ser_gigaset: convert mutex to completion

The ser_gigaset ISDN driver was using a mutex in its close() method for
waiting for other running ldisc methods to finish.  That's what completions
are for.  Incidentally, this also avoids a spurious "BUG: lock held at task
exit time" message when the driver's userspace daemon daemonizes itself.

Signed-off-by: Tilman Schmidt <tilman@imap.cc>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 5 deletions

diff --git a/drivers/isdn/gigaset/ser-gigaset.c b/drivers/isdn/gigaset/ser-gigaset.c
index f2bb1aeb0c80..fceeb1d57682 100644
--- a/drivers/isdn/gigaset/ser-gigaset.c
+++ b/drivers/isdn/gigaset/ser-gigaset.c
@@ -17,6 +17,7 @@
 #include <linux/platform_device.h>
 #include <linux/tty.h>
 #include <linux/poll.h>
+#include <linux/completion.h>
 
 /* Version Information */
 #define DRIVER_AUTHOR "Tilman Schmidt"
@@ -48,7 +49,7 @@ struct ser_cardstate {
         struct platform_device  dev;
         struct tty_struct       *tty;
         atomic_t                refcnt;
-        struct mutex            dead_mutex;
+        struct completion       dead_cmp;
 };
 
 static struct platform_driver device_driver = {
@@ -498,7 +499,7 @@ static struct cardstate *cs_get(struct tty_struct *tty)
 static void cs_put(struct cardstate *cs)
 {
         if (atomic_dec_and_test(&cs->hw.ser->refcnt))
-                mutex_unlock(&cs->hw.ser->dead_mutex);
+                complete(&cs->hw.ser->dead_cmp);
 }
 
 /*
@@ -527,8 +528,8 @@ gigaset_tty_open(struct tty_struct *tty)
 
         cs->dev = &cs->hw.ser->dev.dev;
         cs->hw.ser->tty = tty;
-        mutex_init(&cs->hw.ser->dead_mutex);
         atomic_set(&cs->hw.ser->refcnt, 1);
+        init_completion(&cs->hw.ser->dead_cmp);
 
         tty->disc_data = cs;
 
@@ -543,7 +544,6 @@ gigaset_tty_open(struct tty_struct *tty)
         }
 
         gig_dbg(DEBUG_INIT, "Startup of HLL done");
-        mutex_lock(&cs->hw.ser->dead_mutex);
         return 0;
 
 error:
@@ -577,7 +577,7 @@ gigaset_tty_close(struct tty_struct *tty)
         else {
                 /* wait for running methods to finish */
                 if (!atomic_dec_and_test(&cs->hw.ser->refcnt))
-                        mutex_lock(&cs->hw.ser->dead_mutex);
+                        wait_for_completion(&cs->hw.ser->dead_cmp);
         }
 
         /* stop operations */