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[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>
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1 parent 2320c57 commit 656d9125376006cf696b0836f1c6723a892629ca Martin Schwidefsky committed Feb 17, 2012
Showing with 15 additions and 7 deletions.
  1. +15 −7 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) */
@@ -334,19 +335,23 @@ 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;
}

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