On Wed, Aug 26, 2020 at 10:17 PM Saravana Kannan <sarava...@google.com> wrote: > > On Thu, Aug 20, 2020 at 8:50 PM Dong Aisheng <donga...@gmail.com> wrote: > > > > Hi ALL, > > > > We met the below WARNING during system suspend on an iMX6Q SDB board > > with the latest linus/master branch (v5.9-rc1+) and next-20200820. > > v5.8 kernel is ok. So i did bisect and finally found it's caused by > > the patch below. > > Reverting it can get rid of the warning, but I wonder if there may be > > other potential issues. > > Any ideas? > > > > Defconfig used is: imx_v6_v7_defconfig > > > > ----- 8< ----- Snipped text that was a bit misleading > > > > > Error log: > > # echo mem > /sys/power/state > > [ 39.111865] PM: suspend entry (deep) > > [ 39.148650] Filesystems sync: 0.032 seconds > > [ 39.154034] > > [ 39.155537] ====================================================== > > [ 39.161723] WARNING: possible circular locking dependency detected > > [ 39.167911] 5.9.0-rc1-00103-g7eac66d0456f #37 Not tainted > > [ 39.173315] ------------------------------------------------------ > > [ 39.179500] sh/647 is trying to acquire lock: > > [ 39.183862] c15a310c (dpm_list_mtx){+.+.}-{3:3}, at: > > dpm_for_each_dev+0x20/0x5c > > [ 39.191200] > > [ 39.191200] but task is already holding lock: > > [ 39.197036] c15a37e4 (fw_lock){+.+.}-{3:3}, at: fw_pm_notify+0x90/0xd4 > > [ 39.203582] > > [ 39.203582] which lock already depends on the new lock. > > [ 39.203582] > > [ 39.211763] > > [ 39.211763] the existing dependency chain (in reverse order) is: > > [ 39.219249] > > [ 39.219249] -> #2 (fw_lock){+.+.}-{3:3}: > > [ 39.224673] mutex_lock_nested+0x1c/0x24 > > [ 39.229126] firmware_uevent+0x18/0xa0 > > [ 39.233411] dev_uevent+0xc4/0x1f8 > > [ 39.237343] uevent_show+0x98/0x114 > > [ 39.241362] dev_attr_show+0x18/0x48 > > [ 39.245472] sysfs_kf_seq_show+0x84/0xec > > [ 39.249927] seq_read+0x138/0x550 > > [ 39.253774] vfs_read+0x94/0x164 > > [ 39.257529] ksys_read+0x60/0xe8 > > [ 39.261288] ret_fast_syscall+0x0/0x28 > > [ 39.265564] 0xbed7c808 > > [ 39.268538] > > [ 39.268538] -> #1 (kn->active#3){++++}-{0:0}: > > [ 39.274391] kernfs_remove_by_name_ns+0x40/0x94 > > [ 39.279450] device_del+0x144/0x3fc > > Rafael/Greg, > > I'm not very familiar with the #0 and #2 calls stacks. But poking > around a bit, they are NOT due to the device-link-device. But the new > stuff is the above two lines that are deleting the device-link-device > (that's used to expose device link details in sysfs) when the device > link is deleted. > > Kicking off a workqueue to break this cycle is easy, but the problem > is that if I queue a work to delete the device, then the sysfs folder > won't get removed immediately. And if the same link is created again > before the work is completed, then there'll be a sysfs name collision > and warning. > > So, I'm kinda stuck here. Open to suggestions. Hoping you'll have > better ideas for breaking the cycle. Or point out how I'm > misunderstanding the cycle here. >
Aisheng, Sent out a fix that I think should work. https://lore.kernel.org/lkml/20200831221007.1506441-1-sarava...@google.com/T/#u I wasn't able to reproduce it in my hardware. So, if you can test that patch (and respond to that thread), that'd be great. -Saravana