FROMGIT: Input: uinput - avoid FF flush when destroying device
Normally, when input device supporting force feedback effects is being
destroyed, we try to "flush" currently playing effects, so that the
physical device does not continue vibrating (or executing other effects).
Unfortunately this does not work well for uinput as flushing of the effects
deadlocks with the destroy action:
- if device is being destroyed because the file descriptor is being closed,
then there is noone to even service FF requests;
- if device is being destroyed because userspace sent UI_DEV_DESTROY,
while theoretically it could be possible to service FF requests,
userspace is unlikely to do so (they'd need to make sure FF handling
happens on a separate thread) even if kernel solves the issue with FF
ioctls deadlocking with UI_DEV_DESTROY ioctl on udev->mutex.
To avoid lockups like the one below, let's install a custom input device
flush handler, and avoid trying to flush force feedback effects when we
destroying the device, and instead rely on uinput to shut off the device
properly.
NMI watchdog: Watchdog detected hard LOCKUP on cpu 3
...
<<EOE>> [<ffffffff817a0307>] _raw_spin_lock_irqsave+0x37/0x40
[<ffffffff810e633d>] complete+0x1d/0x50
[<ffffffffa00ba08c>] uinput_request_done+0x3c/0x40 [uinput]
[<ffffffffa00ba587>] uinput_request_submit.part.7+0x47/0xb0 [uinput]
[<ffffffffa00bb62b>] uinput_dev_erase_effect+0x5b/0x76 [uinput]
[<ffffffff815d91ad>] erase_effect+0xad/0xf0
[<ffffffff815d929d>] flush_effects+0x4d/0x90
[<ffffffff815d4cc0>] input_flush_device+0x40/0x60
[<ffffffff815daf1c>] evdev_cleanup+0xac/0xc0
[<ffffffff815daf5b>] evdev_disconnect+0x2b/0x60
[<ffffffff815d74ac>] __input_unregister_device+0xac/0x150
[<ffffffff815d75f7>] input_unregister_device+0x47/0x70
[<ffffffffa00bac45>] uinput_destroy_device+0xb5/0xc0 [uinput]
[<ffffffffa00bb2de>] uinput_ioctl_handler.isra.9+0x65e/0x740 [uinput]
[<ffffffff811231ab>] ? do_futex+0x12b/0xad0
[<ffffffffa00bb3f8>] uinput_ioctl+0x18/0x20 [uinput]
[<ffffffff81241248>] do_vfs_ioctl+0x298/0x480
[<ffffffff81337553>] ? security_file_ioctl+0x43/0x60
[<ffffffff812414a9>] SyS_ioctl+0x79/0x90
[<ffffffff817a04ee>] entry_SYSCALL_64_fastpath+0x12/0x71
Reported-by: Rodrigo Rivas Costa <rodrigorivascosta@gmail.com>
Reported-by: Clément VUCHENER <clement.vuchener@gmail.com>
Fixes: https://bugzilla.kernel.org/show_bug.cgi?id=193741
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@gmail.com>
Bug: 175316710
(cherry picked from commit e8b95728f724797f958912fd9b765a695595d3a6
https://git.kernel.org/pub/scm/linux/kernel/git/dtor/input.git)
Change-Id: I7fd16d72d349fff022dbea3419a7463dfb7d683d
diff --git a/drivers/input/ff-core.c b/drivers/input/ff-core.c
index 8f20424..66a46c8 100644
--- a/drivers/input/ff-core.c
+++ b/drivers/input/ff-core.c
@@ -237,9 +237,15 @@
EXPORT_SYMBOL_GPL(input_ff_erase);
/*
- * flush_effects - erase all effects owned by a file handle
+ * input_ff_flush - erase all effects owned by a file handle
+ * @dev: input device to erase effect from
+ * @file: purported owner of the effects
+ *
+ * This function erases all force-feedback effects associated with
+ * the given owner from specified device. Note that @file may be %NULL,
+ * in which case all effects will be erased.
*/
-static int flush_effects(struct input_dev *dev, struct file *file)
+int input_ff_flush(struct input_dev *dev, struct file *file)
{
struct ff_device *ff = dev->ff;
int i;
@@ -255,6 +261,7 @@
return 0;
}
+EXPORT_SYMBOL_GPL(input_ff_flush);
/**
* input_ff_event() - generic handler for force-feedback events
@@ -343,7 +350,7 @@
mutex_init(&ff->mutex);
dev->ff = ff;
- dev->flush = flush_effects;
+ dev->flush = input_ff_flush;
dev->event = input_ff_event;
__set_bit(EV_FF, dev->evbit);
diff --git a/drivers/input/misc/uinput.c b/drivers/input/misc/uinput.c
index 89d37d0..fcd10a4 100644
--- a/drivers/input/misc/uinput.c
+++ b/drivers/input/misc/uinput.c
@@ -231,6 +231,18 @@
return uinput_request_submit(udev, &request);
}
+static int uinput_dev_flush(struct input_dev *dev, struct file *file)
+{
+ /*
+ * If we are called with file == NULL that means we are tearing
+ * down the device, and therefore we can not handle FF erase
+ * requests: either we are handling UI_DEV_DESTROY (and holding
+ * the udev->mutex), or the file descriptor is closed and there is
+ * nobody on the other side anymore.
+ */
+ return file ? input_ff_flush(dev, file) : 0;
+}
+
static void uinput_destroy_device(struct uinput_device *udev)
{
const char *name, *phys;
@@ -298,6 +310,12 @@
dev->ff->playback = uinput_dev_playback;
dev->ff->set_gain = uinput_dev_set_gain;
dev->ff->set_autocenter = uinput_dev_set_autocenter;
+ /*
+ * The standard input_ff_flush() implementation does
+ * not quite work for uinput as we can't reasonably
+ * handle FF requests during device teardown.
+ */
+ dev->flush = uinput_dev_flush;
}
error = input_register_device(udev->dev);
diff --git a/include/linux/input.h b/include/linux/input.h
index be1969a..4ace837 100644
--- a/include/linux/input.h
+++ b/include/linux/input.h
@@ -545,6 +545,7 @@
int input_ff_upload(struct input_dev *dev, struct ff_effect *effect, struct file *file);
int input_ff_erase(struct input_dev *dev, int effect_id, struct file *file);
+int input_ff_flush(struct input_dev *dev, struct file *file);
int input_ff_create_memless(struct input_dev *dev, void *data,
int (*play_effect)(struct input_dev *, void *, struct ff_effect *));
