ALPHA: srmcons, fix racy singleton structure

The test and the assignment were racy. Make it really a singleton.
This is achieved by one global variable initialized at the module
init.

Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Cc: Richard Henderson <rth@twiddle.net>
Cc: Ivan Kokshaysky <ink@jurassic.park.msu.ru>
Cc: Matt Turner <mattst88@gmail.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 5 insertions, 35 deletions

diff --git a/arch/alpha/kernel/srmcons.c b/arch/alpha/kernel/srmcons.c
index f1fdf178bcb4..2c89ce5c9ab6 100644
--- a/arch/alpha/kernel/srmcons.c
+++ b/arch/alpha/kernel/srmcons.c
@@ -33,7 +33,7 @@ struct srmcons_private {
         struct tty_struct *tty;
         struct timer_list timer;
         spinlock_t lock;
-};
+} srmcons_singleton;
 
 typedef union _srmcons_result {
         struct {
@@ -154,43 +154,10 @@ srmcons_chars_in_buffer(struct tty_struct *tty)
 }
 
 static int
-srmcons_get_private_struct(struct srmcons_private **ps)
-{
-        static struct srmcons_private *srmconsp = NULL;
-        static DEFINE_SPINLOCK(srmconsp_lock);
-        unsigned long flags;
-        int retval = 0;
-
-        if (srmconsp == NULL) {
-                srmconsp = kmalloc(sizeof(*srmconsp), GFP_KERNEL);
-                spin_lock_irqsave(&srmconsp_lock, flags);
-
-                if (srmconsp == NULL)
-                        retval = -ENOMEM;
-                else {
-                        srmconsp->tty = NULL;
-                        spin_lock_init(&srmconsp->lock);
-                        setup_timer(&srmconsp->timer, srmcons_receive_chars,
-                                        (unsigned long)srmconsp);
-                }
-
-                spin_unlock_irqrestore(&srmconsp_lock, flags);
-        }
-
-        *ps = srmconsp;
-        return retval;
-}
-
-static int
 srmcons_open(struct tty_struct *tty, struct file *filp)
 {
-        struct srmcons_private *srmconsp;
+        struct srmcons_private *srmconsp = &srmcons_singleton;
         unsigned long flags;
-        int retval;
-
-        retval = srmcons_get_private_struct(&srmconsp);
-        if (retval)
-                return retval;
 
         spin_lock_irqsave(&srmconsp->lock, flags);
 
@@ -236,6 +203,9 @@ static const struct tty_operations srmcons_ops = {
 static int __init
 srmcons_init(void)
 {
+        spin_lock_init(&srmcons_singleton.lock);
+        setup_timer(&srmcons_singleton.timer, srmcons_receive_chars,
+                        (unsigned long)&srmcons_singleton);
         if (srm_is_registered_console) {
                 struct tty_driver *driver;
                 int err;