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author | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-07-31 20:34:32 (GMT) |
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committer | Paul E. McKenney <paulmck@linux.vnet.ibm.com> | 2015-09-21 04:16:18 (GMT) |
commit | 7922cd0e562cb2b8da2c8a0afda2e1c9bb4a94e2 (patch) | |
tree | dce739485e55be9238c53bf70530a0b5e5a34aa3 /kernel/rcu/tree.c | |
parent | f4ecea309d3e17ba5e90082308125ad23bd5701b (diff) | |
download | linux-7922cd0e562cb2b8da2c8a0afda2e1c9bb4a94e2.tar.xz |
rcu: Move rcu_report_exp_rnp() to allow consolidation
This is a nearly pure code-movement commit, moving rcu_report_exp_rnp(),
sync_rcu_preempt_exp_done(), and rcu_preempted_readers_exp() so
that later commits can make synchronize_sched_expedited() use them.
The non-code-movement portion of this commit tags rcu_report_exp_rnp()
as __maybe_unused to avoid build errors when CONFIG_PREEMPT=n.
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Diffstat (limited to 'kernel/rcu/tree.c')
-rw-r--r-- | kernel/rcu/tree.c | 66 |
1 files changed, 66 insertions, 0 deletions
diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 53d66eb..59af27d 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -3379,6 +3379,72 @@ static bool rcu_exp_gp_seq_done(struct rcu_state *rsp, unsigned long s) return rcu_seq_done(&rsp->expedited_sequence, s); } +/* + * Return non-zero if there are any tasks in RCU read-side critical + * sections blocking the current preemptible-RCU expedited grace period. + * If there is no preemptible-RCU expedited grace period currently in + * progress, returns zero unconditionally. + */ +static int rcu_preempted_readers_exp(struct rcu_node *rnp) +{ + return rnp->exp_tasks != NULL; +} + +/* + * return non-zero if there is no RCU expedited grace period in progress + * for the specified rcu_node structure, in other words, if all CPUs and + * tasks covered by the specified rcu_node structure have done their bit + * for the current expedited grace period. Works only for preemptible + * RCU -- other RCU implementation use other means. + * + * Caller must hold the root rcu_node's exp_funnel_mutex. + */ +static int sync_rcu_preempt_exp_done(struct rcu_node *rnp) +{ + return !rcu_preempted_readers_exp(rnp) && + READ_ONCE(rnp->expmask) == 0; +} + +/* + * Report the exit from RCU read-side critical section for the last task + * that queued itself during or before the current expedited preemptible-RCU + * grace period. This event is reported either to the rcu_node structure on + * which the task was queued or to one of that rcu_node structure's ancestors, + * recursively up the tree. (Calm down, calm down, we do the recursion + * iteratively!) + * + * Caller must hold the root rcu_node's exp_funnel_mutex. + */ +static void __maybe_unused rcu_report_exp_rnp(struct rcu_state *rsp, + struct rcu_node *rnp, bool wake) +{ + unsigned long flags; + unsigned long mask; + + raw_spin_lock_irqsave(&rnp->lock, flags); + smp_mb__after_unlock_lock(); + for (;;) { + if (!sync_rcu_preempt_exp_done(rnp)) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + break; + } + if (rnp->parent == NULL) { + raw_spin_unlock_irqrestore(&rnp->lock, flags); + if (wake) { + smp_mb(); /* EGP done before wake_up(). */ + wake_up(&rsp->expedited_wq); + } + break; + } + mask = rnp->grpmask; + raw_spin_unlock(&rnp->lock); /* irqs remain disabled */ + rnp = rnp->parent; + raw_spin_lock(&rnp->lock); /* irqs already disabled */ + smp_mb__after_unlock_lock(); + rnp->expmask &= ~mask; + } +} + /* Common code for synchronize_{rcu,sched}_expedited() work-done checking. */ static bool sync_exp_work_done(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp, |