6 files changed, 68 insertions, 33 deletions

diff --git a/drivers/char/cyclades.c b/drivers/char/cyclades.c
index 39c61a71176e..cc7acf877dc0 100644
--- a/drivers/char/cyclades.c
+++ b/drivers/char/cyclades.c
@@ -1233,7 +1233,7 @@ cyy_interrupt(int irq, void *dev_id, struct pt_regs *regs)
                             }
                              info->idle_stats.recv_idle = jiffies;
                         }
-                        schedule_delayed_work(&tty->buf.work, 1);
+                        tty_schedule_flip(tty);
                     }
                     /* end of service */
                     cy_writeb(base_addr+(CyRIR<<index), (save_xir & 0x3f));
@@ -1606,7 +1606,7 @@ cyz_handle_rx(struct cyclades_port *info,
             }
 #endif
             info->idle_stats.recv_idle = jiffies;
-            schedule_delayed_work(&tty->buf.work, 1);
+            tty_schedule_flip(tty);
         }
         /* Update rx_get */
         cy_writel(&buf_ctrl->rx_get, new_rx_get);
@@ -1809,7 +1809,7 @@ cyz_handle_cmd(struct cyclades_card *cinfo)
         if(delta_count)
             cy_sched_event(info, Cy_EVENT_DELTA_WAKEUP);
         if(special_count)
-            schedule_delayed_work(&tty->buf.work, 1);
+            tty_schedule_flip(tty);
     }
 }
 
diff --git a/drivers/char/esp.c b/drivers/char/esp.c
index 3f3ac039f4d9..57539d8f9f7c 100644
--- a/drivers/char/esp.c
+++ b/drivers/char/esp.c
@@ -359,7 +359,7 @@ static inline void receive_chars_pio(struct esp_struct *info, int num_bytes)
                 }
         }
 
-        schedule_delayed_work(&tty->buf.work, 1);
+        tty_schedule_flip(tty);
 
         info->stat_flags &= ~ESP_STAT_RX_TIMEOUT;
         release_pio_buffer(pio_buf);
@@ -426,7 +426,7 @@ static inline void receive_chars_dma_done(struct esp_struct *info,
                         }
                         tty_insert_flip_char(tty, dma_buffer[num_bytes - 1], statflag);
                 }
-                schedule_delayed_work(&tty->buf.work, 1);
+                tty_schedule_flip(tty);
         }
 
         if (dma_bytes != num_bytes) {
diff --git a/drivers/char/tty_io.c b/drivers/char/tty_io.c
index eb8b5be4e249..076e07c1da38 100644
--- a/drivers/char/tty_io.c
+++ b/drivers/char/tty_io.c
@@ -253,6 +253,7 @@ static void tty_buffer_free_all(struct tty_struct *tty)
 
 static void tty_buffer_init(struct tty_struct *tty)
 {
+        spin_lock_init(&tty->buf.lock);
         tty->buf.head = NULL;
         tty->buf.tail = NULL;
         tty->buf.free = NULL;
@@ -266,6 +267,7 @@ static struct tty_buffer *tty_buffer_alloc(size_t size)
         p->used = 0;
         p->size = size;
         p->next = NULL;
+        p->active = 0;
         p->char_buf_ptr = (char *)(p->data);
         p->flag_buf_ptr = (unsigned char *)p->char_buf_ptr + size;
 /*      printk("Flip create %p\n", p); */
@@ -312,25 +314,36 @@ static struct tty_buffer *tty_buffer_find(struct tty_struct *tty, size_t size)
 
 int tty_buffer_request_room(struct tty_struct *tty, size_t size)
 {
-        struct tty_buffer *b = tty->buf.tail, *n;
-        int left = 0;
+        struct tty_buffer *b, *n;
+        int left;
+        unsigned long flags;
+
+        spin_lock_irqsave(&tty->buf.lock, flags);
 
         /* OPTIMISATION: We could keep a per tty "zero" sized buffer to
            remove this conditional if its worth it. This would be invisible
            to the callers */
-        if(b != NULL)
+        if ((b = tty->buf.tail) != NULL) {
                 left = b->size - b->used;
-        if(left >= size)
-                return size;
-        /* This is the slow path - looking for new buffers to use */
-        n = tty_buffer_find(tty, size);
-        if(n == NULL)
-                return left;
-        if(b != NULL)
-                b->next = n;
-        else
-                tty->buf.head = n;
-        tty->buf.tail = n;
+                b->active = 1;
+        } else
+                left = 0;
+
+        if (left < size) {
+                /* This is the slow path - looking for new buffers to use */
+                if ((n = tty_buffer_find(tty, size)) != NULL) {
+                        if (b != NULL) {
+                                b->next = n;
+                                b->active = 0;
+                        } else
+                                tty->buf.head = n;
+                        tty->buf.tail = n;
+                        n->active = 1;
+                } else
+                        size = left;
+        }
+
+        spin_unlock_irqrestore(&tty->buf.lock, flags);
         return size;
 }
 
@@ -396,10 +409,12 @@ EXPORT_SYMBOL_GPL(tty_insert_flip_string_flags);
 int tty_prepare_flip_string(struct tty_struct *tty, unsigned char **chars, size_t size)
 {
         int space = tty_buffer_request_room(tty, size);
-        struct tty_buffer *tb = tty->buf.tail;
-        *chars = tb->char_buf_ptr + tb->used;
-        memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
-        tb->used += space;
+        if (likely(space)) {
+                struct tty_buffer *tb = tty->buf.tail;
+                *chars = tb->char_buf_ptr + tb->used;
+                memset(tb->flag_buf_ptr + tb->used, TTY_NORMAL, space);
+                tb->used += space;
+        }
         return space;
 }
 
@@ -416,10 +431,12 @@ EXPORT_SYMBOL_GPL(tty_prepare_flip_string);
 int tty_prepare_flip_string_flags(struct tty_struct *tty, unsigned char **chars, char **flags, size_t size)
 {
         int space = tty_buffer_request_room(tty, size);
-        struct tty_buffer *tb = tty->buf.tail;
-        *chars = tb->char_buf_ptr + tb->used;
-        *flags = tb->flag_buf_ptr + tb->used;
-        tb->used += space;
+        if (likely(space)) {
+                struct tty_buffer *tb = tty->buf.tail;
+                *chars = tb->char_buf_ptr + tb->used;
+                *flags = tb->flag_buf_ptr + tb->used;
+                tb->used += space;
+        }
         return space;
 }
 
@@ -2747,20 +2764,20 @@ static void flush_to_ldisc(void *private_)
                 schedule_delayed_work(&tty->buf.work, 1);
                 goto out;
         }
-        spin_lock_irqsave(&tty->read_lock, flags);
-        while((tbuf = tty->buf.head) != NULL) {
+        spin_lock_irqsave(&tty->buf.lock, flags);
+        while((tbuf = tty->buf.head) != NULL && !tbuf->active) {
                 tty->buf.head = tbuf->next;
                 if (tty->buf.head == NULL)
                         tty->buf.tail = NULL;
-                spin_unlock_irqrestore(&tty->read_lock, flags);
+                spin_unlock_irqrestore(&tty->buf.lock, flags);
                 /* printk("Process buffer %p for %d\n", tbuf, tbuf->used); */
                 disc->receive_buf(tty, tbuf->char_buf_ptr,
                                        tbuf->flag_buf_ptr,
                                        tbuf->used);
-                spin_lock_irqsave(&tty->read_lock, flags);
+                spin_lock_irqsave(&tty->buf.lock, flags);
                 tty_buffer_free(tty, tbuf);
         }
-        spin_unlock_irqrestore(&tty->read_lock, flags);
+        spin_unlock_irqrestore(&tty->buf.lock, flags);
 out:
         tty_ldisc_deref(disc);
 }
@@ -2852,6 +2869,12 @@ EXPORT_SYMBOL(tty_get_baud_rate);
 
 void tty_flip_buffer_push(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);
+
         if (tty->low_latency)
                 flush_to_ldisc((void *) tty);
         else
diff --git a/include/linux/kbd_kern.h b/include/linux/kbd_kern.h
index 45f625d7d0b2..3aed37314ab8 100644
--- a/include/linux/kbd_kern.h
+++ b/include/linux/kbd_kern.h
@@ -151,6 +151,11 @@ extern unsigned int keymap_count;
 
 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 3787102e4b12..a7bd3b4558d2 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -57,6 +57,7 @@ struct tty_buffer {
         unsigned char *flag_buf_ptr;
         int used;
         int size;
+        int active;
         /* Data points here */
         unsigned long data[0];
 };
@@ -64,6 +65,7 @@ struct tty_buffer {
 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 be1400e82482..82961eb19888 100644
--- a/include/linux/tty_flip.h
+++ b/include/linux/tty_flip.h
@@ -17,7 +17,7 @@ _INLINE_ int tty_insert_flip_char(struct tty_struct *tty,
                                    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_ int tty_insert_flip_char(struct tty_struct *tty,
 
 _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);
 }