From fdbb9b315ce40922f3a8d2b8352776d7bc963d84 Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Tue, 20 Dec 2016 07:17:58 -0800 Subject: [PATCH] rcu: Make rcu_cpu_starting() use its "cpu" argument The rcu_cpu_starting() function uses this_cpu_ptr() to locate the incoming CPU's rcu_data structure. This works for the boot CPU and for all CPUs onlined after rcu_init() executes (during very early boot). Currently, this is the full set of CPUs, so all is well. But if anyone ever parallelizes boot before rcu_init() time, it will fail. This commit therefore substitutes the rcu_cpu_starting() function's this_cpu_pointer() for per_cpu_ptr(), future-proofing the code and (arguably) improving readability. This commit inadvertently fixes a latent bug: If there ever had been more than just the boot CPU online at rcu_init() time, the old code would not initialize the non-boot CPUs, but rather would repeatedly initialize the boot CPU. Reported-by: Boqun Feng Signed-off-by: Paul E. McKenney Reviewed-by: Josh Triplett --- kernel/rcu/tree.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index be2301238a23..a4b4762442bb 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3873,7 +3873,7 @@ void rcu_cpu_starting(unsigned int cpu) struct rcu_state *rsp; for_each_rcu_flavor(rsp) { - rdp = this_cpu_ptr(rsp->rda); + rdp = per_cpu_ptr(rsp->rda, cpu); rnp = rdp->mynode; mask = rdp->grpmask; raw_spin_lock_irqsave_rcu_node(rnp, flags);