freebsd-dev/lib/libthr/thread/thr_rtld.c

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/*
* Copyright (c) 2006, 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 unmodified, 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 ``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 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.
*
* $FreeBSD$
*
*/
/*
* A lockless rwlock for rtld.
*/
#include <sys/cdefs.h>
#include <stdlib.h>
#include "rtld_lock.h"
#include "thr_private.h"
#define CACHE_LINE_SIZE 64
#define WAFLAG 0x1
#define RC_INCR 0x2
static int _thr_rtld_clr_flag(int);
static void *_thr_rtld_lock_create(void);
static void _thr_rtld_lock_destroy(void *);
static void _thr_rtld_lock_release(void *);
static void _thr_rtld_rlock_acquire(void *);
static int _thr_rtld_set_flag(int);
static void _thr_rtld_wlock_acquire(void *);
struct rtld_lock {
volatile int lock;
volatile int rd_waiters;
volatile int wr_waiters;
volatile umtx_t rd_cv;
volatile umtx_t wr_cv;
void *base;
};
static void *
_thr_rtld_lock_create(void)
{
void *base;
char *p;
uintptr_t r;
struct rtld_lock *l;
THR_ASSERT(sizeof(struct rtld_lock) <= CACHE_LINE_SIZE,
"rtld_lock too large");
base = calloc(1, CACHE_LINE_SIZE);
p = (char *)base;
if ((uintptr_t)p % CACHE_LINE_SIZE != 0) {
free(base);
base = calloc(1, 2 * CACHE_LINE_SIZE);
p = (char *)base;
if ((r = (uintptr_t)p % CACHE_LINE_SIZE) != 0)
p += CACHE_LINE_SIZE - r;
}
l = (struct rtld_lock *)p;
l->base = base;
return (l);
}
static void
_thr_rtld_lock_destroy(void *lock)
{
struct rtld_lock *l = (struct rtld_lock *)lock;
free(l->base);
}
static void
_thr_rtld_rlock_acquire(void *lock)
{
struct pthread *curthread;
struct rtld_lock *l;
umtx_t v;
curthread = _get_curthread();
l = (struct rtld_lock *)lock;
THR_CRITICAL_ENTER(curthread);
atomic_add_acq_int(&l->lock, RC_INCR);
if (!(l->lock & WAFLAG))
return;
v = l->rd_cv;
atomic_add_int(&l->rd_waiters, 1);
while (l->lock & WAFLAG) {
_thr_umtx_wait(&l->rd_cv, v, NULL);
v = l->rd_cv;
}
atomic_add_int(&l->rd_waiters, -1);
}
static void
_thr_rtld_wlock_acquire(void *lock)
{
struct pthread *curthread;
struct rtld_lock *l;
umtx_t v;
curthread = _get_curthread();
l = (struct rtld_lock *)lock;
_thr_signal_block(curthread);
for (;;) {
if (atomic_cmpset_acq_int(&l->lock, 0, WAFLAG))
return;
v = l->wr_cv;
atomic_add_int(&l->wr_waiters, 1);
while (l->lock != 0) {
_thr_umtx_wait(&l->wr_cv, v, NULL);
v = l->wr_cv;
}
atomic_add_int(&l->wr_waiters, -1);
}
}
static void
_thr_rtld_lock_release(void *lock)
{
struct pthread *curthread;
struct rtld_lock *l;
curthread = _get_curthread();
l = (struct rtld_lock *)lock;
if ((l->lock & WAFLAG) == 0) {
atomic_add_rel_int(&l->lock, -RC_INCR);
if (l->lock == 0 && l->wr_waiters) {
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atomic_add_long(&l->wr_cv, 1);
_thr_umtx_wake(&l->wr_cv, l->wr_waiters);
}
THR_CRITICAL_LEAVE(curthread);
} else {
atomic_add_rel_int(&l->lock, -WAFLAG);
if (l->lock == 0 && l->wr_waiters) {
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atomic_add_long(&l->wr_cv, 1);
_thr_umtx_wake(&l->wr_cv, l->wr_waiters);
} else if (l->rd_waiters) {
atomic_add_long(&l->rd_cv, 1);
_thr_umtx_wake(&l->rd_cv, l->rd_waiters);
}
_thr_signal_unblock(curthread);
}
}
static int
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_thr_rtld_set_flag(int mask __unused)
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{
/*
* The caller's code in rtld-elf is broken, it is not signal safe,
* just return zero to fool it.
*/
return (0);
}
static int
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_thr_rtld_clr_flag(int mask __unused)
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{
return (0);
}
void
_thr_rtld_init(void)
{
struct RtldLockInfo li;
struct pthread *curthread;
umtx_t dummy;
curthread = _get_curthread();
/* force to resolve _umtx_op PLT */
_umtx_op((struct umtx *)&dummy, UMTX_OP_WAKE, 1, 0, 0);
li.lock_create = _thr_rtld_lock_create;
li.lock_destroy = _thr_rtld_lock_destroy;
li.rlock_acquire = _thr_rtld_rlock_acquire;
li.wlock_acquire = _thr_rtld_wlock_acquire;
li.lock_release = _thr_rtld_lock_release;
li.thread_set_flag = _thr_rtld_set_flag;
li.thread_clr_flag = _thr_rtld_clr_flag;
li.at_fork = NULL;
/* mask signals, also force to resolve __sys_sigprocmask PLT */
_thr_signal_block(curthread);
_rtld_thread_init(&li);
_thr_signal_unblock(curthread);
}
void
_thr_rtld_fini(void)
{
struct pthread *curthread;
curthread = _get_curthread();
_thr_signal_block(curthread);
_rtld_thread_init(NULL);
_thr_signal_unblock(curthread);
}