From 656d9125376006cf696b0836f1c6723a892629ca Mon Sep 17 00:00:00 2001 From: Martin Schwidefsky Date: Fri, 17 Feb 2012 10:29:22 +0100 Subject: [PATCH] [S390] 3215 deadlock with tty_wakeup The 3215 driver calls tty_wakeup from irq context while holding the device spinlock. If printk is called by any function on the callchain starting from tty_wakeup the system deadlocks on the device spinlock. Using a tasklet to call tty_wakup solves the problem. Signed-off-by: Martin Schwidefsky --- drivers/s390/char/con3215.c | 22 +++++++++++++++------- 1 file changed, 15 insertions(+), 7 deletions(-) diff --git a/drivers/s390/char/con3215.c b/drivers/s390/char/con3215.c index 934458ad55e5..e71a50d4b221 100644 --- a/drivers/s390/char/con3215.c +++ b/drivers/s390/char/con3215.c @@ -87,6 +87,7 @@ struct raw3215_info { struct tty_struct *tty; /* pointer to tty structure if present */ struct raw3215_req *queued_read; /* pointer to queued read requests */ struct raw3215_req *queued_write;/* pointer to queued write requests */ + struct tasklet_struct tlet; /* tasklet to invoke tty_wakeup */ wait_queue_head_t empty_wait; /* wait queue for flushing */ struct timer_list timer; /* timer for delayed output */ int line_pos; /* position on the line (for tabs) */ @@ -333,20 +334,24 @@ static inline void raw3215_try_io(struct raw3215_info *raw) } } +/* + * Call tty_wakeup from tasklet context + */ +static void raw3215_wakeup(unsigned long data) +{ + struct raw3215_info *raw = (struct raw3215_info *) data; + tty_wakeup(raw->tty); +} + /* * Try to start the next IO and wake up processes waiting on the tty. */ static void raw3215_next_io(struct raw3215_info *raw) { - struct tty_struct *tty; - raw3215_mk_write_req(raw); raw3215_try_io(raw); - tty = raw->tty; - if (tty != NULL && - RAW3215_BUFFER_SIZE - raw->count >= RAW3215_MIN_SPACE) { - tty_wakeup(tty); - } + if (raw->tty && RAW3215_BUFFER_SIZE - raw->count >= RAW3215_MIN_SPACE) + tasklet_schedule(&raw->tlet); } /* @@ -682,6 +687,7 @@ static int raw3215_probe (struct ccw_device *cdev) return -ENOMEM; } init_waitqueue_head(&raw->empty_wait); + tasklet_init(&raw->tlet, raw3215_wakeup, (unsigned long) raw); dev_set_drvdata(&cdev->dev, raw); cdev->handler = raw3215_irq; @@ -901,6 +907,7 @@ static int __init con3215_init(void) raw->flags |= RAW3215_FIXED; init_waitqueue_head(&raw->empty_wait); + tasklet_init(&raw->tlet, raw3215_wakeup, (unsigned long) raw); /* Request the console irq */ if (raw3215_startup(raw) != 0) { @@ -966,6 +973,7 @@ static void tty3215_close(struct tty_struct *tty, struct file * filp) tty->closing = 1; /* Shutdown the terminal */ raw3215_shutdown(raw); + tasklet_kill(&raw->tlet); tty->closing = 0; raw->tty = NULL; } -- 2.20.1