On Tue, Oct 29, 2019 at 10:15:13PM +0200, Ville Syrjälä wrote: > Hi, > > I got some khugepaged spew on a 32bit x86: > > [ 217.490026] BUG: sleeping function called from invalid context at include/linux/mmu_notifier.h:346 > [ 217.492826] in_atomic(): 1, irqs_disabled(): 0, non_block: 0, pid: 25, name: khugepaged > [ 217.495589] INFO: lockdep is turned off. > [ 217.498371] CPU: 1 PID: 25 Comm: khugepaged Not tainted 5.4.0-rc5-elk+ #206 > [ 217.501233] Hardware name: System manufacturer P5Q-EM/P5Q-EM, BIOS 2203 07/08/2009 > [ 217.501697] Call Trace: > [ 217.501697] dump_stack+0x66/0x8e > [ 217.501697] ___might_sleep.cold.96+0x95/0xa6 > [ 217.501697] __might_sleep+0x2e/0x80 > [ 217.501697] collapse_huge_page.isra.51+0x5ac/0x1360 > [ 217.501697] ? __alloc_pages_nodemask+0xec/0xf80 > [ 217.501697] ? __alloc_pages_nodemask+0x191/0xf80 > [ 217.501697] ? trace_hardirqs_on+0x4a/0xf0 > [ 217.501697] khugepaged+0x9a9/0x20f0 > [ 217.501697] ? _raw_spin_unlock+0x21/0x30 > [ 217.501697] ? trace_hardirqs_on+0x4a/0xf0 > [ 217.501697] ? wait_woken+0xa0/0xa0 > [ 217.501697] kthread+0xf5/0x110 > [ 217.501697] ? collapse_pte_mapped_thp+0x3b0/0x3b0 > [ 217.501697] ? kthread_create_worker_on_cpu+0x20/0x20 > [ 217.501697] ret_from_fork+0x2e/0x38 > > Looks like it's due to CONFIG_HIGHPTE=y pte_offset_map()->kmap_atomic() vs. > mmu_notifier_invalidate_range_start(). > > My naive idea would be to just reorder those things, but not sure > if there's some magic ordering constraint here. At least the machine > still boots when I do it :) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 0a1b4b484ac5..f05d27b7183d 100644 > +++ b/mm/khugepaged.c > @@ -1028,12 +1028,13 @@ static void collapse_huge_page(struct mm_struct *mm, > > anon_vma_lock_write(vma->anon_vma); > > - pte = pte_offset_map(pmd, address); > - pte_ptl = pte_lockptr(mm, pmd); > - > mmu_notifier_range_init(&range, MMU_NOTIFY_CLEAR, 0, NULL, mm, > address, address + HPAGE_PMD_SIZE); > mmu_notifier_invalidate_range_start(&range); > + > + pte = pte_offset_map(pmd, address); > + pte_ptl = pte_lockptr(mm, pmd); > + Since pte and pte_ptl don't leak into invalidate_range_start this seems reasonable to me.. Good catch with the new debugging! Jason
