Messages in this thread | | | Date | Fri, 22 Mar 2013 14:03:30 +0400 | From | Glauber Costa <> | Subject | Re: [PATCH] memcg: fix memcg_cache_name() to use cgroup_name() |
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On 03/22/2013 01:48 PM, Michal Hocko wrote: > On Fri 22-03-13 13:41:40, Glauber Costa wrote: >> On 03/22/2013 01:31 PM, Michal Hocko wrote: >>> On Fri 22-03-13 12:22:23, Glauber Costa wrote: >>>> On 03/22/2013 12:17 PM, Li Zefan wrote: >>>>>> GFP_TEMPORARY groups short lived allocations but the mem cache is not >>>>>>> an ideal candidate of this type of allocations.. >>>>>>> >>>>> I'm not sure I'm following you... >>>>> >>>>> char *memcg_cache_name() >>>>> { >>>>> char *name = alloc(); >>>>> return name; >>>>> } >>>>> >>>>> kmem_cache_dup() >>>>> { >>>>> name = memcg_cache_name(); >>>>> kmem_cache_create_memcg(name); >>>>> free(name); >>>>> } >>>>> >>>>> Isn't this a short lived allocation? >>>>> >>>> >>>> Hi, >>>> >>>> Thanks for identifying and fixing this. >>>> >>>> Li is right. The cache name will live long, but this is because the >>>> slab/slub caches will strdup it internally. So the actual memcg >>>> allocation is short lived. >>> >>> OK, I have totally missed that. Sorry about the confusion. Then all the >>> churn around the allocation is pointless, no? >>> What about: >> >> If we're really not concerned about stack, then yes. Even if always >> running from workqueues, a PAGE_SIZEd stack variable seems risky to me. > > This is not on stack. It is static > Ah, right, I totally missed that. And then you're taking the mutex.
But actually, you don't need to take the mutex. All calls to kmem_cache_dup are protected by the memcg_cache_mutex. So you should be able to just use the buffer without further problems.
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