4dcb50723a
some cases we want to improve: 1) if a thread signal got a signal while in cancellation point, it is possible the TDP_WAKEUP may be eaten by signal handler if the handler called some interruptibly system calls. 2) In signal handler, we want to disable cancellation. 3) When thread holding some low level locks, it is better to disable signal, those code need not to worry reentrancy, sigprocmask system call is avoided because it is a bit expensive. The signal handler wrapper works in this way: 1) libthr installs its signal handler if user code invokes sigaction to install its handler, the user handler is recorded in internal array. 2) when a signal is delivered, libthr's signal handler is invoke, libthr checks if thread holds some low level lock or is in critical region, if it is true, the signal is buffered, and all signals are masked, once the thread leaves critical region, correct signal mask is restored and buffered signal is processed. 3) before user signal handler is invoked, cancellation is temporarily disabled, after user signal handler is returned, cancellation state is restored, and pending cancellation is rescheduled.
222 lines
5.2 KiB
C
222 lines
5.2 KiB
C
/*
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* Copyright (c) 2006, David Xu <davidxu@freebsd.org>
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* All rights reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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* 1. Redistributions of source code must retain the above copyright
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* notice unmodified, this list of conditions, and the following
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* disclaimer.
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in the
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* documentation and/or other materials provided with the distribution.
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*
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* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
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* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
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* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
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* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
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* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
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* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* $FreeBSD$
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*
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*/
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/*
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* A lockless rwlock for rtld.
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*/
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#include <sys/cdefs.h>
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#include <stdlib.h>
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#include <string.h>
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#include "rtld_lock.h"
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#include "thr_private.h"
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#undef errno
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extern int errno;
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static int _thr_rtld_clr_flag(int);
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static void *_thr_rtld_lock_create(void);
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static void _thr_rtld_lock_destroy(void *);
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static void _thr_rtld_lock_release(void *);
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static void _thr_rtld_rlock_acquire(void *);
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static int _thr_rtld_set_flag(int);
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static void _thr_rtld_wlock_acquire(void *);
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struct rtld_lock {
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struct urwlock lock;
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char _pad[CACHE_LINE_SIZE - sizeof(struct urwlock)];
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};
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static struct rtld_lock lock_place[MAX_RTLD_LOCKS] __aligned(CACHE_LINE_SIZE);
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static int busy_places;
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static void *
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_thr_rtld_lock_create(void)
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{
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int locki;
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struct rtld_lock *l;
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static const char fail[] = "_thr_rtld_lock_create failed\n";
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for (locki = 0; locki < MAX_RTLD_LOCKS; locki++) {
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if ((busy_places & (1 << locki)) == 0)
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break;
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}
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if (locki == MAX_RTLD_LOCKS) {
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write(2, fail, sizeof(fail) - 1);
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return (NULL);
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}
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busy_places |= (1 << locki);
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l = &lock_place[locki];
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l->lock.rw_flags = URWLOCK_PREFER_READER;
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return (l);
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}
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static void
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_thr_rtld_lock_destroy(void *lock)
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{
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int locki;
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size_t i;
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locki = (struct rtld_lock *)lock - &lock_place[0];
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for (i = 0; i < sizeof(struct rtld_lock); ++i)
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((char *)lock)[i] = 0;
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busy_places &= ~(1 << locki);
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}
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#define SAVE_ERRNO() { \
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if (curthread != _thr_initial) \
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errsave = curthread->error; \
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else \
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errsave = errno; \
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}
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#define RESTORE_ERRNO() { \
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if (curthread != _thr_initial) \
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curthread->error = errsave; \
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else \
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errno = errsave; \
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}
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static void
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_thr_rtld_rlock_acquire(void *lock)
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{
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struct pthread *curthread;
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struct rtld_lock *l;
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int errsave;
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curthread = _get_curthread();
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SAVE_ERRNO();
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l = (struct rtld_lock *)lock;
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THR_CRITICAL_ENTER(curthread);
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while (_thr_rwlock_rdlock(&l->lock, 0, NULL) != 0)
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;
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curthread->rdlock_count++;
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RESTORE_ERRNO();
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}
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static void
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_thr_rtld_wlock_acquire(void *lock)
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{
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struct pthread *curthread;
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struct rtld_lock *l;
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int errsave;
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curthread = _get_curthread();
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SAVE_ERRNO();
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l = (struct rtld_lock *)lock;
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THR_CRITICAL_ENTER(curthread);
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while (_thr_rwlock_wrlock(&l->lock, NULL) != 0)
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;
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RESTORE_ERRNO();
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}
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static void
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_thr_rtld_lock_release(void *lock)
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{
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struct pthread *curthread;
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struct rtld_lock *l;
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int32_t state;
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int errsave;
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curthread = _get_curthread();
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SAVE_ERRNO();
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l = (struct rtld_lock *)lock;
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state = l->lock.rw_state;
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if (_thr_rwlock_unlock(&l->lock) == 0) {
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if ((state & URWLOCK_WRITE_OWNER) == 0)
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curthread->rdlock_count--;
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THR_CRITICAL_LEAVE(curthread);
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}
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RESTORE_ERRNO();
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}
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static int
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_thr_rtld_set_flag(int mask __unused)
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{
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/*
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* The caller's code in rtld-elf is broken, it is not signal safe,
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* just return zero to fool it.
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*/
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return (0);
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}
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static int
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_thr_rtld_clr_flag(int mask __unused)
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{
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return (0);
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}
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void
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_thr_rtld_init(void)
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{
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struct RtldLockInfo li;
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struct pthread *curthread;
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long dummy = -1;
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curthread = _get_curthread();
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/* force to resolve _umtx_op PLT */
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_umtx_op_err((struct umtx *)&dummy, UMTX_OP_WAKE, 1, 0, 0);
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/* force to resolve errno() PLT */
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__error();
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/* force to resolve memcpy PLT */
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memcpy(&dummy, &dummy, sizeof(dummy));
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li.lock_create = _thr_rtld_lock_create;
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li.lock_destroy = _thr_rtld_lock_destroy;
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li.rlock_acquire = _thr_rtld_rlock_acquire;
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li.wlock_acquire = _thr_rtld_wlock_acquire;
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li.lock_release = _thr_rtld_lock_release;
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li.thread_set_flag = _thr_rtld_set_flag;
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li.thread_clr_flag = _thr_rtld_clr_flag;
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li.at_fork = NULL;
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/* mask signals, also force to resolve __sys_sigprocmask PLT */
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_thr_signal_block(curthread);
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_rtld_thread_init(&li);
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_thr_signal_unblock(curthread);
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}
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void
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_thr_rtld_fini(void)
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{
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struct pthread *curthread;
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curthread = _get_curthread();
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_thr_signal_block(curthread);
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_rtld_thread_init(NULL);
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_thr_signal_unblock(curthread);
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}
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