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Message-Id: <1524452624-27589-3-git-send-email-paulmck@linux.vnet.ibm.com> Date: Sun, 22 Apr 2018 20:03:26 -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 03/21] rcu: Add accessor macros for the ->need_future_gp[] array Accessors for the ->need_future_gp[] array are currently open-coded, which makes them difficult to change. To improve maintainability, this commit adds need_future_gp_mask() to compute the indexing mask from the array size, need_future_gp_element() to access the element corresponding to the specified grace-period number, and need_any_future_gp() to determine if any future grace period is needed. This commit also applies need_future_gp_element() to existing open-coded single-element accesses. Signed-off-by: Paul E. McKenney <paulmck@...ux.vnet.ibm.com> --- kernel/rcu/tree.c | 16 +++++++--------- kernel/rcu/tree.h | 15 +++++++++++++++ kernel/rcu/tree_plugin.h | 2 +- 3 files changed, 23 insertions(+), 10 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 4bbba17422cd..79fb99951a0c 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -718,11 +718,9 @@ static struct rcu_node *rcu_get_root(struct rcu_state *rsp) static int rcu_future_needs_gp(struct rcu_state *rsp) { struct rcu_node *rnp = rcu_get_root(rsp); - int idx = (READ_ONCE(rnp->completed) + 1) & 0x1; - int *fp = &rnp->need_future_gp[idx]; lockdep_assert_irqs_disabled(); - return READ_ONCE(*fp); + return READ_ONCE(need_future_gp_element(rnp, rnp->completed)); } /* @@ -1699,7 +1697,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, */ c = rcu_cbs_completed(rdp->rsp, rnp); trace_rcu_future_gp(rnp, rdp, c, TPS("Startleaf")); - if (rnp->need_future_gp[c & 0x1]) { + if (need_future_gp_element(rnp, c)) { trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartleaf")); goto out; } @@ -1711,7 +1709,7 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, * current grace period, we don't need to explicitly start one. */ if (rnp->gpnum != rnp->completed) { - rnp->need_future_gp[c & 0x1]++; + need_future_gp_element(rnp, c)++; trace_rcu_future_gp(rnp, rdp, c, TPS("Startedleaf")); goto out; } @@ -1737,13 +1735,13 @@ rcu_start_future_gp(struct rcu_node *rnp, struct rcu_data *rdp, * If the needed for the required grace period is already * recorded, trace and leave. */ - if (rnp_root->need_future_gp[c & 0x1]) { + if (need_future_gp_element(rnp_root, c)) { trace_rcu_future_gp(rnp, rdp, c, TPS("Prestartedroot")); goto unlock_out; } /* Record the need for the future grace period. */ - rnp_root->need_future_gp[c & 0x1]++; + need_future_gp_element(rnp_root, c)++; /* If a grace period is not already in progress, start one. */ if (rnp_root->gpnum != rnp_root->completed) { @@ -1771,8 +1769,8 @@ static int rcu_future_gp_cleanup(struct rcu_state *rsp, struct rcu_node *rnp) int needmore; struct rcu_data *rdp = this_cpu_ptr(rsp->rda); - rnp->need_future_gp[c & 0x1] = 0; - needmore = rnp->need_future_gp[(c + 1) & 0x1]; + need_future_gp_element(rnp, c) = 0; + needmore = need_future_gp_element(rnp, c + 1); trace_rcu_future_gp(rnp, rdp, c, needmore ? TPS("CleanupMore") : TPS("Cleanup")); return needmore; diff --git a/kernel/rcu/tree.h b/kernel/rcu/tree.h index f491ab4f2e8e..18b091474ffa 100644 --- a/kernel/rcu/tree.h +++ b/kernel/rcu/tree.h @@ -159,6 +159,21 @@ struct rcu_node { wait_queue_head_t exp_wq[4]; } ____cacheline_internodealigned_in_smp; +/* Accessors for ->need_future_gp[] array. */ +#define need_future_gp_mask() \ + (ARRAY_SIZE(((struct rcu_node *)NULL)->need_future_gp) - 1) +#define need_future_gp_element(rnp, c) \ + ((rnp)->need_future_gp[(c) & need_future_gp_mask()]) +#define need_any_future_gp(rnp) \ +({ \ + int __i; \ + bool __nonzero = false; \ + \ + for (__i = 0; __i < ARRAY_SIZE((rnp)->need_future_gp); __i++) \ + __nonzero = __nonzero || (rnp)->need_future_gp[__i]; \ + __nonzero; \ +}) + /* * Bitmasks in an rcu_node cover the interval [grplo, grphi] of CPU IDs, and * are indexed relative to this interval rather than the global CPU ID space. diff --git a/kernel/rcu/tree_plugin.h b/kernel/rcu/tree_plugin.h index 84fbee4686d3..640ea927d8a4 100644 --- a/kernel/rcu/tree_plugin.h +++ b/kernel/rcu/tree_plugin.h @@ -1790,7 +1790,7 @@ static void rcu_nocb_gp_cleanup(struct swait_queue_head *sq) */ static void rcu_nocb_gp_set(struct rcu_node *rnp, int nrq) { - rnp->need_future_gp[(rnp->completed + 1) & 0x1] += nrq; + need_future_gp_element(rnp, rnp->completed + 1) += nrq; } static struct swait_queue_head *rcu_nocb_gp_get(struct rcu_node *rnp) -- 2.5.2
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