Re: [PATCH] input: fix locking context in ml_ff_set_gain
From: Dmitry Torokhov
Date: Tue Nov 03 2009 - 00:45:07 EST
On Sun, Nov 01, 2009 at 10:38:19PM -0800, Dmitry Torokhov wrote:
> Hi Arjan,
>
> On Sat, Oct 31, 2009 at 02:19:25PM -0700, Arjan van de Ven wrote:
> > From 177c4e7a84c40925605d485f6d5367deb44a84c8 Mon Sep 17 00:00:00 2001
> > From: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
> > Date: Sat, 31 Oct 2009 14:13:40 -0700
> > Subject: [PATCH] input: fix locking context in ml_ff_set_gain
> >
> > the ml_ff_set_gain() function uses spin_lock_bh/spin_unlock_bh
> > for locking. Unfortunately, this function can be called with irqs
> > off:
> > vfs_write ->
> > evdev_write ->
> > input_inject_event (disables interrupts) ->
> > input_handle_event ->
> > input_ff_event ->
> > ml_ff_set_gain
> >
> > and doing spin_unlock_bh() with interrupts off is not allowed
> > (and causes a nice warning as a result).
> >
> > This patch fixes this by turning the locking into the _irqsave variant.
>
> Thank you for the patch but it seems that the rest of the locking in
> ff-memless.c is screwqed up ever since locking (dev->event_lock) was
> added to the input core and this change plugs one hole but exposes
> others. I think I need to convert ff-memless.c over to rely on
> event_lock instead of the private timer_lock, but I will need a couple
> of days.
>
OK, it ended up being pretty simple. Anssi, any chance you could test it
to make sure I did not screw up? Thanks!
--
Dmitry
Input: fix locking in memoryless force-feedback devices
From: Dmitry Torokhov <dmitry.torokhov@xxxxxxxxx>
Now that input core acquires dev->event_lock spinlock and disables
interrupts when propagating input events, using spin_lock_bh() in
ff-memless driver is not allowed. Actually, the timer_lock itself
is not needed anymore, we should simply use dev->event_lock
as well.
Also do a small cleanup in force-feedback core.
Reported-by: kerneloops.org
Reported-by: http://www.kerneloops.org/searchweek.php?search=ml_ff_set_gain
Reported-by: Arjan van de Ven <arjan@xxxxxxxxxxxxxxx>
Signed-off-by: Dmitry Torokhov <dtor@xxxxxxx>
---
drivers/input/ff-core.c | 20 +++++++++++---------
drivers/input/ff-memless.c | 25 ++++++++++---------------
include/linux/input.h | 4 ++++
3 files changed, 25 insertions(+), 24 deletions(-)
diff --git a/drivers/input/ff-core.c b/drivers/input/ff-core.c
index 72c63e5..38df81f 100644
--- a/drivers/input/ff-core.c
+++ b/drivers/input/ff-core.c
@@ -337,16 +337,16 @@ int input_ff_create(struct input_dev *dev, int max_effects)
dev->ff = ff;
dev->flush = flush_effects;
dev->event = input_ff_event;
- set_bit(EV_FF, dev->evbit);
+ __set_bit(EV_FF, dev->evbit);
/* Copy "true" bits into ff device bitmap */
for (i = 0; i <= FF_MAX; i++)
if (test_bit(i, dev->ffbit))
- set_bit(i, ff->ffbit);
+ __set_bit(i, ff->ffbit);
/* we can emulate RUMBLE with periodic effects */
if (test_bit(FF_PERIODIC, ff->ffbit))
- set_bit(FF_RUMBLE, dev->ffbit);
+ __set_bit(FF_RUMBLE, dev->ffbit);
return 0;
}
@@ -362,12 +362,14 @@ EXPORT_SYMBOL_GPL(input_ff_create);
*/
void input_ff_destroy(struct input_dev *dev)
{
- clear_bit(EV_FF, dev->evbit);
- if (dev->ff) {
- if (dev->ff->destroy)
- dev->ff->destroy(dev->ff);
- kfree(dev->ff->private);
- kfree(dev->ff);
+ struct ff_device *ff = dev->ff;
+
+ __clear_bit(EV_FF, dev->evbit);
+ if (ff) {
+ if (ff->destroy)
+ ff->destroy(ff);
+ kfree(ff->private);
+ kfree(ff);
dev->ff = NULL;
}
}
diff --git a/drivers/input/ff-memless.c b/drivers/input/ff-memless.c
index 2d1415e..2e8b4e3 100644
--- a/drivers/input/ff-memless.c
+++ b/drivers/input/ff-memless.c
@@ -61,7 +61,6 @@ struct ml_device {
struct ml_effect_state states[FF_MEMLESS_EFFECTS];
int gain;
struct timer_list timer;
- spinlock_t timer_lock;
struct input_dev *dev;
int (*play_effect)(struct input_dev *dev, void *data,
@@ -371,35 +370,34 @@ static void ml_effect_timer(unsigned long timer_data)
debug("timer: updating effects");
- spin_lock(&ml->timer_lock);
+ spin_lock_irq(&dev->event_lock);
ml_play_effects(ml);
- spin_unlock(&ml->timer_lock);
+ spin_unlock_irq(&dev->event_lock);
}
+/*
+ * Sets requested gain for FF effects. Called with dev->event_lock held.
+ */
static void ml_ff_set_gain(struct input_dev *dev, u16 gain)
{
struct ml_device *ml = dev->ff->private;
int i;
- spin_lock_bh(&ml->timer_lock);
-
ml->gain = gain;
for (i = 0; i < FF_MEMLESS_EFFECTS; i++)
__clear_bit(FF_EFFECT_PLAYING, &ml->states[i].flags);
ml_play_effects(ml);
-
- spin_unlock_bh(&ml->timer_lock);
}
+/*
+ * Start/stop specified FF effect. Called with dev->event_lock held.
+ */
static int ml_ff_playback(struct input_dev *dev, int effect_id, int value)
{
struct ml_device *ml = dev->ff->private;
struct ml_effect_state *state = &ml->states[effect_id];
- unsigned long flags;
-
- spin_lock_irqsave(&ml->timer_lock, flags);
if (value > 0) {
debug("initiated play");
@@ -425,8 +423,6 @@ static int ml_ff_playback(struct input_dev *dev, int effect_id, int value)
ml_play_effects(ml);
}
- spin_unlock_irqrestore(&ml->timer_lock, flags);
-
return 0;
}
@@ -436,7 +432,7 @@ static int ml_ff_upload(struct input_dev *dev,
struct ml_device *ml = dev->ff->private;
struct ml_effect_state *state = &ml->states[effect->id];
- spin_lock_bh(&ml->timer_lock);
+ spin_lock_irq(&dev->event_lock);
if (test_bit(FF_EFFECT_STARTED, &state->flags)) {
__clear_bit(FF_EFFECT_PLAYING, &state->flags);
@@ -448,7 +444,7 @@ static int ml_ff_upload(struct input_dev *dev,
ml_schedule_timer(ml);
}
- spin_unlock_bh(&ml->timer_lock);
+ spin_unlock_irq(&dev->event_lock);
return 0;
}
@@ -482,7 +478,6 @@ int input_ff_create_memless(struct input_dev *dev, void *data,
ml->private = data;
ml->play_effect = play_effect;
ml->gain = 0xffff;
- spin_lock_init(&ml->timer_lock);
setup_timer(&ml->timer, ml_effect_timer, (unsigned long)dev);
set_bit(FF_GAIN, dev->ffbit);
diff --git a/include/linux/input.h b/include/linux/input.h
index 0ccfc30..c2b1a7d 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -1377,6 +1377,10 @@ extern struct class input_class;
* methods; erase() is optional. set_gain() and set_autocenter() need
* only be implemented if driver sets up FF_GAIN and FF_AUTOCENTER
* bits.
+ *
+ * Note that playback(), set_gain() and set_autocenter() are called with
+ * dev->event_lock spinlock held and interrupts off and thus may not
+ * sleep.
*/
struct ff_device {
int (*upload)(struct input_dev *dev, struct ff_effect *effect,
--
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