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>

diff --git a/drivers/isdn/gigaset/ser-gigaset.c b/drivers/isdn/gigaset/ser-gigaset.c
index f2bb1ae..fceeb1d 100644 (file)
--- 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 */