[PATCH] rcu: Convert rcu_state.ofl_lock to raw_spinlock_t

[Mike Galbraith]

1e64b15a4b10 ("rcu: Fix grace-period hangs due to race with CPU offline")
added spinlock_t ofl_lock to the rcu_state structure, then takes it with
preemption disabled during CPU offline, giving RT sleeping lock heartburn.

Convert it to raw_spinlock_t.

Signed-off-by: Mike Galbraith <efa...@gmx.de>
---
 kernel/rcu/tree.c |   12 ++++++------
 kernel/rcu/tree.h |    2 +-
 2 files changed, 7 insertions(+), 7 deletions(-)

--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -111,7 +111,7 @@ struct rcu_state sname##_state = { \
        .abbr = sabbr, \
        .exp_mutex = __MUTEX_INITIALIZER(sname##_state.exp_mutex), \
        .exp_wake_mutex = __MUTEX_INITIALIZER(sname##_state.exp_wake_mutex), \
-       .ofl_lock = __SPIN_LOCK_UNLOCKED(sname##_state.ofl_lock), \
+       .ofl_lock = __RAW_SPIN_LOCK_UNLOCKED(sname##_state.ofl_lock), \
 }
 
 RCU_STATE_INITIALIZER(rcu_sched, 's', call_rcu_sched);
@@ -1962,13 +1962,13 @@ static bool rcu_gp_init(struct rcu_state
         */
        rsp->gp_state = RCU_GP_ONOFF;
        rcu_for_each_leaf_node(rsp, rnp) {
-               spin_lock(&rsp->ofl_lock);
+               raw_spin_lock(&rsp->ofl_lock);
                raw_spin_lock_irq_rcu_node(rnp);
                if (rnp->qsmaskinit == rnp->qsmaskinitnext &&
                    !rnp->wait_blkd_tasks) {
                        /* Nothing to do on this leaf rcu_node structure. */
                        raw_spin_unlock_irq_rcu_node(rnp);
-                       spin_unlock(&rsp->ofl_lock);
+                       raw_spin_unlock(&rsp->ofl_lock);
                        continue;
                }
 
@@ -2004,7 +2004,7 @@ static bool rcu_gp_init(struct rcu_state
                }
 
                raw_spin_unlock_irq_rcu_node(rnp);
-               spin_unlock(&rsp->ofl_lock);
+               raw_spin_unlock(&rsp->ofl_lock);
        }
        rcu_gp_slow(rsp, gp_preinit_delay); /* Races with CPU hotplug. */
 
@@ -3892,7 +3892,7 @@ static void rcu_cleanup_dying_idle_cpu(i
 
        /* Remove outgoing CPU from mask in the leaf rcu_node structure. */
        mask = rdp->grpmask;
-       spin_lock(&rsp->ofl_lock);
+       raw_spin_lock(&rsp->ofl_lock);
        raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order 
guarantee. */
        rdp->rcu_ofl_gp_seq = READ_ONCE(rsp->gp_seq);
        rdp->rcu_ofl_gp_flags = READ_ONCE(rsp->gp_flags);
@@ -3903,7 +3903,7 @@ static void rcu_cleanup_dying_idle_cpu(i
        }
        rnp->qsmaskinitnext &= ~mask;
        raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
-       spin_unlock(&rsp->ofl_lock);
+       raw_spin_unlock(&rsp->ofl_lock);
 }
 
 /*
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -368,7 +368,7 @@ struct rcu_state {
        char abbr;                              /* Abbreviated name. */
        struct list_head flavors;               /* List of RCU flavors. */
 
-       spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
+       raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
                                                /* Synchronize offline with */
                                                /*  GP pre-initialization. */
 };