/
lwkt_token.c
907 lines (829 loc) · 23.4 KB
/
lwkt_token.c
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/*
* Copyright (c) 2003,2004,2009 The DragonFly Project. All rights reserved.
*
* This code is derived from software contributed to The DragonFly Project
* by Matthew Dillon <dillon@backplane.com>
*
* 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.
* 3. Neither the name of The DragonFly Project 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 COPYRIGHT HOLDERS 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
* COPYRIGHT HOLDERS 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.
*/
/*
* lwkt_token - Implement soft token locks.
*
* Tokens are locks which serialize a thread only while the thread is
* running. If the thread blocks all tokens are released, then reacquired
* when the thread resumes.
*
* This implementation requires no critical sections or spin locks, but
* does use atomic_cmpset_ptr().
*
* Tokens may be recursively acquired by the same thread. However the
* caller must be sure to release such tokens in reverse order.
*/
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
#include <sys/proc.h>
#include <sys/rtprio.h>
#include <sys/queue.h>
#include <sys/sysctl.h>
#include <sys/ktr.h>
#include <sys/kthread.h>
#include <machine/cpu.h>
#include <sys/lock.h>
#include <sys/caps.h>
#include <sys/spinlock.h>
#include <sys/thread2.h>
#include <sys/spinlock2.h>
#include <sys/mplock2.h>
#include <vm/vm.h>
#include <vm/vm_param.h>
#include <vm/vm_kern.h>
#include <vm/vm_object.h>
#include <vm/vm_page.h>
#include <vm/vm_map.h>
#include <vm/vm_pager.h>
#include <vm/vm_extern.h>
#include <vm/vm_zone.h>
#include <machine/stdarg.h>
#include <machine/smp.h>
extern int lwkt_sched_debug;
#ifndef LWKT_NUM_POOL_TOKENS
#define LWKT_NUM_POOL_TOKENS 4001 /* prime number */
#endif
static lwkt_token pool_tokens[LWKT_NUM_POOL_TOKENS];
#define TOKEN_STRING "REF=%p TOK=%p TD=%p"
#define TOKEN_ARGS lwkt_tokref_t ref, lwkt_token_t tok, struct thread *td
#define CONTENDED_STRING TOKEN_STRING " (contention started)"
#define UNCONTENDED_STRING TOKEN_STRING " (contention stopped)"
#if !defined(KTR_TOKENS)
#define KTR_TOKENS KTR_ALL
#endif
KTR_INFO_MASTER(tokens);
KTR_INFO(KTR_TOKENS, tokens, fail, 0, TOKEN_STRING, TOKEN_ARGS);
KTR_INFO(KTR_TOKENS, tokens, succ, 1, TOKEN_STRING, TOKEN_ARGS);
#if 0
KTR_INFO(KTR_TOKENS, tokens, release, 2, TOKEN_STRING, TOKEN_ARGS);
KTR_INFO(KTR_TOKENS, tokens, remote, 3, TOKEN_STRING, TOKEN_ARGS);
KTR_INFO(KTR_TOKENS, tokens, reqremote, 4, TOKEN_STRING, TOKEN_ARGS);
KTR_INFO(KTR_TOKENS, tokens, reqfail, 5, TOKEN_STRING, TOKEN_ARGS);
KTR_INFO(KTR_TOKENS, tokens, drain, 6, TOKEN_STRING, TOKEN_ARGS);
KTR_INFO(KTR_TOKENS, tokens, contention_start, 7, CONTENDED_STRING, TOKEN_ARGS);
KTR_INFO(KTR_TOKENS, tokens, contention_stop, 7, UNCONTENDED_STRING, TOKEN_ARGS);
#endif
#define logtoken(name, ref) \
KTR_LOG(tokens_ ## name, ref, ref->tr_tok, curthread)
/*
* Global tokens. These replace the MP lock for major subsystem locking.
* These tokens are initially used to lockup both global and individual
* operations.
*
* Once individual structures get their own locks these tokens are used
* only to protect global lists & other variables and to interlock
* allocations and teardowns and such.
*
* The UP initializer causes token acquisition to also acquire the MP lock
* for maximum compatibility. The feature may be enabled and disabled at
* any time, the MP state is copied to the tokref when the token is acquired
* and will not race against sysctl changes.
*/
struct lwkt_token mp_token = LWKT_TOKEN_INITIALIZER(mp_token);
struct lwkt_token pmap_token = LWKT_TOKEN_INITIALIZER(pmap_token);
struct lwkt_token dev_token = LWKT_TOKEN_INITIALIZER(dev_token);
struct lwkt_token vm_token = LWKT_TOKEN_INITIALIZER(vm_token);
struct lwkt_token vmspace_token = LWKT_TOKEN_INITIALIZER(vmspace_token);
struct lwkt_token kvm_token = LWKT_TOKEN_INITIALIZER(kvm_token);
struct lwkt_token proc_token = LWKT_TOKEN_INITIALIZER(proc_token);
struct lwkt_token tty_token = LWKT_TOKEN_INITIALIZER(tty_token);
struct lwkt_token vnode_token = LWKT_TOKEN_INITIALIZER(vnode_token);
struct lwkt_token vmobj_token = LWKT_TOKEN_INITIALIZER(vmobj_token);
static int lwkt_token_spin = 5;
SYSCTL_INT(_lwkt, OID_AUTO, token_spin, CTLFLAG_RW,
&lwkt_token_spin, 0, "Decontention spin loops");
static int lwkt_token_delay = 0;
SYSCTL_INT(_lwkt, OID_AUTO, token_delay, CTLFLAG_RW,
&lwkt_token_delay, 0, "Decontention spin delay in ns");
/*
* The collision count is bumped every time the LWKT scheduler fails
* to acquire needed tokens in addition to a normal lwkt_gettoken()
* stall.
*/
SYSCTL_LONG(_lwkt, OID_AUTO, mp_collisions, CTLFLAG_RW,
&mp_token.t_collisions, 0, "Collision counter of mp_token");
SYSCTL_LONG(_lwkt, OID_AUTO, pmap_collisions, CTLFLAG_RW,
&pmap_token.t_collisions, 0, "Collision counter of pmap_token");
SYSCTL_LONG(_lwkt, OID_AUTO, dev_collisions, CTLFLAG_RW,
&dev_token.t_collisions, 0, "Collision counter of dev_token");
SYSCTL_LONG(_lwkt, OID_AUTO, vm_collisions, CTLFLAG_RW,
&vm_token.t_collisions, 0, "Collision counter of vm_token");
SYSCTL_LONG(_lwkt, OID_AUTO, vmspace_collisions, CTLFLAG_RW,
&vmspace_token.t_collisions, 0, "Collision counter of vmspace_token");
SYSCTL_LONG(_lwkt, OID_AUTO, kvm_collisions, CTLFLAG_RW,
&kvm_token.t_collisions, 0, "Collision counter of kvm_token");
SYSCTL_LONG(_lwkt, OID_AUTO, proc_collisions, CTLFLAG_RW,
&proc_token.t_collisions, 0, "Collision counter of proc_token");
SYSCTL_LONG(_lwkt, OID_AUTO, tty_collisions, CTLFLAG_RW,
&tty_token.t_collisions, 0, "Collision counter of tty_token");
SYSCTL_LONG(_lwkt, OID_AUTO, vnode_collisions, CTLFLAG_RW,
&vnode_token.t_collisions, 0, "Collision counter of vnode_token");
#ifdef DEBUG_LOCKS_LATENCY
static long tokens_add_latency;
SYSCTL_LONG(_debug, OID_AUTO, tokens_add_latency, CTLFLAG_RW,
&tokens_add_latency, 0,
"Add spinlock latency");
#endif
static int _lwkt_getalltokens_sorted(thread_t td);
#ifdef SMP
/*
* Acquire the initial mplock
*
* (low level boot only)
*/
void
cpu_get_initial_mplock(void)
{
KKASSERT(mp_token.t_ref == NULL);
if (lwkt_trytoken(&mp_token) == FALSE)
panic("cpu_get_initial_mplock");
}
#endif
/*
* Return a pool token given an address. Use a prime number to reduce
* overlaps.
*/
static __inline
lwkt_token_t
_lwkt_token_pool_lookup(void *ptr)
{
u_int i;
i = (u_int)(uintptr_t)ptr % LWKT_NUM_POOL_TOKENS;
return(&pool_tokens[i]);
}
/*
* Initialize a tokref_t prior to making it visible in the thread's
* token array.
*/
static __inline
void
_lwkt_tokref_init(lwkt_tokref_t ref, lwkt_token_t tok, thread_t td, long excl)
{
ref->tr_tok = tok;
ref->tr_count = excl;
ref->tr_owner = td;
}
/*
* 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) {
/* XXX EXCLREQ should work */
/*
* It is possible to get the token shared.
*/
if (atomic_cmpset_long(&tok->t_count, count,
count + TOK_INCR)) {
return TRUE;
}
/* 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 */
}
}
}
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;
}
/*
* 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 */
}
}
/*
* Obtain all the tokens required by the specified thread on the current
* cpu, return 0 on failure and non-zero on success. If a failure occurs
* any partially acquired tokens will be released prior to return.
*
* lwkt_getalltokens is called by the LWKT scheduler to re-acquire all
* tokens that the thread had to release when it switched away.
*
* If spinning is non-zero this function acquires the tokens in a particular
* order to deal with potential deadlocks. We simply use address order for
* the case.
*
* Called from a critical section.
*/
int
lwkt_getalltokens(thread_t td, int spinning)
{
lwkt_tokref_t scan;
lwkt_token_t tok;
if (spinning)
return(_lwkt_getalltokens_sorted(td));
/*
* Acquire tokens in forward order, assign or validate tok->t_ref.
*/
for (scan = &td->td_toks_base; scan < td->td_toks_stop; ++scan) {
tok = scan->tr_tok;
for (;;) {
/*
* Only try really hard on the last token
*/
if (scan == td->td_toks_stop - 1) {
if (_lwkt_trytokref_spin(scan, td, scan->tr_count))
break;
} else {
if (_lwkt_trytokref(scan, td, scan->tr_count))
break;
}
/*
* Otherwise we failed to acquire all the tokens.
* Release whatever we did get.
*/
strncpy(td->td_gd->gd_cnt.v_token_name,
tok->t_desc,
sizeof(td->td_gd->gd_cnt.v_token_name) - 1);
if (lwkt_sched_debug > 0) {
--lwkt_sched_debug;
kprintf("toka %p %s %s\n",
tok, tok->t_desc, td->td_comm);
}
td->td_wmesg = tok->t_desc;
++tok->t_collisions;
while (--scan >= &td->td_toks_base)
_lwkt_reltokref(scan, td);
return(FALSE);
}
}
return (TRUE);
}
/*
* Release all tokens owned by the specified thread on the current cpu.
*
* This code is really simple. Even in cases where we own all the tokens
* note that t_ref may not match the scan for recursively held tokens which
* are held deeper in the stack, or for the case where a lwkt_getalltokens()
* failed.
*
* Tokens are released in reverse order to reduce chasing race failures.
*
* Called from a critical section.
*/
void
lwkt_relalltokens(thread_t td)
{
lwkt_tokref_t scan;
/*
* Weird order is to try to avoid a panic loop
*/
if (td->td_toks_have) {
scan = td->td_toks_have;
td->td_toks_have = NULL;
} else {
scan = td->td_toks_stop;
}
while (--scan >= &td->td_toks_base)
_lwkt_reltokref(scan, td);
}
/*
* This is the decontention version of lwkt_getalltokens(). The tokens are
* acquired in address-sorted order to deal with any deadlocks. Ultimately
* token failures will spin into the scheduler and get here.
*
* Called from critical section
*/
static
int
_lwkt_getalltokens_sorted(thread_t td)
{
lwkt_tokref_t sort_array[LWKT_MAXTOKENS];
lwkt_tokref_t scan;
lwkt_token_t tok;
int i;
int j;
int n;
/*
* Sort the token array. Yah yah, I know this isn't fun.
*
* NOTE: Recursively acquired tokens are ordered the same as in the
* td_toks_array so we can always get the earliest one first.
*/
i = 0;
scan = &td->td_toks_base;
while (scan < td->td_toks_stop) {
for (j = 0; j < i; ++j) {
if (scan->tr_tok < sort_array[j]->tr_tok)
break;
}
if (j != i) {
bcopy(sort_array + j, sort_array + j + 1,
(i - j) * sizeof(lwkt_tokref_t));
}
sort_array[j] = scan;
++scan;
++i;
}
n = i;
/*
* Acquire tokens in forward order, assign or validate tok->t_ref.
*/
for (i = 0; i < n; ++i) {
scan = sort_array[i];
tok = scan->tr_tok;
for (;;) {
/*
* Only try really hard on the last token
*/
if (scan == td->td_toks_stop - 1) {
if (_lwkt_trytokref_spin(scan, td, scan->tr_count))
break;
} else {
if (_lwkt_trytokref(scan, td, scan->tr_count))
break;
}
/*
* Otherwise we failed to acquire all the tokens.
* Release whatever we did get.
*/
if (lwkt_sched_debug > 0) {
--lwkt_sched_debug;
kprintf("tokb %p %s %s\n",
tok, tok->t_desc, td->td_comm);
}
td->td_wmesg = tok->t_desc;
++tok->t_collisions;
while (--i >= 0) {
scan = sort_array[i];
_lwkt_reltokref(scan, td);
}
return(FALSE);
}
}
/*
* We were successful, there is no need for another core to signal
* us.
*/
return (TRUE);
}
/*
* 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);
}
/*
* 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]) &&
(tok < &pool_tokens[LWKT_NUM_POOL_TOKENS]))
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;
lwkt_switch();
logtoken(succ, ref);
}
/*
* 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;
}
void
lwkt_gettoken_hard(lwkt_token_t tok)
{
lwkt_gettoken(tok);
crit_enter_hard();
}
lwkt_token_t
lwkt_getpooltoken(void *ptr)
{
lwkt_token_t tok;
tok = _lwkt_token_pool_lookup(ptr);
lwkt_gettoken(tok);
return (tok);
}
/*
* Release a serializing token.
*
* WARNING! All tokens must be released in reverse order. This will be
* asserted.
*/
void
lwkt_reltoken(lwkt_token_t tok)
{
thread_t td = curthread;
lwkt_tokref_t ref;
/*
* Remove ref from thread token list and assert that it matches
* the token passed in. Tokens must be released in reverse order.
*/
ref = td->td_toks_stop - 1;
KKASSERT(ref >= &td->td_toks_base && ref->tr_tok == tok);
_lwkt_reltokref(ref, td);
cpu_sfence();
td->td_toks_stop = ref;
}
void
lwkt_reltoken_hard(lwkt_token_t tok)
{
lwkt_reltoken(tok);
crit_exit_hard();
}
/*
* It is faster for users of lwkt_getpooltoken() to use the returned
* token and just call lwkt_reltoken(), but for convenience we provide
* this function which looks the token up based on the ident.
*/
void
lwkt_relpooltoken(void *ptr)
{
lwkt_token_t tok = _lwkt_token_pool_lookup(ptr);
lwkt_reltoken(tok);
}
/*
* Return a count of the number of token refs the thread has to the
* specified token, whether it currently owns the token or not.
*/
int
lwkt_cnttoken(lwkt_token_t tok, thread_t td)
{
lwkt_tokref_t scan;
int count = 0;
for (scan = &td->td_toks_base; scan < td->td_toks_stop; ++scan) {
if (scan->tr_tok == tok)
++count;
}
return(count);
}
/*
* Pool tokens are used to provide a type-stable serializing token
* pointer that does not race against disappearing data structures.
*
* This routine is called in early boot just after we setup the BSP's
* globaldata structure.
*/
void
lwkt_token_pool_init(void)
{
int i;
for (i = 0; i < LWKT_NUM_POOL_TOKENS; ++i)
lwkt_token_init(&pool_tokens[i], "pool");
}
lwkt_token_t
lwkt_token_pool_lookup(void *ptr)
{
return (_lwkt_token_pool_lookup(ptr));
}
/*
* Initialize a token.
*/
void
lwkt_token_init(lwkt_token_t tok, const char *desc)
{
tok->t_count = 0;
tok->t_ref = NULL;
tok->t_collisions = 0;
tok->t_desc = desc;
}
void
lwkt_token_uninit(lwkt_token_t tok)
{
/* empty */
}
/*
* Exchange the two most recent tokens on the tokref stack. This allows
* you to release a token out of order.
*
* We have to be careful about the case where the top two tokens are
* the same token. In this case tok->t_ref will point to the deeper
* ref and must remain pointing to the deeper ref. If we were to swap
* it the first release would clear the token even though a second
* ref is still present.
*
* Only exclusively held tokens contain a reference to the tokref which
* has to be flipped along with the swap.
*/
void
lwkt_token_swap(void)
{
lwkt_tokref_t ref1, ref2;
lwkt_token_t tok1, tok2;
long count1, count2;
thread_t td = curthread;
crit_enter();
ref1 = td->td_toks_stop - 1;
ref2 = td->td_toks_stop - 2;
KKASSERT(ref1 >= &td->td_toks_base);
KKASSERT(ref2 >= &td->td_toks_base);
tok1 = ref1->tr_tok;
tok2 = ref2->tr_tok;
count1 = ref1->tr_count;
count2 = ref2->tr_count;
if (tok1 != tok2) {
ref1->tr_tok = tok2;
ref1->tr_count = count2;
ref2->tr_tok = tok1;
ref2->tr_count = count1;
if (tok1->t_ref == ref1)
tok1->t_ref = ref2;
if (tok2->t_ref == ref2)
tok2->t_ref = ref1;
}
crit_exit();
}