make SysRq-T show all tasks again

show_state() (SysRq-T) developed the buggy habbit of not showing
TASK_RUNNING tasks. This was due to the mistaken belief that state_filter
== -1 would be a pass-through filter - while in reality it did not let
TASK_RUNNING == 0 p->state values through.

Fix this by restoring the original '!state_filter means all tasks'
special-case i had in the original version. Test-built and test-booted on
i686, SysRq-T now works as intended.

Signed-off-by: Ingo Molnar <[e-mail]>
Signed-off-by: Andrew Morton <[e-mail]>
Signed-off-by: Linus Torvalds <[e-mail]>

include/linux/sched.h

···
 extern cpumask_t nohz_cpu_mask;
 
 /*
- * Only dump TASK_* tasks. (-1 for all tasks)
+ * Only dump TASK_* tasks. (0 for all tasks)
  */
 extern void show_state_filter(unsigned long state_filter);
 
 static inline void show_state(void)
 {
-	show_state_filter(-1);
+	show_state_filter(0);
 }
 
 extern void show_regs(struct pt_regs *);

kernel/sched.c

···
 		 * console might take alot of time:
 		 */
 		touch_nmi_watchdog();
-		if (p->state & state_filter)
+		if (!state_filter || (p->state & state_filter))
 			show_task(p);
 	} while_each_thread(g, p);