From 70d932985757fbe978024db313001218e9f8fe5c Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Tue, 18 Aug 2020 15:57:36 +0200 Subject: notifier: Fix broken error handling pattern 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) Signed-off-by: Ingo Molnar Acked-by: Rafael J. Wysocki Link: https://lore.kernel.org/r/20200818135804.325626653@infradead.org --- kernel/cpu_pm.c | 48 ++++++++++++++++++------------------------------ 1 file changed, 18 insertions(+), 30 deletions(-) (limited to 'kernel/cpu_pm.c') diff --git a/kernel/cpu_pm.c b/kernel/cpu_pm.c index 44a259338e33..f7e1d0eccdbc 100644 --- a/kernel/cpu_pm.c +++ b/kernel/cpu_pm.c @@ -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); -- cgit v1.2.3