linux-kernel - Re: [PATCH] irqchip: gic-v3-its: fix build for !SMP

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Date:   Mon, 24 Jan 2022 12:39:03 +0000
From:   Valentin Schneider <valentin.schneider@....com>
To:     Ard Biesheuvel <ardb@...nel.org>, linux-kernel@...r.kernel.org
Cc:     maz@...nel.org, Ard Biesheuvel <ardb@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] irqchip: gic-v3-its: fix build for !SMP

On 22/01/22 16:16, Ard Biesheuvel wrote:
> Commit 835f442fdbce ("irqchip/gic-v3-its: Limit memreserve cpuhp state
> lifetime") added a reference to cpus_booted_once_mask, which does not
> exist on !SMP builds, breaking the build for such configurations.
>
> Given the intent of the check, short circuit it to always pass.
>
> Cc: Valentin Schneider <valentin.schneider@....com>
> Fixes: 835f442fdbce ("irqchip/gic-v3-its: Limit memreserve cpuhp state lifetime")
> Signed-off-by: Ard Biesheuvel <ardb@...nel.org>

Sorry about that, and thanks for the fix.

This looks fine to me, though one alternative to prevent future
IS_ENABLED() proliferations would be to make cpus_booted_once_mask exist
for !SMP - the online, active, present and possible masks exist for !SMP
already after all.

---
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 407a2568f35e..7487b7061f2c 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -84,9 +84,7 @@ static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
 	.fail = CPUHP_INVALID,
 };
 
-#ifdef CONFIG_SMP
 cpumask_t cpus_booted_once_mask;
-#endif
 
 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
 static struct lockdep_map cpuhp_state_up_map =
@@ -2662,9 +2660,7 @@ void __init boot_cpu_init(void)
  */
 void __init boot_cpu_hotplug_init(void)
 {
-#ifdef CONFIG_SMP
 	cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
-#endif
 	this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
 }