OpenBSD-4.6/lib/libpthread/uthread/uthread_fd.c
/* $OpenBSD: uthread_fd.c,v 1.31 2008/10/02 23:27:24 deraadt Exp $ */
/*
* Copyright (c) 1995-1998 John Birrell <jb@cimlogic.com.au>
* 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, 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. All advertising materials mentioning features or use of this software
* must display the following acknowledgement:
* This product includes software developed by John Birrell.
* 4. Neither the name of the author nor the names of any co-contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY JOHN BIRRELL 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 AUTHOR 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.
*
* $FreeBSD: uthread_fd.c,v 1.13 1999/08/28 00:03:31 peter Exp $
*
*/
#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#ifdef _THREAD_SAFE
#include <pthread.h>
#include "pthread_private.h"
/* Static variables: */
static spinlock_t fd_table_lock = _SPINLOCK_INITIALIZER;
/*
* Build a new fd entry and return it.
*/
static struct fs_flags *
_thread_fs_flags_entry(void)
{
struct fs_flags *entry;
entry = (struct fs_flags *) malloc(sizeof(struct fs_flags));
if (entry != NULL) {
memset(entry, 0, sizeof *entry);
_SPINLOCK_INIT(&entry->lock);
}
return entry;
}
/*
* Initialize a new status_flags entry and set system
* file descriptor non-blocking.
*/
static int
_thread_fs_flags_init(struct fs_flags *status_flags, int fd)
{
int ret = 0;
int saved_errno;
status_flags->flags = _thread_sys_fcntl(fd, F_GETFL, 0);
if (status_flags->flags == -1)
/* use the errno fcntl returned */
ret = -1;
else {
/*
* Make the file descriptor non-blocking.
* This might fail if the device driver does
* not support non-blocking calls, or if the
* driver is naturally non-blocking.
*/
if ((status_flags->flags & O_NONBLOCK) == 0) {
saved_errno = errno;
_thread_sys_fcntl(fd, F_SETFL,
status_flags->flags | O_NONBLOCK);
errno = saved_errno;
}
}
return (ret);
}
/*
* If existing entry's status_flags don't match new one,
* then replace the current status flags with the new one.
* It is assumed the entry is locked with a FD_RDWR_CLOSE
* lock when this function is called.
*/
void
_thread_fs_flags_replace(int fd, struct fs_flags *new_status_flags)
{
struct fd_table_entry *entry = _thread_fd_table[fd];
struct fs_flags *old_status_flags;
struct stat sb;
int flags;
int saved_errno;
if (entry->status_flags != new_status_flags) {
if (entry->status_flags != NULL) {
old_status_flags = entry->status_flags;
_SPINLOCK(&old_status_flags->lock);
old_status_flags->refcnt -= 1;
if (old_status_flags->refcnt <= 0) {
/*
* Check if the file should be left as blocking.
*
* This is so that the file descriptors shared with a parent
* process aren't left set to non-blocking if the child
* closes them prior to exit. An example where this causes
* problems with /bin/sh is when a child closes stdin.
*
* Setting a file as blocking causes problems if a threaded
* parent accesses the file descriptor before the child exits.
* Once the threaded parent receives a SIGCHLD then it resets
* all of its files to non-blocking, and so it is then safe
* to access them.
*
* Pipes are not set to blocking when they are closed, as
* the parent and child will normally close the file
* descriptor of the end of the pipe that they are not
* using, which would then cause any reads to block
* indefinitely. However, stdin/out/err will be reset
* to avoid leaving them as non-blocking indefinitely.
*
* Files that we cannot fstat are probably not regular
* so we don't bother with them.
*
* Also don't reset fd to blocking if we are replacing
* the status flags with a shared version.
*/
saved_errno = errno;
if (new_status_flags == NULL &&
(old_status_flags->flags & O_NONBLOCK) == 0 &&
(fd < 3 || (_thread_sys_fstat(fd, &sb) == 0 &&
(S_ISREG(sb.st_mode) || S_ISCHR(sb.st_mode)))))
{
/* Get the current flags: */
flags = _thread_sys_fcntl(fd, F_GETFL, NULL);
/* Clear the nonblocking file descriptor flag: */
_thread_sys_fcntl(fd, F_SETFL, flags & ~O_NONBLOCK);
}
free(old_status_flags);
errno = saved_errno;
} else
_SPINUNLOCK(&old_status_flags->lock);
}
/* replace with new status flags */
if (new_status_flags != NULL) {
_SPINLOCK(&new_status_flags->lock);
new_status_flags->refcnt += 1;
_SPINUNLOCK(&new_status_flags->lock);
}
entry->status_flags = new_status_flags;
}
}
/*
* Build a new fd entry and return it.
*/
static struct fd_table_entry *
_thread_fd_entry(void)
{
struct fd_table_entry *entry;
entry = (struct fd_table_entry *) malloc(sizeof(struct fd_table_entry));
if (entry != NULL) {
memset(entry, 0, sizeof *entry);
_SPINLOCK_INIT(&entry->lock);
TAILQ_INIT(&entry->r_queue);
TAILQ_INIT(&entry->w_queue);
entry->state = FD_ENTRY_CLOSED;
entry->init_mode = FD_INIT_UNKNOWN;
}
return entry;
}
/*
* Initialize the thread fd table for dup-ed fds, typically the stdio
* fds.
*/
void
_thread_fd_init(void)
{
int saved_errno;
int fd;
int fd2;
int flag;
int *flags;
struct fd_table_entry *entry1, *entry2;
struct fs_flags *status_flags;
saved_errno = errno;
flags = calloc((size_t)_thread_init_fdtsize, sizeof *flags);
if (flags == NULL)
PANIC("Cannot allocate memory for flags table");
/* read the current file flags */
for (fd = 0; fd < _thread_init_fdtsize; fd += 1)
flags[fd] = _thread_sys_fcntl(fd, F_GETFL, 0);
/*
* Now toggle the sync flags and see what other fd's
* change. Those are the dup-ed fd's. Dup-ed fd's are
* added to the table, all others are NOT added to the
* table. They MUST NOT be added as the fds may belong
* to dlopen. As dlclose doesn't go through the thread code
* so the entries would never be cleaned.
*/
_SPINLOCK(&fd_table_lock);
for (fd = 0; fd < _thread_init_fdtsize; fd += 1) {
if (flags[fd] == -1)
continue;
entry1 = _thread_fd_entry();
status_flags = _thread_fs_flags_entry();
if (entry1 != NULL && status_flags != NULL) {
_thread_sys_fcntl(fd, F_SETFL,
flags[fd] ^ O_SYNC);
for (fd2 = fd + 1; fd2 < _thread_init_fdtsize; fd2 += 1) {
if (flags[fd2] == -1)
continue;
flag = _thread_sys_fcntl(fd2, F_GETFL, 0);
if (flag != flags[fd2]) {
entry2 = _thread_fd_entry();
if (entry2 != NULL) {
status_flags->refcnt += 1;
entry2->status_flags = status_flags;
entry2->state = FD_ENTRY_OPEN;
entry2->init_mode = FD_INIT_DUP2;
_thread_fd_table[fd2] = entry2;
} else
PANIC("Cannot allocate memory for flags table");
flags[fd2] = -1;
}
}
if (status_flags->refcnt) {
status_flags->refcnt += 1;
status_flags->flags = flags[fd];
entry1->status_flags = status_flags;
entry1->state = FD_ENTRY_OPEN;
entry1->init_mode = FD_INIT_DUP2;
_thread_fd_table[fd] = entry1;
flags[fd] |= O_NONBLOCK;
} else {
free(entry1);
free(status_flags);
}
} else {
PANIC("Cannot allocate memory for flags table");
}
}
_SPINUNLOCK(&fd_table_lock);
/* lastly, restore the file flags. Flags for files that we
know to be duped have been modified so set the non-blocking'
flag. Other files will be set to non-blocking when the
thread code is forced to take notice of the file. */
for (fd = 0; fd < _thread_init_fdtsize; fd += 1)
if (flags[fd] != -1)
_thread_sys_fcntl(fd, F_SETFL, flags[fd]);
free(flags);
errno = saved_errno;
}
/*
* Initialize the fd_table entry for the given fd.
*
* This function *must* return -1 and set the thread specific errno
* as a system call. This is because the error return from this
* function is propagated directly back from thread-wrapped system
* calls.
*/
int
_thread_fd_table_init(int fd, enum fd_entry_mode init_mode, struct fs_flags *status_flags)
{
int ret = 0;
int saved_errno;
struct fd_table_entry *entry;
struct fs_flags *new_status_flags;
if (fd < 0 || fd >= _thread_max_fdtsize) {
/*
* file descriptor is out of range, Return a bad file
* descriptor error:
*/
errno = EBADF;
return (-1);
}
if (_thread_fd_table[fd] == NULL) {
/* First time for this fd, build an entry */
entry = _thread_fd_entry();
if (entry == NULL) {
/* use _thread_fd_entry errno */
ret = -1;
} else {
/* Lock the file descriptor table: */
_SPINLOCK(&fd_table_lock);
/*
* Check if another thread allocated the
* file descriptor entry while this thread
* was doing the same thing. The table wasn't
* kept locked during this operation because
* it has the potential to recurse.
*/
if (_thread_fd_table[fd] == NULL) {
/* This thread wins: */
_thread_fd_table[fd] = entry;
entry = NULL;
}
/* Unlock the file descriptor table: */
_SPINUNLOCK(&fd_table_lock);
/*
* If another thread initialized the table entry
* throw the new entry away.
*/
if (entry != NULL)
free(entry);
}
}
if (ret == 0) {
entry = _thread_fd_table[fd];
_SPINLOCK(&entry->lock);
switch (init_mode) {
case FD_INIT_UNKNOWN:
/*
* If the entry is closed, try to open it
* anyway since we may have inherited it or
* it may have been created by an unwrapped
* call such as openpty(3). Since we allow
* FD_RDWR_CLOSE locks on closed entries,
* we ignore EBADF status flags errors and
* return a closed entry. If the entry is
* not closed then there's nothing to do.
*/
if (entry->state == FD_ENTRY_CLOSED) {
new_status_flags = _thread_fs_flags_entry();
if (new_status_flags == NULL) {
/* use _thread_fs_flags_entry errno */
ret = -1;
} else {
saved_errno = errno;
ret = _thread_fs_flags_init(new_status_flags, fd);
if (ret == 0) {
errno = saved_errno;
new_status_flags->refcnt = 1;
entry->status_flags = new_status_flags;
new_status_flags = NULL;
entry->state = FD_ENTRY_OPEN;
entry->init_mode = init_mode;
} else if (errno == EBADF) {
errno = saved_errno;
ret = 0;
}
}
/* if flags init failed free new flags */
if (new_status_flags != NULL)
free(new_status_flags);
}
break;
case FD_INIT_NEW:
/*
* If the entry was initialized and opened
* by another thread (i.e. FD_INIT_DUP2 or
* FD_INIT_UNKNOWN), the status flags will
* be correct.
*/
if (entry->state == FD_ENTRY_CLOSED) {
new_status_flags = _thread_fs_flags_entry();
if (new_status_flags == NULL) {
/* use _thread_fs_flags_entry errno */
ret = -1;
} else {
ret = _thread_fs_flags_init(new_status_flags, fd);
}
if (ret == 0) {
new_status_flags->refcnt = 1;
entry->status_flags = new_status_flags;
new_status_flags = NULL;
entry->state = FD_ENTRY_OPEN;
entry->init_mode = init_mode;
}
/* if flags init failed free new flags */
if (new_status_flags != NULL)
free(new_status_flags);
}
break;
case FD_INIT_BLOCKING:
/*
* If the entry was initialized and opened
* by another thread with FD_INIT_DUP2, the
* status flags will be correct. However,
* if FD_INIT_UNKNOWN raced in before us
* it means the app is not well behaved and
* tried to use the fd before it was returned
* to the client.
*/
if (entry->state == FD_ENTRY_CLOSED) {
new_status_flags = _thread_fs_flags_entry();
if (new_status_flags == NULL) {
/* use _thread_fs_flags_entry errno */
ret = -1;
} else {
ret = _thread_fs_flags_init(new_status_flags, fd);
}
if (ret == 0) {
/* set user's view of status flags to blocking */
new_status_flags->flags &= ~O_NONBLOCK;
new_status_flags->refcnt = 1;
entry->status_flags = new_status_flags;
new_status_flags = NULL;
entry->state = FD_ENTRY_OPEN;
entry->init_mode = init_mode;
}
/* if flags init failed free new flags */
if (new_status_flags != NULL)
free(new_status_flags);
} else if (entry->state == FD_ENTRY_OPEN &&
entry->init_mode == FD_INIT_UNKNOWN) {
entry->status_flags->flags &= ~O_NONBLOCK;
}
break;
case FD_INIT_DUP:
/*
* If the entry was initialized and opened
* by another thread with FD_INIT_DUP2 then
* keep it. However, if FD_INIT_UNKNOWN raced
* in before us it means the app is not well
* behaved and tried to use the fd before it
* was returned to the client.
*/
if (entry->state == FD_ENTRY_CLOSED) {
_thread_fs_flags_replace(fd, status_flags);
entry->state = FD_ENTRY_OPEN;
entry->init_mode = init_mode;
} else if (entry->state == FD_ENTRY_OPEN &&
entry->init_mode == FD_INIT_UNKNOWN) {
_thread_fs_flags_replace(fd, status_flags);
}
break;
case FD_INIT_DUP2:
/*
* This is only called when FD_RDWR_CLOSE
* is held and in state FD_ENTRY_CLOSING.
* Just replace flags and open entry.
* FD_INIT_UNKNOWN can't race in since we
* are in state FD_ENTRY_CLOSING before
* the _thread_sys_dup2 happens.
*/
_thread_fs_flags_replace(fd, status_flags);
entry->state = FD_ENTRY_OPEN;
entry->init_mode = init_mode;
break;
}
_SPINUNLOCK(&entry->lock);
}
/* Return the completion status: */
return (ret);
}
/*
* Close an fd entry. Replace existing status flags
* with NULL. The entry is assummed to be locked with
* a FD_RDWR_CLOSE lock and in state FD_ENTRY_CLOSING.
*/
void
_thread_fd_entry_close(int fd)
{
_thread_fs_flags_replace(fd, NULL);
_thread_fd_table[fd]->state = FD_ENTRY_CLOSED;
}
/*
* Unlock an fd table entry for the given fd and lock type.
*/
void
_thread_fd_unlock(int fd, int lock_type)
{
struct pthread *thread = _get_curthread();
struct fd_table_entry *entry;
/*
* If file descriptor is out of range or uninitialized,
* do nothing.
*/
if (fd >= 0 && fd < _thread_max_fdtsize && _thread_fd_table[fd] != NULL) {
entry = _thread_fd_table[fd];
/*
* Defer signals to protect the scheduling queues from
* access by the signal handler:
*/
_thread_kern_sig_defer();
/*
* Lock the file descriptor table entry to prevent
* other threads for clashing with the current
* thread's accesses:
*/
_SPINLOCK(&entry->lock);
/* Check if the running thread owns the read lock: */
if (entry->r_owner == thread &&
(lock_type & FD_READ)) {
/*
* Decrement the read lock count for the
* running thread:
*/
entry->r_lockcount--;
if (entry->r_lockcount == 0) {
/*
* no read locks, dequeue any threads
* waiting for a read lock
*/
entry->r_owner = TAILQ_FIRST(&entry->r_queue);
if (entry->r_owner != NULL) {
TAILQ_REMOVE(&entry->r_queue,
entry->r_owner, qe);
/*
* Set the state of the new owner of
* the thread to running:
*/
PTHREAD_NEW_STATE(entry->r_owner,
PS_RUNNING);
/*
* Reset the number of read locks.
* This will be incremented by the new
* owner of the lock when it sees that
*it has the lock.
*/
entry->r_lockcount = 0;
}
}
}
/* Check if the running thread owns the write lock: */
if (entry->w_owner == thread &&
(lock_type & FD_WRITE)) {
/*
* Decrement the write lock count for the
* running thread:
*/
entry->w_lockcount--;
if (entry->w_lockcount == 0) {
/*
* no write locks, dequeue any threads
* waiting on a write lock.
*/
entry->w_owner = TAILQ_FIRST(&entry->w_queue);
if (entry->w_owner != NULL) {
/* Remove this thread from the queue: */
TAILQ_REMOVE(&entry->w_queue,
entry->w_owner, qe);
/*
* Set the state of the new owner of
* the thread to running:
*/
PTHREAD_NEW_STATE(entry->w_owner,
PS_RUNNING);
/*
* Reset the number of write locks.
* This will be incremented by the
* new owner of the lock when it
* sees that it has the lock.
*/
entry->w_lockcount = 0;
}
}
}
/* Unlock the file descriptor table entry: */
_SPINUNLOCK(&entry->lock);
/*
* Undefer and handle pending signals, yielding if
* necessary:
*/
_thread_kern_sig_undefer();
}
}
/*
* Lock an fd table entry for the given fd and lock type.
*/
int
_thread_fd_lock(int fd, int lock_type, struct timespec * timeout)
{
struct pthread *curthread = _get_curthread();
struct fd_table_entry *entry;
int ret;
/*
* Check that the file descriptor table is initialised for this
* entry:
*/
ret = _thread_fd_table_init(fd, FD_INIT_UNKNOWN, NULL);
if (ret == 0) {
entry = _thread_fd_table[fd];
/*
* Lock the file descriptor table entry to prevent
* other threads for clashing with the current
* thread's accesses:
*/
_SPINLOCK(&entry->lock);
/* reject all new locks on entries that are closing */
if (entry->state == FD_ENTRY_CLOSING) {
ret = -1;
errno = EBADF;
} else if (lock_type == FD_RDWR_CLOSE) {
/* allow closing locks on open and closed entries */
entry->state = FD_ENTRY_CLOSING;
} else if (entry->state == FD_ENTRY_CLOSED) {
ret = -1;
errno = EBADF;
}
/* Handle read locks */
if (ret == 0 && (lock_type & FD_READ)) {
/*
* Enter a loop to wait for the file descriptor to be
* locked for read for the current thread:
*/
while (entry->r_owner != curthread) {
/*
* Check if the file descriptor is locked by
* another thread:
*/
if (entry->r_owner != NULL) {
/*
* Another thread has locked the file
* descriptor for read, so join the
* queue of threads waiting for a
* read lock on this file descriptor:
*/
TAILQ_INSERT_TAIL(&entry->r_queue,
curthread, qe);
/*
* Save the file descriptor details
* in the thread structure for the
* running thread:
*/
curthread->data.fd.fd = fd;
/* Set the timeout: */
_thread_kern_set_timeout(timeout);
/*
* Unlock the file descriptor
* table entry:
*/
_SPINUNLOCK(&entry->lock);
/*
* Schedule this thread to wait on
* the read lock. It will only be
* woken when it becomes the next in
* the queue and is granted access
* to the lock by the thread that is
* unlocking the file descriptor.
*/
_thread_kern_sched_state(PS_FDLR_WAIT,
__FILE__,
__LINE__);
/*
* Lock the file descriptor
* table entry again:
*/
_SPINLOCK(&entry->lock);
} else {
/*
* The running thread now owns the
* read lock on this file descriptor:
*/
entry->r_owner = curthread;
/*
* Reset the number of read locks for
* this file descriptor:
*/
entry->r_lockcount = 0;
}
}
/* Increment the read lock count: */
entry->r_lockcount++;
}
/* Handle write locks */
if (ret == 0 && (lock_type & FD_WRITE)) {
/*
* Enter a loop to wait for the file descriptor to be
* locked for write for the current thread:
*/
while (entry->w_owner != curthread) {
/*
* Check if the file descriptor is locked by
* another thread:
*/
if (entry->w_owner != NULL) {
/*
* Another thread has locked the file
* descriptor for write, so join the
* queue of threads waiting for a
* write lock on this file
* descriptor:
*/
TAILQ_INSERT_TAIL(&entry->w_queue,
curthread, qe);
/*
* Save the file descriptor details
* in the thread structure for the
* running thread:
*/
curthread->data.fd.fd = fd;
/* Set the timeout: */
_thread_kern_set_timeout(timeout);
/*
* Unlock the file descriptor
* table entry:
*/
_SPINUNLOCK(&entry->lock);
/*
* Schedule this thread to wait on
* the write lock. It will only be
* woken when it becomes the next in
* the queue and is granted access to
* the lock by the thread that is
* unlocking the file descriptor.
*/
_thread_kern_sched_state(PS_FDLW_WAIT,
__FILE__,
__LINE__);
/*
* Lock the file descriptor
* table entry again:
*/
_SPINLOCK(&entry->lock);
} else {
/*
* The running thread now owns the
* write lock on this file descriptor:
*/
entry->w_owner = curthread;
/*
* Reset the number of write locks
* for this file descriptor:
*/
entry->w_lockcount = 0;
}
}
/* Increment the write lock count: */
entry->w_lockcount++;
}
/* Unlock the file descriptor table entry: */
_SPINUNLOCK(&entry->lock);
}
/* Return the completion status: */
return (ret);
}
#endif