PM / suspend: Prevent might sleep splats

timekeeping suspend/resume calls read_persistent_clock() which takes
rtc_lock. That results in might sleep warnings because at that point
we run with interrupts disabled.

We cannot convert rtc_lock to a raw spinlock as that would trigger
other might sleep warnings.

As a workaround we disable the might sleep warnings by setting
system_state to SYSTEM_SUSPEND before calling sysdev_suspend() and
restoring it to SYSTEM_RUNNING afer sysdev_resume(). There is no lock
contention because hibernate / suspend to RAM is single-CPU at this
point.

In s2idle's case the system_state is set to SYSTEM_SUSPEND before
timekeeping_suspend() which is invoked by the last CPU. In the resume
case it set back to SYSTEM_RUNNING after timekeeping_resume() which is
invoked by the first CPU in the resume case. The other CPUs will block
on tick_freeze_lock.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
[bigeasy: cover s2idle in tick_freeze() / tick_unfreeze()]
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

4 files changed, 14 insertions, 0 deletions

diff --git a/include/linux/kernel.h b/include/linux/kernel.h
index 6a1eb0b0aad9..7aed92624531 100644
--- a/include/linux/kernel.h
+++ b/include/linux/kernel.h
@@ -542,6 +542,7 @@ extern enum system_states {
         SYSTEM_HALT,
         SYSTEM_POWER_OFF,
         SYSTEM_RESTART,
+        SYSTEM_SUSPEND,
 } system_state;
 
 /* This cannot be an enum because some may be used in assembly source. */
diff --git a/kernel/power/hibernate.c b/kernel/power/hibernate.c
index 5454cc639a8d..9c85c7822383 100644
--- a/kernel/power/hibernate.c
+++ b/kernel/power/hibernate.c
@@ -287,6 +287,8 @@ static int create_image(int platform_mode)
 
         local_irq_disable();
 
+        system_state = SYSTEM_SUSPEND;
+
         error = syscore_suspend();
         if (error) {
                 pr_err("Some system devices failed to power down, aborting hibernation\n");
@@ -317,6 +319,7 @@ static int create_image(int platform_mode)
         syscore_resume();
 
  Enable_irqs:
+        system_state = SYSTEM_RUNNING;
         local_irq_enable();
 
  Enable_cpus:
@@ -445,6 +448,7 @@ static int resume_target_kernel(bool platform_mode)
                 goto Enable_cpus;
 
         local_irq_disable();
+        system_state = SYSTEM_SUSPEND;
 
         error = syscore_suspend();
         if (error)
@@ -478,6 +482,7 @@ static int resume_target_kernel(bool platform_mode)
         syscore_resume();
 
  Enable_irqs:
+        system_state = SYSTEM_RUNNING;
         local_irq_enable();
 
  Enable_cpus:
@@ -563,6 +568,7 @@ int hibernation_platform_enter(void)
                 goto Enable_cpus;
 
         local_irq_disable();
+        system_state = SYSTEM_SUSPEND;
         syscore_suspend();
         if (pm_wakeup_pending()) {
                 error = -EAGAIN;
@@ -575,6 +581,7 @@ int hibernation_platform_enter(void)
 
  Power_up:
         syscore_resume();
+        system_state = SYSTEM_RUNNING;
         local_irq_enable();
 
  Enable_cpus:
diff --git a/kernel/power/suspend.c b/kernel/power/suspend.c
index 4c10be0f4843..5149c77506b3 100644
--- a/kernel/power/suspend.c
+++ b/kernel/power/suspend.c
@@ -428,6 +428,8 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
         arch_suspend_disable_irqs();
         BUG_ON(!irqs_disabled());
 
+        system_state = SYSTEM_SUSPEND;
+
         error = syscore_suspend();
         if (!error) {
                 *wakeup = pm_wakeup_pending();
@@ -443,6 +445,8 @@ static int suspend_enter(suspend_state_t state, bool *wakeup)
                 syscore_resume();
         }
 
+        system_state = SYSTEM_RUNNING;
+
         arch_suspend_enable_irqs();
         BUG_ON(irqs_disabled());
 
diff --git a/kernel/time/tick-common.c b/kernel/time/tick-common.c
index 49edc1c4f3e6..14de3727b18e 100644
--- a/kernel/time/tick-common.c
+++ b/kernel/time/tick-common.c
@@ -490,6 +490,7 @@ void tick_freeze(void)
         if (tick_freeze_depth == num_online_cpus()) {
                 trace_suspend_resume(TPS("timekeeping_freeze"),
                                      smp_processor_id(), true);
+                system_state = SYSTEM_SUSPEND;
                 timekeeping_suspend();
         } else {
                 tick_suspend_local();
@@ -513,6 +514,7 @@ void tick_unfreeze(void)
 
         if (tick_freeze_depth == num_online_cpus()) {
                 timekeeping_resume();
+                system_state = SYSTEM_RUNNING;
                 trace_suspend_resume(TPS("timekeeping_freeze"),
                                      smp_processor_id(), false);
         } else {