From 249f7b3e1383d6889889927351b7b018532d2ca1 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Thu, 5 Jun 2014 16:24:47 +0200 Subject: vt: Fix replacement console check when unbinding I don't fully understand the magic of the vt register/unregister logic, but apparently everything but the inital console (as set in the conswitchp pointer) is marked with FLAG_MODULE. Which means if something unregistered the boot vt driver (e.g. i915.ko kicking out vga_con) there's nothing left when trying to unbind e.g. fbcon through sysfs. But in most cases have the dummy console hanging around besides the boot console, so this test is fairly dubious. What we actually want is simply a different console than the one we want to unbind. v2: Correct the commit message to clarify that the dummy console isn't always around, but only in most cases (David). Cc: Greg Kroah-Hartman Cc: Jiri Slaby Cc: David Herrmann Reviewed-by: David Herrmann Acked-by: Greg Kroah-Hartman Signed-off-by: Daniel Vetter --- drivers/tty/vt/vt.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) (limited to 'drivers/tty/vt/vt.c') diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 3ad0b61..ea600f4 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -3155,8 +3155,7 @@ int do_unbind_con_driver(const struct consw *csw, int first, int last, int deflt for (i = 0; i < MAX_NR_CON_DRIVER; i++) { con_back = ®istered_con_driver[i]; - if (con_back->con && - !(con_back->flag & CON_DRIVER_FLAG_MODULE)) { + if (con_back->con && con_back->con != csw) { defcsw = con_back->con; retval = 0; break; -- cgit v1.1 From d9c660e750fdf982e1e2bdd0e76c1e6c4db4217b Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Thu, 5 Jun 2014 16:29:56 +0200 Subject: vt: Fix up unregistration of vt drivers A bunch of issues: - We should not kick out the default console (which is tracked in conswitchp), so check for that. - Add better error codes so callers can differentiate between "something went wrong" and "your driver isn't registered already". i915 needs that so it doesn't fall over when reloading the driver and hence vga_con is already unregistered. - There's a mess with the driver flags: What we need to check for is that the driver isn't used any more, i.e. unbound completely (FLAG_INIT). And not whether it's the boot console or not (which is the only one which doesn't have FLAG_MODULE). Otherwise there's no way to kick out the boot console, which i915 wants to do to prevent havoc with vga_con interferring (which tends to hang machines). Cc: Greg Kroah-Hartman Cc: Jiri Slaby Reviewed-by: David Herrmann Acked-by: Greg Kroah-Hartman Signed-off-by: Daniel Vetter --- drivers/tty/vt/vt.c | 16 +++++++++------- 1 file changed, 9 insertions(+), 7 deletions(-) (limited to 'drivers/tty/vt/vt.c') diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index ea600f4..5077fe8 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -3573,17 +3573,20 @@ err: */ int do_unregister_con_driver(const struct consw *csw) { - int i, retval = -ENODEV; + int i; /* cannot unregister a bound driver */ if (con_is_bound(csw)) - goto err; + return -EBUSY; + + if (csw == conswitchp) + return -EINVAL; for (i = 0; i < MAX_NR_CON_DRIVER; i++) { struct con_driver *con_driver = ®istered_con_driver[i]; if (con_driver->con == csw && - con_driver->flag & CON_DRIVER_FLAG_MODULE) { + con_driver->flag & CON_DRIVER_FLAG_INIT) { vtconsole_deinit_device(con_driver); device_destroy(vtconsole_class, MKDEV(0, con_driver->node)); @@ -3594,12 +3597,11 @@ int do_unregister_con_driver(const struct consw *csw) con_driver->flag = 0; con_driver->first = 0; con_driver->last = 0; - retval = 0; - break; + return 0; } } -err: - return retval; + + return -ENODEV; } EXPORT_SYMBOL_GPL(do_unregister_con_driver); -- cgit v1.1 From f418f2ec440ab8c014f37539ef0b19271afb1186 Mon Sep 17 00:00:00 2001 From: Daniel Vetter Date: Thu, 5 Jun 2014 16:33:24 +0200 Subject: vt: Don't ignore unbind errors in vt_unbind Otherwise the loop will never stop since we don't make any forward progress. Noticed while breaking this accidentally in a painful attempt to make vga_con unregistering work. With this patch we'll bail out on the first attempt, which at least leaves a useful enough system behind for debugging. Livelocks on console_lock just aren't fun. Cc: Greg Kroah-Hartman Cc: Jiri Slaby Reviewed-by: David Herrmann Acked-by: Greg Kroah-Hartman Signed-off-by: Daniel Vetter --- drivers/tty/vt/vt.c | 5 ++++- 1 file changed, 4 insertions(+), 1 deletion(-) (limited to 'drivers/tty/vt/vt.c') diff --git a/drivers/tty/vt/vt.c b/drivers/tty/vt/vt.c index 5077fe8..3c00dcb 100644 --- a/drivers/tty/vt/vt.c +++ b/drivers/tty/vt/vt.c @@ -3260,6 +3260,7 @@ static int vt_unbind(struct con_driver *con) { const struct consw *csw = NULL; int i, more = 1, first = -1, last = -1, deflt = 0; + int ret; if (!con->con || !(con->flag & CON_DRIVER_FLAG_MODULE) || con_is_graphics(con->con, con->first, con->last)) @@ -3285,8 +3286,10 @@ static int vt_unbind(struct con_driver *con) if (first != -1) { console_lock(); - do_unbind_con_driver(csw, first, last, deflt); + ret = do_unbind_con_driver(csw, first, last, deflt); console_unlock(); + if (ret != 0) + return ret; } first = -1; -- cgit v1.1