[3.13.y.z extended stable] Patch "Staging: speakup: Move pasting into a work item" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    Staging: speakup: Move pasting into a work item

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 39740c6fd8e7f01246ffa9115efcd466d2831a54 Mon Sep 17 00:00:00 2001
From: Ben Hutchings <ben at decadent.org.uk>
Date: Mon, 19 May 2014 00:56:22 +0100
Subject: Staging: speakup: Move pasting into a work item

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 at debian.org>
Reported-and-tested-by: Jarek Czekalski <jarekczek at poczta.onet.pl>
Signed-off-by: Ben Hutchings <ben at decadent.org.uk>
Signed-off-by: Greg Kroah-Hartman <gregkh at linuxfoundation.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/staging/speakup/main.c      |  1 +
 drivers/staging/speakup/selection.c | 38 +++++++++++++++++++++++++++++++------
 drivers/staging/speakup/speakup.h   |  1 +
 3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/drivers/staging/speakup/main.c b/drivers/staging/speakup/main.c
index 47502fa..8d6123b 100644
--- a/drivers/staging/speakup/main.c
+++ b/drivers/staging/speakup/main.c
@@ -2220,6 +2220,7 @@ 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
--- 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 0126f71..74fe724 100644
--- a/drivers/staging/speakup/speakup.h
+++ b/drivers/staging/speakup/speakup.h
@@ -77,6 +77,7 @@ 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);
--
1.9.1