linux/arch/um/os-Linux/sigio.c

550 lines
12 KiB
C

/*
* Copyright (C) 2002 - 2008 Jeff Dike (jdike@{addtoit,linux.intel}.com)
* Licensed under the GPL
*/
#include <unistd.h>
#include <errno.h>
#include <fcntl.h>
#include <poll.h>
#include <pty.h>
#include <sched.h>
#include <signal.h>
#include <string.h>
#include "kern_constants.h"
#include "kern_util.h"
#include "init.h"
#include "os.h"
#include "process.h"
#include "sigio.h"
#include "um_malloc.h"
#include "user.h"
/*
* Protected by sigio_lock(), also used by sigio_cleanup, which is an
* exitcall.
*/
static int write_sigio_pid = -1;
static unsigned long write_sigio_stack;
/*
* These arrays are initialized before the sigio thread is started, and
* the descriptors closed after it is killed. So, it can't see them change.
* On the UML side, they are changed under the sigio_lock.
*/
#define SIGIO_FDS_INIT {-1, -1}
static int write_sigio_fds[2] = SIGIO_FDS_INIT;
static int sigio_private[2] = SIGIO_FDS_INIT;
struct pollfds {
struct pollfd *poll;
int size;
int used;
};
/*
* Protected by sigio_lock(). Used by the sigio thread, but the UML thread
* synchronizes with it.
*/
static struct pollfds current_poll;
static struct pollfds next_poll;
static struct pollfds all_sigio_fds;
static int write_sigio_thread(void *unused)
{
struct pollfds *fds, tmp;
struct pollfd *p;
int i, n, respond_fd;
char c;
signal(SIGWINCH, SIG_IGN);
fds = &current_poll;
while (1) {
n = poll(fds->poll, fds->used, -1);
if (n < 0) {
if (errno == EINTR)
continue;
printk(UM_KERN_ERR "write_sigio_thread : poll returned "
"%d, errno = %d\n", n, errno);
}
for (i = 0; i < fds->used; i++) {
p = &fds->poll[i];
if (p->revents == 0)
continue;
if (p->fd == sigio_private[1]) {
CATCH_EINTR(n = read(sigio_private[1], &c,
sizeof(c)));
if (n != sizeof(c))
printk(UM_KERN_ERR
"write_sigio_thread : "
"read on socket failed, "
"err = %d\n", errno);
tmp = current_poll;
current_poll = next_poll;
next_poll = tmp;
respond_fd = sigio_private[1];
}
else {
respond_fd = write_sigio_fds[1];
fds->used--;
memmove(&fds->poll[i], &fds->poll[i + 1],
(fds->used - i) * sizeof(*fds->poll));
}
CATCH_EINTR(n = write(respond_fd, &c, sizeof(c)));
if (n != sizeof(c))
printk(UM_KERN_ERR "write_sigio_thread : "
"write on socket failed, err = %d\n",
errno);
}
}
return 0;
}
static int need_poll(struct pollfds *polls, int n)
{
struct pollfd *new;
if (n <= polls->size)
return 0;
new = uml_kmalloc(n * sizeof(struct pollfd), UM_GFP_ATOMIC);
if (new == NULL) {
printk(UM_KERN_ERR "need_poll : failed to allocate new "
"pollfds\n");
return -ENOMEM;
}
memcpy(new, polls->poll, polls->used * sizeof(struct pollfd));
kfree(polls->poll);
polls->poll = new;
polls->size = n;
return 0;
}
/*
* Must be called with sigio_lock held, because it's needed by the marked
* critical section.
*/
static void update_thread(void)
{
unsigned long flags;
int n;
char c;
flags = set_signals(0);
CATCH_EINTR(n = write(sigio_private[0], &c, sizeof(c)));
if (n != sizeof(c)) {
printk(UM_KERN_ERR "update_thread : write failed, err = %d\n",
errno);
goto fail;
}
CATCH_EINTR(n = read(sigio_private[0], &c, sizeof(c)));
if (n != sizeof(c)) {
printk(UM_KERN_ERR "update_thread : read failed, err = %d\n",
errno);
goto fail;
}
set_signals(flags);
return;
fail:
/* Critical section start */
if (write_sigio_pid != -1) {
os_kill_process(write_sigio_pid, 1);
free_stack(write_sigio_stack, 0);
}
write_sigio_pid = -1;
close(sigio_private[0]);
close(sigio_private[1]);
close(write_sigio_fds[0]);
close(write_sigio_fds[1]);
/* Critical section end */
set_signals(flags);
}
int add_sigio_fd(int fd)
{
struct pollfd *p;
int err = 0, i, n;
sigio_lock();
for (i = 0; i < all_sigio_fds.used; i++) {
if (all_sigio_fds.poll[i].fd == fd)
break;
}
if (i == all_sigio_fds.used)
goto out;
p = &all_sigio_fds.poll[i];
for (i = 0; i < current_poll.used; i++) {
if (current_poll.poll[i].fd == fd)
goto out;
}
n = current_poll.used;
err = need_poll(&next_poll, n + 1);
if (err)
goto out;
memcpy(next_poll.poll, current_poll.poll,
current_poll.used * sizeof(struct pollfd));
next_poll.poll[n] = *p;
next_poll.used = n + 1;
update_thread();
out:
sigio_unlock();
return err;
}
int ignore_sigio_fd(int fd)
{
struct pollfd *p;
int err = 0, i, n = 0;
/*
* This is called from exitcalls elsewhere in UML - if
* sigio_cleanup has already run, then update_thread will hang
* or fail because the thread is no longer running.
*/
if (write_sigio_pid == -1)
return -EIO;
sigio_lock();
for (i = 0; i < current_poll.used; i++) {
if (current_poll.poll[i].fd == fd)
break;
}
if (i == current_poll.used)
goto out;
err = need_poll(&next_poll, current_poll.used - 1);
if (err)
goto out;
for (i = 0; i < current_poll.used; i++) {
p = &current_poll.poll[i];
if (p->fd != fd)
next_poll.poll[n++] = *p;
}
next_poll.used = current_poll.used - 1;
update_thread();
out:
sigio_unlock();
return err;
}
static struct pollfd *setup_initial_poll(int fd)
{
struct pollfd *p;
p = uml_kmalloc(sizeof(struct pollfd), UM_GFP_KERNEL);
if (p == NULL) {
printk(UM_KERN_ERR "setup_initial_poll : failed to allocate "
"poll\n");
return NULL;
}
*p = ((struct pollfd) { .fd = fd,
.events = POLLIN,
.revents = 0 });
return p;
}
static void write_sigio_workaround(void)
{
struct pollfd *p;
int err;
int l_write_sigio_fds[2];
int l_sigio_private[2];
int l_write_sigio_pid;
/* We call this *tons* of times - and most ones we must just fail. */
sigio_lock();
l_write_sigio_pid = write_sigio_pid;
sigio_unlock();
if (l_write_sigio_pid != -1)
return;
err = os_pipe(l_write_sigio_fds, 1, 1);
if (err < 0) {
printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 1 failed, "
"err = %d\n", -err);
return;
}
err = os_pipe(l_sigio_private, 1, 1);
if (err < 0) {
printk(UM_KERN_ERR "write_sigio_workaround - os_pipe 2 failed, "
"err = %d\n", -err);
goto out_close1;
}
p = setup_initial_poll(l_sigio_private[1]);
if (!p)
goto out_close2;
sigio_lock();
/*
* Did we race? Don't try to optimize this, please, it's not so likely
* to happen, and no more than once at the boot.
*/
if (write_sigio_pid != -1)
goto out_free;
current_poll = ((struct pollfds) { .poll = p,
.used = 1,
.size = 1 });
if (write_sigio_irq(l_write_sigio_fds[0]))
goto out_clear_poll;
memcpy(write_sigio_fds, l_write_sigio_fds, sizeof(l_write_sigio_fds));
memcpy(sigio_private, l_sigio_private, sizeof(l_sigio_private));
write_sigio_pid = run_helper_thread(write_sigio_thread, NULL,
CLONE_FILES | CLONE_VM,
&write_sigio_stack);
if (write_sigio_pid < 0)
goto out_clear;
sigio_unlock();
return;
out_clear:
write_sigio_pid = -1;
write_sigio_fds[0] = -1;
write_sigio_fds[1] = -1;
sigio_private[0] = -1;
sigio_private[1] = -1;
out_clear_poll:
current_poll = ((struct pollfds) { .poll = NULL,
.size = 0,
.used = 0 });
out_free:
sigio_unlock();
kfree(p);
out_close2:
close(l_sigio_private[0]);
close(l_sigio_private[1]);
out_close1:
close(l_write_sigio_fds[0]);
close(l_write_sigio_fds[1]);
}
void sigio_broken(int fd, int read)
{
int err;
write_sigio_workaround();
sigio_lock();
err = need_poll(&all_sigio_fds, all_sigio_fds.used + 1);
if (err) {
printk(UM_KERN_ERR "maybe_sigio_broken - failed to add pollfd "
"for descriptor %d\n", fd);
goto out;
}
all_sigio_fds.poll[all_sigio_fds.used++] =
((struct pollfd) { .fd = fd,
.events = read ? POLLIN : POLLOUT,
.revents = 0 });
out:
sigio_unlock();
}
/* Changed during early boot */
static int pty_output_sigio;
static int pty_close_sigio;
void maybe_sigio_broken(int fd, int read)
{
if (!isatty(fd))
return;
if ((read || pty_output_sigio) && (!read || pty_close_sigio))
return;
sigio_broken(fd, read);
}
static void sigio_cleanup(void)
{
if (write_sigio_pid == -1)
return;
os_kill_process(write_sigio_pid, 1);
free_stack(write_sigio_stack, 0);
write_sigio_pid = -1;
}
__uml_exitcall(sigio_cleanup);
/* Used as a flag during SIGIO testing early in boot */
static int got_sigio;
static void __init handler(int sig)
{
got_sigio = 1;
}
struct openpty_arg {
int master;
int slave;
int err;
};
static void openpty_cb(void *arg)
{
struct openpty_arg *info = arg;
info->err = 0;
if (openpty(&info->master, &info->slave, NULL, NULL, NULL))
info->err = -errno;
}
static int async_pty(int master, int slave)
{
int flags;
flags = fcntl(master, F_GETFL);
if (flags < 0)
return -errno;
if ((fcntl(master, F_SETFL, flags | O_NONBLOCK | O_ASYNC) < 0) ||
(fcntl(master, F_SETOWN, os_getpid()) < 0))
return -errno;
if ((fcntl(slave, F_SETFL, flags | O_NONBLOCK) < 0))
return -errno;
return 0;
}
static void __init check_one_sigio(void (*proc)(int, int))
{
struct sigaction old, new;
struct openpty_arg pty = { .master = -1, .slave = -1 };
int master, slave, err;
initial_thread_cb(openpty_cb, &pty);
if (pty.err) {
printk(UM_KERN_ERR "check_one_sigio failed, errno = %d\n",
-pty.err);
return;
}
master = pty.master;
slave = pty.slave;
if ((master == -1) || (slave == -1)) {
printk(UM_KERN_ERR "check_one_sigio failed to allocate a "
"pty\n");
return;
}
/* Not now, but complain so we now where we failed. */
err = raw(master);
if (err < 0) {
printk(UM_KERN_ERR "check_one_sigio : raw failed, errno = %d\n",
-err);
return;
}
err = async_pty(master, slave);
if (err < 0) {
printk(UM_KERN_ERR "check_one_sigio : sigio_async failed, "
"err = %d\n", -err);
return;
}
if (sigaction(SIGIO, NULL, &old) < 0) {
printk(UM_KERN_ERR "check_one_sigio : sigaction 1 failed, "
"errno = %d\n", errno);
return;
}
new = old;
new.sa_handler = handler;
if (sigaction(SIGIO, &new, NULL) < 0) {
printk(UM_KERN_ERR "check_one_sigio : sigaction 2 failed, "
"errno = %d\n", errno);
return;
}
got_sigio = 0;
(*proc)(master, slave);
close(master);
close(slave);
if (sigaction(SIGIO, &old, NULL) < 0)
printk(UM_KERN_ERR "check_one_sigio : sigaction 3 failed, "
"errno = %d\n", errno);
}
static void tty_output(int master, int slave)
{
int n;
char buf[512];
printk(UM_KERN_INFO "Checking that host ptys support output SIGIO...");
memset(buf, 0, sizeof(buf));
while (write(master, buf, sizeof(buf)) > 0) ;
if (errno != EAGAIN)
printk(UM_KERN_ERR "tty_output : write failed, errno = %d\n",
errno);
while (((n = read(slave, buf, sizeof(buf))) > 0) &&
!({ barrier(); got_sigio; }))
;
if (got_sigio) {
printk(UM_KERN_CONT "Yes\n");
pty_output_sigio = 1;
} else if (n == -EAGAIN)
printk(UM_KERN_CONT "No, enabling workaround\n");
else
printk(UM_KERN_CONT "tty_output : read failed, err = %d\n", n);
}
static void tty_close(int master, int slave)
{
printk(UM_KERN_INFO "Checking that host ptys support SIGIO on "
"close...");
close(slave);
if (got_sigio) {
printk(UM_KERN_CONT "Yes\n");
pty_close_sigio = 1;
} else
printk(UM_KERN_CONT "No, enabling workaround\n");
}
static void __init check_sigio(void)
{
if ((access("/dev/ptmx", R_OK) < 0) &&
(access("/dev/ptyp0", R_OK) < 0)) {
printk(UM_KERN_WARNING "No pseudo-terminals available - "
"skipping pty SIGIO check\n");
return;
}
check_one_sigio(tty_output);
check_one_sigio(tty_close);
}
/* Here because it only does the SIGIO testing for now */
void __init os_check_bugs(void)
{
check_sigio();
}