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Message-Id: <1524452624-27589-15-git-send-email-paulmck@linux.vnet.ibm.com> Date: Sun, 22 Apr 2018 20:03:38 -0700 From: "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> To: linux-kernel@...r.kernel.org Cc: mingo@...nel.org, jiangshanlai@...il.com, dipankar@...ibm.com, akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com, josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org, rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com, fweisbec@...il.com, oleg@...hat.com, joel.opensrc@...il.com, torvalds@...ux-foundation.org, npiggin@...il.com, "Paul E. McKenney" <paulmck@...ux.vnet.ibm.com> Subject: [PATCH tip/core/rcu 15/21] rcu: Make rcu_start_future_gp() caller select grace period The rcu_accelerate_cbs() function selects a grace-period target, which it uses to have rcu_segcblist_accelerate() assign numbers to recently queued callbacks. Then it invokes rcu_start_future_gp(), which selects a grace-period target again, which is a bit pointless. This commit therefore changes rcu_start_future_gp() to take the grace-period target as a parameter, thus avoiding double selection. This commit also changes the name of rcu_start_future_gp() to rcu_start_this_gp() to reflect this change in functionality, and also makes a similar change to the name of trace_rcu_future_gp(). Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> --- kernel/rcu/tree.c | 53 ++++++++++++++++++++---------------------------- kernel/rcu/tree_plugin.h | 9 ++++---- 2 files changed, 27 insertions(+), 35 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 4433f68a1c7b..94519c7d552f 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -1659,12 +1659,9 @@ static unsigned long rcu_cbs_completed(struct rcu_state *rsp, return rnp->completed + 2; } -/* - * Trace-event helper function for rcu_start_future_gp() and - * rcu_nocb_wait_gp(). - */ -static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, - unsigned long c, const char *s) +/* Trace-event wrapper function for trace_rcu_future_grace_period. */ +static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, + unsigned long c, const char *s) { trace_rcu_future_grace_period(rdp->rsp->name, rnp->gpnum, rnp->completed, c, rnp->level, @@ -1672,33 +1669,27 @@ static void trace_rcu_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, } /* - * Start some future grace period, as needed to handle newly arrived + * Start the specified grace period, as needed to handle newly arrived * callbacks. The required future grace periods are recorded in each - * rcu_node structure's ->need_future_gp field. Returns true if there + * 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, 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, - unsigned long *c_out) +static bool rcu_start_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, + unsigned long c) { - unsigned long c; bool ret = false; struct rcu_state *rsp = rdp->rsp; struct rcu_node *rnp_root = rcu_get_root(rsp); raw_lockdep_assert_held_rcu_node(rnp); - /* - * 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(rsp, rnp); - trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); + /* If the specified GP is already known needed, return to caller. */ + trace_rcu_this_gp(rnp, rdp, c, TPS("Startleaf")); if (need_future_gp_element(rnp, c)) { - trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); + trace_rcu_this_gp(rnp, rdp, c, TPS("Prestartleaf")); goto out; } @@ -1710,7 +1701,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, */ if (rnp->gpnum != rnp->completed) { need_future_gp_element(rnp, c) = true; - trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); + trace_rcu_this_gp(rnp, rdp, c, TPS("Startedleaf")); goto out; } @@ -1736,7 +1727,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, * recorded, trace and leave. */ if (need_future_gp_element(rnp_root, c)) { - trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot")); + trace_rcu_this_gp(rnp, rdp, c, TPS("Prestartedroot")); goto unlock_out; } @@ -1745,9 +1736,9 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, /* If a grace period is not already in progress, start one. */ if (rnp_root->gpnum != rnp_root->completed) { - trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleafroot")); + trace_rcu_this_gp(rnp, rdp, c, TPS("Startedleafroot")); } else { - trace_rcu_future_gp(rnp, rdp, c, TPS("Startedroot")); + trace_rcu_this_gp(rnp, rdp, c, TPS("Startedroot")); if (!rsp->gp_kthread) goto unlock_out; /* No grace-period kthread yet! */ WRITE_ONCE(rsp->gp_flags, rsp->gp_flags | RCU_GP_FLAG_INIT); @@ -1759,8 +1750,6 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, if (rnp != rnp_root) raw_spin_unlock_rcu_node(rnp_root); out: - if (c_out != NULL) - *c_out = c; return ret; } @@ -1776,8 +1765,8 @@ static bool rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) need_future_gp_element(rnp, c) = false; needmore = need_any_future_gp(rnp); - trace_rcu_future_gp(rnp, rdp, c, - needmore ? TPS("CleanupMore") : TPS("Cleanup")); + trace_rcu_this_gp(rnp, rdp, c, + needmore ? TPS("CleanupMore") : TPS("Cleanup")); return needmore; } @@ -1812,6 +1801,7 @@ static void rcu_gp_kthread_wake(struct rcu_state *rsp) static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, struct rcu_data *rdp) { + unsigned long c; bool ret = false; raw_lockdep_assert_held_rcu_node(rnp); @@ -1830,8 +1820,9 @@ static bool rcu_accelerate_cbs(struct rcu_state *rsp, struct rcu_node *rnp, * accelerating callback invocation to an earlier grace-period * number. */ - if (rcu_segcblist_accelerate(&rdp->cblist, rcu_cbs_completed(rsp, rnp))) - ret = rcu_start_future_gp(rnp, rdp, NULL); + c = rcu_cbs_completed(rsp, rnp); + if (rcu_segcblist_accelerate(&rdp->cblist, c)) + ret = rcu_start_this_gp(rnp, rdp, c); /* Trace depending on how much we were able to accelerate. */ if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL)) @@ -2174,8 +2165,8 @@ static void rcu_gp_cleanup(struct rcu_state *rsp) /* Check for GP requests since above loop. */ rdp = this_cpu_ptr(rsp->rda); if (need_any_future_gp(rnp)) { - trace_rcu_future_gp(rnp, rdp, rsp->completed - 1, - TPS("CleanupMore")); + trace_rcu_this_gp(rnp, rdp, rsp->completed - 1, + TPS("CleanupMore")); needgp = true; } /* Advance CBs to reduce false positives below. */ diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 313b77d9cf06..322777492fff 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -2035,7 +2035,8 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp) struct rcu_node *rnp = rdp->mynode; raw_spin_lock_irqsave_rcu_node(rnp, flags); - needwake = rcu_start_future_gp(rnp, rdp, &c); + c = rcu_cbs_completed(rdp->rsp, rnp); + needwake = rcu_start_this_gp(rnp, rdp, c); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); if (needwake) rcu_gp_kthread_wake(rdp->rsp); @@ -2044,7 +2045,7 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp) * Wait for the grace period. Do so interruptibly to avoid messing * up the load average. */ - trace_rcu_future_gp(rnp, rdp, c, TPS("StartWait")); + trace_rcu_this_gp(rnp, rdp, c, TPS("StartWait")); for (;;) { swait_event_interruptible( rnp->nocb_gp_wq[c & 0x1], @@ -2052,9 +2053,9 @@ static void rcu_nocb_wait_gp(struct rcu_data *rdp) if (likely(d)) break; WARN_ON(signal_pending(current)); - trace_rcu_future_gp(rnp, rdp, c, TPS("ResumeWait")); + trace_rcu_this_gp(rnp, rdp, c, TPS("ResumeWait")); } - trace_rcu_future_gp(rnp, rdp, c, TPS("EndWait")); + trace_rcu_this_gp(rnp, rdp, c, TPS("EndWait")); smp_mb(); /* Ensure that CB invocation happens after GP end. */ } -- 2.5.2
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