Messages in this thread |  | | Date | Tue, 11 Dec 2012 09:53:12 +0530 | From | Preeti U Murthy <> | Subject | Re: [PATCH 01/18] sched: select_task_rq_fair clean up |
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Hi Alex,
On 12/10/2012 01:52 PM, Alex Shi wrote: > It is impossible to miss a task allowed cpu in a eligible group.
The one thing I am concerned with here is if there is a possibility of the task changing its tsk_cpus_allowed() while this code is running.
i.e find_idlest_group() finds an idle group,then the tsk_cpus_allowed() for the task changes,perhaps by the user himself,which might not include the cpus in the idle group.After this find_idlest_cpu() is called.I mean a race condition in short.Then we might not have an eligible cpu in that group right?
> And since find_idlest_group only return a different group which > excludes old cpu, it's also imporissible to find a new cpu same as old > cpu.
This I agree with.
> Signed-off-by: Alex Shi <alex.shi@intel.com> > --- > kernel/sched/fair.c | 5 ----- > 1 files changed, 0 insertions(+), 5 deletions(-) > > diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c > index 59e072b..df99456 100644 > --- a/kernel/sched/fair.c > +++ b/kernel/sched/fair.c > @@ -3150,11 +3150,6 @@ select_task_rq_fair(struct task_struct *p, int sd_flag, int wake_flags) > } > > new_cpu = find_idlest_cpu(group, p, cpu); > - if (new_cpu == -1 || new_cpu == cpu) { > - /* Now try balancing at a lower domain level of cpu */ > - sd = sd->child; > - continue; > - } > > /* Now try balancing at a lower domain level of new_cpu */ > cpu = new_cpu; > Regards Preeti U Murthy
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