[PATCH v2 5/5] PM: domains: Do not call device_pm_check_callbacks() when holding genpd_lock()

[Krzysztof Kozlowski]

If PM domain on PREEMPT_RT is marked as GENPD_FLAG_RT_SAFE(), the
genpd_lock() will be a raw spin lock, thus device_pm_check_callbacks()
must be called outside of the domain lock.

This solves on PREEMPT_RT:

  [ BUG: Invalid wait context ]
  6.1.0-rt5-00325-g8a5f56bcfcca #8 Tainted: G        W
  -----------------------------
  swapper/0/1 is trying to lock:
  ffff76e045dec9a0 (&dev->power.lock){+.+.}-{3:3}, at: device_pm_check_callbacks+0x20/0xf0
  other info that might help us debug this:
  context-{5:5}
  3 locks held by swapper/0/1:
   #0: ffff76e045deb8e8 (&dev->mutex){....}-{4:4}, at: __device_attach+0x38/0x1c0
   #1: ffffa92b81f825e0 (gpd_list_lock){+.+.}-{4:4}, at: __genpd_dev_pm_attach+0x7c/0x250
   #2: ffff76e04105c7a0 (&genpd->rslock){....}-{2:2}, at: genpd_lock_rawspin+0x1c/0x30
  stack backtrace:
  CPU: 5 PID: 1 Comm: swapper/0 Tainted: G        W          6.1.0-rt5-00325-g8a5f56bcfcca #8
  Hardware name: Qualcomm Technologies, Inc. Robotics RB5 (DT)
  Call trace:
   dump_backtrace.part.0+0xe0/0xf0
   show_stack+0x18/0x40
   dump_stack_lvl+0x8c/0xb8
   dump_stack+0x18/0x34
   __lock_acquire+0x938/0x2100
   lock_acquire.part.0+0x104/0x28c
   lock_acquire+0x68/0x84
   rt_spin_lock+0x40/0x100
   device_pm_check_callbacks+0x20/0xf0
   dev_pm_domain_set+0x54/0x64
   genpd_add_device+0x258/0x340
   __genpd_dev_pm_attach+0xa8/0x250
   genpd_dev_pm_attach_by_id+0xc4/0x190
   genpd_dev_pm_attach_by_name+0x3c/0x60
   dev_pm_domain_attach_by_name+0x20/0x30
   dt_idle_attach_cpu+0x24/0x90
   psci_cpuidle_probe+0x300/0x4b0
   platform_probe+0x68/0xe0
   really_probe+0xbc/0x2dc
   __driver_probe_device+0x78/0xe0
   driver_probe_device+0x3c/0x160
   __device_attach_driver+0xb8/0x140
   bus_for_each_drv+0x78/0xd0
   __device_attach+0xa8/0x1c0
   device_initial_probe+0x14/0x20
   bus_probe_device+0x9c/0xa4
   device_add+0x3b4/0x8dc
   platform_device_add+0x114/0x234
   platform_device_register_full+0x108/0x1a4
   psci_idle_init+0x6c/0xb0
   do_one_initcall+0x74/0x450
   kernel_init_freeable+0x2e0/0x350
   kernel_init+0x24/0x130
   ret_from_fork+0x10/0x20

Cc: Adrien Thierry <athierry@xxxxxxxxxx>
Cc: Brian Masney <bmasney@xxxxxxxxxx>
Cc: linux-rt-users@xxxxxxxxxxxxxxx
Signed-off-by: Krzysztof Kozlowski <krzysztof.kozlowski@xxxxxxxxxx>
---
 drivers/base/power/domain.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/drivers/base/power/domain.c b/drivers/base/power/domain.c
index 4dfce1d476f4..db499ba40497 100644
--- a/drivers/base/power/domain.c
+++ b/drivers/base/power/domain.c
@@ -1666,10 +1666,14 @@ static int genpd_add_device(struct generic_pm_domain *genpd, struct device *dev,
 	if (ret)
 		goto out;
 
+
+	/* PREEMPT_RT: Must be outside of genpd_lock */
+	device_pm_check_callbacks(dev);
+
 	genpd_lock(genpd);
 
 	genpd_set_cpumask(genpd, gpd_data->cpu);
-	dev_pm_domain_set(dev, &genpd->domain);
+	dev_pm_domain_set_no_cb(dev, &genpd->domain);
 
 	genpd->device_count++;
 	if (gd)
-- 
2.34.1