Hi Bjorn and Dmitry,
Yu reported a lockdep warning coming from the gdsc driver. It looks like
the runtime PM usage in gdsc.c is causing lockdep to see an AA deadlock
possibility with 'genpd->mlock'. I suspect this is because we have
commit 1b771839de05 ("clk: qcom: gdsc: enable optional power domain
support"), and that is now calling runtime PM code from within the genpd
code. I think genpd already has nested lock support, so the only
solution is to not use runtime PM from within genpd code and start
expressing genpd parent relationships in genpd itself? Or maybe genpd
needs to drop locks while calling down into gdsc_disable() and reacquire
them after that?
============================================
WARNING: possible recursive locking detected
5.19.0-rc2-lockdep+ #7 Not tainted
--------------------------------------------
kworker/2:1/49 is trying to acquire lock:
ffffffeea0370788 (&genpd->mlock){+.+.}-{3:3}, at: genpd_lock_mtx+0x24/0x30
but task is already holding lock:
ffffffeea03710a8 (&genpd->mlock){+.+.}-{3:3}, at: genpd_lock_mtx+0x24/0x30
other info that might help us debug this:
Possible unsafe locking scenario:
CPU0
----
lock(&genpd->mlock);
lock(&genpd->mlock);
*** DEADLOCK ***
May be due to missing lock nesting notation
3 locks held by kworker/2:1/49:
#0: 74ffff80811a5748 ((wq_completion)pm){+.+.}-{0:0}, at:
process_one_work+0x320/0x5fc
#1: ffffffc008537cf8
((work_completion)(&genpd->power_off_work)){+.+.}-{0:0}, at:
process_one_work+0x354/0x5fc
#2: ffffffeea03710a8 (&genpd->mlock){+.+.}-{3:3}, at: genpd_lock_mtx+0x24/0x30
stack backtrace:
CPU: 2 PID: 49 Comm: kworker/2:1 Not tainted 5.19.0-rc2-lockdep+ #7
Hardware name: Google Lazor (rev3 - 8) with KB Backlight (DT)
Workqueue: pm genpd_power_off_work_fn
Call trace:
dump_backtrace+0x1a0/0x200
show_stack+0x24/0x30
dump_stack_lvl+0x7c/0xa0
dump_stack+0x18/0x44
__lock_acquire+0xb38/0x3634
lock_acquire+0x180/0x2d4
__mutex_lock_common+0x118/0xe30
mutex_lock_nested+0x70/0x7c
genpd_lock_mtx+0x24/0x30
genpd_runtime_suspend+0x2f0/0x414
__rpm_callback+0xdc/0x1b8
rpm_callback+0x4c/0xcc
rpm_suspend+0x21c/0x5f0
rpm_idle+0x17c/0x1e0
__pm_runtime_idle+0x78/0xcc
gdsc_disable+0x24c/0x26c
_genpd_power_off+0xd4/0x1c4
genpd_power_off+0x2d8/0x41c
genpd_power_off_work_fn+0x60/0x94
process_one_work+0x398/0x5fc
worker_thread+0x42c/0x6c4
kthread+0x194/0x1b4
ret_from_fork+0x10/0x20
