[PATCH 3.4 10/88] Staging: speakup: Move pasting into a work item

Greg Kroah-Hartman
2014-06-10T00:22:00Z

From: Ben Hutchings <ben@decadent.org.uk>

commit d7500135802ca55b3f4e01a16544e8b34082f8c3 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/staging/speakup/main.c | 1
drivers/staging/speakup/selection.c | 40 +++++++++++++++++++++++++++++-------
drivers/staging/speakup/speakup.h | 1
3 files changed, 35 insertions(+), 7 deletions(-)

--- a/drivers/staging/speakup/main.c
+++ b/drivers/staging/speakup/main.c
@@ -2219,6 +2219,7 @@ 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;
--- a/drivers/staging/speakup/selection.c
+++ b/drivers/staging/speakup/selection.c
@@ -3,6 +3,8 @@
#include <linux/interrupt.h>
#include <linux/sched.h>
#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_str
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_s
}
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);
+}
--- a/drivers/staging/speakup/speakup.h
+++ b/drivers/staging/speakup/speakup.h
@@ -84,6 +84,7 @@ 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);