diff options
Diffstat (limited to 'arch/powerpc/include/asm/paravirt.h')
| -rw-r--r-- | arch/powerpc/include/asm/paravirt.h | 18 |
1 files changed, 17 insertions, 1 deletions
diff --git a/arch/powerpc/include/asm/paravirt.h b/arch/powerpc/include/asm/paravirt.h index 39f173961f6a..eb7df559ae74 100644 --- a/arch/powerpc/include/asm/paravirt.h +++ b/arch/powerpc/include/asm/paravirt.h @@ -110,7 +110,23 @@ static inline bool vcpu_is_preempted(int cpu) #ifdef CONFIG_PPC_SPLPAR if (!is_kvm_guest()) { - int first_cpu = cpu_first_thread_sibling(smp_processor_id()); + int first_cpu; + + /* + * The result of vcpu_is_preempted() is used in a + * speculative way, and is always subject to invalidation + * by events internal and external to Linux. While we can + * be called in preemptable context (in the Linux sense), + * we're not accessing per-cpu resources in a way that can + * race destructively with Linux scheduler preemption and + * migration, and callers can tolerate the potential for + * error introduced by sampling the CPU index without + * pinning the task to it. So it is permissible to use + * raw_smp_processor_id() here to defeat the preempt debug + * warnings that can arise from using smp_processor_id() + * in arbitrary contexts. + */ + first_cpu = cpu_first_thread_sibling(raw_smp_processor_id()); /* * The PowerVM hypervisor dispatches VMs on a whole core |