[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 <schwidefsky@de.ibm.com>

diff --git a/drivers/s390/char/con3215.c b/drivers/s390/char/con3215.c
index 934458ad55e51782c7b595b48c5f3088393b8495..e71a50d4b2217b22fb262338f31aa1fe98931349 100644 (file)
--- 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;
 }