2016-03-14 13:43 GMT+03:00 Alexander Potapenko <glider@xxxxxxxxxx>:
> +
> + rec = this_cpu_ptr(&depot_recursion);
> + /* Don't store the stack if we've been called recursively. */
> + if (unlikely(*rec))
> + goto fast_exit;
> + *rec = true;
This just can't work. As long as preemption enabled, task could
migrate on another cpu anytime.
You could use per-task flag, although it's possible to miss some
in-irq stacktraces:
depot_save_stack()
if (current->stackdeport_recursion)
goto fast_exit;
current->stackdepot_recursion++
<IRQ>
....
depot_save_stack()
if (current->stackdeport_recursion)
goto fast_exit;
> + if (unlikely(!smp_load_acquire(&next_slab_inited))) {
> + /* Zero out zone modifiers, as we don't have specific zone
> + * requirements. Keep the flags related to allocation in atomic
> + * contexts and I/O.
> + */
> + alloc_flags &= ~GFP_ZONEMASK;
> + alloc_flags &= (GFP_ATOMIC | GFP_KERNEL);
> + /* When possible, allocate using vmalloc() to reduce physical
> + * address space fragmentation. vmalloc() doesn't work if
> + * kmalloc caches haven't been initialized or if it's being
> + * called from an interrupt handler.
> + */
> + if (kmalloc_caches[KMALLOC_SHIFT_HIGH] && !in_interrupt()) {
This is clearly a wrong way to check whether is slab available or not.
Besides you need to check
vmalloc() for availability, not slab.
Given that STAC_ALLOC_ORDER is 2 now, I think it should be fine to use
alloc_pages() all the time.
Or fix condition, up to you.
> + prealloc = __vmalloc(
> + STACK_ALLOC_SIZE, alloc_flags, PAGE_KERNEL);
> + } else {
> + page = alloc_pages(alloc_flags, STACK_ALLOC_ORDER);
> + if (page)
> + prealloc = page_address(page);
> + }
> + }
> +
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