Re: [PATCH] sched: Make nr_uninterruptible count a signed value
From: Michael Wang
Date: Thu May 10 2012 - 10:16:33 EST
On 05/10/2012 02:55 AM, Diwakar Tundlam wrote:
>>> - P(nr_uninterruptible);
>>> + P((signed long)nr_uninterruptible);
> I thought of it too, but it won't compile because the P macro expands to dereferencing rq->nr_uninterruptible, so with your change, it will show up as rq->(signed long)nr_uninterruptible which is a syntax error.
oh, I see, so looks like it's a little hard to avoid some ugly change...
> -----Original Message-----
> From: Michael Wang [mailto:wangyun@xxxxxxxxxxxxxxxxxx]
> Sent: Wednesday, May 09, 2012 12:49 AM
> To: Diwakar Tundlam
> Cc: 'Peter Zijlstra'; 'Ingo Molnar'; 'David Rientjes'; 'linux-kernel@xxxxxxxxxxxxxxx'; Peter De Schrijver
> Subject: Re: [PATCH] sched: Make nr_uninterruptible count a signed value
> On 05/09/2012 06:46 AM, Diwakar Tundlam wrote:
>>> No that's right. nr_uninterruptible counts the number of tasks in
>>> uninterruptible sleep, so deactivate_task puts a task to sleep, so we
>>> need to increment the number of sleeping tasks, activate_task wakes a
>>> task up so we need to decrement the number of sleeping tasks.
>> Yep, I looked at the code for task_contributes_to_load() and I understand what it is all about.
>> The ++ and -- are correct, I see it now.
>> On the -ve values, strangely inspite of %Ld in the print statement, in my kernel, I see high unsigned values instead of -ve values for nr_uninterruptible.
>> But the sum is always 0, though.
>> Maybe it is an artifact of 32-bit machine displaying 64-bit print format.
>> An (unsigned long)(-24) promoted to (signed long long) ends up as 4294967272.
>> As seen in my output of sched_debug.
> This may do some help.
> Michael Wang
> kernel/sched/debug.c | 2 +-
> 1 files changed, 1 insertions(+), 1 deletions(-)
> diff --git a/kernel/sched/debug.c b/kernel/sched/debug.c index 09acaa1..ab9d53f 100644
> --- a/kernel/sched/debug.c
> +++ b/kernel/sched/debug.c
> @@ -270,7 +270,7 @@ static void print_cpu(struct seq_file *m, int cpu)
> - P(nr_uninterruptible);
> + P((signed long)nr_uninterruptible);
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/