Paul Jackson <[email protected]> wrote:
>
> It's ok to not complete the refresh_mems() operation
> if we notice we are already holding mmap_sem. We
> will try again, next time we allocate memory.
What's the call path? alloc_pages_current() and alloc_page_vma()?
>
> --- 2.6.14-rc5-mm1-cpuset-patches.orig/kernel/cpuset.c 2005-11-03 21:18:26.783391082 -0800
> +++ 2.6.14-rc5-mm1-cpuset-patches/kernel/cpuset.c 2005-11-03 23:11:15.480042373 -0800
> @@ -656,7 +656,12 @@ static void refresh_mems(void)
> if (current->cpuset_mems_generation != my_cpusets_mem_gen) {
> struct cpuset *cs;
> nodemask_t oldmem = current->mems_allowed;
> + struct mm_struct *mm = current->mm;
>
> + /* numa_policy_rebind() needs mmap_sem - don't nest */
> + if (!mm || !down_write_trylock(&mm->mmap_sem))
> + return;
> + up_write(&mm->mmap_sem);
What happens if the task is doing _all_ its allocation under
down_read(mmap_sem)? Like, memset(malloc(lots))? Does all that memory end
up in the wrong place, or what?
Something less hacky^W^W more deterministic would be nice.
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