On Sat, 12 Nov 2022 20:15:37 +0800 Zhen Lei <thunder.leizhen@xxxxxxxxxx> wrote: > The function mem_dump_obj() can sometimes provide valuable debugging > information, but it cannot be called in an interrupt context because > spinlock vmap_area_lock has not been protected against IRQs. If the > current task has held the lock before hard/soft interrupt handler calls > mem_dump_obj(), simply abandoning the dump operation can avoid deadlock. > That is, no deadlock occurs in extreme cases, and dump succeeds in most > cases. > > ... > > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -4034,6 +4034,9 @@ bool vmalloc_dump_obj(void *object) > struct vm_struct *vm; > void *objp = (void *)PAGE_ALIGN((unsigned long)object); > > + if (unlikely(spin_is_locked(&vmap_area_lock))) > + return false; > + > vm = find_vm_area(objp); > if (!vm) > return false; Yes, but this will worsen the current uses of this function. Consider the case where task A wants to call vmalloc_dump_obj() but task B holds vmap_area_lock. No problem, task A will simply spin until task B is done. But after this patch, task A's call to vmalloc_dump_obj() will return without having done anything.
