tty: introduce wait_event_interruptible_tty

Calling wait_event_interruptible implicitly
releases the BKL when it sleeps, but we need
to do this explcitly when we have converted
it to a mutex.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Alan Cox <alan@lxorguk.ukuu.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

7 files changed, 59 insertions, 10 deletions

diff --git a/drivers/char/cyclades.c b/drivers/char/cyclades.c
index 51acfe39a438..27aad9422332 100644
--- a/drivers/char/cyclades.c
+++ b/drivers/char/cyclades.c
@@ -1607,7 +1607,7 @@ static int cy_open(struct tty_struct *tty, struct file *filp)
          * If the port is the middle of closing, bail out now
          */
         if (tty_hung_up_p(filp) || (info->port.flags & ASYNC_CLOSING)) {
-                wait_event_interruptible(info->port.close_wait,
+                wait_event_interruptible_tty(info->port.close_wait,
                                 !(info->port.flags & ASYNC_CLOSING));
                 return (info->port.flags & ASYNC_HUP_NOTIFY) ? -EAGAIN: -ERESTARTSYS;
         }
diff --git a/drivers/char/istallion.c b/drivers/char/istallion.c
index 5e9a81d8ebcf..be28391adb79 100644
--- a/drivers/char/istallion.c
+++ b/drivers/char/istallion.c
@@ -954,7 +954,7 @@ static int stli_rawopen(struct stlibrd *brdp, struct stliport *portp, unsigned l
  *      order of opens and closes may not be preserved across shared
  *      memory, so we must wait until it is complete.
  */
-        wait_event_interruptible(portp->raw_wait,
+        wait_event_interruptible_tty(portp->raw_wait,
                         !test_bit(ST_CLOSING, &portp->state));
         if (signal_pending(current)) {
                 return -ERESTARTSYS;
@@ -989,7 +989,7 @@ static int stli_rawopen(struct stlibrd *brdp, struct stliport *portp, unsigned l
         set_bit(ST_OPENING, &portp->state);
         spin_unlock_irqrestore(&brd_lock, flags);
 
-        wait_event_interruptible(portp->raw_wait,
+        wait_event_interruptible_tty(portp->raw_wait,
                         !test_bit(ST_OPENING, &portp->state));
         if (signal_pending(current))
                 rc = -ERESTARTSYS;
@@ -1020,7 +1020,7 @@ static int stli_rawclose(struct stlibrd *brdp, struct stliport *portp, unsigned
  *      occurs on this port.
  */
         if (wait) {
-                wait_event_interruptible(portp->raw_wait,
+                wait_event_interruptible_tty(portp->raw_wait,
                                 !test_bit(ST_CLOSING, &portp->state));
                 if (signal_pending(current)) {
                         return -ERESTARTSYS;
@@ -1052,7 +1052,7 @@ static int stli_rawclose(struct stlibrd *brdp, struct stliport *portp, unsigned
  *      to come back.
  */
         rc = 0;
-        wait_event_interruptible(portp->raw_wait,
+        wait_event_interruptible_tty(portp->raw_wait,
                         !test_bit(ST_CLOSING, &portp->state));
         if (signal_pending(current))
                 rc = -ERESTARTSYS;
@@ -1073,6 +1073,10 @@ static int stli_rawclose(struct stlibrd *brdp, struct stliport *portp, unsigned
 
 static int stli_cmdwait(struct stlibrd *brdp, struct stliport *portp, unsigned long cmd, void *arg, int size, int copyback)
 {
+        /*
+         * no need for wait_event_tty because clearing ST_CMDING cannot block
+         * on BTM
+         */
         wait_event_interruptible(portp->raw_wait,
                         !test_bit(ST_CMDING, &portp->state));
         if (signal_pending(current))
diff --git a/drivers/char/n_r3964.c b/drivers/char/n_r3964.c
index f4bd2591e39f..a98290d7a2c5 100644
--- a/drivers/char/n_r3964.c
+++ b/drivers/char/n_r3964.c
@@ -1079,7 +1079,7 @@ static ssize_t r3964_read(struct tty_struct *tty, struct file *file,
                                 goto unlock;
                         }
                         /* block until there is a message: */
-                        wait_event_interruptible(pInfo->read_wait,
+                        wait_event_interruptible_tty(pInfo->read_wait,
                                         (pMsg = remove_msg(pInfo, pClient)));
                 }
 
diff --git a/drivers/char/tty_port.c b/drivers/char/tty_port.c
index a3bd1d0b66cf..35eb30402f18 100644
--- a/drivers/char/tty_port.c
+++ b/drivers/char/tty_port.c
@@ -231,7 +231,7 @@ int tty_port_block_til_ready(struct tty_port *port,
 
         /* block if port is in the process of being closed */
         if (tty_hung_up_p(filp) || port->flags & ASYNC_CLOSING) {
-                wait_event_interruptible(port->close_wait,
+                wait_event_interruptible_tty(port->close_wait,
                                 !(port->flags & ASYNC_CLOSING));
                 if (port->flags & ASYNC_HUP_NOTIFY)
                         return -EAGAIN;
diff --git a/drivers/char/vt_ioctl.c b/drivers/char/vt_ioctl.c
index cf87c5336229..2bbeaaea46e9 100644
--- a/drivers/char/vt_ioctl.c
+++ b/drivers/char/vt_ioctl.c
@@ -133,7 +133,7 @@ static void vt_event_wait(struct vt_event_wait *vw)
         list_add(&vw->list, &vt_events);
         spin_unlock_irqrestore(&vt_event_lock, flags);
         /* Wait for it to pass */
-        wait_event_interruptible(vt_event_waitqueue, vw->done);
+        wait_event_interruptible_tty(vt_event_waitqueue, vw->done);
         /* Dequeue it */
         spin_lock_irqsave(&vt_event_lock, flags);
         list_del(&vw->list);
@@ -1761,10 +1761,13 @@ int vt_move_to_console(unsigned int vt, int alloc)
                 return -EIO;
         }
         release_console_sem();
+        tty_lock();
         if (vt_waitactive(vt + 1)) {
                 pr_debug("Suspend: Can't switch VCs.");
+                tty_unlock();
                 return -EINTR;
         }
+        tty_unlock();
         return prev;
 }
 
diff --git a/drivers/serial/crisv10.c b/drivers/serial/crisv10.c
index f848e188deae..94bfb9f238e1 100644
--- a/drivers/serial/crisv10.c
+++ b/drivers/serial/crisv10.c
@@ -3992,7 +3992,7 @@ block_til_ready(struct tty_struct *tty, struct file * filp,
          */
         if (tty_hung_up_p(filp) ||
             (info->flags & ASYNC_CLOSING)) {
-                wait_event_interruptible(info->close_wait,
+                wait_event_interruptible_tty(info->close_wait,
                         !(info->flags & ASYNC_CLOSING));
 #ifdef SERIAL_DO_RESTART
                 if (info->flags & ASYNC_HUP_NOTIFY)
@@ -4150,7 +4150,7 @@ rs_open(struct tty_struct *tty, struct file * filp)
          */
         if (tty_hung_up_p(filp) ||
             (info->flags & ASYNC_CLOSING)) {
-                wait_event_interruptible(info->close_wait,
+                wait_event_interruptible_tty(info->close_wait,
                         !(info->flags & ASYNC_CLOSING));
 #ifdef SERIAL_DO_RESTART
                 return ((info->flags & ASYNC_HUP_NOTIFY) ?
diff --git a/include/linux/tty.h b/include/linux/tty.h
index 6ead6b60c743..955d72ea71c0 100644
--- a/include/linux/tty.h
+++ b/include/linux/tty.h
@@ -607,5 +607,47 @@ static inline void tty_unlock(void) __releases(kernel_lock)
 }
 #define tty_locked()            (kernel_locked())
 
+/*
+ * wait_event_interruptible_tty -- wait for a condition with the tty lock held
+ *
+ * The condition we are waiting for might take a long time to
+ * become true, or might depend on another thread taking the
+ * BTM. In either case, we need to drop the BTM to guarantee
+ * forward progress. This is a leftover from the conversion
+ * from the BKL and should eventually get removed as the BTM
+ * falls out of use.
+ *
+ * Do not use in new code.
+ */
+#define wait_event_interruptible_tty(wq, condition)                     \
+({                                                                      \
+        int __ret = 0;                                                  \
+        if (!(condition)) {                                             \
+                __wait_event_interruptible_tty(wq, condition, __ret);   \
+        }                                                               \
+        __ret;                                                          \
+})
+
+#define __wait_event_interruptible_tty(wq, condition, ret)              \
+do {                                                                    \
+        DEFINE_WAIT(__wait);                                            \
+                                                                        \
+        for (;;) {                                                      \
+                prepare_to_wait(&wq, &__wait, TASK_INTERRUPTIBLE);      \
+                if (condition)                                          \
+                        break;                                          \
+                if (!signal_pending(current)) {                         \
+                        tty_unlock();                                   \
+                        schedule();                                     \
+                        tty_lock();                                     \
+                        continue;                                       \
+                }                                                       \
+                ret = -ERESTARTSYS;                                     \
+                break;                                                  \
+        }                                                               \
+        finish_wait(&wq, &__wait);                                      \
+} while (0)
+
+
 #endif /* __KERNEL__ */
 #endif