printk/sched: Introduce special printk_sched() for those awkward moments

There's a few awkward printk()s inside of scheduler guts that people
prefer to keep but really are rather deadlock prone. Fudge around it
by storing the text in a per-cpu buffer and poll it using the existing
printk_tick() handler.

This will drop output when its more frequent than once a tick, however
only the affinity thing could possible go that fast and for that just
one should suffice to notify the admin he's done something silly..

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/n/tip-wua3lmkt3dg8nfts66o6brne@git.kernel.org
Signed-off-by: Ingo Molnar <mingo@elte.hu>

2 files changed, 8 insertions, 2 deletions

diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b1ccce819ce2..8781cec7c3e6 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1284,7 +1284,7 @@ static int select_fallback_rq(int cpu, struct task_struct *p)
          * leave kernel.
          */
         if (p->mm && printk_ratelimit()) {
-                printk(KERN_INFO "process %d (%s) no longer affine to cpu%d\n",
+                printk_sched("process %d (%s) no longer affine to cpu%d\n",
                                 task_pid_nr(p), p->comm, cpu);
         }
 
diff --git a/kernel/sched/rt.c b/kernel/sched/rt.c
index 7f7e7cdcb472..b60dad720173 100644
--- a/kernel/sched/rt.c
+++ b/kernel/sched/rt.c
@@ -864,8 +864,14 @@ static int sched_rt_runtime_exceeded(struct rt_rq *rt_rq)
                  * but accrue some time due to boosting.
                  */
                 if (likely(rt_b->rt_runtime)) {
+                        static bool once = false;
+
                         rt_rq->rt_throttled = 1;
-                        printk_once(KERN_WARNING "sched: RT throttling activated\n");
+
+                        if (!once) {
+                                once = true;
+                                printk_sched("sched: RT throttling activated\n");
+                        }
                 } else {
                         /*
                          * In case we did anyway, make it go away,