suspend: Prevent might sleep splats

timekeeping suspend/resume calls read_persistant_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 temporary 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().

Needs to be revisited.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

include/linux/kernel.h

@@ -531,6 +531,7 @@ extern enum system_states {
  SYSTEM_HALT,
  SYSTEM_POWER_OFF,
  SYSTEM_RESTART,
+ SYSTEM_SUSPEND,
 } system_state;
 
 #define TAINT_PROPRIETARY_MODULE 0

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:

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());