@@ -2476,7 +2476,8 @@ static bool pte_spinlock(struct vm_fault *vmf)
goto out;
vmf->ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
- spin_lock(vmf->ptl);
+ if (unlikely(!spin_trylock(vmf->ptl)))
+ goto out;
if (vma_has_changed(vmf)) {
spin_unlock(vmf->ptl);
@@ -2521,8 +2522,20 @@ static bool pte_map_lock(struct vm_fault *vmf)
if (vma_has_changed(vmf))
goto out;
- pte = pte_offset_map_lock(vmf->vma->vm_mm, vmf->pmd,
- vmf->address, &ptl);
+ /*
+ * Same as pte_offset_map_lock() except that we call
+ * spin_trylock() in place of spin_lock() to avoid race with
+ * unmap path which may have the lock and wait for this CPU
+ * to invalidate TLB but this CPU has irq disabled.
+ * Since we are in a speculative patch, accept it could fail
+ */
+ ptl = pte_lockptr(vmf->vma->vm_mm, vmf->pmd);
+ pte = pte_offset_map(vmf->pmd, vmf->address);
+ if (unlikely(!spin_trylock(ptl))) {
+ pte_unmap(pte);
+ goto out;
+ }
+
if (vma_has_changed(vmf)) {
pte_unmap_unlock(pte, ptl);
goto out;
There is a deadlock when a CPU is doing a speculative page fault and another one is calling do_unmap(). The deadlock occurred because the speculative path try to spinlock the pte while the interrupt are disabled. When the other CPU in the unmap's path has locked the pte then is waiting for all the CPU to invalidate the TLB. As the CPU doing the speculative fault have the interrupt disable it can't invalidate the TLB, and can't get the lock. Since we are in a speculative path, we can race with other mm action. So let assume that the lock may not get acquired and fail the speculative page fault. Here are the stacks captured during the deadlock: CPU 0 native_flush_tlb_others+0x7c/0x260 flush_tlb_mm_range+0x6a/0x220 tlb_flush_mmu_tlbonly+0x63/0xc0 unmap_page_range+0x897/0x9d0 ? unmap_single_vma+0x7d/0xe0 ? release_pages+0x2b3/0x360 unmap_single_vma+0x7d/0xe0 unmap_vmas+0x51/0xa0 unmap_region+0xbd/0x130 do_munmap+0x279/0x460 SyS_munmap+0x53/0x70 CPU 1 do_raw_spin_lock+0x14e/0x160 _raw_spin_lock+0x5d/0x80 ? pte_map_lock+0x169/0x1b0 pte_map_lock+0x169/0x1b0 handle_pte_fault+0xbf2/0xd80 ? trace_hardirqs_on+0xd/0x10 handle_speculative_fault+0x272/0x280 handle_speculative_fault+0x5/0x280 __do_page_fault+0x187/0x580 trace_do_page_fault+0x52/0x260 do_async_page_fault+0x19/0x70 async_page_fault+0x28/0x30 Signed-off-by: Laurent Dufour <ldufour@linux.vnet.ibm.com> --- mm/memory.c | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-)