kernel/watchdog.c:touch_softlockup_watchdog(): use raw_cpu_write()

Fix:

  BUG: using __this_cpu_write() in preemptible [00000000] code: systemd-udevd/497
  caller is __this_cpu_preempt_check+0x13/0x20
  CPU: 3 PID: 497 Comm: systemd-udevd Tainted: G        W     3.15.0-rc1 #9
  Hardware name: Hewlett-Packard HP EliteBook 8470p/179B, BIOS 68ICF Ver. F.02 04/27/2012
  Call Trace:
    check_preemption_disabled+0xe1/0xf0
    __this_cpu_preempt_check+0x13/0x20
    touch_nmi_watchdog+0x28/0x40

Reported-by: Luis Henriques <luis.henriques@canonical.com>
Tested-by: Luis Henriques <luis.henriques@canonical.com>
Cc: Eric Piel <eric.piel@tremplin-utc.net>
Cc: Robert Moore <robert.moore@intel.com>
Cc: Lv Zheng <lv.zheng@intel.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@intel.com>
Cc: Len Brown <lenb@kernel.org>
Cc: Christoph Lameter <cl@linux.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/kernel/watchdog.c b/kernel/watchdog.c
index e90089fd78e0..516203e665fc 100644
--- a/kernel/watchdog.c
+++ b/kernel/watchdog.c
@@ -138,7 +138,11 @@ static void __touch_watchdog(void)
 
 void touch_softlockup_watchdog(void)
 {
-        __this_cpu_write(watchdog_touch_ts, 0);
+        /*
+         * Preemption can be enabled.  It doesn't matter which CPU's timestamp
+         * gets zeroed here, so use the raw_ operation.
+         */
+        raw_cpu_write(watchdog_touch_ts, 0);
 }
 EXPORT_SYMBOL(touch_softlockup_watchdog);