Messages in this thread Patch in this message | | | Date | Tue, 25 Sep 2012 19:45:50 +0800 | From | Tang Chen <> | Subject | Re: [PATCH] Update sched_domains_numa_masks when new cpus are onlined. |
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Hi Peter~
Sorry about the confusing log, and thanks for the patient. :)
Here, I want to say something more about the sched_domains_numa_levels to make myself more clear. :)
Let's have an example here.
sched_init_numa() { ... // A loop set sched_domains_numa_levels to level.-------------1
// I set sched_domains_numa_levels to 0. sched_domains_numa_levels = 0;--------------------------------2
// A loop allocating memory for sched_domains_numa_masks[][] for (i = 0; i < level; i++) { ...... // Allocate memory for sched_domains_numa_masks[i]----3 ...... } ......
// I reset sched_domains_numa_levels to level. sched_domains_numa_levels = level;----------------------------4 }
// A new function I added. static void sched_domains_numa_masks_clear(int cpu) { int i, j; for (i = 0; i < sched_domains_numa_levels; i++)---------------5 for (j = 0; j < nr_node_ids; j++) cpumask_clear_cpu(cpu, sched_domains_numa_masks[i][j]); }
Suppose level is 10, and at step 1, sched_domains_numa_levels is 10.
If I didn't set sched_domains_numa_levels to 0 at step 2, it will be 10 all the time.
If memory allocation at step 3 fails when i = 5, the array sched_domains_numa_masks[][] will only have 5 members, and sched_domains_numa_levels is 10.
As you see, I added 2 functions using sched_domains_numa_levels to iterate sched_domains_numa_masks[][], such as at step 5. In this case, the iteration will break out when i = 5.
This could be dangerous.
So, I set sched_domains_numa_levels to 0 at step 2. This way, even if any memory allocation at step 3 fails, and sched_init_numa() returns, anyone uses sched_domains_numa_levels (which is 0) won't be wrong.
I'm not sure if this is the best way to settle this problem. If you have a better idea, please tell me. Thanks. :)
On 09/25/2012 06:33 PM, Peter Zijlstra wrote: > On Tue, 2012-09-25 at 10:39 +0800, Tang Chen wrote: >>>> @@ -6765,11 +6773,64 @@ static void sched_init_numa(void) >>>> } >>>> >>>> sched_domain_topology = tl; >>>> + >>>> + sched_domains_numa_levels = level; >> >> And I set it to level here again. >> > But its already set there.. its set every time we find a new level. > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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