Messages in this thread | | | Date | Mon, 20 Oct 2014 11:13:11 +0200 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/numa: fix unsafe get_task_struct() in task_numa_assign() |
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OK, I think I'm finally awake enough to see what you're all talking about :-)
On Sun, Oct 19, 2014 at 09:37:44PM +0200, Oleg Nesterov wrote: > > > RT tree has: > > > > > > https://git.kernel.org/cgit/linux/kernel/git/paulg/3.10-rt-patches.git/ > > > tree/patches/sched-delay-put-task.patch
(answering the other email asking about this)
RT does this because we call put_task_struct() with preempt disabled and on RT the memory allocator has sleeping locks.
> > Yes, and this obviously implies more rcu callbacks in flight, and another > > gp before __put_task_struct(). but may be we will need to do this anyway... > > Forgot to mention... Or we can make task_struct_cachep SLAB_DESTROY_BY_RCU, > in this case ->curr (or any other "task_struct *" ponter) can not go away > under rcu_read_lock(). task_numa_compare() still needs the PF_EXITING check, > but we do not need to recheck ->curr or probe_kernel_read().
I think I would prefer SLAB_DESTROY_BY_RCU for this, because as you pointed out, I'm not sure mainline would like the extra callbacks.
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