[PATCH] dell-laptop: defer dell_rfkill_update to worker thread

[Chase Douglas]

From: Chase Douglas <cndougla at emerald.redvoodoo.org>

dell_rfkill_update fires an SMI, which must occur on cpu 0. Thus, if called
on a different cpu, the task will block. Since it's called in hard irq
context, we must defer this to the worker thread.

It is potentially possible that two rfkill key events could be processed
before the work completes on the first. The second event is dropped with a
KERN_NOTICE message.

BugLink: http://bugs.launchpad.net/bugs/555261

Signed-off-by: Chase Douglas <chase.douglas at canonical.com>
---
 drivers/platform/x86/dell-laptop.c |    9 +++++++--
 1 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/drivers/platform/x86/dell-laptop.c b/drivers/platform/x86/dell-laptop.c
index 8bf7ac7..15d96a0 100644
--- a/drivers/platform/x86/dell-laptop.c
+++ b/drivers/platform/x86/dell-laptop.c
@@ -288,8 +288,10 @@ static const struct rfkill_ops dell_rfkill_ops = {
 /*
  * Called for each KEY_WLAN key press event. Note that a physical
  * rf-kill switch change also causes the BIOS to emit a KEY_WLAN.
+ *
+ * dell_rfkill_set may block, so schedule it on a worker thread.
  */
-static void dell_rfkill_update(void)
+static void dell_rfkill_update(struct work_struct *work)
 {
 	hw_switch_status ^= BIT(HW_SWITCH_MASK);
 	if (wifi_rfkill && (hw_switch_status & BIT(WLAN_SWITCH_MASK))) {
@@ -307,6 +309,7 @@ static void dell_rfkill_update(void)
 		dell_rfkill_set((void*)3, rfkill_blocked(wwan_rfkill));
 	}
 }
+DECLARE_WORK(dell_rfkill_update_work, &dell_rfkill_update);
 
 static int dell_setup_rfkill(void)
 {
@@ -431,7 +434,9 @@ static bool dell_input_filter(struct input_handle *handle, unsigned int type,
 			     unsigned int code, int value)
 {
 	if (type == EV_KEY && code == KEY_WLAN && value == 1) {
-		dell_rfkill_update();
+		if (!schedule_work(&dell_rfkill_update_work))
+			printk(KERN_NOTICE "rfkill switch handling already "
+					   "scheduled, dropping this event\n");
 		return 1;
 	}
 
-- 
1.6.3.3