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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 <boqun.feng@gmail.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Reviewed-by: Josh Triplett <josh@joshtriplett.org>
This commit is contained in:
Paul E. McKenney 2016-12-20 07:17:58 -08:00
parent 09e2db37ec
commit fdbb9b315c
1 changed files with 1 additions and 1 deletions
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2
kernel/rcu/tree.c
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@ -3873,7 +3873,7 @@ void rcu_cpu_starting(unsigned int cpu)
struct rcu_state *rsp; struct rcu_state *rsp;
for_each_rcu_flavor(rsp) { for_each_rcu_flavor(rsp) {
rdp = this_cpu_ptr(rsp->rda); rdp = per_cpu_ptr(rsp->rda, cpu);
rnp = rdp->mynode; rnp = rdp->mynode;
mask = rdp->grpmask; mask = rdp->grpmask;
raw_spin_lock_irqsave_rcu_node(rnp, flags); raw_spin_lock_irqsave_rcu_node(rnp, flags);