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notifier: Fix broken error handling pattern

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The current notifiers have the following error handling pattern all
over the place:

	int err, nr;

	err = __foo_notifier_call_chain(&chain, val_up, v, -1, &nr);
	if (err & NOTIFIER_STOP_MASK)
		__foo_notifier_call_chain(&chain, val_down, v, nr-1, NULL)

And aside from the endless repetition thereof, it is broken. Consider
blocking notifiers; both calls take and drop the rwsem, this means
that the notifier list can change in between the two calls, making @nr
meaningless.

Fix this by replacing all the __foo_notifier_call_chain() functions
with foo_notifier_call_chain_robust() that embeds the above pattern,
but ensures it is inside a single lock region.

Note: I switched atomic_notifier_call_chain_robust() to use
      the spinlock, since RCU cannot provide the guarantee
      required for the recovery.

Note: software_resume() error handling was broken afaict.

Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Link: https://lore.kernel.org/r/20200818135804.325626653@infradead.org
This commit is contained in:
Peter Zijlstra 2020-08-18 15:57:36 +02:00 • committed by Ingo Molnar
parent f75aef392f
commit 70d9329857
9 changed files with 147 additions and 140 deletions
Download patch file Download diff file Expand all files Collapse all files

48
kernel/cpu_pm.c
View file

@ -15,18 +15,28 @@
static ATOMIC_NOTIFIER_HEAD(cpu_pm_notifier_chain);
static int cpu_pm_notify(enum cpu_pm_event event, int nr_to_call, int *nr_calls)
static int cpu_pm_notify(enum cpu_pm_event event)
{
int ret;
/*
* __atomic_notifier_call_chain has a RCU read critical section, which
* atomic_notifier_call_chain has a RCU read critical section, which
* could be disfunctional in cpu idle. Copy RCU_NONIDLE code to let
* RCU know this.
*/
rcu_irq_enter_irqson();
ret = __atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL,
nr_to_call, nr_calls);
ret = atomic_notifier_call_chain(&cpu_pm_notifier_chain, event, NULL);
rcu_irq_exit_irqson();
return notifier_to_errno(ret);
}
static int cpu_pm_notify_robust(enum cpu_pm_event event_up, enum cpu_pm_event event_down)
{
int ret;
rcu_irq_enter_irqson();
ret = atomic_notifier_call_chain_robust(&cpu_pm_notifier_chain, event_up, event_down, NULL);
rcu_irq_exit_irqson();
return notifier_to_errno(ret);
@ -80,18 +90,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_unregister_notifier);
*/
int cpu_pm_enter(void)
{
int nr_calls = 0;
int ret = 0;
ret = cpu_pm_notify(CPU_PM_ENTER, -1, &nr_calls);
if (ret)
/*
* Inform listeners (nr_calls - 1) about failure of CPU PM
* PM entry who are notified earlier to prepare for it.
*/
cpu_pm_notify(CPU_PM_ENTER_FAILED, nr_calls - 1, NULL);
return ret;
return cpu_pm_notify_robust(CPU_PM_ENTER, CPU_PM_ENTER_FAILED);
}
EXPORT_SYMBOL_GPL(cpu_pm_enter);
@ -109,7 +108,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_enter);
*/
int cpu_pm_exit(void)
{
return cpu_pm_notify(CPU_PM_EXIT, -1, NULL);
return cpu_pm_notify(CPU_PM_EXIT);
}
EXPORT_SYMBOL_GPL(cpu_pm_exit);
@ -131,18 +130,7 @@ EXPORT_SYMBOL_GPL(cpu_pm_exit);
*/
int cpu_cluster_pm_enter(void)
{
int nr_calls = 0;
int ret = 0;
ret = cpu_pm_notify(CPU_CLUSTER_PM_ENTER, -1, &nr_calls);
if (ret)
/*
* Inform listeners (nr_calls - 1) about failure of CPU cluster
* PM entry who are notified earlier to prepare for it.
*/
cpu_pm_notify(CPU_CLUSTER_PM_ENTER_FAILED, nr_calls - 1, NULL);
return ret;
return cpu_pm_notify_robust(CPU_CLUSTER_PM_ENTER, CPU_CLUSTER_PM_ENTER_FAILED);
}
EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
@ -163,7 +151,7 @@ EXPORT_SYMBOL_GPL(cpu_cluster_pm_enter);
*/
int cpu_cluster_pm_exit(void)
{
return cpu_pm_notify(CPU_CLUSTER_PM_EXIT, -1, NULL);
return cpu_pm_notify(CPU_CLUSTER_PM_EXIT);
}
EXPORT_SYMBOL_GPL(cpu_cluster_pm_exit);