rcu: Convert rcu_state.ofl_lock to raw_spinlock_t

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, which gives the -rt patchset's
sleeping spinlock heartburn.

This commit therefore converts ->ofl_lock to raw_spinlock_t.

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>

diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c
index 85c2c2dc4c4a0c92edc5662bf2b178e84b9d59c6..58aa6c2fd7fa048c94381fa70a54b57e44f2d327 100644 (file)
--- a/kernel/rcu/tree.c
+++ b/kernel/rcu/tree.c
@@ -97,7 +97,7 @@ struct rcu_state rcu_state = {
        .abbr = RCU_ABBR,
        .exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex),
        .exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex),
-       .ofl_lock = __SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock),
+       .ofl_lock = __RAW_SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock),
 };
 
 /* Dump rcu_node combining tree at boot to verify correct setup. */
@@ -1776,13 +1776,13 @@ static bool rcu_gp_init(void)
         */
        rcu_state.gp_state = RCU_GP_ONOFF;
        rcu_for_each_leaf_node(rnp) {
-               spin_lock(&rcu_state.ofl_lock);
+               raw_spin_lock(&rcu_state.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(&rcu_state.ofl_lock);
+                       raw_spin_unlock(&rcu_state.ofl_lock);
                        continue;
                }
 
@@ -1818,7 +1818,7 @@ static bool rcu_gp_init(void)
                }
 
                raw_spin_unlock_irq_rcu_node(rnp);
-               spin_unlock(&rcu_state.ofl_lock);
+               raw_spin_unlock(&rcu_state.ofl_lock);
        }
        rcu_gp_slow(gp_preinit_delay); /* Races with CPU hotplug. */
 
@@ -3377,7 +3377,7 @@ void rcu_report_dead(unsigned int cpu)
 
        /* Remove outgoing CPU from mask in the leaf rcu_node structure. */
        mask = rdp->grpmask;
-       spin_lock(&rcu_state.ofl_lock);
+       raw_spin_lock(&rcu_state.ofl_lock);
        raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */
        rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq);
        rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags);
@@ -3388,7 +3388,7 @@ void rcu_report_dead(unsigned int cpu)
        }
        rnp->qsmaskinitnext &= ~mask;
        raw_spin_unlock_irqrestore_rcu_node(rnp, flags);
-       spin_unlock(&rcu_state.ofl_lock);
+       raw_spin_unlock(&rcu_state.ofl_lock);
 
        per_cpu(rcu_cpu_started, cpu) = 0;
 }

diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h
index bfbf97a1c29d439fffcf6d462c9761c6ddb2fec0..703e19ff532d4d866a560ea973cd5134d9113de5 100644 (file)
--- a/kernel/rcu/tree.h
+++ b/kernel/rcu/tree.h
@@ -343,7 +343,7 @@ struct rcu_state {
        const char *name;                       /* Name of structure. */
        char abbr;                              /* Abbreviated name. */
 
-       spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
+       raw_spinlock_t ofl_lock ____cacheline_internodealigned_in_smp;
                                                /* Synchronize offline with */
                                                /*  GP pre-initialization. */
 };