kgdb_nmi uses tasklets on the assumption they will not be scheduled until the next timer tick. This assumption is invalid and can lead to live lock, continually servicing the kgdb_nmi tasklet. This is fixed by using the timer API instead.
Signed-off-by: Daniel Thompson daniel.thompson@linaro.org --- drivers/tty/serial/kgdb_nmi.c | 30 +++++++++--------------------- 1 file changed, 9 insertions(+), 21 deletions(-)
diff --git a/drivers/tty/serial/kgdb_nmi.c b/drivers/tty/serial/kgdb_nmi.c index d51b2a1..20d21d0 100644 --- a/drivers/tty/serial/kgdb_nmi.c +++ b/drivers/tty/serial/kgdb_nmi.c @@ -80,24 +80,10 @@ static struct console kgdb_nmi_console = {
struct kgdb_nmi_tty_priv { struct tty_port port; - struct tasklet_struct tlet; + struct timer_list timer; STRUCT_KFIFO(char, KGDB_NMI_FIFO_SIZE) fifo; };
-/* - * Our debugging console is polled in a tasklet, so we'll check for input - * every tick. In HZ-less mode, we should program the next tick. We have - * to use the lowlevel stuff as no locks should be grabbed. - */ -#ifdef CONFIG_HIGH_RES_TIMERS -static void kgdb_tty_poke(void) -{ - tick_program_event(ktime_get(), 0); -} -#else -static inline void kgdb_tty_poke(void) {} -#endif - static struct tty_port *kgdb_nmi_port;
static void kgdb_tty_recv(int ch) @@ -108,14 +94,13 @@ static void kgdb_tty_recv(int ch) if (!kgdb_nmi_port || ch < 0) return; /* - * Can't use port->tty->driver_data as tty might be not there. Tasklet + * Can't use port->tty->driver_data as tty might be not there. Timer * will check for tty and will get the ref, but here we don't have to * do that, and actually, we can't: we're in NMI context, no locks are * possible. */ priv = container_of(kgdb_nmi_port, struct kgdb_nmi_tty_priv, port); kfifo_in(&priv->fifo, &c, 1); - kgdb_tty_poke(); }
static int kgdb_nmi_poll_one_knock(void) @@ -199,7 +184,8 @@ static void kgdb_nmi_tty_receiver(unsigned long data) struct kgdb_nmi_tty_priv *priv = (void *)data; char ch;
- tasklet_schedule(&priv->tlet); + priv->timer.expires = jiffies + (HZ/100); + add_timer(&priv->timer);
if (likely(!kgdb_nmi_tty_enabled || !kfifo_len(&priv->fifo))) return; @@ -215,7 +201,9 @@ static int kgdb_nmi_tty_activate(struct tty_port *port, struct tty_struct *tty) container_of(port, struct kgdb_nmi_tty_priv, port);
kgdb_nmi_port = port; - tasklet_schedule(&priv->tlet); + priv->timer.expires = jiffies + (HZ/100); + add_timer(&priv->timer); + return 0; }
@@ -224,7 +212,7 @@ static void kgdb_nmi_tty_shutdown(struct tty_port *port) struct kgdb_nmi_tty_priv *priv = container_of(port, struct kgdb_nmi_tty_priv, port);
- tasklet_kill(&priv->tlet); + del_timer(&priv->timer); kgdb_nmi_port = NULL; }
@@ -243,7 +231,7 @@ static int kgdb_nmi_tty_install(struct tty_driver *drv, struct tty_struct *tty) return -ENOMEM;
INIT_KFIFO(priv->fifo); - tasklet_init(&priv->tlet, kgdb_nmi_tty_receiver, (unsigned long)priv); + setup_timer(&priv->timer, kgdb_nmi_tty_receiver, (unsigned long)priv); tty_port_init(&priv->port); priv->port.ops = &kgdb_nmi_tty_port_ops; tty->driver_data = priv;