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[PATCH] Detaching fbcon: fix give_up_console()

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To allow for detaching fbcon, it must be able to give up the console.
However, the function give_up_console() is plain broken.  It just sets the
entries in the console driver map to NULL, it leaves the vt layer without a
console driver, and does not decrement the module reference count.  Calling
give_up_console() is guaranteed to hang the machine..

To fix this problem, ensure that the virtual consoles are not left dangling
without a driver.  All systems have a default boot driver (either vgacon or
dummycon) which is never unloaded.  For those vt's that lost their driver, the
default boot driver is reassigned back to them.

Signed-off-by: Antonino Daplas <adaplas@pol.net>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Antonino A. Daplas 2006-06-26 00:27:03 -07:00 committed by Linus Torvalds
parent 50ec42edd9
commit 1c8ce271fe
1 changed files with 21 additions and 8 deletions
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29
drivers/char/vt.c
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@ -100,6 +100,7 @@
const struct consw *conswitchp;
static struct consw *defcsw; /* default console */
/* A bitmap for codes <32. A bit of 1 indicates that the code
* corresponding to that bit number invokes some special action
@ -2673,17 +2674,23 @@ int take_over_console(const struct consw *csw, int first, int last, int deflt)
if (!try_module_get(owner))
return -ENODEV;
acquire_console_sem();
/* save default console, for possible recovery later on */
if (!defcsw)
defcsw = (struct consw *) conswitchp;
acquire_console_sem();
desc = csw->con_startup();
if (!desc) {
release_console_sem();
module_put(owner);
return -ENODEV;
}
if (deflt) {
if (conswitchp)
module_put(conswitchp->owner);
__module_get(owner);
conswitchp = csw;
}
@ -2701,6 +2708,7 @@ int take_over_console(const struct consw *csw, int first, int last, int deflt)
continue;
j = i;
if (CON_IS_VISIBLE(vc)) {
k = i;
save_screen(vc);
@ -2709,10 +2717,8 @@ int take_over_console(const struct consw *csw, int first, int last, int deflt)
old_was_color = vc->vc_can_do_color;
vc->vc_sw->con_deinit(vc);
vc->vc_origin = (unsigned long)vc->vc_screenbuf;
vc->vc_visible_origin = vc->vc_origin;
vc->vc_scr_end = vc->vc_origin + vc->vc_screenbuf_size;
vc->vc_pos = vc->vc_origin + vc->vc_size_row * vc->vc_y + 2 * vc->vc_x;
visual_init(vc, i, 0);
set_origin(vc);
update_attr(vc);
/* If the console changed between mono <-> color, then
@ -2741,22 +2747,29 @@ int take_over_console(const struct consw *csw, int first, int last, int deflt)
printk("to %s\n", desc);
release_console_sem();
module_put(owner);
return 0;
}
void give_up_console(const struct consw *csw)
{
int i;
int i, first = -1, last = -1, deflt = 0;
for(i = 0; i < MAX_NR_CONSOLES; i++)
for (i = 0; i < MAX_NR_CONSOLES; i++)
if (con_driver_map[i] == csw) {
if (first == -1)
first = i;
last = i;
module_put(csw->owner);
con_driver_map[i] = NULL;
}
}
if (first != -1 && defcsw) {
if (first == 0 && last == MAX_NR_CONSOLES - 1)
deflt = 1;
take_over_console(defcsw, first, last, deflt);
}
}
#endif
/*