static __inline
int
_lwkt_trytokref_spin(lwkt_tokref_t ref, thread_t td, long mode)
{
int spin;
if (_lwkt_trytokref(ref, td, mode)) {
#ifdef DEBUG_LOCKS_LATENCY
long j;
for (j = tokens_add_latency; j > 0; --j)
cpu_ccfence();
#endif
return TRUE;
}
for (spin = lwkt_token_spin; spin > 0; --spin) {
if (lwkt_token_delay)
tsc_delay(lwkt_token_delay);
else
cpu_pause();
if (_lwkt_trytokref(ref, td, mode)) {
#ifdef DEBUG_LOCKS_LATENCY
long j;
for (j = tokens_add_latency; j > 0; --j)
cpu_ccfence();
#endif
return TRUE;
}
}
return FALSE;
}
/*
* Attempt to acquire a spinlock, if we fail we must undo the
* gd->gd_spinlocks_wr/gd->gd_curthead->td_critcount predisposition.
*
* Returns 0 on success, EAGAIN on failure.
*/
int
_mtx_spinlock_try(mtx_t mtx)
{
globaldata_t gd = mycpu;
u_int lock;
u_int nlock;
int res = 0;
for (;;) {
lock = mtx->mtx_lock;
if (lock == 0) {
nlock = MTX_EXCLUSIVE | 1;
if (atomic_cmpset_int(&mtx->mtx_lock, 0, nlock)) {
mtx->mtx_owner = gd->gd_curthread;
break;
}
} else if ((lock & MTX_EXCLUSIVE) &&
mtx->mtx_owner == gd->gd_curthread) {
KKASSERT((lock & MTX_MASK) != MTX_MASK);
nlock = lock + 1;
if (atomic_cmpset_int(&mtx->mtx_lock, lock, nlock))
break;
} else {
--gd->gd_spinlocks_wr;
cpu_ccfence();
--gd->gd_curthread->td_critcount;
res = EAGAIN;
break;
}
cpu_pause();
++mtx_collision_count;
}
return res;
}
/*
* If the lock is held exclusively it must be owned by the caller. If the
* lock is already a shared lock this operation is a NOP. A panic will
* occur if the lock is not held either shared or exclusive.
*
* The exclusive count is converted to a shared count.
*/
void
_mtx_downgrade(mtx_t *mtx)
{
u_int lock;
u_int nlock;
for (;;) {
lock = mtx->mtx_lock;
cpu_ccfence();
/*
* NOP if already shared.
*/
if ((lock & MTX_EXCLUSIVE) == 0) {
KKASSERT((lock & MTX_MASK) > 0);
break;
}
/*
* Transfer count to shared. Any additional pending shared
* waiters must be woken up.
*/
if (lock & MTX_SHWANTED) {
if (mtx_chain_link_sh(mtx, lock))
break;
/* retry */
} else {
nlock = lock & ~MTX_EXCLUSIVE;
if (atomic_cmpset_int(&mtx->mtx_lock, lock, nlock))
break;
/* retry */
}
cpu_pause();
}
}
/*
* Print out information about state of a lock. Used by VOP_PRINT
* routines to display status about contained locks.
*/
void
lockmgr_printinfo(struct lock *lkp)
{
struct thread *td = lkp->lk_lockholder;
struct proc *p;
int count;
count = lkp->lk_count;
cpu_ccfence();
if (td && td != LK_KERNTHREAD && td != LK_NOTHREAD)
p = td->td_proc;
else
p = NULL;
if (count & LKC_EXCL) {
kprintf(" lock type %s: EXCLUS (count %08x) by td %p pid %d",
lkp->lk_wmesg, count, td,
p ? p->p_pid : -99);
} else if (count & LKC_MASK) {
kprintf(" lock type %s: SHARED (count %08x)",
lkp->lk_wmesg, count);
} else {
kprintf(" lock type %s: NOTHELD", lkp->lk_wmesg);
}
if (count & (LKC_EXREQ|LKC_SHREQ))
kprintf(" with waiters\n");
else
kprintf("\n");
}
/*
* Upgrade a shared lock to an exclusive lock. The upgrade will fail if
* the shared lock has a count other then 1. Optimize the most likely case
* but note that a single cmpset can fail due to WANTED races.
*
* If the lock is held exclusively it must be owned by the caller and
* this function will simply return without doing anything. A panic will
* occur if the lock is held exclusively by someone other then the caller.
*
* Returns 0 on success, EDEADLK on failure.
*/
int
_mtx_upgrade_try(mtx_t *mtx)
{
u_int lock;
u_int nlock;
int error = 0;
for (;;) {
lock = mtx->mtx_lock;
cpu_ccfence();
if ((lock & ~MTX_EXWANTED) == 1) {
nlock = lock | MTX_EXCLUSIVE;
if (atomic_cmpset_int(&mtx->mtx_lock, lock, nlock)) {
mtx->mtx_owner = curthread;
break;
}
} else if (lock & MTX_EXCLUSIVE) {
KKASSERT(mtx->mtx_owner == curthread);
break;
} else {
error = EDEADLK;
break;
}
cpu_pause();
}
return (error);
}
/*
* Add a (pmap, va) pair to the invalidation list and protect access
* as appropriate.
*
* CPUMASK_LOCK is used to interlock thread switchins, otherwise another
* cpu can switch in a pmap that we are unaware of and interfere with our
* pte operation.
*/
void
pmap_inval_interlock(pmap_inval_info_t info, pmap_t pmap, vm_offset_t va)
{
cpumask_t oactive;
#ifdef SMP
cpumask_t nactive;
DEBUG_PUSH_INFO("pmap_inval_interlock");
for (;;) {
oactive = pmap->pm_active;
cpu_ccfence();
nactive = oactive | CPUMASK_LOCK;
if ((oactive & CPUMASK_LOCK) == 0 &&
atomic_cmpset_cpumask(&pmap->pm_active, oactive, nactive)) {
break;
}
lwkt_process_ipiq();
cpu_pause();
}
DEBUG_POP_INFO();
#else
oactive = pmap->pm_active & ~CPUMASK_LOCK;
#endif
KKASSERT((info->pir_flags & PIRF_CPUSYNC) == 0);
info->pir_va = va;
info->pir_flags = PIRF_CPUSYNC;
lwkt_cpusync_init(&info->pir_cpusync, oactive, pmap_inval_callback, info);
lwkt_cpusync_interlock(&info->pir_cpusync);
}
/*
* Drop an inode reference, freeing the inode when the last reference goes
* away.
*/
void
hammer2_inode_drop(hammer2_inode_t *ip)
{
hammer2_pfs_t *pmp;
u_int refs;
while (ip) {
if (hammer2_debug & 0x80000) {
kprintf("INODE-1 %p (%d->%d)\n",
ip, ip->refs, ip->refs - 1);
print_backtrace(8);
}
refs = ip->refs;
cpu_ccfence();
if (refs == 1) {
/*
* Transition to zero, must interlock with
* the inode inumber lookup tree (if applicable).
* It should not be possible for anyone to race
* the transition to 0.
*/
pmp = ip->pmp;
KKASSERT(pmp);
hammer2_spin_ex(&pmp->inum_spin);
if (atomic_cmpset_int(&ip->refs, 1, 0)) {
KKASSERT(hammer2_mtx_refs(&ip->lock) == 0);
if (ip->flags & HAMMER2_INODE_ONRBTREE) {
atomic_clear_int(&ip->flags,
HAMMER2_INODE_ONRBTREE);
RB_REMOVE(hammer2_inode_tree,
&pmp->inum_tree, ip);
--pmp->inum_count;
}
hammer2_spin_unex(&pmp->inum_spin);
ip->pmp = NULL;
/*
* Cleaning out ip->cluster isn't entirely
* trivial.
*/
hammer2_inode_repoint(ip, NULL, NULL);
kfree(ip, pmp->minode);
atomic_add_long(&pmp->inmem_inodes, -1);
ip = NULL; /* will terminate loop */
} else {
hammer2_spin_unex(&ip->pmp->inum_spin);
}
} else {
/*
* Non zero transition
*/
if (atomic_cmpset_int(&ip->refs, refs, refs - 1))
break;
}
}
}
/*
* Similar to gettoken but we acquire a shared token instead of an exclusive
* token.
*/
void
lwkt_gettoken_shared(lwkt_token_t tok)
{
thread_t td = curthread;
lwkt_tokref_t ref;
ref = td->td_toks_stop;
KKASSERT(ref < &td->td_toks_end);
++td->td_toks_stop;
cpu_ccfence();
_lwkt_tokref_init(ref, tok, td, TOK_EXCLREQ);
#ifdef DEBUG_LOCKS
/*
* Taking a pool token in shared mode is a bad idea; other
* addresses deeper in the call stack may hash to the same pool
* token and you may end up with an exclusive-shared livelock.
* Warn in this condition.
*/
if ((tok >= &pool_tokens[0].token) &&
(tok < &pool_tokens[LWKT_NUM_POOL_TOKENS].token))
kprintf("Warning! Taking pool token %p in shared mode\n", tok);
#endif
if (_lwkt_trytokref_spin(ref, td, TOK_EXCLREQ))
return;
/*
* Give up running if we can't acquire the token right now.
*
* Since the tokref is already active the scheduler now
* takes care of acquisition, so we need only call
* lwkt_switch().
*
* Since we failed this was not a recursive token so upon
* return tr_tok->t_ref should be assigned to this specific
* ref.
*/
td->td_wmesg = tok->t_desc;
++tok->t_collisions;
logtoken(fail, ref);
td->td_toks_have = td->td_toks_stop - 1;
if (tokens_debug_output > 0) {
--tokens_debug_output;
spin_lock(&tok_debug_spin);
kprintf("Shar Token thread %p %s %s\n",
td, tok->t_desc, td->td_comm);
print_backtrace(6);
kprintf("\n");
spin_unlock(&tok_debug_spin);
}
lwkt_switch();
logtoken(succ, ref);
}
/*
* Get a serializing token. This routine can block.
*/
void
lwkt_gettoken(lwkt_token_t tok)
{
thread_t td = curthread;
lwkt_tokref_t ref;
ref = td->td_toks_stop;
KKASSERT(ref < &td->td_toks_end);
++td->td_toks_stop;
cpu_ccfence();
_lwkt_tokref_init(ref, tok, td, TOK_EXCLUSIVE|TOK_EXCLREQ);
#ifdef DEBUG_LOCKS
/*
* Taking an exclusive token after holding it shared will
* livelock. Scan for that case and assert.
*/
lwkt_tokref_t tk;
int found = 0;
for (tk = &td->td_toks_base; tk < ref; tk++) {
if (tk->tr_tok != tok)
continue;
found++;
if (tk->tr_count & TOK_EXCLUSIVE)
goto good;
}
/* We found only shared instances of this token if found >0 here */
KASSERT((found == 0), ("Token %p s/x livelock", tok));
good:
#endif
if (_lwkt_trytokref_spin(ref, td, TOK_EXCLUSIVE|TOK_EXCLREQ))
return;
/*
* Give up running if we can't acquire the token right now.
*
* Since the tokref is already active the scheduler now
* takes care of acquisition, so we need only call
* lwkt_switch().
*
* Since we failed this was not a recursive token so upon
* return tr_tok->t_ref should be assigned to this specific
* ref.
*/
td->td_wmesg = tok->t_desc;
++tok->t_collisions;
logtoken(fail, ref);
td->td_toks_have = td->td_toks_stop - 1;
lwkt_switch();
logtoken(succ, ref);
KKASSERT(tok->t_ref == ref);
}
static
void
timersig(int nada, siginfo_t *info, void *ctxp)
{
globaldata_t gd = mycpu;
thread_t td = gd->gd_curthread;
int save;
save = errno;
if (td->td_critcount == 0) {
crit_enter_raw(td);
++gd->gd_intr_nesting_level;
cpu_ccfence();
vktimer_intr(NULL);
cpu_ccfence();
--gd->gd_intr_nesting_level;
crit_exit_raw(td);
} else {
need_timer();
}
errno = save;
}
/*
* Return non-zero if the caller owns the lock shared or exclusive.
* We can only guess re: shared locks.
*/
int
lockowned(struct lock *lkp)
{
thread_t td = curthread;
int count;
count = lkp->lk_count;
cpu_ccfence();
if (count & LKC_EXCL)
return(lkp->lk_lockholder == td);
else
return((count & LKC_MASK) != 0);
}
/*
* Simple version without a timeout which can also return EINTR
*/
int
_thr_umtx_wait_intr(volatile umtx_t *mtx, int exp)
{
int ret = 0;
int errval;
cpu_ccfence();
for (;;) {
if (*mtx != exp)
return (0);
errval = _umtx_sleep_err(mtx, exp, 10000000);
if (errval == 0)
break;
if (errval == EBUSY)
break;
if (errval == EINTR) {
ret = errval;
break;
}
cpu_ccfence();
}
return (ret);
}
/*
* Attempt to acquire a token, return TRUE on success, FALSE on failure.
*
* We setup the tokref in case we actually get the token (if we switch later
* it becomes mandatory so we set TOK_EXCLREQ), but we call trytokref without
* TOK_EXCLREQ in case we fail.
*/
int
lwkt_trytoken(lwkt_token_t tok)
{
thread_t td = curthread;
lwkt_tokref_t ref;
ref = td->td_toks_stop;
KKASSERT(ref < &td->td_toks_end);
++td->td_toks_stop;
cpu_ccfence();
_lwkt_tokref_init(ref, tok, td, TOK_EXCLUSIVE|TOK_EXCLREQ);
if (_lwkt_trytokref(ref, td, TOK_EXCLUSIVE))
return TRUE;
/*
* Failed, unpend the request
*/
cpu_ccfence();
--td->td_toks_stop;
++tok->t_collisions;
return FALSE;
}
/*
* This function is used to acquire a contested lock.
*
* A *mtx value of 1 indicates locked normally.
* A *mtx value of 2 indicates locked and contested.
*/
int
__thr_umtx_lock(volatile umtx_t *mtx, int id, int timo)
{
int v;
int errval;
int ret = 0;
int retry = 4;
v = *mtx;
cpu_ccfence();
id &= 0x3FFFFFFF;
for (;;) {
cpu_pause();
if (v == 0) {
if (atomic_fcmpset_int(mtx, &v, id))
break;
continue;
}
if (--retry) {
sched_yield();
v = *mtx;
continue;
}
/*
* Set the waiting bit. If the fcmpset fails v is loaded
* with the current content of the mutex, and if the waiting
* bit is already set, we can also sleep.
*/
if (atomic_fcmpset_int(mtx, &v, v|0x40000000) ||
(v & 0x40000000)) {
if (timo == 0) {
_umtx_sleep_err(mtx, v|0x40000000, timo);
} else if ((errval = _umtx_sleep_err(mtx, v|0x40000000, timo)) > 0) {
if (errval == EAGAIN) {
if (atomic_cmpset_acq_int(mtx, 0, id))
ret = 0;
else
ret = ETIMEDOUT;
break;
}
}
}
retry = 4;
}
return (ret);
}
/*
* Release a ref on an active or inactive vnode.
*
* Caller has no other requirements.
*
* If VREF_FINALIZE is set this will deactivate the vnode on the 1->0
* transition, otherwise we leave the vnode in the active list and
* do a lockless transition to 0, which is very important for the
* critical path.
*
* (vrele() is not called when a vnode is being destroyed w/kfree)
*/
void
vrele(struct vnode *vp)
{
for (;;) {
int count = vp->v_refcnt;
cpu_ccfence();
KKASSERT((count & VREF_MASK) > 0);
KKASSERT(vp->v_state == VS_ACTIVE ||
vp->v_state == VS_INACTIVE);
/*
* 2+ case
*/
if ((count & VREF_MASK) > 1) {
if (atomic_cmpset_int(&vp->v_refcnt, count, count - 1))
break;
continue;
}
/*
* 1->0 transition case must handle possible finalization.
* When finalizing we transition 1->0x40000000. Note that
* cachedvnodes is only adjusted on transitions to ->0.
*
* WARNING! VREF_TERMINATE can be cleared at any point
* when the refcnt is non-zero (by vget()) and
* the vnode has not been reclaimed. Thus
* transitions out of VREF_TERMINATE do not have
* to mess with cachedvnodes.
*/
if (count & VREF_FINALIZE) {
vx_lock(vp);
if (atomic_cmpset_int(&vp->v_refcnt,
count, VREF_TERMINATE)) {
vnode_terminate(vp);
break;
}
vx_unlock(vp);
} else {
if (atomic_cmpset_int(&vp->v_refcnt, count, 0)) {
atomic_add_int(&mycpu->gd_cachedvnodes, 1);
break;
}
}
/* retry */
}
}
/*
* Determine the status of a lock.
*/
int
lockstatus(struct lock *lkp, struct thread *td)
{
int lock_type = 0;
int count;
count = lkp->lk_count;
cpu_ccfence();
if (count & LKC_EXCL) {
if (td == NULL || lkp->lk_lockholder == td)
lock_type = LK_EXCLUSIVE;
else
lock_type = LK_EXCLOTHER;
} else if (count & LKC_MASK) {
lock_type = LK_SHARED;
}
return (lock_type);
}
/*
* Clear ARMED after finishing adjustments to the callout, potentially
* allowing other cpus to take over. We can only do this if the IPI mask
* is 0.
*/
static __inline
int
callout_maybe_clear_armed(struct callout *c)
{
int flags;
int nflags;
for (;;) {
flags = c->c_flags;
cpu_ccfence();
if (flags & (CALLOUT_PENDING | CALLOUT_IPI_MASK))
break;
nflags = flags & ~CALLOUT_ARMED;
if (atomic_cmpset_int(&c->c_flags, flags, nflags))
break;
cpu_pause();
/* retry */
}
return flags;
}
/*
* Clear PENDING and, if possible, also clear ARMED and WAITING. Returns
* the flags prior to the clear, atomically (used to check for WAITING).
*
* Clearing the cpu association (ARMED) can significantly improve the
* performance of the next callout_reset*() call.
*/
static __inline
int
callout_unpend_disarm(struct callout *c)
{
int flags;
int nflags;
for (;;) {
flags = c->c_flags;
cpu_ccfence();
nflags = flags & ~(CALLOUT_PENDING | CALLOUT_WAITING);
if ((flags & CALLOUT_IPI_MASK) == 0)
nflags &= ~CALLOUT_ARMED;
if (atomic_cmpset_int(&c->c_flags, flags, nflags)) {
break;
}
cpu_pause();
/* retry */
}
return flags;
}
/*
* Release a token that we hold.
*/
static __inline
void
_lwkt_reltokref(lwkt_tokref_t ref, thread_t td)
{
lwkt_token_t tok;
long count;
tok = ref->tr_tok;
for (;;) {
count = tok->t_count;
cpu_ccfence();
if (tok->t_ref == ref) {
/*
* We are an exclusive holder. We must clear tr_ref
* before we clear the TOK_EXCLUSIVE bit. If we are
* unable to clear the bit we must restore
* tok->t_ref.
*/
KKASSERT(count & TOK_EXCLUSIVE);
tok->t_ref = NULL;
if (atomic_cmpset_long(&tok->t_count, count,
count & ~TOK_EXCLUSIVE)) {
return;
}
tok->t_ref = ref;
/* retry */
} else {
/*
* We are a shared holder
*/
KKASSERT(count & TOK_COUNTMASK);
if (atomic_cmpset_long(&tok->t_count, count,
count - TOK_INCR)) {
return;
}
/* retry */
}
/* retry */
}
}
/*
* Helper function to wait for a reference count to become zero.
* We set REFCNTF_WAITING and sleep if the reference count is not zero.
*
* In the case where REFCNTF_WAITING is already set the atomic op validates
* that it is still set after the tsleep_interlock() call.
*
* Users of this waiting API must use refcount_release_wakeup() to release
* refs instead of refcount_release(). refcount_release() will not wake
* up waiters.
*/
void
_refcount_wait(volatile u_int *countp, const char *wstr)
{
u_int n;
int base_ticks = ticks;
for (;;) {
n = *countp;
cpu_ccfence();
if (n == 0)
break;
if ((int)(ticks - base_ticks) >= hz*60 - 1) {
kprintf("warning: refcount_wait %s: long wait\n",
wstr);
base_ticks = ticks;
}
KKASSERT(n != REFCNTF_WAITING); /* impossible state */
tsleep_interlock(countp, 0);
if (atomic_cmpset_int(countp, n, n | REFCNTF_WAITING))
tsleep(countp, PINTERLOCKED, wstr, hz*10);
}
}
/*
* This helper function implements the release-with-wakeup API. It is
* executed for the non-trivial case or if the atomic op races.
*
* On the i->0 transition is REFCNTF_WAITING is set it will be cleared
* and a wakeup() will be issued.
*
* On any other transition we simply subtract (i) and leave the
* REFCNTF_WAITING flag intact.
*
* This function returns TRUE(1) on the last release, whether a wakeup
* occured or not, and FALSE(0) otherwise.
*
* NOTE! (i) cannot be 0
*/
int
_refcount_release_wakeup_n(volatile u_int *countp, u_int i)
{
u_int n;
for (;;) {
n = *countp;
cpu_ccfence();
if (n == (REFCNTF_WAITING | i)) {
if (atomic_cmpset_int(countp, n, 0)) {
wakeup(countp);
n = i;
break;
}
} else {
KKASSERT(n != REFCNTF_WAITING); /* illegal state */
if (atomic_cmpset_int(countp, n, n - i))
break;
}
}
return (n == i);
}
static void
pmap_inval_init(pmap_t pmap)
{
cpulock_t olock;
cpulock_t nlock;
crit_enter_id("inval");
if (pmap != &kernel_pmap) {
for (;;) {
olock = pmap->pm_active_lock;
cpu_ccfence();
nlock = olock | CPULOCK_EXCL;
if (olock != nlock &&
atomic_cmpset_int(&pmap->pm_active_lock,
olock, nlock)) {
break;
}
lwkt_process_ipiq();
cpu_pause();
}
atomic_add_acq_long(&pmap->pm_invgen, 1);
}
}
/*
* Unlock a lock. The caller must hold the lock either shared or exclusive.
*
* On the last release we handle any pending chains.
*/
void
_mtx_unlock(mtx_t *mtx)
{
thread_t td __debugvar = curthread;
u_int lock;
u_int nlock;
for (;;) {
lock = mtx->mtx_lock;
cpu_ccfence();
switch(lock) {
case MTX_EXCLUSIVE | 1:
/*
* Last release, exclusive lock.
* No exclusive or shared requests pending.
*/
KKASSERT(mtx->mtx_owner == td ||
mtx->mtx_owner == NULL);
mtx->mtx_owner = NULL;
nlock = 0;
if (atomic_cmpset_int(&mtx->mtx_lock, lock, nlock))
goto done;
break;
case MTX_EXCLUSIVE | MTX_EXWANTED | 1:
case MTX_EXCLUSIVE | MTX_EXWANTED | MTX_SHWANTED | 1:
/*
* Last release, exclusive lock.
* Exclusive requests pending.
* Exclusive requests have priority over shared reqs.
*/
KKASSERT(mtx->mtx_owner == td ||
mtx->mtx_owner == NULL);
mtx->mtx_owner = NULL;
if (mtx_chain_link_ex(mtx, lock))
goto done;
break;
case MTX_EXCLUSIVE | MTX_SHWANTED | 1:
/*
* Last release, exclusive lock.
*
* Shared requests are pending. Transfer our count (1)
* to the first shared request, wakeup all shared reqs.
*/
KKASSERT(mtx->mtx_owner == td ||
mtx->mtx_owner == NULL);
mtx->mtx_owner = NULL;
if (mtx_chain_link_sh(mtx, lock))
goto done;
break;
case 1:
/*
* Last release, shared lock.
* No exclusive or shared requests pending.
*/
nlock = 0;
if (atomic_cmpset_int(&mtx->mtx_lock, lock, nlock))
goto done;
break;
case MTX_EXWANTED | 1:
case MTX_EXWANTED | MTX_SHWANTED | 1:
/*
* Last release, shared lock.
*
* Exclusive requests are pending. Upgrade this
* final shared lock to exclusive and transfer our
* count (1) to the next exclusive request.
*
* Exclusive requests have priority over shared reqs.
*/
if (mtx_chain_link_ex(mtx, lock))
goto done;
break;
case MTX_SHWANTED | 1:
/*
* Last release, shared lock.
* Shared requests pending.
*/
if (mtx_chain_link_sh(mtx, lock))
goto done;
break;
default:
/*
* We have to loop if this is the last release but
* someone is fiddling with LINKSPIN.
*/
if ((lock & MTX_MASK) == 1) {
KKASSERT(lock & MTX_LINKSPIN);
break;
}
/*
* Not the last release (shared or exclusive)
*/
nlock = lock - 1;
KKASSERT((nlock & MTX_MASK) != MTX_MASK);
if (atomic_cmpset_int(&mtx->mtx_lock, lock, nlock))
goto done;
break;
}
/* loop try again */
cpu_pause();
}
done:
;
}
/*
* Regular umtx wait that cannot return EINTR
*/
int
_thr_umtx_wait(volatile umtx_t *mtx, int exp, const struct timespec *timeout,
int clockid)
{
struct timespec ts, ts2, ts3;
int timo, errval, ret = 0;
cpu_ccfence();
if (*mtx != exp)
return (0);
if (timeout == NULL) {
/*
* NOTE: If no timeout, EINTR cannot be returned. Ignore
* EINTR.
*/
while ((errval = _umtx_sleep_err(mtx, exp, 10000000)) > 0) {
if (errval == EBUSY)
break;
#if 0
if (errval == ETIMEDOUT || errval == EWOULDBLOCK) {
if (*mtx != exp) {
fprintf(stderr,
"thr_umtx_wait: FAULT VALUE CHANGE "
"%d -> %d oncond %p\n",
exp, *mtx, mtx);
}
}
#endif
if (*mtx != exp)
return(0);
}
return (ret);
}
/*
* Timed waits can return EINTR
*/
if ((timeout->tv_sec < 0) ||
(timeout->tv_sec == 0 && timeout->tv_nsec <= 0))
return (ETIMEDOUT);
clock_gettime(clockid, &ts);
TIMESPEC_ADD(&ts, &ts, timeout);
ts2 = *timeout;
for (;;) {
if (ts2.tv_nsec) {
timo = (int)(ts2.tv_nsec / 1000);
if (timo == 0)
timo = 1;
} else {
timo = 1000000;
}
if ((errval = _umtx_sleep_err(mtx, exp, timo)) > 0) {
if (errval == EBUSY) {
ret = 0;
break;
}
if (errval == EINTR) {
ret = EINTR;
break;
}
}
clock_gettime(clockid, &ts3);
TIMESPEC_SUB(&ts2, &ts, &ts3);
if (ts2.tv_sec < 0 || (ts2.tv_sec == 0 && ts2.tv_nsec <= 0)) {
ret = ETIMEDOUT;
break;
}
}
return (ret);
}
/*
* Stop a running timer and ensure that any running callout completes before
* returning. If the timer is running on another cpu this function may block
* to interlock against the callout. If the callout is currently executing
* or blocked in another thread this function may also block to interlock
* against the callout.
*
* The caller must be careful to avoid deadlocks, either by using
* callout_init_lk() (which uses the lockmgr lock cancelation feature),
* by using tokens and dealing with breaks in the serialization, or using
* the lockmgr lock cancelation feature yourself in the callout callback
* function.
*
* callout_stop() returns non-zero if the callout was pending.
*/
static int
_callout_stop(struct callout *c, int issync)
{
globaldata_t gd = mycpu;
globaldata_t tgd;
softclock_pcpu_t sc;
int flags;
int nflags;
int rc;
int cpuid;
#ifdef INVARIANTS
if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
callout_init(c);
kprintf(
"callout_stop(%p) from %p: callout was not initialized\n",
c, ((int **)&c)[-1]);
print_backtrace(-1);
}
#endif
crit_enter_gd(gd);
/*
* Fast path operations:
*
* If ARMED and owned by our cpu, or not ARMED, and other simple
* conditions are met, we can just clear ACTIVE and EXECUTED
* and we are done.
*/
for (;;) {
flags = c->c_flags;
cpu_ccfence();
cpuid = CALLOUT_FLAGS_TO_CPU(flags);
/*
* Can't handle an armed callout in the fast path if it is
* not on the current cpu. We must atomically increment the
* IPI count for the IPI we intend to send and break out of
* the fast path to enter the slow path.
*/
if (flags & CALLOUT_ARMED) {
if (gd->gd_cpuid != cpuid) {
nflags = flags + 1;
if (atomic_cmpset_int(&c->c_flags,
flags, nflags)) {
/* break to slow path */
break;
}
continue; /* retry */
}
} else {
cpuid = gd->gd_cpuid;
KKASSERT((flags & CALLOUT_IPI_MASK) == 0);
KKASSERT((flags & CALLOUT_PENDING) == 0);
}
/*
* Process pending IPIs and retry (only if not called from
* an IPI).
*/
if (flags & CALLOUT_IPI_MASK) {
lwkt_process_ipiq();
continue; /* retry */
}
/*
* Transition to the stopped state, recover the EXECUTED
* status. If pending we cannot clear ARMED until after
* we have removed (c) from the callwheel.
*
* NOTE: The callout might already not be armed but in this
* case it should also not be pending.
*/
nflags = flags & ~(CALLOUT_ACTIVE |
CALLOUT_EXECUTED |
CALLOUT_WAITING |
CALLOUT_PENDING);
/* NOTE: IPI_MASK already tested */
if ((flags & CALLOUT_PENDING) == 0)
nflags &= ~CALLOUT_ARMED;
if (atomic_cmpset_int(&c->c_flags, flags, nflags)) {
/*
* Can only remove from callwheel if currently
* pending.
*/
if (flags & CALLOUT_PENDING) {
sc = &softclock_pcpu_ary[gd->gd_cpuid];
if (sc->next == c)
sc->next = TAILQ_NEXT(c, c_links.tqe);
TAILQ_REMOVE(
&sc->callwheel[c->c_time & cwheelmask],
c,
c_links.tqe);
c->c_func = NULL;
/*
* NOTE: Can't clear ARMED until we have
* physically removed (c) from the
* callwheel.
*
* NOTE: WAITING bit race exists when doing
* unconditional bit clears.
*/
callout_maybe_clear_armed(c);
if (c->c_flags & CALLOUT_WAITING)
flags |= CALLOUT_WAITING;
}
/*
* ARMED has been cleared at this point and (c)
* might now be stale. Only good for wakeup()s.
*/
if (flags & CALLOUT_WAITING)
wakeup(c);
goto skip_slow;
}
/* retry */
}
/*
* Slow path (and not called via an IPI).
*
* When ARMED to a different cpu the stop must be processed on that
* cpu. Issue the IPI and wait for completion. We have already
* incremented the IPI count.
*/
tgd = globaldata_find(cpuid);
lwkt_send_ipiq3(tgd, callout_stop_ipi, c, issync);
for (;;) {
int flags;
int nflags;
flags = c->c_flags;
cpu_ccfence();
if ((flags & CALLOUT_IPI_MASK) == 0) /* fast path */
break;
nflags = flags | CALLOUT_WAITING;
tsleep_interlock(c, 0);
if (atomic_cmpset_int(&c->c_flags, flags, nflags)) {
tsleep(c, PINTERLOCKED, "cstp1", 0);
}
}
skip_slow:
/*
* If (issync) we must also wait for any in-progress callbacks to
* complete, unless the stop is being executed from the callback
* itself. The EXECUTED flag is set prior to the callback
* being made so our existing flags status already has it.
*
* If auto-lock mode is being used, this is where we cancel any
* blocked lock that is potentially preventing the target cpu
* from completing the callback.
*/
while (issync) {
intptr_t *runp;
intptr_t runco;
sc = &softclock_pcpu_ary[cpuid];
if (gd->gd_curthread == &sc->thread) /* stop from cb */
break;
runp = &sc->running;
runco = *runp;
cpu_ccfence();
if ((runco & ~(intptr_t)1) != (intptr_t)c)
break;
if (c->c_flags & CALLOUT_AUTOLOCK)
lockmgr(c->c_lk, LK_CANCEL_BEG);
tsleep_interlock(c, 0);
if (atomic_cmpset_long(runp, runco, runco | 1))
tsleep(c, PINTERLOCKED, "cstp3", 0);
if (c->c_flags & CALLOUT_AUTOLOCK)
lockmgr(c->c_lk, LK_CANCEL_END);
}
crit_exit_gd(gd);
rc = (flags & CALLOUT_EXECUTED) != 0;
return rc;
}
/*
* Drop an inode reference, freeing the inode when the last reference goes
* away.
*/
void
hammer2_inode_drop(hammer2_inode_t *ip)
{
hammer2_pfsmount_t *pmp;
hammer2_inode_t *pip;
u_int refs;
while (ip) {
refs = ip->refs;
cpu_ccfence();
if (refs == 1) {
/*
* Transition to zero, must interlock with
* the inode inumber lookup tree (if applicable).
*
* NOTE: The super-root inode has no pmp.
*/
pmp = ip->pmp;
if (pmp)
spin_lock(&pmp->inum_spin);
if (atomic_cmpset_int(&ip->refs, 1, 0)) {
KKASSERT(ip->topo_cst.count == 0);
if (ip->flags & HAMMER2_INODE_ONRBTREE) {
atomic_clear_int(&ip->flags,
HAMMER2_INODE_ONRBTREE);
RB_REMOVE(hammer2_inode_tree,
&pmp->inum_tree, ip);
}
if (pmp)
spin_unlock(&pmp->inum_spin);
pip = ip->pip;
ip->pip = NULL;
ip->pmp = NULL;
/*
* Cleaning out ip->chain isn't entirely
* trivial.
*/
hammer2_inode_repoint(ip, NULL, NULL);
/*
* We have to drop pip (if non-NULL) to
* dispose of our implied reference from
* ip->pip. We can simply loop on it.
*/
if (pmp) {
KKASSERT((ip->flags &
HAMMER2_INODE_SROOT) == 0);
kfree(ip, pmp->minode);
atomic_add_long(&pmp->inmem_inodes, -1);
} else {
KKASSERT(ip->flags &
HAMMER2_INODE_SROOT);
kfree(ip, M_HAMMER2);
}
ip = pip;
/* continue with pip (can be NULL) */
} else {
if (pmp)
spin_unlock(&ip->pmp->inum_spin);
}
} else {
/*
* Non zero transition
*/
if (atomic_cmpset_int(&ip->refs, refs, refs - 1))
break;
}
}
}
static
void
callout_stop_ipi(void *arg, int issync, struct intrframe *frame)
{
globaldata_t gd = mycpu;
struct callout *c = arg;
softclock_pcpu_t sc;
/*
* Only the fast path can run in an IPI. Chain the stop request
* if we are racing cpu changes.
*/
for (;;) {
globaldata_t tgd;
int flags;
int nflags;
int cpuid;
flags = c->c_flags;
cpu_ccfence();
/*
* Can't handle an armed callout in the fast path if it is
* not on the current cpu. We must atomically increment the
* IPI count and break out of the fast path.
*
* If called from an IPI we chain the IPI instead.
*/
if (flags & CALLOUT_ARMED) {
cpuid = CALLOUT_FLAGS_TO_CPU(flags);
if (gd->gd_cpuid != cpuid) {
tgd = globaldata_find(cpuid);
lwkt_send_ipiq3(tgd, callout_stop_ipi,
c, issync);
break;
}
}
/*
* NOTE: As an IPI ourselves we cannot wait for other IPIs
* to complete, and we are being executed in-order.
*/
/*
* Transition to the stopped state, recover the EXECUTED
* status, decrement the IPI count. If pending we cannot
* clear ARMED until after we have removed (c) from the
* callwheel, and only if there are no more IPIs pending.
*/
nflags = flags & ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
nflags = nflags - 1; /* dec ipi count */
if ((flags & (CALLOUT_IPI_MASK | CALLOUT_PENDING)) == 1)
nflags &= ~CALLOUT_ARMED;
if ((flags & CALLOUT_IPI_MASK) == 1)
nflags &= ~(CALLOUT_WAITING | CALLOUT_EXECUTED);
if (atomic_cmpset_int(&c->c_flags, flags, nflags)) {
/*
* Can only remove from callwheel if currently
* pending.
*/
if (flags & CALLOUT_PENDING) {
sc = &softclock_pcpu_ary[gd->gd_cpuid];
if (sc->next == c)
sc->next = TAILQ_NEXT(c, c_links.tqe);
TAILQ_REMOVE(
&sc->callwheel[c->c_time & cwheelmask],
c,
c_links.tqe);
c->c_func = NULL;
/*
* NOTE: Can't clear ARMED until we have
* physically removed (c) from the
* callwheel.
*
* NOTE: WAITING bit race exists when doing
* unconditional bit clears.
*/
callout_maybe_clear_armed(c);
if (c->c_flags & CALLOUT_WAITING)
flags |= CALLOUT_WAITING;
}
/*
* ARMED has been cleared at this point and (c)
* might now be stale. Only good for wakeup()s.
*/
if (flags & CALLOUT_WAITING)
wakeup(c);
break;
}
/* retry */
}
}
/*
* Stop a running timer. WARNING! If called on a cpu other then the one
* the callout was started on this function will liveloop on its IPI to
* the target cpu to process the request. It is possible for the callout
* to execute in that case.
*
* WARNING! This function may be called from any cpu but the caller must
* serialize callout_stop() and callout_reset() calls on the passed
* structure regardless of cpu.
*
* WARNING! This routine may be called from an IPI
*
* WARNING! This function can return while it's c_func is still running
* in the callout thread, a secondary check may be needed.
* Use callout_stop_sync() to wait for any callout function to
* complete before returning, being sure that no deadlock is
* possible if you do.
*/
int
callout_stop(struct callout *c)
{
globaldata_t gd = mycpu;
globaldata_t tgd;
softclock_pcpu_t sc;
#ifdef INVARIANTS
if ((c->c_flags & CALLOUT_DID_INIT) == 0) {
callout_init(c);
kprintf(
"callout_stop(%p) from %p: callout was not initialized\n",
c, ((int **)&c)[-1]);
print_backtrace(-1);
}
#endif
crit_enter_gd(gd);
/*
* Don't attempt to delete a callout that's not on the queue. The
* callout may not have a cpu assigned to it. Callers do not have
* to be on the issuing cpu but must still serialize access to the
* callout structure.
*
* We are not cpu-localized here and cannot safely modify the
* flags field in the callout structure. Note that most of the
* time CALLOUT_ACTIVE will be 0 if CALLOUT_PENDING is also 0.
*
* If we race another cpu's dispatch of this callout it is possible
* for CALLOUT_ACTIVE to be set with CALLOUT_PENDING unset. This
* will cause us to fall through and synchronize with the other
* cpu.
*/
if ((c->c_flags & CALLOUT_PENDING) == 0) {
if ((c->c_flags & CALLOUT_ACTIVE) == 0) {
crit_exit_gd(gd);
return (0);
}
if (c->c_gd == NULL || c->c_gd == gd) {
c->c_flags &= ~CALLOUT_ACTIVE;
crit_exit_gd(gd);
return (0);
}
}
if ((tgd = c->c_gd) != gd) {
/*
* If the callout is owned by a different CPU we have to
* execute the function synchronously on the target cpu.
*/
int seq;
cpu_ccfence(); /* don't let tgd alias c_gd */
seq = lwkt_send_ipiq(tgd, (void *)callout_stop, c);
lwkt_wait_ipiq(tgd, seq);
} else {
/*
* If the callout is owned by the same CPU we can
* process it directly, but if we are racing our helper
* thread (sc->next), we have to adjust sc->next. The
* race is interlocked by a critical section.
*/
sc = &softclock_pcpu_ary[gd->gd_cpuid];
c->c_flags &= ~(CALLOUT_ACTIVE | CALLOUT_PENDING);
if (sc->next == c)
sc->next = TAILQ_NEXT(c, c_links.tqe);
TAILQ_REMOVE(&sc->callwheel[c->c_time & callwheelmask],
c, c_links.tqe);
c->c_func = NULL;
}
crit_exit_gd(gd);
return (1);
}
/*
* Exclusive-lock a mutex, block until acquired unless link is async.
* Recursion is allowed.
*
* Returns 0 on success, the tsleep() return code on failure, EINPROGRESS
* if async. If immediately successful an async exclusive lock will return 0
* and not issue the async callback or link the link structure. The caller
* must handle this case (typically this is an optimal code path).
*
* A tsleep() error can only be returned if PCATCH is specified in the flags.
*/
static __inline int
__mtx_lock_ex(mtx_t *mtx, mtx_link_t *link, int flags, int to)
{
thread_t td;
u_int lock;
u_int nlock;
int error;
int isasync;
for (;;) {
lock = mtx->mtx_lock;
cpu_ccfence();
if (lock == 0) {
nlock = MTX_EXCLUSIVE | 1;
if (atomic_cmpset_int(&mtx->mtx_lock, 0, nlock)) {
mtx->mtx_owner = curthread;
cpu_sfence();
link->state = MTX_LINK_ACQUIRED;
error = 0;
break;
}
continue;
}
if ((lock & MTX_EXCLUSIVE) && mtx->mtx_owner == curthread) {
KKASSERT((lock & MTX_MASK) != MTX_MASK);
nlock = lock + 1;
if (atomic_cmpset_int(&mtx->mtx_lock, lock, nlock)) {
cpu_sfence();
link->state = MTX_LINK_ACQUIRED;
error = 0;
break;
}
continue;
}
/*
* We need MTX_LINKSPIN to manipulate exlink or
* shlink.
*
* We must set MTX_EXWANTED with MTX_LINKSPIN to indicate
* pending exclusive requests. It cannot be set as a separate
* operation prior to acquiring MTX_LINKSPIN.
*
* To avoid unnecessary cpu cache traffic we poll
* for collisions. It is also possible that EXWANTED
* state failing the above test was spurious, so all the
* tests must be repeated if we cannot obtain LINKSPIN
* with the prior state tests intact (i.e. don't reload
* the (lock) variable here, for heaven's sake!).
*/
if (lock & MTX_LINKSPIN) {
cpu_pause();
continue;
}
td = curthread;
nlock = lock | MTX_EXWANTED | MTX_LINKSPIN;
crit_enter_raw(td);
if (atomic_cmpset_int(&mtx->mtx_lock, lock, nlock) == 0) {
crit_exit_raw(td);
continue;
}
/*
* Check for early abort.
*/
if (link->state == MTX_LINK_ABORTED) {
if (mtx->mtx_exlink == NULL) {
atomic_clear_int(&mtx->mtx_lock,
MTX_LINKSPIN |
MTX_EXWANTED);
} else {
atomic_clear_int(&mtx->mtx_lock,
MTX_LINKSPIN);
}
crit_exit_raw(td);
link->state = MTX_LINK_IDLE;
error = ENOLCK;
break;
}
/*
* Add our link to the exlink list and release LINKSPIN.
*/
link->owner = td;
link->state = MTX_LINK_LINKED_EX;
if (mtx->mtx_exlink) {
link->next = mtx->mtx_exlink;
link->prev = link->next->prev;
link->next->prev = link;
link->prev->next = link;
} else {
link->next = link;
link->prev = link;
mtx->mtx_exlink = link;
}
isasync = (link->callback != NULL);
atomic_clear_int(&mtx->mtx_lock, MTX_LINKSPIN);
crit_exit_raw(td);
/*
* If asynchronous lock request return without
* blocking, leave link structure linked.
*/
if (isasync) {
error = EINPROGRESS;
break;
}
/*
* Wait for lock
*/
error = mtx_wait_link(mtx, link, flags, to);
break;
}
return (error);
}
/*
* Attempt to acquire a shared or exclusive token. Returns TRUE on success,
* FALSE on failure.
*
* If TOK_EXCLUSIVE is set in mode we are attempting to get an exclusive
* token, otherwise are attempting to get a shared token.
*
* If TOK_EXCLREQ is set in mode this is a blocking operation, otherwise
* it is a non-blocking operation (for both exclusive or shared acquisions).
*/
static __inline
int
_lwkt_trytokref(lwkt_tokref_t ref, thread_t td, long mode)
{
lwkt_token_t tok;
lwkt_tokref_t oref;
long count;
tok = ref->tr_tok;
KASSERT(((mode & TOK_EXCLREQ) == 0 || /* non blocking */
td->td_gd->gd_intr_nesting_level == 0 ||
panic_cpu_gd == mycpu),
("Attempt to acquire token %p not already "
"held in hard code section", tok));
if (mode & TOK_EXCLUSIVE) {
/*
* Attempt to get an exclusive token
*/
for (;;) {
count = tok->t_count;
oref = tok->t_ref; /* can be NULL */
cpu_ccfence();
if ((count & ~TOK_EXCLREQ) == 0) {
/*
* It is possible to get the exclusive bit.
* We must clear TOK_EXCLREQ on successful
* acquisition.
*/
if (atomic_cmpset_long(&tok->t_count, count,
(count & ~TOK_EXCLREQ) |
TOK_EXCLUSIVE)) {
KKASSERT(tok->t_ref == NULL);
tok->t_ref = ref;
return TRUE;
}
/* retry */
} else if ((count & TOK_EXCLUSIVE) &&
oref >= &td->td_toks_base &&
oref < td->td_toks_stop) {
/*
* Our thread already holds the exclusive
* bit, we treat this tokref as a shared
* token (sorta) to make the token release
* code easier.
*
* NOTE: oref cannot race above if it
* happens to be ours, so we're good.
* But we must still have a stable
* variable for both parts of the
* comparison.
*
* NOTE: Since we already have an exclusive
* lock and don't need to check EXCLREQ
* we can just use an atomic_add here
*/
atomic_add_long(&tok->t_count, TOK_INCR);
ref->tr_count &= ~TOK_EXCLUSIVE;
return TRUE;
} else if ((mode & TOK_EXCLREQ) &&
(count & TOK_EXCLREQ) == 0) {
/*
* Unable to get the exclusive bit but being
* asked to set the exclusive-request bit.
* Since we are going to retry anyway just
* set the bit unconditionally.
*/
atomic_set_long(&tok->t_count, TOK_EXCLREQ);
return FALSE;
} else {
/*
* Unable to get the exclusive bit and not
* being asked to set the exclusive-request
* (aka lwkt_trytoken()), or EXCLREQ was
* already set.
*/
cpu_pause();
return FALSE;
}
/* retry */
}
} else {
/*
* Attempt to get a shared token. Note that TOK_EXCLREQ
* for shared tokens simply means the caller intends to
* block. We never actually set the bit in tok->t_count.
*/
for (;;) {
count = tok->t_count;
oref = tok->t_ref; /* can be NULL */
cpu_ccfence();
if ((count & (TOK_EXCLUSIVE/*|TOK_EXCLREQ*/)) == 0) {
/*
* It may be possible to get the token shared.
*/
if ((atomic_fetchadd_long(&tok->t_count, TOK_INCR) & TOK_EXCLUSIVE) == 0) {
return TRUE;
}
atomic_fetchadd_long(&tok->t_count, -TOK_INCR);
/* retry */
} else if ((count & TOK_EXCLUSIVE) &&
oref >= &td->td_toks_base &&
oref < td->td_toks_stop) {
/*
* We own the exclusive bit on the token so
* we can in fact also get it shared.
*/
atomic_add_long(&tok->t_count, TOK_INCR);
return TRUE;
} else {
/*
* We failed to get the token shared
*/
return FALSE;
}
/* retry */
}
}
}