On 1/2/19 1:06 PM, Mel Gorman wrote: > While I recognise there is no test case available, how often does this > trigger in syzbot as it would be nice to have some confirmation any > patch is really fixing the problem. I think I did manage to trigger this every time running a mmap() workload causing swapping and a low-memory situation [1]. [1] https://github.com/linux-test-project/ltp/blob/master/testcases/kernel/mem/oom/oom01.c [ 507.192079] ====================================================== [ 507.198294] WARNING: possible circular locking dependency detected [ 507.204510] 4.20.0+ #27 Not tainted [ 507.208018] ------------------------------------------------------ [ 507.214233] oom01/7666 is trying to acquire lock: [ 507.218965] 00000000bc163d02 (&p->pi_lock){-.-.}, at: try_to_wake_up+0x10a/0xe80 [ 507.226415] [ 507.226415] but task is already holding lock: [ 507.232280] 0000000064eb4795 (&pgdat->kswapd_wait){....}, at: __wake_up_common_lock+0x112/0x1c0 [ 507.241036] [ 507.241036] which lock already depends on the new lock. [ 507.241036] [ 507.249260] [ 507.249260] the existing dependency chain (in reverse order) is: [ 507.256787] [ 507.256787] -> #3 (&pgdat->kswapd_wait){....}: [ 507.262748] lock_acquire+0x1b3/0x3c0 [ 507.266960] _raw_spin_lock_irqsave+0x35/0x50 [ 507.271867] __wake_up_common_lock+0x112/0x1c0 [ 507.276863] wakeup_kswapd+0x3d0/0x560 [ 507.281159] steal_suitable_fallback+0x40b/0x4e0 [ 507.286330] rmqueue_bulk.constprop.26+0xa36/0x1090 [ 507.291760] get_page_from_freelist+0xb79/0x28f0 [ 507.296930] __alloc_pages_nodemask+0x453/0x21f0 [ 507.302099] alloc_pages_vma+0x87/0x280 [ 507.306482] do_anonymous_page+0x443/0xb80 [ 507.311128] __handle_mm_fault+0xbb8/0xc80 [ 507.315773] handle_mm_fault+0x3ae/0x68b [ 507.320243] __do_page_fault+0x329/0x6d0 [ 507.324712] do_page_fault+0x119/0x53c [ 507.329008] page_fault+0x1b/0x20 [ 507.332863] [ 507.332863] -> #2 (&(&zone->lock)->rlock){-.-.}: [ 507.338997] lock_acquire+0x1b3/0x3c0 [ 507.343205] _raw_spin_lock_irqsave+0x35/0x50 [ 507.348111] get_page_from_freelist+0x108f/0x28f0 [ 507.353368] __alloc_pages_nodemask+0x453/0x21f0 [ 507.358538] alloc_page_interleave+0x6a/0x1b0 [ 507.363446] allocate_slab+0x319/0xa20 [ 507.367742] new_slab+0x41/0x60 [ 507.371427] ___slab_alloc+0x509/0x8a0 [ 507.375721] __slab_alloc+0x3a/0x70 [ 507.379754] kmem_cache_alloc+0x29c/0x310 [ 507.384312] __debug_object_init+0x984/0x9b0 [ 507.389130] hrtimer_init+0x9b/0x310 [ 507.393250] init_dl_task_timer+0x1c/0x40 [ 507.397808] __sched_fork+0x187/0x290 [ 507.402015] init_idle+0xa1/0x3a0 [ 507.405875] fork_idle+0x122/0x150 [ 507.409823] idle_threads_init+0xea/0x17a [ 507.414379] smp_init+0x16/0xf2 [ 507.418064] kernel_init_freeable+0x31f/0x7ae [ 507.422971] kernel_init+0xc/0x127 [ 507.426916] ret_from_fork+0x3a/0x50 [ 507.431034] [ 507.431034] -> #1 (&rq->lock){-.-.}: [ 507.436119] lock_acquire+0x1b3/0x3c0 [ 507.440326] _raw_spin_lock+0x2c/0x40 [ 507.444535] task_fork_fair+0x93/0x310 [ 507.448830] sched_fork+0x194/0x380 [ 507.452863] copy_process+0x1446/0x41f0 [ 507.457247] _do_fork+0x16a/0xac0 [ 507.461107] kernel_thread+0x25/0x30 [ 507.465226] rest_init+0x28/0x319 [ 507.469085] start_kernel+0x634/0x674 [ 507.473296] secondary_startup_64+0xb6/0xc0 [ 507.478026] [ 507.478026] -> #0 (&p->pi_lock){-.-.}: [ 507.483286] __lock_acquire+0x46d/0x860 [ 507.487670] lock_acquire+0x1b3/0x3c0 [ 507.491879] _raw_spin_lock_irqsave+0x35/0x50 [ 507.496787] try_to_wake_up+0x10a/0xe80 [ 507.501170] autoremove_wake_function+0x7e/0x1a0 [ 507.506338] __wake_up_common+0x12d/0x380 [ 507.510895] __wake_up_common_lock+0x149/0x1c0 [ 507.515889] wakeup_kswapd+0x3d0/0x560 [ 507.520184] steal_suitable_fallback+0x40b/0x4e0 [ 507.525354] rmqueue_bulk.constprop.26+0xa36/0x1090 [ 507.530786] get_page_from_freelist+0xb79/0x28f0 [ 507.535955] __alloc_pages_nodemask+0x453/0x21f0 [ 507.541124] alloc_pages_vma+0x87/0x280 [ 507.545506] do_anonymous_page+0x443/0xb80 [ 507.550152] __handle_mm_fault+0xbb8/0xc80 [ 507.554797] handle_mm_fault+0x3ae/0x68b [ 507.559267] __do_page_fault+0x329/0x6d0 [ 507.563738] do_page_fault+0x119/0x53c [ 507.568034] page_fault+0x1b/0x20 [ 507.571890] [ 507.571890] other info that might help us debug this: [ 507.571890] [ 507.579938] Chain exists of: [ 507.579938] &p->pi_lock --> &(&zone->lock)->rlock --> &pgdat->kswapd_wait [ 507.579938] [ 507.591311] Possible unsafe locking scenario: [ 507.591311] [ 507.597265] CPU0 CPU1 [ 507.601821] ---- ---- [ 507.606375] lock(&pgdat->kswapd_wait); [ 507.610321] lock(&(&zone->lock)->rlock); [ 507.616973] lock(&pgdat->kswapd_wait); [ 507.623452] lock(&p->pi_lock); [ 507.626698] [ 507.626698] *** DEADLOCK *** [ 507.626698] [ 507.632652] 3 locks held by oom01/7666: [ 507.636509] #0: 000000000ed9e0f8 (&mm->mmap_sem){++++}, at: __do_page_fault+0x236/0x6d0 [ 507.644653] #1: 00000000592a7e32 (&(&zone->lock)->rlock){-.-.}, at: rmqueue_bulk.constprop.26+0x16f/0x1090 [ 507.654453] #2: 0000000064eb4795 (&pgdat->kswapd_wait){....}, at: __wake_up_common_lock+0x112/0x1c0 [ 507.663644] [ 507.663644] stack backtrace: [ 507.668027] CPU: 75 PID: 7666 Comm: oom01 Kdump: loaded Not tainted 4.20.0+ #27 [ 507.675378] Hardware name: HPE ProLiant DL380 Gen10/ProLiant DL380 Gen10, BIOS U30 06/20/2018 [ 507.683953] Call Trace: [ 507.686416] dump_stack+0xd1/0x160 [ 507.689840] ? dump_stack_print_info.cold.0+0x1b/0x1b [ 507.694923] ? print_stack_trace+0x8f/0xa0 [ 507.699044] print_circular_bug.isra.10.cold.34+0x20f/0x297 [ 507.704651] ? print_circular_bug_header+0x50/0x50 [ 507.709473] check_prev_add.constprop.19+0x7ad/0xad0 [ 507.714468] ? check_usage+0x3e0/0x3e0 [ 507.718241] ? graph_lock+0xef/0x190 [ 507.721838] ? usage_match+0x27/0x40 [ 507.725435] validate_chain.isra.14+0xbd5/0x16c0 [ 507.730082] ? check_prev_add.constprop.19+0xad0/0xad0 [ 507.735252] ? stack_access_ok+0x35/0x80 [ 507.739200] ? deref_stack_reg+0xa2/0xf0 [ 507.743148] ? __read_once_size_nocheck.constprop.4+0x10/0x10 [ 507.748929] ? debug_lockdep_rcu_enabled.part.0+0x16/0x30 [ 507.754362] ? ftrace_ops_trampoline+0x131/0le_mm_fault+0xbb8/0xc80 [ 508.142595] ? handle_mm_fault+0x3ae/0x68b [ 508.146716] ? __do_page_fault+0x329/0x6d0 [ 508.150836] ? trace_hardirqs_off+0x9d/0x230 [ 508.155132] ? trace_hardirqs_on_caller+0x230/0x230 [ 508.160038] ? pageset_set_high_and_batch+0x180/0x180 [ 508.165122] get_page_from_freelist+0xb79/0x28f0 [ 508.169772] ? __isolate_free_page+0x430/0x430 [ 508.174242] ? print_irqtrace_events+0x110/0x110 [ 508.178885] ? __isolate_free_page+0x430/0x430 [ 508.183355] ? free_unref_page_list+0x3e6/0x570 [ 508.187914] ? mark_held_locks+0x8b/0xb0 [ 508.191861] ? free_unref_page_list+0x3e6/0x570 [ 508.196418] ? free_unref_page_list+0x3e6/0x570 [ 508.200976] ? lockdep_hardirqs_on+0x1a4/0x290 [ 508.205445] ? trace_hardirqs_on+0x9d/0x230 [ 508.209654] ? ftrace_destroy_function_files+0x50/0x50 [ 508.214823] ? validate_chain.isra.14+0x16c/0x16c0 [ 508.219642] ? check_chain_key+0x13b/0x200 [ 508.223766] ? page_mapping+0x2be/0x460 [ 508.227627] ? page_evictable+0x1de/0x320 [ 508.231660] ? __page_frag_cache_drain+0x180ad0 [ 508.619426] ? lock_downgrade+0x360/0x360 [ 508.623458] ? rwlock_bug.part.0+0x60/0x60 [ 508.627580] ? do_raw_spin_unlock+0x157/0x220 [ 508.631963] ? do_raw_spin_trylock+0x180/0x180 [ 508.636434] ? do_raw_spin_lock+0x137/0x1f0 [ 508.640641] ? mark_lock+0x11c/0xd80 [ 508.644238] alloc_pages_vma+0x87/0x280 [ 508.648097] do_anonymous_page+0x443/0xb80 [ 508.652219] ? mark_lock+0x11c/0xd80 [ 508.655815] ? mark_lock+0x11c/0xd80 [ 508.659412] ? finish_fault+0xf0/0xf0 [ 508.663096] ? print_irqtrace_events+0x110/0x110 [ 508.667741] ? check_flags.part.18+0x220/0x220 [ 508.672213] ? do_raw_spin_unlock+0x157/0x220 [ 508.676598] ? do_raw_spin_trylock+0x180/0x180 [ 508.681070] ? rwlock_bug.part.0+0x60/0x60 [ 508.685191] ? check_chain_key+0x13b/0x200 [ 508.689313] ? __lock_acquire+0x4c0/0x860 [ 508.693347] ? check_chain_key+0x13b/0x200 [ 508.697469] ? handle_mm_fault+0x315/0x68b [ 508.701590] __handle_mm_fault+0xbb8/0xc80 [ 508.705711] ? handle_mm_fault+0x4c3/0x68b
