[PATCH v2 2/2] arm64: hibernate: Don't hibernate on systems with stuck CPUs

[james.morse@arm.com (James Morse)]

Hibernate relies on cpu hotplug to prevent secondary cores executing
the kernel text while it is being restored.

Add a call to cpus_are_stuck_in_kernel() to determine if there are
CPUs not counted by 'num_online_cpus()', and prevent hibernate in this
case.

Fixes: 82869ac57b5 ("arm64: kernel: Add support for hibernate/suspend-to-disk")
Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/arm64/kernel/hibernate.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/arm64/kernel/hibernate.c b/arch/arm64/kernel/hibernate.c
index f8df75d740f4..21ab5df9fa76 100644
--- a/arch/arm64/kernel/hibernate.c
+++ b/arch/arm64/kernel/hibernate.c
@@ -33,6 +33,7 @@
 #include <asm/pgtable.h>
 #include <asm/pgtable-hwdef.h>
 #include <asm/sections.h>
+#include <asm/smp.h>
 #include <asm/suspend.h>
 #include <asm/virt.h>
 
@@ -236,6 +237,11 @@ int swsusp_arch_suspend(void)
 	unsigned long flags;
 	struct sleep_stack_data state;
 
+	if (cpus_are_stuck_in_kernel()) {
+		pr_err("Can't hibernate: no mechanism to offline secondary CPUs.\n");
+		return -EBUSY;
+	}
+
 	local_dbg_save(flags);
 
 	if (__cpu_suspend_enter(&state)) {
-- 
2.8.0.rc3