[PATCH v1] USB: core: hub: fix usb_hub worker blocking drain_all_pages() worker issue

[PATCH v1] USB: core: hub: fix usb_hub worker blocking drain_all_pages() worker issue

[Zhu Zhongjie]

From: Zhongjie Zhu <zhongjiezhu1@gmail.com>

When disconnecting a usb mass storege, if there are a lot of inodes
like 10 thousands files need to be freed, the invalidate_inodes() will
run for a loog time to freeing all inodes, this will block other worker
to run on the cpu, so mark the usb_hub workqueue to WQ_CPU_INTENSIVE to
avoid this situation.

Sometimes the flowing call stack will hanppen: the cma_alloc() will be
blocked at __flush_work() by the hub_event worker.

usb_hub worker:
Call trace:
[<ffffffc010335e84>] invalidate_inodes+0xc0/0x294
<ffffffc0103659cc>] __invalidate_device+0x44/0xbc
[<ffffffc01059efe4>] invalidate_partition+0x7c/0xac
[<ffffffc01059ed54>] del_gendisk+0x148/0x35c
[<ffffffc0107620e4>] sd_remove+0x58/0xc4
[<ffffffc01070cb3c>] device_release_driver_internal+0x184/0x248
[<ffffffc010709e40>] bus_remove_device+0xdc/0x104
[<ffffffc0107068dc>] device_del+0x2b0/0x534
[<ffffffc01075c1a8>] __scsi_remove_device+0xc8/0x14c
[<ffffffc01075b788>] scsi_forget_host+0x60/0x7c
[<ffffffc010750040>] scsi_remove_host+0x84/0x130
[<ffffffc010882d60>] usb_stor_disconnect+0x7c/0xd0
[<ffffffc010828430>] usb_unbind_interface+0xc0/0x25c
[<ffffffc01070cb3c>] device_release_driver_internal+0x184/0x248
[<ffffffc010709e40>] bus_remove_device+0xdc/0x104
[<ffffffc0107068dc>] device_del+0x2b0/0x534
[<ffffffc010825b38>] usb_disable_device+0x80/0x180
[<ffffffc010817ef0>] usb_disconnect+0x128/0x314
[<ffffffc01081c95c>] hub_event+0x99c/0x16c8
[<ffffffc01011ed94>] process_one_work+0x2e8/0x574
[<ffffffc01011f2cc>] worker_thread+0x2ac/0x5e8
[<ffffffc0101252b4>] kthread+0x14c/0x15c
[<ffffffc010083ff0>] ret_from_fork+0x10/0x18

cma_alloc():
Call trace
[<ffffffc010090c18>] __switch_to+0x244/0x264
[<ffffffc0112153e0>] __schedule+0x564/0x754
[<ffffffc011215660>] schedule+0x90/0xc4
[<ffffffc011219468>] schedule_timeout+0x4c/0x1d0
[<ffffffc011216814>] do_wait_for_common+0xf8/0x1b4
[<ffffffc0112163bc>] wait_for_completion+0x50/0x68
[<ffffffc010119d94>] __flush_work.llvm.11756653060903382828+0x270/0x324
[<ffffffc0102d51e4>] drain_all_pages+0x224/0x2a8
[<ffffffc0103031fc>] start_isolate_page_range+0x1e4/0x2dc
[<ffffffc010e25624>] aml_cma_alloc_range+0xfc/0x3ec
[<ffffffc0103072e0>] cma_alloc+0x1ac/0x6d8

Signed-off-by: Zhongjie Zhu <zhongjiezhu1@gmail.com>
---
 drivers/usb/core/hub.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index 9eca403af2a8..850549b30277 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -5904,7 +5904,8 @@ int usb_hub_init(void)
 	 * device was gone before the EHCI controller had handed its port
 	 * over to the companion full-speed controller.
 	 */
-	hub_wq = alloc_workqueue("usb_hub_wq", WQ_FREEZABLE, 0);
+	hub_wq = alloc_workqueue("usb_hub_wq",
+			WQ_FREEZABLE | WQ_CPU_INTENSIVE, 0);
 	if (hub_wq)
 		return 0;
 
-- 
2.34.1