On Fri, Jun 03, 2016 at 09:32:01AM +0800, Wang Sheng-Hui wrote: > This patch is based on https://patchwork.ozlabs.org/patch/574623/. > > Tejun submitted commit 23d11a58a9a6 ("workqueue: skip flush dependency > checks for legacy workqueues") for the legacy create*_workqueue() > interface. But some workq created by alloc_workqueue still reports > warning on memory reclaim, e.g nvme_workq with flag WQ_MEM_RECLAIM set: > > [ 0.153902] workqueue: WQ_MEM_RECLAIM nvme:nvme_reset_work is > flushing !WQ_MEM_RECLAIM events:lru_add_drain_per_cpu > [ 0.153907] ------------[ cut here ]------------ > [ 0.153912] WARNING: CPU: 0 PID: 6 at > SoC/linux/kernel/workqueue.c:2448 > check_flush_dependency+0xb4/0x10c > ... > [ 0.154083] [<fffffc00080d6de0>] check_flush_dependency+0xb4/0x10c > [ 0.154088] [<fffffc00080d8e80>] flush_work+0x54/0x140 > [ 0.154092] [<fffffc0008166a0c>] lru_add_drain_all+0x138/0x188 > [ 0.154097] [<fffffc00081ab2dc>] migrate_prep+0xc/0x18 > [ 0.154101] [<fffffc0008160e88>] alloc_contig_range+0xf4/0x350 > [ 0.154105] [<fffffc00081bcef8>] cma_alloc+0xec/0x1e4 > [ 0.154110] [<fffffc0008446ad0>] dma_alloc_from_contiguous+0x38/0x40 > [ 0.154114] [<fffffc00080a093c>] __dma_alloc+0x74/0x25c > [ 0.154119] [<fffffc00084828d8>] nvme_alloc_queue+0xcc/0x36c > [ 0.154123] [<fffffc0008484b2c>] nvme_reset_work+0x5c4/0xda8 > [ 0.154128] [<fffffc00080d9528>] process_one_work+0x128/0x2ec > [ 0.154132] [<fffffc00080d9744>] worker_thread+0x58/0x434 > [ 0.154136] [<fffffc00080df0ec>] kthread+0xd4/0xe8 > [ 0.154141] [<fffffc0008093ac0>] ret_from_fork+0x10/0x50 > > That's because lru_add_drain_all() will schedule the drain work on > system_wq, whose flag is set to 0, !WQ_MEM_RECLAIM. > > Introduce a dedicated WQ_MEM_RECLAIM workqueue to do lru_add_drain_all(), > aiding in getting memory freed. > > Compared with v1: > * The key flag is WQ_MEM_RECLAIM. Drop the flag WQ_UNBOUND. > * Reserve the warn in lru_init as init code during bootup ignore > return code from early_initcall functions. > * Instead of falling back to system_wq, crash directly if the wq > is used in lru_add_drain_all but was not created in lru_init > at init stage. > > Signed-off-by: Wang Sheng-Hui <shhuiw@xxxxxxxxxxx> Acked-by: Tejun Heo <tj@xxxxxxxxxx> Thanks. -- tejun -- 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=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>