@@ -106,6 +106,7 @@ static struct hvc_struct *hvc_get_by_index(int index)
spin_lock_irqsave(&hp->lock, flags);
if (hp->index == index) {
kref_get(&hp->kref);
+ tty_kref_get(hp->tty);
spin_unlock_irqrestore(&hp->lock, flags);
spin_unlock(&hvc_structs_lock);
return hp;
@@ -390,6 +391,7 @@ static void hvc_close(struct tty_struct *tty, struct file * filp)
}
kref_put(&hp->kref, destroy_hvc_struct);
+ tty_kref_put(tty);
}
static void hvc_hangup(struct tty_struct *tty)
@@ -806,6 +808,7 @@ int hvc_remove(struct hvc_struct *hp)
unsigned long flags;
struct tty_struct *tty;
+ tty_kref_get(hp->tty);
spin_lock_irqsave(&hp->lock, flags);
tty = hp->tty;
@@ -830,7 +833,9 @@ int hvc_remove(struct hvc_struct *hp)
* cleaned up the hvc_struct.
*/
if (tty)
- tty_hangup(tty);
+ tty_vhangup(tty);
+
+ tty_kref_put(hp->tty);
return 0;
}
EXPORT_SYMBOL_GPL(hvc_remove);
Alan pointed out a race in the code where hvc_remove is invoked. The recent virtio_console work is the first user of hvc_remove(). Alan describes it thus: The hvc_console assumes that a close and remove call can't occur at the same time. In addition tty_hangup(tty) is problematic as tty_hangup is asynchronous itself.... So this can happen hvc_close hvc_remove hung up ? - no lock tty = hp->tty unlock lock hp->tty = NULL unlock notify del kref_put the hvc struct close completes tty is destroyed tty_hangup dead tty tty->ops will be NULL NULL->... This patch adds some tty krefs and also converts to using tty_vhangup() before putting the tty kref. Reported-by: Alan Cox <alan@lxorguk.ukuu.org.uk> Signed-off-by: Amit Shah <amit.shah@redhat.com> CC: Alan Cox <alan@lxorguk.ukuu.org.uk> CC: linuxppc-dev@ozlabs.org CC: Rusty Russell <rusty@rustcorp.com.au> --- I can't be sure if this is all that's needed. tty people, please take a look! drivers/char/hvc_console.c | 7 ++++++- 1 files changed, 6 insertions(+), 1 deletions(-)