[PATCH] new tty buffering locking fix
Change locking in the new tty buffering facility from using tty->read_lock,
which is currently ignored by drivers and thus ineffective. New locking
uses a new tty buffering specific lock enforced centrally in the tty
buffering code.
Two drivers (esp and cyclades) are updated to use the tty buffering
functions instead of accessing tty buffering internals directly. This is
required for the new locking to work.
Minor checks for NULL buffers added to
tty_prepare_flip_string/tty_prepare_flip_string_flags
Signed-off-by: Paul Fulghum <paulkf@microgate.com>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
diff --git a/include/linux/kbd_kern.h b/include/linux/kbd_kern.h
index 45f625d..3aed373 100644
--- a/include/linux/kbd_kern.h
+++ b/include/linux/kbd_kern.h
@@ -151,6 +151,11 @@
static inline void con_schedule_flip(struct tty_struct *t)
{
+ unsigned long flags;
+ spin_lock_irqsave(&t->buf.lock, flags);
+ if (t->buf.tail != NULL)
+ t->buf.tail->active = 0;
+ spin_unlock_irqrestore(&t->buf.lock, flags);
schedule_work(&t->buf.work);
}
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 3787102..a7bd3b4 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -57,6 +57,7 @@
unsigned char *flag_buf_ptr;
int used;
int size;
+ int active;
/* Data points here */
unsigned long data[0];
};
@@ -64,6 +65,7 @@
struct tty_bufhead {
struct work_struct work;
struct semaphore pty_sem;
+ spinlock_t lock;
struct tty_buffer *head; /* Queue head */
struct tty_buffer *tail; /* Active buffer */
struct tty_buffer *free; /* Free queue head */
diff --git a/include/linux/tty_flip.h b/include/linux/tty_flip.h
index be1400e..82961eb 100644
--- a/include/linux/tty_flip.h
+++ b/include/linux/tty_flip.h
@@ -17,7 +17,7 @@
unsigned char ch, char flag)
{
struct tty_buffer *tb = tty->buf.tail;
- if (tb && tb->used < tb->size) {
+ if (tb && tb->active && tb->used < tb->size) {
tb->flag_buf_ptr[tb->used] = flag;
tb->char_buf_ptr[tb->used++] = ch;
return 1;
@@ -27,6 +27,11 @@
_INLINE_ void tty_schedule_flip(struct tty_struct *tty)
{
+ unsigned long flags;
+ spin_lock_irqsave(&tty->buf.lock, flags);
+ if (tty->buf.tail != NULL)
+ tty->buf.tail->active = 0;
+ spin_unlock_irqrestore(&tty->buf.lock, flags);
schedule_delayed_work(&tty->buf.work, 1);
}