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elinks/src/main/select.c
Kalle Olavi Niemitalo a0d624cd61 Hurd bug 22861: Do not select() exceptions from pipes. 
The GNU Hurd has a bug that can make select() report an exception in a
pipe even though none has actually occurred.  The typical result is
that ELinks closes the pipe through which it internally passes all
input events, such as keypresses.  It then no longer reacts to what
the user is trying to do.

Work around the Hurd bug by making set_handlers() check whether the
file descriptor refers to a pipe, and if so, pretend the caller did
not provide any handler for exceptions.  This is a minimal change that
avoids slowing down the select() loop itself and does not require
careful analysis of the callers to statically find out which file
descriptors might refer to pipes.  The extra stat() calls may slow
ELinks down somewhat, but anyway it'll work better than it did without
the patch, and if the Hurd bug is ever fixed, we can remove the
workaround at that time.
2008-09-07 22:52:47 +03:00

364 lines
7.3 KiB
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/* File descriptors managment and switching */
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <errno.h>
#include <signal.h>
#include <string.h> /* FreeBSD FD_ZERO() macro calls bzero() */
#ifdef HAVE_SYS_SIGNAL_H
#include <sys/signal.h>
#endif
#ifdef __GNU__ /* For GNU Hurd bug workaround in set_handlers() */
#include <sys/stat.h> /* OS/2 needs this after sys/types.h */
#endif
#include <sys/types.h>
#ifdef HAVE_SYS_WAIT_H
#include <sys/wait.h>
#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
/* This must be here, thanks to BSD. */
#ifdef HAVE_INTTYPES_H
#include <inttypes.h> /* OMG */
#endif
#ifdef HAVE_SYS_SELECT_H
#include <sys/select.h>
#endif
#include "elinks.h"
#include "intl/gettext/libintl.h"
#include "main/main.h"
#include "main/select.h"
#include "main/timer.h"
#include "osdep/signals.h"
#include "terminal/terminal.h"
#include "util/error.h"
#include "util/memory.h"
#include "util/time.h"
#ifndef FD_SETSIZE
#define FD_SETSIZE 1024
#endif
struct thread {
select_handler_T read_func;
select_handler_T write_func;
select_handler_T error_func;
void *data;
};
static struct thread threads[FD_SETSIZE];
static fd_set w_read;
static fd_set w_write;
static fd_set w_error;
static fd_set x_read;
static fd_set x_write;
static fd_set x_error;
static int w_max;
int
get_file_handles_count(void)
{
int i = 0, j;
for (j = 0; j < FD_SETSIZE; j++)
if (threads[j].read_func
|| threads[j].write_func
|| threads[j].error_func)
i++;
return i;
}
struct bottom_half {
LIST_HEAD(struct bottom_half);
select_handler_T fn;
void *data;
};
static INIT_LIST_OF(struct bottom_half, bottom_halves);
int
register_bottom_half_do(select_handler_T fn, void *data)
{
struct bottom_half *bh;
foreach (bh, bottom_halves)
if (bh->fn == fn && bh->data == data)
return 0;
bh = mem_alloc(sizeof(*bh));
if (!bh) return -1;
bh->fn = fn;
bh->data = data;
add_to_list(bottom_halves, bh);
return 0;
}
void
check_bottom_halves(void)
{
while (!list_empty(bottom_halves)) {
struct bottom_half *bh = bottom_halves.prev;
select_handler_T fn = bh->fn;
void *data = bh->data;
del_from_list(bh);
mem_free(bh);
fn(data);
}
}
select_handler_T
get_handler(int fd, enum select_handler_type tp)
{
#ifndef CONFIG_OS_WIN32
assertm(fd >= 0 && fd < FD_SETSIZE,
"get_handler: handle %d >= FD_SETSIZE %d",
fd, FD_SETSIZE);
if_assert_failed return NULL;
#endif
switch (tp) {
case SELECT_HANDLER_READ: return threads[fd].read_func;
case SELECT_HANDLER_WRITE: return threads[fd].write_func;
case SELECT_HANDLER_ERROR: return threads[fd].error_func;
case SELECT_HANDLER_DATA: return threads[fd].data;
}
INTERNAL("get_handler: bad type %d", tp);
return NULL;
}
void
set_handlers(int fd, select_handler_T read_func, select_handler_T write_func,
select_handler_T error_func, void *data)
{
#ifndef CONFIG_OS_WIN32
assertm(fd >= 0 && fd < FD_SETSIZE,
"set_handlers: handle %d >= FD_SETSIZE %d",
fd, FD_SETSIZE);
if_assert_failed return;
#endif
#ifdef __GNU__
/* GNU Hurd pflocal bug <http://savannah.gnu.org/bugs/?22861>:
* If ELinks does a select() where the initial exceptfds set
* includes a pipe that is not listed in the other fd_sets,
* then select() always reports an exception there. That
* makes Elinks think the pipe has failed and close it.
* To work around this bug, do not monitor exceptions for
* pipes on the Hurd. */
if (error_func) {
struct stat st;
if (fstat(fd, &st) == 0 && S_ISFIFO(st.st_mode))
error_func = NULL;
}
#endif /* __GNU__ */
threads[fd].read_func = read_func;
threads[fd].write_func = write_func;
threads[fd].error_func = error_func;
threads[fd].data = data;
if (read_func) {
FD_SET(fd, &w_read);
} else {
FD_CLR(fd, &w_read);
FD_CLR(fd, &x_read);
}
if (write_func) {
FD_SET(fd, &w_write);
} else {
FD_CLR(fd, &w_write);
FD_CLR(fd, &x_write);
}
if (error_func) {
FD_SET(fd, &w_error);
} else {
FD_CLR(fd, &w_error);
FD_CLR(fd, &x_error);
}
if (read_func || write_func || error_func) {
if (fd >= w_max) w_max = fd + 1;
} else if (fd == w_max - 1) {
int i;
for (i = fd - 1; i >= 0; i--)
if (FD_ISSET(i, &w_read)
|| FD_ISSET(i, &w_write)
|| FD_ISSET(i, &w_error))
break;
w_max = i + 1;
}
}
void
select_loop(void (*init)(void))
{
timeval_T last_time;
int select_errors = 0;
clear_signal_mask_and_handlers();
FD_ZERO(&w_read);
FD_ZERO(&w_write);
FD_ZERO(&w_error);
w_max = 0;
timeval_now(&last_time);
#ifdef SIGPIPE
signal(SIGPIPE, SIG_IGN);
#endif
init();
check_bottom_halves();
while (!program.terminate) {
struct timeval *timeout = NULL;
int n, i, has_timer;
timeval_T t;
check_signals();
check_timers(&last_time);
redraw_all_terminals();
memcpy(&x_read, &w_read, sizeof(fd_set));
memcpy(&x_write, &w_write, sizeof(fd_set));
memcpy(&x_error, &w_error, sizeof(fd_set));
if (program.terminate) break;
has_timer = get_next_timer_time(&t);
if (!w_max && !has_timer) break;
critical_section = 1;
if (check_signals()) {
critical_section = 0;
continue;
}
#if 0
{
int i;
printf("\nR:");
for (i = 0; i < 256; i++)
if (FD_ISSET(i, &x_read)) printf("%d,", i);
printf("\nW:");
for (i = 0; i < 256; i++)
if (FD_ISSET(i, &x_write)) printf("%d,", i);
printf("\nE:");
for (i = 0; i < 256; i++)
if (FD_ISSET(i, &x_error)) printf("%d,", i);
fflush(stdout);
}
#endif
if (has_timer) {
/* Be sure timeout is not negative. */
timeval_limit_to_zero_or_one(&t);
timeout = (struct timeval *) &t;
}
n = select(w_max, &x_read, &x_write, &x_error, timeout);
if (n < 0) {
/* The following calls (especially gettext)
* might change errno. */
const int errno_from_select = errno;
critical_section = 0;
uninstall_alarm();
if (errno_from_select != EINTR) {
ERROR(gettext("The call to %s failed: %d (%s)"),
"select()", errno_from_select, (unsigned char *) strerror(errno_from_select));
if (++select_errors > 10) /* Infinite loop prevention. */
INTERNAL(gettext("%d select() failures."),
select_errors);
}
continue;
}
select_errors = 0;
critical_section = 0;
uninstall_alarm();
check_signals();
/*printf("sel: %d\n", n);*/
check_timers(&last_time);
i = -1;
while (n > 0 && ++i < w_max) {
int k = 0;
#if 0
printf("C %d : %d,%d,%d\n", i, FD_ISSET(i, &w_read),
FD_ISSET(i, &w_write), FD_ISSET(i, &w_error));
printf("A %d : %d,%d,%d\n", i, FD_ISSET(i, &x_read),
FD_ISSET(i, &x_write), FD_ISSET(i, &x_error));
#endif
if (FD_ISSET(i, &x_read)) {
if (threads[i].read_func) {
threads[i].read_func(threads[i].data);
check_bottom_halves();
}
k = 1;
}
if (FD_ISSET(i, &x_write)) {
if (threads[i].write_func) {
threads[i].write_func(threads[i].data);
check_bottom_halves();
}
k = 1;
}
if (FD_ISSET(i, &x_error)) {
if (threads[i].error_func) {
threads[i].error_func(threads[i].data);
check_bottom_halves();
}
k = 1;
}
n -= k;
}
}
}
static int
can_read_or_write(int fd, int write)
{
struct timeval tv = {0, 0};
fd_set fds;
fd_set *rfds = NULL;
fd_set *wfds = NULL;
FD_ZERO(&fds);
FD_SET(fd, &fds);
if (write)
wfds = &fds;
else
rfds = &fds;
return select(fd + 1, rfds, wfds, NULL, &tv);
}
int
can_read(int fd)
{
return can_read_or_write(fd, 0);
}
int
can_write(int fd)
{
return can_read_or_write(fd, 1);
}
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