From: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <peterz@infradead.org>,
Andrew Theurer <habanero@linux.vnet.ibm.com>
Subject: Re: [PATCH 2/2] sched: Check if lowest_mask is initialized in find_lowest_rq
Date: Tue, 14 Jun 2011 17:40:45 -0700 [thread overview]
Message-ID: <20110615004045.GU2288@linux.vnet.ibm.com> (raw)
In-Reply-To: <20110614223657.824872966@goodmis.org>
On Tue, Jun 14, 2011 at 06:36:25PM -0400, Steven Rostedt wrote:
> From: Steven Rostedt <rostedt@goodmis.org>
>
> On system boot up, the lowest_mask is initialized with early_initcall.
> But RT tasks may wake up on other early_initcall callers before the
> lowest_mask is initialized, causing a system crash.
>
> The commit d72bce0e67 rcu: Cure load woes
> was the first commit to wake up RT tasks in early init. Before this
> commit this bug should not happen.
I never was able to reproduce this, but after adding Shaohua's patch, I
need this one too on some systems. So:
Tested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
> Cc: Peter Zijlstra <peterz@infradead.org>
> Cc: Paul McKenney <paulmck@linux.vnet.ibm.com>
> Reported-by: Andrew Theurer <habanero@linux.vnet.ibm.com>
> Tested-by: Andrew Theurer <habanero@linux.vnet.ibm.com>
> Link: http://lkml.kernel.org/r/1308014683.9218.107.camel@gandalf.stny.rr.com
> Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
> ---
> kernel/sched_rt.c | 4 ++++
> 1 files changed, 4 insertions(+), 0 deletions(-)
>
> diff --git a/kernel/sched_rt.c b/kernel/sched_rt.c
> index 9b8d5dc..10d0182 100644
> --- a/kernel/sched_rt.c
> +++ b/kernel/sched_rt.c
> @@ -1239,6 +1239,10 @@ static int find_lowest_rq(struct task_struct *task)
> int this_cpu = smp_processor_id();
> int cpu = task_cpu(task);
>
> + /* Make sure the mask is initialized first */
> + if (unlikely(!lowest_mask))
> + return -1;
> +
> if (task->rt.nr_cpus_allowed == 1)
> return -1; /* No other targets possible */
>
> --
> 1.7.4.4
>
>
next prev parent reply other threads:[~2011-06-15 0:40 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-06-14 22:36 [PATCH 0/2] [GIT PULL][v3.0] sched: various fixes Steven Rostedt
2011-06-14 22:36 ` [PATCH 1/2] sched: Fix need_resched() when checking peempt Steven Rostedt
2011-06-15 9:50 ` [tip:sched/urgent] " tip-bot for Hillf Danton
2011-06-14 22:36 ` [PATCH 2/2] sched: Check if lowest_mask is initialized in find_lowest_rq Steven Rostedt
2011-06-15 0:40 ` Paul E. McKenney [this message]
2011-06-15 8:17 ` Peter Zijlstra
2011-06-15 9:50 ` [tip:sched/urgent] sched: Check if lowest_mask is initialized in find_lowest_rq() tip-bot for Steven Rostedt
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