path: root/arch/arm64/include
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authorJames Morse <>2016-06-22 10:06:12 +0100
committerWill Deacon <>2016-06-22 15:48:09 +0100
commit5c492c3f5255bd34f7ff8867515ecf98dcba2a2e (patch)
treeeea6ba5d5f8b8ef37f6218bda83c03e081d95e9d /arch/arm64/include
parent20c27a4270c775d7ed661491af8ac03264d60fc6 (diff)
arm64: smp: Add function to determine if cpus are stuck in the kernel
kernel/smp.c has a fancy counter that keeps track of the number of CPUs it marked as not-present and left in cpu_park_loop(). If there are any CPUs spinning in here, features like kexec or hibernate may release them by overwriting this memory. This problem also occurs on machines using spin-tables to release secondary cores. After commit 44dbcc93ab67 ("arm64: Fix behavior of maxcpus=N") we bring all known cpus into the secondary holding pen, meaning this memory can't be re-used by kexec or hibernate. Add a function cpus_are_stuck_in_kernel() to determine if either of these cases have occurred. Signed-off-by: James Morse <> Acked-by: Mark Rutland <> Reviewed-by: Suzuki K Poulose <> Signed-off-by: Will Deacon <>
Diffstat (limited to 'arch/arm64/include')
1 files changed, 12 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/smp.h b/arch/arm64/include/asm/smp.h
index 433e50405274..022644704a93 100644
--- a/arch/arm64/include/asm/smp.h
+++ b/arch/arm64/include/asm/smp.h
@@ -124,6 +124,18 @@ static inline void cpu_panic_kernel(void)
+ * If a secondary CPU enters the kernel but fails to come online,
+ * (e.g. due to mismatched features), and cannot exit the kernel,
+ * we increment cpus_stuck_in_kernel and leave the CPU in a
+ * quiesecent loop within the kernel text. The memory containing
+ * this loop must not be re-used for anything else as the 'stuck'
+ * core is executing it.
+ *
+ * This function is used to inhibit features like kexec and hibernate.
+ */
+bool cpus_are_stuck_in_kernel(void);
#endif /* ifndef __ASSEMBLY__ */
#endif /* ifndef __ASM_SMP_H */