jrcu: introduce an alternate implementation of rcu_cpu().
This new implementation is based on smp_processor_id().
It is for those architectures which do not have
thread_info->cpu.
(We prefer the thread_info version as it works in early
boot where smp_processor_id() has not yet been set up).
Signed-off-by: Joe Korty <[email protected]>
Index: b/kernel/jrcu.c
===================================================================
--- a/kernel/jrcu.c
+++ b/kernel/jrcu.c
@@ -140,11 +140,27 @@ static u64 rcu_timestamp;
* know what that is. For RCU to work correctly, a cpu named '0' must
* eventually be present (but need not ever be online).
*/
+#ifdef HAVE_THREAD_INFO_CPU
static inline int rcu_cpu(void)
{
return current_thread_info()->cpu;
}
+#else
+
+static unsigned rcu_cpu_early_flag __read_mostly = 1;
+
+static inline int rcu_cpu(void)
+{
+ if (unlikely(rcu_cpu_early_flag)) {
+ if (!(rcu_scheduler_active && nr_cpu_ids > 1))
+ return 0;
+ rcu_cpu_early_flag = 0;
+ }
+ return raw_smp_processor_id();
+}
+#endif /* HAVE_THREAD_INFO_CPU */
+
/*
* Invoke whenever the calling CPU consents to end-of-batch. All CPUs
* must so consent before the batch is truly ended.
Index: b/arch/x86/include/asm/thread_info.h
===================================================================
--- a/arch/x86/include/asm/thread_info.h
+++ b/arch/x86/include/asm/thread_info.h
@@ -29,6 +29,7 @@ struct thread_info {
__u32 flags; /* low level flags */
__u32 status; /* thread synchronous flags */
__u32 cpu; /* current CPU */
+#define HAVE_THREAD_INFO_CPU 1
int preempt_count; /* 0 => preemptable,
<0 => BUG */
mm_segment_t addr_limit;