path: root/kernel
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authorSteven Rostedt <rostedt@goodmis.org>2014-02-19 13:53:35 -0500
committerThomas Gleixner <tglx@linutronix.de>2014-02-21 21:27:09 +0100
commit4df1638cfaf9b2b7ad993979a41965acab9cd156 (patch)
tree054e7a3fe260b5509bb46f12be416fc07e11dcb5 /kernel
parent3d5f35bdfdef5fd627afe9b4bf9c4f32d17f4593 (diff)
sched/deadline: Fix overflow to handle period==0 and deadline!=0
While debugging the crash with the bad nr_running accounting, I hit another bug where, after running my sched deadline test, I was getting failures to take a CPU offline. It was giving me a -EBUSY error. Adding a bunch of trace_printk()s around, I found that the cpu notifier that called sched_cpu_inactive() was returning a failure. The overflow value was coming up negative? Talking this over with Juri, the problem is that the total_bw update was suppose to be made by dl_overflow() which, during my tests, seemed to not be called. Adding more trace_printk()s, it wasn't that it wasn't called, but it exited out right away with the check of new_bw being equal to p->dl.dl_bw. The new_bw calculates the ratio between period and runtime. The bug is that if you set a deadline, you do not need to set a period if you plan on the period being equal to the deadline. That is, if period is zero and deadline is not, then the system call should set the period to be equal to the deadline. This is done elsewhere in the code. The fix is easy, check if period is set, and if it is not, then use the deadline. Cc: Juri Lelli <juri.lelli@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Steven Rostedt <rostedt@goodmis.org> Signed-off-by: Peter Zijlstra <peterz@infradead.org> Link: http://lkml.kernel.org/r/20140219135335.7e74abd4@gandalf.local.home Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Diffstat (limited to 'kernel')
1 files changed, 1 insertions, 1 deletions
diff --git a/kernel/sched/core.c b/kernel/sched/core.c
index b46131ef6aa..24914488da4 100644
--- a/kernel/sched/core.c
+++ b/kernel/sched/core.c
@@ -1952,7 +1952,7 @@ static int dl_overflow(struct task_struct *p, int policy,
struct dl_bw *dl_b = dl_bw_of(task_cpu(p));
- u64 period = attr->sched_period;
+ u64 period = attr->sched_period ?: attr->sched_deadline;
u64 runtime = attr->sched_runtime;
u64 new_bw = dl_policy(policy) ? to_ratio(period, runtime) : 0;
int cpus, err = -1;