RFC: soft/hardlookup: taint kernel

There's the soft/hardlookup_panic sysctls, but that's a bit an extreme
measure. As a fallback taint at least the machine.

Our CI uses this to decide when a reboot is necessary, plus to figure
out whether the kernel is still happy.

References: https://gitlab.freedesktop.org/drm/intel/-/issues/8035


Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Valdis Kletnieks <valdis.kletnieks@vt.edu>
Cc: Laurence Oberman <loberman@redhat.com>
Cc: Vincent Whitchurch <vincent.whitchurch@axis.com>
Cc: Don Zickus <dzickus@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Sinan Kaya <okaya@kernel.org>
Cc: Daniel Vetter <daniel.vetter@ffwll.ch>
Acked-by: Chris Wilson <chris@chris-wilson.co.uk> (for core-for-CI)
Link: https://patchwork.freedesktop.org/patch/msgid/20190502194208.3535-2-daniel.vetter@ffwll.ch


Signed-off-by: Jani Nikula <jani.nikula@intel.com>
Signed-off-by: Rodrigo Vivi <rodrigo.vivi@intel.com>

kernel/watchdog.c

@@ -214,6 +214,8 @@ void watchdog_hardlockup_check(unsigned int cpu, struct pt_regs *regs)
 
 		if (hardlockup_panic)
 			nmi_panic(regs, "Hard LOCKUP");
+		else
+			add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
 
 		per_cpu(watchdog_hardlockup_warned, cpu) = true;
 	} else {
@@ -778,6 +780,8 @@ static enum hrtimer_restart watchdog_timer_fn(struct hrtimer *hrtimer)
 		add_taint(TAINT_SOFTLOCKUP, LOCKDEP_STILL_OK);
 		if (softlockup_panic)
 			panic("softlockup: hung tasks");
+		else
+			add_taint(TAINT_WARN, LOCKDEP_STILL_OK);
 	}
 
 	return HRTIMER_RESTART;