Staging: speakup: Move pasting into a work item

Input is handled in softirq context, but when pasting we may
need to sleep.  speakup_paste_selection() currently tries to
bodge this by busy-waiting if in_atomic(), but that doesn't
help because the ldisc may also sleep.

For bonus breakage, speakup_paste_selection() changes the
state of current, even though it's not running in process
context.

Move it into a work item and make sure to cancel it on exit.

References: https://bugs.debian.org/735202
References: https://bugs.debian.org/744015
Reported-by: Paul Gevers <elbrus@debian.org>
Reported-and-tested-by: Jarek Czekalski <jarekczek@poczta.onet.pl>
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/staging/speakup/main.c b/drivers/staging/speakup/main.c
index 3b6e535..7de79d5 100644 (file)
--- a/drivers/staging/speakup/main.c
+++ b/drivers/staging/speakup/main.c
@@ -2218,6 +2218,7 @@ static void __exit speakup_exit(void)
        unregister_keyboard_notifier(&keyboard_notifier_block);
        unregister_vt_notifier(&vt_notifier_block);
        speakup_unregister_devsynth();
+       speakup_cancel_paste();
        del_timer(&cursor_timer);
        kthread_stop(speakup_task);
        speakup_task = NULL;

diff --git a/drivers/staging/speakup/selection.c b/drivers/staging/speakup/selection.c
index f0fb003..f67941e 100644 (file)
--- a/drivers/staging/speakup/selection.c
+++ b/drivers/staging/speakup/selection.c
@@ -4,6 +4,8 @@
 #include <linux/sched.h>
 #include <linux/device.h> /* for dev_warn */
 #include <linux/selection.h>
+#include <linux/workqueue.h>
+#include <asm/cmpxchg.h>
 
 #include "speakup.h"
 
@@ -121,20 +123,24 @@ int speakup_set_selection(struct tty_struct *tty)
        return 0;
 }
 
-/* TODO: move to some helper thread, probably.  That'd fix having to check for
- * in_atomic().  */
-int speakup_paste_selection(struct tty_struct *tty)
+struct speakup_paste_work {
+       struct work_struct work;
+       struct tty_struct *tty;
+};
+
+static void __speakup_paste_selection(struct work_struct *work)
 {
+       struct speakup_paste_work *spw =
+               container_of(work, struct speakup_paste_work, work);
+       struct tty_struct *tty = xchg(&spw->tty, NULL);
        struct vc_data *vc = (struct vc_data *) tty->driver_data;
        int pasted = 0, count;
        DECLARE_WAITQUEUE(wait, current);
+
        add_wait_queue(&vc->paste_wait, &wait);
        while (sel_buffer && sel_buffer_lth > pasted) {
                set_current_state(TASK_INTERRUPTIBLE);
                if (test_bit(TTY_THROTTLED, &tty->flags)) {
-                       if (in_atomic())
-                               /* if we are in an interrupt handler, abort */
-                               break;
                        schedule();
                        continue;
                }
@@ -146,6 +152,26 @@ int speakup_paste_selection(struct tty_struct *tty)
        }
        remove_wait_queue(&vc->paste_wait, &wait);
        current->state = TASK_RUNNING;
+       tty_kref_put(tty);
+}
+
+static struct speakup_paste_work speakup_paste_work = {
+       .work = __WORK_INITIALIZER(speakup_paste_work.work,
+                                  __speakup_paste_selection)
+};
+
+int speakup_paste_selection(struct tty_struct *tty)
+{
+       if (cmpxchg(&speakup_paste_work.tty, NULL, tty) != NULL)
+               return -EBUSY;
+
+       tty_kref_get(tty);
+       schedule_work_on(WORK_CPU_UNBOUND, &speakup_paste_work.work);
        return 0;
 }
 
+void speakup_cancel_paste(void)
+{
+       cancel_work_sync(&speakup_paste_work.work);
+       tty_kref_put(speakup_paste_work.tty);
+}

diff --git a/drivers/staging/speakup/speakup.h b/drivers/staging/speakup/speakup.h
index a7bccee..898dce5 100644 (file)
--- a/drivers/staging/speakup/speakup.h
+++ b/drivers/staging/speakup/speakup.h
@@ -75,6 +75,7 @@ extern void synth_buffer_clear(void);
 extern void speakup_clear_selection(void);
 extern int speakup_set_selection(struct tty_struct *tty);
 extern int speakup_paste_selection(struct tty_struct *tty);
+extern void speakup_cancel_paste(void);
 extern void speakup_register_devsynth(void);
 extern void speakup_unregister_devsynth(void);
 extern void synth_write(const char *buf, size_t count);