Commit ba2bbfbf6307 (PM / Domains: Remove intermediate states from the
power off sequence) removed the mutex_unlock()/_lock() around powering on
a genpd's master domain in __genpd_poweron().
Since all genpd's share a mutex lockdep class, this causes a "possible
recursive locking detected" lockdep warning on boot when trying to power
on a genpd slave domain:
[ 1.893137] =============================================
[ 1.893139] [ INFO: possible recursive locking detected ]
[ 1.893143] 3.18.0 #531 Not tainted
[ 1.893145] ---------------------------------------------
[ 1.893148] kworker/u8:4/113 is trying to acquire lock:
[ 1.893167] (&genpd->lock){+.+...}, at: [<ffffffc000573818>] genpd_poweron+0x30/0x70
[ 1.893169]
[ 1.893169] but task is already holding lock:
[ 1.893179] (&genpd->lock){+.+...}, at: [<ffffffc000573818>] genpd_poweron+0x30/0x70
[ 1.893182]
[ 1.893182] other info that might help us debug this:
[ 1.893184] Possible unsafe locking scenario:
[ 1.893184]
[ 1.893185] CPU0
[ 1.893187] ----
[ 1.893191] lock(&genpd->lock);
[ 1.893195] lock(&genpd->lock);
[ 1.893196]
[ 1.893196] *** DEADLOCK ***
[ 1.893196]
[ 1.893198] May be due to missing lock nesting notation
[ 1.893198]
[ 1.893201] 4 locks held by kworker/u8:4/113:
[ 1.893217] #0: ("%s""deferwq"){++++.+}, at: [<ffffffc00023b4e0>] process_one_work+0x1f8/0x50c
[ 1.893229] #1: (deferred_probe_work){+.+.+.}, at: [<ffffffc00023b4e0>] process_one_work+0x1f8/0x50c
[ 1.893241] #2: (&dev->mutex){......}, at: [<ffffffc000560920>] __device_attach+0x40/0x12c
[ 1.893251] #3: (&genpd->lock){+.+...}, at: [<ffffffc000573818>] genpd_poweron+0x30/0x70
[ 1.893253]
[ 1.893253] stack backtrace:
[ 1.893259] CPU: 2 PID: 113 Comm: kworker/u8:4 Not tainted 3.18.0 #531
[ 1.893269] Workqueue: deferwq deferred_probe_work_func
[ 1.893271] Call trace:
[ 1.893295] [<ffffffc000269dcc>] __lock_acquire+0x68c/0x19a8
[ 1.893299] [<ffffffc00026b954>] lock_acquire+0x128/0x164
[ 1.893304] [<ffffffc00084e090>] mutex_lock_nested+0x90/0x3b4
[ 1.893308] [<ffffffc000573814>] genpd_poweron+0x2c/0x70
[ 1.893312] [<ffffffc0005738ac>] __genpd_poweron.part.14+0x54/0xcc
[ 1.893316] [<ffffffc000573834>] genpd_poweron+0x4c/0x70
[ 1.893321] [<ffffffc00057447c>] genpd_dev_pm_attach+0x160/0x19c
[ 1.893326] [<ffffffc00056931c>] dev_pm_domain_attach+0x1c/0x2c
...
Fix this by releasing the slaves mutex before acquiring the master's,
which restores the old behavior.
Cc: stable@xxxxxxxxxxxxxxx
Fixes: 5d837eef7b99 ("PM / Domains: Remove intermediate states from the power off sequence")
Signed-off-by: Daniel Kurtz <djkurtz@xxxxxxxxxxxx>
---
drivers/base/power/domain.c | 5 +++++
1 file changed, 5 insertions(+)
diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 65f50ec..56fa335 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -196,7 +196,12 @@ static int __genpd_poweron(struct generic_pm_domain *genpd)
list_for_each_entry(link, &genpd->slave_links, slave_node) {
genpd_sd_counter_inc(link->master);
+ mutex_unlock(&genpd->lock);
+
ret = genpd_poweron(link->master);
+
+ mutex_lock(&genpd->lock);
+
if (ret) {
genpd_sd_counter_dec(link->master);
goto err;
--
2.6.0.rc2.230.g3dd15c0
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