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Date: Thu, 20 Feb 2014 08:47:40 +0100 From: Juri Lelli <juri.lelli@...il.com> To: Steven Rostedt <rostedt@...dmis.org>, LKML <linux-kernel@...r.kernel.org> CC: Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>, Linus Torvalds <torvalds@...ux-foundation.org>, Andrew Morton <akpm@...ux-foundation.org>, Thomas Gleixner <tglx@...utronix.de> Subject: Re: [PATCH] sched/deadline: Fix overflow to handle period==0 and deadline!=0 On 02/19/2014 07:53 PM, Steven Rostedt wrote: > 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. > > Signed-off-by: Steven Rostedt <rostedt@...dmis.org> > --- > diff --git a/kernel/sched/core.c b/kernel/sched/core.c > index b46131e..2491448 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; > Thanks! - Juri -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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