Messages in this thread | | | From | Rusty Russell <> | Subject | Re: [PATCH 05/16] staging/lustre: fix up obsolete cpu function usage. | Date | Tue, 03 Mar 2015 10:09:07 +1030 |
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Oleg Drokin <green@linuxhacker.ru> writes: > Thanks! > Seems there was a midair collsion with my own patch that was not as comprehensive > wrt functions touched: https://lkml.org/lkml/2015/3/2/10
Yep, I posted this for completeness (and for your reference), but figured you'd handle it.
> But on the other hand I also tried to clean up > some of the NR_CPUS usage while I was at it and this raises > this question, from me, in the code like: > > for_each_cpu_mask(i, blah) { > blah > if (something) > break; > } > if (i == NR_CPUS) > blah; > > when we are replacing for_each_cpu_mask with for_each_cpu, > what do we check the counter against now to see that the entire loop was executed > and we did not exit prematurely? nr_cpu_ids?
You want >= nr_cpu_ids here.
> Also I assume we still want to get rid of direct cpumask assignments like >> mask = *cpumask_of_node(cpu_to_node(index));
Yes, but this code is wrong anyway:
mask = *cpumask_of_node(cpu_to_node(index)); for (i = max; i < num_online_cpus(); i++) cpumask_clear_cpu(i, &mask);
*Never* iterate to num_online_cpus(). eg. if cpus 0 and 3 are online, num_online_cpus() == 2. I'm not sure what this code is doing, but it's not doing it well :)
There are several issues here. You need to handle cpus going offline (during this routine, as well as after). You need to use a cpumask_var_t, like so:
cpumask_var_t mask;
... case PDB_POLICY_NEIGHBOR: if (!alloc_cpumask_var(&mask, GFP_???)) { rc = -ENOMEM; break; } ...
Or get rid of the mask altogether, eg:
pc->pc_npartners = -1; for_each_cpu(i, cpu_online_mask) { if (i < max) pc->pc_npartners++; } ...
pidx = 0; for_each_cpu(i, cpu_online_mask) { if (i >= max) break; ppc = &ptlrpcds->pd_threads[i]; pc->pc_partners[pidx++] = ppc; ppc->pc_partners[ppc->pc_npartners++] = pc; }
[ This is off the top of my head, no idea if it's right...]
Thanks, Rusty.
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