linux-kernel - Re: [tip:smp/hotplug] cpu/hotplug: Abort disabling secondary CPUs if wakeup is pending

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Date:   Fri, 27 Mar 2020 12:06:44 +0100
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Boqun Feng <boqun.feng@...il.com>, peterz@...radead.org,
        linux-kernel@...r.kernel.org, len.brown@...el.com,
        pkondeti@...eaurora.org, jpoimboe@...hat.com, pavel@....cz,
        konrad.wilk@...cle.com, mojha@...eaurora.org, jkosina@...e.cz,
        mingo@...nel.org, hpa@...or.com, rjw@...ysocki.net
Cc:     linux-tip-commits@...r.kernel.org
Subject: Re: [tip:smp/hotplug] cpu/hotplug: Abort disabling secondary CPUs if wakeup is pending

Boqun Feng <boqun.feng@...il.com> writes:
> From the commit message, it makes sense to add the pm_wakeup_pending()
> check if freeze_secondary_cpus() is used for system suspend. However,
> freeze_secondary_cpus() is also used in kexec path on arm64:

Bah!

> 	kernel_kexec():
> 	  machine_shutdown():
> 	    disable_nonboot_cpus():
> 	      freeze_secondary_cpus()
>
> , so I wonder whether the pm_wakeup_pending() makes sense in this
> situation? Because IIUC, in this case we want to reboot the system
> regardlessly, the pm_wakeup_pending() checking seems to be inappropriate
> then.

Fix below.

Thanks,

        tglx

8<------------

--- a/include/linux/cpu.h
+++ b/include/linux/cpu.h
@@ -133,12 +133,18 @@ static inline void get_online_cpus(void)
 static inline void put_online_cpus(void) { cpus_read_unlock(); }
 
 #ifdef CONFIG_PM_SLEEP_SMP
-extern int freeze_secondary_cpus(int primary);
+int __freeze_secondary_cpus(int primary, bool suspend);
+static inline int freeze_secondary_cpus(int primary)
+{
+	return __freeze_secondary_cpus(primary, true);
+}
+
 static inline int disable_nonboot_cpus(void)
 {
-	return freeze_secondary_cpus(0);
+	return __freeze_secondary_cpus(0, false);
 }
-extern void enable_nonboot_cpus(void);
+
+void enable_nonboot_cpus(void);
 
 static inline int suspend_disable_secondary_cpus(void)
 {
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1200,7 +1200,7 @@ EXPORT_SYMBOL_GPL(cpu_up);
 #ifdef CONFIG_PM_SLEEP_SMP
 static cpumask_var_t frozen_cpus;
 
-int freeze_secondary_cpus(int primary)
+int __freeze_secondary_cpus(int primary, bool suspend)
 {
 	int cpu, error = 0;
 
@@ -1225,7 +1225,7 @@ int freeze_secondary_cpus(int primary)
 		if (cpu == primary)
 			continue;
 
-		if (pm_wakeup_pending()) {
+		if (suspend && pm_wakeup_pending()) {
 			pr_info("Wakeup pending. Abort CPU freeze\n");
 			error = -EBUSY;
 			break;