diff options
| -rw-r--r-- | drivers/s390/char/con3215.c | 25 | ||||
| -rw-r--r-- | drivers/s390/char/con3270.c | 31 | ||||
| -rw-r--r-- | drivers/s390/char/raw3270.c | 15 | ||||
| -rw-r--r-- | drivers/s390/char/raw3270.h | 1 | ||||
| -rw-r--r-- | drivers/s390/char/sclp_con.c | 26 | ||||
| -rw-r--r-- | drivers/s390/char/sclp_vt220.c | 42 |
6 files changed, 83 insertions, 57 deletions
diff --git a/drivers/s390/char/con3215.c b/drivers/s390/char/con3215.c index f356607835d8..4ae07c7e2175 100644 --- a/drivers/s390/char/con3215.c +++ b/drivers/s390/char/con3215.c @@ -771,35 +771,36 @@ static struct tty_driver *con3215_device(struct console *c, int *index) } /* - * panic() calls con3215_flush through a panic_notifier - * before the system enters a disabled, endless loop. + * The below function is called as a panic/reboot notifier before the + * system enters a disabled, endless loop. + * + * Notice we must use the spin_trylock() alternative, to prevent lockups + * in atomic context (panic routine runs with secondary CPUs, local IRQs + * and preemption disabled). */ -static void con3215_flush(void) +static int con3215_notify(struct notifier_block *self, + unsigned long event, void *data) { struct raw3215_info *raw; unsigned long flags; raw = raw3215[0]; /* console 3215 is the first one */ - spin_lock_irqsave(get_ccwdev_lock(raw->cdev), flags); + if (!spin_trylock_irqsave(get_ccwdev_lock(raw->cdev), flags)) + return NOTIFY_DONE; raw3215_make_room(raw, RAW3215_BUFFER_SIZE); spin_unlock_irqrestore(get_ccwdev_lock(raw->cdev), flags); -} -static int con3215_notify(struct notifier_block *self, - unsigned long event, void *data) -{ - con3215_flush(); - return NOTIFY_OK; + return NOTIFY_DONE; } static struct notifier_block on_panic_nb = { .notifier_call = con3215_notify, - .priority = 0, + .priority = INT_MIN + 1, /* run the callback late */ }; static struct notifier_block on_reboot_nb = { .notifier_call = con3215_notify, - .priority = 0, + .priority = INT_MIN + 1, /* run the callback late */ }; /* diff --git a/drivers/s390/char/con3270.c b/drivers/s390/char/con3270.c index e4592890f20a..10f6a37fb153 100644 --- a/drivers/s390/char/con3270.c +++ b/drivers/s390/char/con3270.c @@ -535,20 +535,26 @@ con3270_wait_write(struct con3270 *cp) } /* - * panic() calls con3270_flush through a panic_notifier - * before the system enters a disabled, endless loop. + * The below function is called as a panic/reboot notifier before the + * system enters a disabled, endless loop. + * + * Notice we must use the spin_trylock() alternative, to prevent lockups + * in atomic context (panic routine runs with secondary CPUs, local IRQs + * and preemption disabled). */ -static void -con3270_flush(void) +static int con3270_notify(struct notifier_block *self, + unsigned long event, void *data) { struct con3270 *cp; unsigned long flags; cp = condev; if (!cp->view.dev) - return; - raw3270_activate_view(&cp->view); - spin_lock_irqsave(&cp->view.lock, flags); + return NOTIFY_DONE; + if (!raw3270_view_lock_unavailable(&cp->view)) + raw3270_activate_view(&cp->view); + if (!spin_trylock_irqsave(&cp->view.lock, flags)) + return NOTIFY_DONE; con3270_wait_write(cp); cp->nr_up = 0; con3270_rebuild_update(cp); @@ -560,23 +566,18 @@ con3270_flush(void) con3270_wait_write(cp); } spin_unlock_irqrestore(&cp->view.lock, flags); -} -static int con3270_notify(struct notifier_block *self, - unsigned long event, void *data) -{ - con3270_flush(); - return NOTIFY_OK; + return NOTIFY_DONE; } static struct notifier_block on_panic_nb = { .notifier_call = con3270_notify, - .priority = 0, + .priority = INT_MIN + 1, /* run the callback late */ }; static struct notifier_block on_reboot_nb = { .notifier_call = con3270_notify, - .priority = 0, + .priority = INT_MIN + 1, /* run the callback late */ }; /* diff --git a/drivers/s390/char/raw3270.c b/drivers/s390/char/raw3270.c index dfde0d941c3c..4e2b3a1a3b2e 100644 --- a/drivers/s390/char/raw3270.c +++ b/drivers/s390/char/raw3270.c @@ -831,6 +831,21 @@ raw3270_create_device(struct ccw_device *cdev) } /* + * This helper just validates that it is safe to activate a + * view in the panic() context, due to locking restrictions. + */ +int raw3270_view_lock_unavailable(struct raw3270_view *view) +{ + struct raw3270 *rp = view->dev; + + if (!rp) + return -ENODEV; + if (spin_is_locked(get_ccwdev_lock(rp->cdev))) + return -EBUSY; + return 0; +} + +/* * Activate a view. */ int diff --git a/drivers/s390/char/raw3270.h b/drivers/s390/char/raw3270.h index c6645167cd2b..4cb6b5ee44ca 100644 --- a/drivers/s390/char/raw3270.h +++ b/drivers/s390/char/raw3270.h @@ -160,6 +160,7 @@ struct raw3270_view { }; int raw3270_add_view(struct raw3270_view *, struct raw3270_fn *, int, int); +int raw3270_view_lock_unavailable(struct raw3270_view *view); int raw3270_activate_view(struct raw3270_view *); void raw3270_del_view(struct raw3270_view *); void raw3270_deactivate_view(struct raw3270_view *); diff --git a/drivers/s390/char/sclp_con.c b/drivers/s390/char/sclp_con.c index fe5ee2646fcf..e5d947c763ea 100644 --- a/drivers/s390/char/sclp_con.c +++ b/drivers/s390/char/sclp_con.c @@ -220,30 +220,34 @@ sclp_console_device(struct console *c, int *index) } /* - * Make sure that all buffers will be flushed to the SCLP. + * This panic/reboot notifier makes sure that all buffers + * will be flushed to the SCLP. */ -static void -sclp_console_flush(void) +static int sclp_console_notify(struct notifier_block *self, + unsigned long event, void *data) { + /* + * Perform the lock check before effectively getting the + * lock on sclp_conbuf_emit() / sclp_console_sync_queue() + * to prevent potential lockups in atomic context. + */ + if (spin_is_locked(&sclp_con_lock)) + return NOTIFY_DONE; + sclp_conbuf_emit(); sclp_console_sync_queue(); -} -static int sclp_console_notify(struct notifier_block *self, - unsigned long event, void *data) -{ - sclp_console_flush(); - return NOTIFY_OK; + return NOTIFY_DONE; } static struct notifier_block on_panic_nb = { .notifier_call = sclp_console_notify, - .priority = 1, + .priority = INT_MIN + 1, /* run the callback late */ }; static struct notifier_block on_reboot_nb = { .notifier_call = sclp_console_notify, - .priority = 1, + .priority = INT_MIN + 1, /* run the callback late */ }; /* diff --git a/drivers/s390/char/sclp_vt220.c b/drivers/s390/char/sclp_vt220.c index 3b4e7e5d9b71..a32f34a1c6d2 100644 --- a/drivers/s390/char/sclp_vt220.c +++ b/drivers/s390/char/sclp_vt220.c @@ -769,21 +769,6 @@ __initcall(sclp_vt220_tty_init); #ifdef CONFIG_SCLP_VT220_CONSOLE -static void __sclp_vt220_flush_buffer(void) -{ - unsigned long flags; - - sclp_vt220_emit_current(); - spin_lock_irqsave(&sclp_vt220_lock, flags); - del_timer(&sclp_vt220_timer); - while (sclp_vt220_queue_running) { - spin_unlock_irqrestore(&sclp_vt220_lock, flags); - sclp_sync_wait(); - spin_lock_irqsave(&sclp_vt220_lock, flags); - } - spin_unlock_irqrestore(&sclp_vt220_lock, flags); -} - static void sclp_vt220_con_write(struct console *con, const char *buf, unsigned int count) { @@ -797,22 +782,41 @@ sclp_vt220_con_device(struct console *c, int *index) return sclp_vt220_driver; } +/* + * This panic/reboot notifier runs in atomic context, so + * locking restrictions apply to prevent potential lockups. + */ static int sclp_vt220_notify(struct notifier_block *self, unsigned long event, void *data) { - __sclp_vt220_flush_buffer(); - return NOTIFY_OK; + unsigned long flags; + + if (spin_is_locked(&sclp_vt220_lock)) + return NOTIFY_DONE; + + sclp_vt220_emit_current(); + + spin_lock_irqsave(&sclp_vt220_lock, flags); + del_timer(&sclp_vt220_timer); + while (sclp_vt220_queue_running) { + spin_unlock_irqrestore(&sclp_vt220_lock, flags); + sclp_sync_wait(); + spin_lock_irqsave(&sclp_vt220_lock, flags); + } + spin_unlock_irqrestore(&sclp_vt220_lock, flags); + + return NOTIFY_DONE; } static struct notifier_block on_panic_nb = { .notifier_call = sclp_vt220_notify, - .priority = 1, + .priority = INT_MIN + 1, /* run the callback late */ }; static struct notifier_block on_reboot_nb = { .notifier_call = sclp_vt220_notify, - .priority = 1, + .priority = INT_MIN + 1, /* run the callback late */ }; /* Structure needed to register with printk */ |