From d5cd96851d520e5caff13ddf99e3b2b759ae3b1d Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Thu, 12 Apr 2018 10:45:06 -0700 Subject: [PATCH] rcu: Inline rcu_start_gp_advanced() into rcu_start_future_gp() The rcu_start_gp_advanced() is invoked only from rcu_start_future_gp() and much of its code is redundant when invoked from that context. This commit therefore inlines rcu_start_gp_advanced() into rcu_start_future_gp(), then removes rcu_start_gp_advanced(). Signed-off-by: Paul E. McKenney Tested-by: Nicholas Piggin --- kernel/rcu/tree.c | 56 ++++++++++------------------------------------- 1 file changed, 12 insertions(+), 44 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 25dbbc753fef..4433f68a1c7b 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -524,8 +524,6 @@ module_param(rcu_kick_kthreads, bool, 0644); static ulong jiffies_till_sched_qs = HZ / 10; module_param(jiffies_till_sched_qs, ulong, 0444); -static bool rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, - struct rcu_data *rdp); static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp)); static void force_quiescent_state(struct rcu_state *rsp); static int rcu_pending(void); @@ -1679,7 +1677,8 @@ static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, * rcu_node structure's ->need_future_gp field. Returns true if there * is reason to awaken the grace-period kthread. * - * The caller must hold the specified rcu_node structure's ->lock. + * The caller must hold the specified rcu_node structure's ->lock, which + * is why the caller is responsible for waking the grace-period kthread. */ static bool __maybe_unused rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, @@ -1687,7 +1686,8 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, { unsigned long c; bool ret = false; - struct rcu_node *rnp_root = rcu_get_root(rdp->rsp); + struct rcu_state *rsp = rdp->rsp; + struct rcu_node *rnp_root = rcu_get_root(rsp); raw_lockdep_assert_held_rcu_node(rnp); @@ -1695,7 +1695,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, * Pick up grace-period number for new callbacks. If this * grace period is already marked as needed, return to the caller. */ - c = rcu_cbs_completed(rdp->rsp, rnp); + c = rcu_cbs_completed(rsp, rnp); trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); if (need_future_gp_element(rnp, c)) { trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); @@ -1727,7 +1727,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, * period in progress, it will be smaller than the one we obtained * earlier. Adjust callbacks as needed. */ - c = rcu_cbs_completed(rdp->rsp, rnp_root); + c = rcu_cbs_completed(rsp, rnp_root); if (!rcu_is_nocb_cpu(rdp->cpu)) (void)rcu_segcblist_accelerate(&rdp->cblist, c); @@ -1748,7 +1748,12 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot")); } else { trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot")); - ret = rcu_start_gp_advanced(rdp->rsp, rnp_root, rdp); + if (!rsp->gp_kthread) + goto unlock_out; /* No grace-period kthread yet! */ + WRITE_ONCE(rsp->gp_flags, rsp->gp_flags | RCU_GP_FLAG_INIT); + trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), + TPS("newreq")); + ret = true; /* Caller must wake GP kthread. */ } unlock_out: if (rnp != rnp_root) @@ -2298,43 +2303,6 @@ static int __noreturn rcu_gp_kthread(void *arg) } } -/* - * Start a new RCU grace period if warranted, re-initializing the hierarchy - * in preparation for detecting the next grace period. The caller must hold - * the root node's ->lock and hard irqs must be disabled. - * - * Note that it is legal for a dying CPU (which is marked as offline) to - * invoke this function. This can happen when the dying CPU reports its - * quiescent state. - * - * Returns true if the grace-period kthread must be awakened. - */ -static bool -rcu_start_gp_advanced(struct rcu_state *rsp, struct rcu_node *rnp, - struct rcu_data *rdp) -{ - raw_lockdep_assert_held_rcu_node(rnp); - if (!rsp->gp_kthread || !cpu_needs_another_gp(rsp, rdp)) { - /* - * Either we have not yet spawned the grace-period - * task, this CPU does not need another grace period, - * or a grace period is already in progress. - * Either way, don't start a new grace period. - */ - return false; - } - WRITE_ONCE(rsp->gp_flags, RCU_GP_FLAG_INIT); - trace_rcu_grace_period(rsp->name, READ_ONCE(rsp->gpnum), - TPS("newreq")); - - /* - * We can't do wakeups while holding the rnp->lock, as that - * could cause possible deadlocks with the rq->lock. Defer - * the wakeup to our caller. - */ - return true; -} - /* * Report a full set of quiescent states to the specified rcu_state data * structure. Invoke rcu_gp_kthread_wake() to awaken the grace-period