sx_lock))
#define sx_xlocked(sx) \
(((sx)->sx_lock & ~(SX_LOCK_FLAGMASK & ~SX_LOCK_SHARED)) == \
(uintptr_t)curthread)
#define sx_unlock_(sx, file, line) do { \
if (sx_xlocked(sx)) \
sx_xunlock_(sx, file, line); \
else \
sx_sunlock_(sx, file, line); \
} while (0)
#define sx_unlock(sx) sx_unlock_((sx), LOCK_FILE, LOCK_LINE)
#define sx_sleep(chan, sx, pri, wmesg, timo) \
_sleep((chan), &(sx)->lock_object, (pri), (wmesg), \
tick_sbt * (timo), 0, C_HARDCLOCK)
/*
* Options passed to sx_init_flags().
*/
#define SX_DUPOK 0x01
#define SX_NOPROFILE 0x02
#define SX_NOWITNESS 0x04
#define SX_QUIET 0x08
#define SX_NOADAPTIVE 0x10
#define SX_RECURSE 0x20
#define SX_NEW 0x40
/*
* Options passed to sx_*lock_hard().
*/
#define SX_INTERRUPTIBLE 0x40
#if defined(INVARIANTS) || defined(INVARIANT_SUPPORT)
#define SA_LOCKED LA_LOCKED
#define SA_SLOCKED LA_SLOCKED
#define SA_XLOCKED LA_XLOCKED
#define SA_UNLOCKED LA_UNLOCKED
#define SA_RECURSED LA_RECURSED
#define SA_NOTRECURSED LA_NOTRECURSED
/* Backwards compatability. */
#define SX_LOCKED LA_LOCKED
#define SX_SLOCKED LA_SLOCKED
#define SX_XLOCKED LA_XLOCKED
#define SX_UNLOCKED LA_UNLOCKED
#define SX_RECURSED LA_RECURSED
#define SX_NOTRECURSED LA_NOTRECURSED
#endif
#endif /* _KERNEL */
#endif /* !_SYS_SX_H_ */
