On Wed, May 24, 2017 at 12:56:10PM -0700, Andrew Morton wrote: > On Wed, 24 May 2017 16:47:28 +0100 Punit Agrawal <punit.agrawal@xxxxxxx> wrote: > > > On failing to migrate a page, soft_offline_huge_page() performs the > > necessary update to the hugepage ref-count. When > > !hugepage_migration_supported() , unmap_and_move_hugepage() also > > decrements the page ref-count for the hugepage. The combined behaviour > > leaves the ref-count in an inconsistent state. > > > > This leads to soft lockups when running the overcommitted hugepage test > > from mce-tests suite. > > > > Soft offlining pfn 0x83ed600 at process virtual address 0x400000000000 > > soft offline: 0x83ed600: migration failed 1, type > > 1fffc00000008008 (uptodate|head) > > INFO: rcu_preempt detected stalls on CPUs/tasks: > > Tasks blocked on level-0 rcu_node (CPUs 0-7): P2715 > > (detected by 7, t=5254 jiffies, g=963, c=962, q=321) > > thugetlb_overco R running task 0 2715 2685 0x00000008 > > Call trace: > > [<ffff000008089f90>] dump_backtrace+0x0/0x268 > > [<ffff00000808a2d4>] show_stack+0x24/0x30 > > [<ffff000008100d34>] sched_show_task+0x134/0x180 > > [<ffff0000081c90fc>] rcu_print_detail_task_stall_rnp+0x54/0x7c > > [<ffff00000813cfd4>] rcu_check_callbacks+0xa74/0xb08 > > [<ffff000008143a3c>] update_process_times+0x34/0x60 > > [<ffff0000081550e8>] tick_sched_handle.isra.7+0x38/0x70 > > [<ffff00000815516c>] tick_sched_timer+0x4c/0x98 > > [<ffff0000081442e0>] __hrtimer_run_queues+0xc0/0x300 > > [<ffff000008144fa4>] hrtimer_interrupt+0xac/0x228 > > [<ffff0000089a56d4>] arch_timer_handler_phys+0x3c/0x50 > > [<ffff00000812f1bc>] handle_percpu_devid_irq+0x8c/0x290 > > [<ffff0000081297fc>] generic_handle_irq+0x34/0x50 > > [<ffff000008129f00>] __handle_domain_irq+0x68/0xc0 > > [<ffff0000080816b4>] gic_handle_irq+0x5c/0xb0 > > > > Fix this by dropping the ref-count decrement in > > unmap_and_move_hugepage() when !hugepage_migration_supported(). > > > > Fixes: 32665f2bbfed ("mm/migrate: correct failure handling if !hugepage_migration_support()") > > Reported-by: Manoj Iyer <manoj.iyer@xxxxxxxxxxxxx> > > Signed-off-by: Punit Agrawal <punit.agrawal@xxxxxxx> > > Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx> > > Cc: Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> > > Cc: Wanpeng Li <liwanp@xxxxxxxxxxxxxxxxxx> > > Cc: Christoph Lameter <cl@xxxxxxxxx> > > 32665f2bbfed was three years ago. Do you have any theory as to why > this took so long to be detected? My per-release testing only ran for "hugepage_migration_supported() == true" setting (i.e. x86 with CONFIG_HUGETLB_PAGE=y). I need extend the coverage. And other arch's developers recently have come to have interest in hugepage migration. > And do you believe a -stable > backport is warranted? I agree to send the fix to stable, so the stable tag is wanted. Cc: stable@xxxxxxxxxx # v3.14+ Thanks, Naoya Horiguchi -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href