Hi Abhishek, > Unregister from suspend notifications and cancel suspend preparations > before running hci_dev_do_close. Otherwise, the suspend notifier may > race with unregister and cause cmd_timeout even after hdev has been > freed. > > Signed-off-by: Abhishek Pandit-Subedi <abhishekpandit@xxxxxxxxxxxx> > Reviewed-by: Miao-chen Chou <mcchou@xxxxxxxxxxxx> > --- > Hi Marcel, > > This fixes a race between hci_unregister_dev and the suspend notifier. > Without these changes, we encountered the following kernel panic when > a USB disconnect (with btusb) occurred on resume: > > [ 832.578518] Bluetooth: hci_core.c:hci_cmd_timeout() hci0: command 0x0c05 tx timeout > [ 832.586200] BUG: kernel NULL pointer dereference, address: 0000000000000000 > [ 832.586203] #PF: supervisor read access in kernel mode > [ 832.586205] #PF: error_code(0x0000) - not-present page > [ 832.586206] PGD 0 P4D 0 > [ 832.586210] PM: suspend exit > [ 832.608870] Oops: 0000 [#1] PREEMPT SMP NOPTI > [ 832.613232] CPU: 3 PID: 10755 Comm: kworker/3:7 Not tainted 5.4.44-04894-g1e9dbb96a161 #1 > [ 832.630036] Workqueue: events hci_cmd_timeout [bluetooth] > [ 832.630046] RIP: 0010:__queue_work+0xf0/0x374 > [ 832.630051] RSP: 0018:ffff9b5285f1fdf8 EFLAGS: 00010046 > [ 832.674033] RAX: ffff8a97681bac00 RBX: 0000000000000000 RCX: ffff8a976a000600 > [ 832.681162] RDX: 0000000000000000 RSI: 0000000000000009 RDI: ffff8a976a000748 > [ 832.688289] RBP: ffff9b5285f1fe38 R08: 0000000000000000 R09: ffff8a97681bac00 > [ 832.695418] R10: 0000000000000002 R11: ffff8a976a0006d8 R12: ffff8a9745107600 > [ 832.698045] usb 1-6: new full-speed USB device number 119 using xhci_hcd > [ 832.702547] R13: ffff8a9673658850 R14: 0000000000000040 R15: 000000000000001e > [ 832.702549] FS: 0000000000000000(0000) GS:ffff8a976af80000(0000) knlGS:0000000000000000 > [ 832.702550] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 > [ 832.702550] CR2: 0000000000000000 CR3: 000000010415a000 CR4: 00000000003406e0 > [ 832.702551] Call Trace: > [ 832.702558] queue_work_on+0x3f/0x68 > [ 832.702562] process_one_work+0x1db/0x396 > [ 832.747397] worker_thread+0x216/0x375 > [ 832.751147] kthread+0x138/0x140 > [ 832.754377] ? pr_cont_work+0x58/0x58 > [ 832.758037] ? kthread_blkcg+0x2e/0x2e > [ 832.761787] ret_from_fork+0x22/0x40 > [ 832.846191] ---[ end trace fa93f466da517212 ]--- > > The suspend notifier handler seemed to be scheduling commands even after > it was cleaned up and this was resulting in a panic in cmd_timeout (when > it tries to requeue the cmd_timer). > > This was tested on 5.4 kernel with a suspend+resume stress test for 500+ > iterations. I also confirmed that after a usb disconnect, the suspend > notifier times out before the USB device is probed again (fixing the > original race between the usb_disconnect + probe and the notifier). Can you please structure the commit message so that the oops is included. It is valuable information Everything after --- is a personal note to the maintainer. And we might want to include a Fixes tag as well. Regards Marcel
