Messages in this thread Patch in this message | | | Date | Wed, 1 Oct 2014 23:29:10 +0200 | From | Samuel Thibault <> | Subject | Re: [PATCH] Route keyboard LEDs through the generic LEDs layer. |
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Andrew Morton, le Wed 01 Oct 2014 11:42:57 -0700, a écrit : > On Mon, 31 Mar 2014 14:23:23 +0200 Samuel Thibault <samuel.thibault@ens-lyon.org> wrote: > > This permits to reassign keyboard LEDs to something else than keyboard "leds" > > state, by adding keyboard led and modifier triggers connected to a series > > of VT input LEDs, themselves connected to VT input triggers, which > > per-input device LEDs use by default. Userland can thus easily change the LED > > behavior of (a priori) all input devices, or of particular input devices. > > > > This also permits to fix #7063 from userland by using a modifier to implement > > proper CapsLock behavior and have the keyboard caps lock led show that modifier > > state. > > When this patch is combined with current linux-next I'm getting the > below lockdep splat. Config: http://ozlabs.org/~akpm/config-akpm2.txt
Yes, this was reported and I sent a fix some time ago (Tue, 26 Aug 2014 11:17:25 +0200), here is the patch again:
Subject: Defer input led work to workqueue
When the kbd changes its led state (e.g. caps lock), this triggers (led_trigger_event) the kbd-capsl trigger, which is by default used by the vt::capsl LED, which triggers (led_trigger_event) the vt-capsl trigger. These two nested led_trigger_event calls take a trig->leddev_list_lock lock and thus lockdep complains.
Actually the user can make the vt::capsl LED use its own vt-capsl trigger and thus build a loop. This produces an immediate oops.
This changeset defers the second led_trigger_event call into a workqueue, which avoids the nested locking altogether. This does not prevent the user from shooting himself in the foot by creating a vt::capsl <-> vt-capsl loop, but the only consequence is the workqueue threads eating some CPU until the user breaks the loop, which is not too bad.
Signed-off-by: Samuel Thibault <samuel.thibault@ens-lyon.org>
--- a/drivers/input/leds.c +++ b/drivers/input/leds.c @@ -100,13 +100,24 @@ static unsigned long vt_led_registered[B /* Number of input devices having each LED */ static int vt_led_references[LED_CNT]; +static int vt_led_state[LED_CNT]; +static struct work_struct vt_led_work[LED_CNT]; + +static void vt_led_cb(struct work_struct *work) +{ + int led = work - vt_led_work; + + led_trigger_event(&vt_led_triggers[led], vt_led_state[led]); +} + /* VT LED state change, tell the VT trigger. */ static void vt_led_set(struct led_classdev *cdev, enum led_brightness brightness) { int led = cdev - vt_leds; - led_trigger_event(&vt_led_triggers[led], !!brightness); + vt_led_state[led] = !!brightness; + schedule_work(&vt_led_work[led]); } /* LED state change for some keyboard, notify that keyboard. */ @@ -244,6 +255,22 @@ void input_led_disconnect(struct input_d mutex_unlock(&vt_led_registered_lock); } +static int __init input_led_init(void) +{ + unsigned i; + + for (i = 0; i < LED_CNT; i++) + INIT_WORK(&vt_led_work[i], vt_led_cb); + + return 0; +} + +static void __exit input_led_exit(void) +{ +} + MODULE_LICENSE("GPL"); MODULE_DESCRIPTION("User LED support for input layer"); MODULE_AUTHOR("Samuel Thibault <samuel.thibault@ens-lyon.org>"); +module_init(input_led_init); +module_exit(input_led_exit); -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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