Alan,
patch against -ac20 fixes a few things:
- console.c: reviewed and commented locking rules
- tioclinux(): set_selection() was racy wrt console writes, which
causes mouse droppings on the screen when using gpm. It was
always SMP racy. Removing the console_lock make it UP-racy.
Now fixed.
- con_flush_chars(): this is being called from timer context,
and for a couple of people it was going splat on a BUG() I
added when they were switching from X back to the console.
We just skip the flush in this case.
This could possibly cause the cursor to not be present until
a character is output immediately after switching out of X,
but it works for me, and it's not obvious that this is worth
straining over.
- In reset_vc(), don't call set_pallette() in interrupt context.
It's racy. This only happens when SAK is used.
- keyboard.c: poke the cosole after printing, rather than before.
See below for details...
- printk.c: fix the off-by-one which prevented a bare
printk(KERN_ERR);
from working.
- add lib/bust_spinlocks.c for archs which don't provide one.
Outstanding problems (of which I'm aware):
1: riva_hw.c:ShowHideCursor() is called from a timer
handler and a race here could cause registers to get the
wrong values. It was always racy on SMP. The driver
needs locking.
2: This code:
printk(KERN_ERR "something");
console_loglevel = something_else;
is now racy, because the actual printing of the output
could be deferred if someone currently holds console_sem().
The only known instance of this is the sysrq handler, and
I fixed that.
The corresponding patch against 2.4.3-pre6 is at
http://www.uow.edu.au/~andrewm/linux/console.html
--- linux-2.4.2-ac20/drivers/char/console.c Tue Mar 13 20:29:21 2001
+++ ac/drivers/char/console.c Thu Mar 22 21:29:10 2001
@@ -69,6 +69,9 @@
*
* Removed old-style timers, introduced console_timer, made timer
* deletion SMP-safe. 17Jun00, Andrew Morton <[email protected]>
+ *
+ * Removed console_lock, enabled interrupts across all console operations
+ * 13 March 2001, Andrew Morton
*/
#include <linux/module.h>
@@ -1034,6 +1037,7 @@
color = def_color;
}
+/* console_sem is held */
static void csi_m(int currcons)
{
int i;
@@ -1173,6 +1177,7 @@
return report_mouse;
}
+/* console_sem is held */
static void set_mode(int currcons, int on_off)
{
int i;
@@ -1238,6 +1243,7 @@
}
}
+/* console_sem is held */
static void setterm_command(int currcons)
{
switch(par[0]) {
@@ -1292,19 +1298,7 @@
}
}
-static void insert_line(int currcons, unsigned int nr)
-{
- scrdown(currcons,y,bottom,nr);
- need_wrap = 0;
-}
-
-
-static void delete_line(int currcons, unsigned int nr)
-{
- scrup(currcons,y,bottom,nr);
- need_wrap = 0;
-}
-
+/* console_sem is held */
static void csi_at(int currcons, unsigned int nr)
{
if (nr > video_num_columns - x)
@@ -1314,15 +1308,18 @@
insert_char(currcons, nr);
}
+/* console_sem is held */
static void csi_L(int currcons, unsigned int nr)
{
if (nr > video_num_lines - y)
nr = video_num_lines - y;
else if (!nr)
nr = 1;
- insert_line(currcons, nr);
+ scrdown(currcons,y,bottom,nr);
+ need_wrap = 0;
}
+/* console_sem is held */
static void csi_P(int currcons, unsigned int nr)
{
if (nr > video_num_columns - x)
@@ -1332,15 +1329,18 @@
delete_char(currcons, nr);
}
+/* console_sem is held */
static void csi_M(int currcons, unsigned int nr)
{
if (nr > video_num_lines - y)
nr = video_num_lines - y;
else if (!nr)
nr=1;
- delete_line(currcons, nr);
+ scrup(currcons,y,bottom,nr);
+ need_wrap = 0;
}
+/* console_sem is held (except via vc_init->reset_terminal */
static void save_cur(int currcons)
{
saved_x = x;
@@ -1355,6 +1355,7 @@
saved_G1 = G1_charset;
}
+/* console_sem is held */
static void restore_cur(int currcons)
{
gotoxy(currcons,saved_x,saved_y);
@@ -1375,6 +1376,7 @@
EShash, ESsetG0, ESsetG1, ESpercent, ESignore, ESnonstd,
ESpalette };
+/* console_sem is held (except via vc_init()) */
static void reset_terminal(int currcons, int do_clear)
{
top = 0;
@@ -1430,6 +1432,7 @@
csi_J(currcons,2);
}
+/* console_sem is held */
static void do_con_trol(struct tty_struct *tty, unsigned int currcons, int c)
{
/*
@@ -1810,6 +1813,7 @@
#define CON_BUF_SIZE PAGE_SIZE
DECLARE_MUTEX(con_buf_sem);
+/* acquires console_sem */
static int do_con_write(struct tty_struct * tty, int from_user,
const unsigned char *buf, int count)
{
@@ -2049,7 +2053,7 @@
void set_console(int nr)
{
want_console = nr;
- schedule_task(&console_callback_tq);
+ schedule_console_callback();
}
#ifdef CONFIG_VT_CONSOLE
@@ -2171,9 +2175,21 @@
* Handling of Linux-specific VC ioctls
*/
+/*
+ * Generally a bit racy with respect to console_sem().
+ *
+ * There are some functions which don't need it.
+ *
+ * There are some functions which can sleep for arbitrary periods (paste_selection)
+ * but we don't need the lock there anyway.
+ *
+ * set_selection has locking, and definitely needs it
+ */
+
int tioclinux(struct tty_struct *tty, unsigned long arg)
{
char type, data;
+ int ret;
if (tty->driver.type != TTY_DRIVER_TYPE_CONSOLE)
return -EINVAL;
@@ -2181,17 +2197,23 @@
return -EPERM;
if (get_user(type, (char *)arg))
return -EFAULT;
+ ret = 0;
switch (type)
{
case 2:
- return set_selection(arg, tty, 1);
+ acquire_console_sem();
+ ret = set_selection(arg, tty, 1);
+ release_console_sem();
+ break;
case 3:
- return paste_selection(tty);
+ ret = paste_selection(tty);
+ break;
case 4:
unblank_screen();
- return 0;
+ break;
case 5:
- return sel_loadlut(arg);
+ ret = sel_loadlut(arg);
+ break;
case 6:
/*
@@ -2201,24 +2223,33 @@
* related to the kernel should not use this.
*/
data = shift_state;
- return __put_user(data, (char *) arg);
+ ret = __put_user(data, (char *) arg);
+ break;
case 7:
data = mouse_reporting();
- return __put_user(data, (char *) arg);
+ ret = __put_user(data, (char *) arg);
+ break;
case 10:
set_vesa_blanking(arg);
- return 0;
+ break;;
case 11: /* set kmsg redirect */
- if (!capable(CAP_SYS_ADMIN))
- return -EPERM;
- if (get_user(data, (char *)arg+1))
- return -EFAULT;
- kmsg_redirect = data;
- return 0;
+ if (!capable(CAP_SYS_ADMIN)) {
+ ret = -EPERM;
+ } else {
+ if (get_user(data, (char *)arg+1))
+ ret = -EFAULT;
+ else
+ kmsg_redirect = data;
+ }
+ break;
case 12: /* get fg_console */
- return fg_console;
+ ret = fg_console;
+ break;
+ default:
+ ret = -EINVAL;
+ break;
}
- return -EINVAL;
+ return ret;
}
/*
@@ -2304,6 +2335,9 @@
static void con_flush_chars(struct tty_struct *tty)
{
struct vt_struct *vt = (struct vt_struct *)tty->driver_data;
+
+ if (in_interrupt()) /* from flush_to_ldisc */
+ return;
pm_access(pm_con);
acquire_console_sem();
--- linux-2.4.2-ac20/drivers/video/fbcon.c Tue Mar 13 20:29:28 2001
+++ ac/drivers/video/fbcon.c Thu Mar 22 21:29:10 2001
@@ -1149,8 +1149,8 @@
start++;
}
}
- console_conditional_schedule();
scr_writew(c, d);
+ console_conditional_schedule();
s++;
d++;
} while (s < le);
--- linux-2.4.2-ac20/drivers/char/vt.c Tue Mar 13 20:29:22 2001
+++ ac/drivers/char/vt.c Thu Mar 22 21:29:10 2001
@@ -23,6 +23,7 @@
#include <linux/major.h>
#include <linux/fs.h>
#include <linux/console.h>
+#include <linux/irq.h>
#include <asm/io.h>
#include <asm/uaccess.h>
@@ -1169,7 +1170,8 @@
vt_cons[new_console]->vt_mode.frsig = 0;
vt_cons[new_console]->vt_pid = -1;
vt_cons[new_console]->vt_newvt = -1;
- reset_palette (new_console) ;
+ if (!in_interrupt()) /* Via keyboard.c:SAK() - akpm */
+ reset_palette (new_console) ;
}
/*
--- linux-2.4.2-ac20/drivers/char/keyboard.c Tue Mar 13 20:29:21 2001
+++ ac/drivers/char/keyboard.c Thu Mar 22 21:29:10 2001
@@ -205,9 +205,6 @@
char raw_mode;
pm_access(pm_kbd);
-
- do_poke_blanked_console = 1;
- schedule_console_callback();
add_keyboard_randomness(scancode | up_flag);
tty = ttytab? ttytab[fg_console]: NULL;
@@ -233,7 +230,7 @@
* Convert scancode to keycode
*/
if (!kbd_translate(scancode, &keycode, raw_mode))
- return;
+ goto out;
/*
* At this point the variable `keycode' contains the keycode.
@@ -252,11 +249,11 @@
#ifdef CONFIG_MAGIC_SYSRQ /* Handle the SysRq Hack */
if (keycode == SYSRQ_KEY) {
sysrq_pressed = !up_flag;
- return;
+ goto out;
} else if (sysrq_pressed) {
if (!up_flag) {
handle_sysrq(kbd_sysrq_xlate[keycode], kbd_pt_regs, kbd, tty);
- return;
+ goto out;
}
}
#endif
@@ -298,7 +295,7 @@
if (type >= 0xf0) {
type -= 0xf0;
if (raw_mode && ! (TYPES_ALLOWED_IN_RAW_MODE & (1 << type)))
- return;
+ goto out;
if (type == KT_LETTER) {
type = KT_LATIN;
if (vc_kbd_led(kbd, VC_CAPSLOCK)) {
@@ -329,6 +326,9 @@
#endif
}
}
+out:
+ do_poke_blanked_console = 1;
+ schedule_console_callback();
}
--- linux-2.4.2-ac20/drivers/char/sysrq.c Tue Mar 13 20:29:22 2001
+++ ac/drivers/char/sysrq.c Thu Mar 22 21:29:10 2001
@@ -58,7 +58,6 @@
* This function is called by the keyboard handler when SysRq is pressed
* and any other keycode arrives.
*/
-
void handle_sysrq(int key, struct pt_regs *pt_regs,
struct kbd_struct *kbd, struct tty_struct *tty)
{
@@ -153,6 +152,15 @@
/* Don't use 'A' as it's handled specially on the Sparc */
}
+ /*
+ * There's a race here. keyboard.c:handle_scancode() has done a
+ * schedule_task(console_callback). On another CPU, console_callback()
+ * will acquire the console_sem. So the above printk()'s _could_ end up
+ * getting buffered in log_buf, and will be printed by keventd in console_callback()'s
+ * release_console_sem(). But by the time that happens, this CPU has changed
+ * console_loglevel, so the output won't be shown on the console. The workaround
+ * was to move the console poking to the end of handle_scancode().
+ */
console_loglevel = orig_log_level;
}
--- linux-2.4.2-ac20/kernel/printk.c Tue Mar 13 20:29:30 2001
+++ ac/kernel/printk.c Thu Mar 22 22:49:36 2001
@@ -267,6 +267,7 @@
spin_lock_irq(&logbuf_lock);
error = log_end - log_start;
spin_unlock_irq(&logbuf_lock);
+ break;
default:
error = -EINVAL;
break;
@@ -328,7 +329,7 @@
start_print = start;
while (cur_index != end) {
if ( msg_level < 0 &&
- ((end - cur_index) > 3) &&
+ ((end - cur_index) >= 3) &&
LOG_BUF(cur_index + 0) == '<' &&
LOG_BUF(cur_index + 1) >= '0' &&
LOG_BUF(cur_index + 1) <= '7' &&
@@ -343,6 +344,15 @@
cur_index++;
if (c == '\n') {
+ if (msg_level < 0) {
+ /*
+ * printk() has already given us loglevel tags in
+ * the buffer. This code is here in case the
+ * log buffer has wrapped right round and scribbled
+ * on those tags
+ */
+ msg_level = default_message_loglevel;
+ }
_call_console_drivers(start_print, cur_index, msg_level);
msg_level = -1;
start_print = cur_index;
@@ -373,6 +383,10 @@
* into the log buffer and return. The current holder of the console_sem will
* notice the new output in release_console_sem() and will send it to the
* consoles before releasing the semaphore.
+ *
+ * One effect of this deferred printing is that code which calls printk() and
+ * then changes console_loglevel may break. This is because console_loglevel
+ * is inspected when the actual printing occurs.
*/
asmlinkage int printk(const char *fmt, ...)
{
@@ -479,10 +493,11 @@
{
unsigned long flags;
unsigned long _con_start, _log_end;
- unsigned long must_wake_klogd;
+ unsigned long must_wake_klogd = 0;
for ( ; ; ) {
spin_lock_irqsave(&logbuf_lock, flags);
+ must_wake_klogd |= log_start - log_end;
if (con_start == log_end)
break; /* Nothing to print */
_con_start = con_start;
@@ -491,7 +506,6 @@
spin_unlock_irqrestore(&logbuf_lock, flags);
call_console_drivers(_con_start, _log_end);
}
- must_wake_klogd = log_start - log_end;
console_may_schedule = 0;
up(&console_sem);
spin_unlock_irqrestore(&logbuf_lock, flags);
--- linux-2.4.2-ac20/lib/Makefile Sat Dec 30 09:07:24 2000
+++ ac/lib/Makefile Thu Mar 22 21:29:10 2001
@@ -10,7 +10,7 @@
export-objs := cmdline.o
-obj-y := errno.o ctype.o string.o vsprintf.o brlock.o cmdline.o
+obj-y := errno.o ctype.o string.o vsprintf.o brlock.o cmdline.o bust_spinlocks.o
ifneq ($(CONFIG_HAVE_DEC_LOCK),y)
obj-y += dec_and_lock.o
--- linux-2.4.2-ac20/lib/bust_spinlocks.c Thu Jan 1 00:00:00 1970
+++ ac/lib/bust_spinlocks.c Thu Mar 22 21:29:10 2001
@@ -0,0 +1,38 @@
+/*
+ * lib/bust_spinlocks.c
+ *
+ * Provides a minimal bust_spinlocks for architectures which don't have one of their own.
+ *
+ * bust_spinlocks() clears any spinlocks which would prevent oops, die(), BUG()
+ * and panic() information from reaching the user.
+ */
+
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/tty.h>
+#include <linux/wait.h>
+#include <linux/vt_kern.h>
+
+extern spinlock_t timerlist_lock;
+
+void bust_spinlocks(int yes)
+{
+ spin_lock_init(&timerlist_lock);
+ if (yes) {
+ oops_in_progress = 1;
+ } else {
+ int loglevel_save = console_loglevel;
+ unblank_screen();
+ oops_in_progress = 0;
+ /*
+ * OK, the message is on the console. Now we call printk()
+ * without oops_in_progress set so that printk() will give klogd
+ * and the blanked console a poke. Hold onto your hats...
+ */
+ console_loglevel = 15; /* NMI oopser may have shut the console up */
+ printk(" ");
+ console_loglevel = loglevel_save;
+ }
+}
+
+