From c9a24e2d0c7d33b141167f5fa13f95cf6d35cb1e Mon Sep 17 00:00:00 2001 From: "Paul E. McKenney" Date: Fri, 27 Apr 2018 14:54:46 -0700 Subject: [PATCH] rcu: Make quiescent-state reporting use ->gp_seq This commit switches the functions reporting quiescent states from use of ->gpnum to ->gp_seq. In either case, the point is to handle races where a given grace period ends before a quiescent state can be reported. Failing to catch these races would result in too-short grace periods, hence the checking. Signed-off-by: Paul E. McKenney --- kernel/rcu/tree.c | 18 +++++++++--------- 1 file changed, 9 insertions(+), 9 deletions(-) diff --git a/kernel/rcu/tree.c b/kernel/rcu/tree.c index 002f85357226..a54587dc13f0 100644 --- a/kernel/rcu/tree.c +++ b/kernel/rcu/tree.c @@ -2242,7 +2242,7 @@ static void rcu_report_qs_rsp(struct rcu_state *rsp, unsigned long flags) * must be represented by the same rcu_node structure (which need not be a * leaf rcu_node structure, though it often will be). The gps parameter * is the grace-period snapshot, which means that the quiescent states - * are valid only if rnp->gpnum is equal to gps. That structure's lock + * are valid only if rnp->gp_seq is equal to gps. That structure's lock * must be held upon entry, and it is released before return. */ static void @@ -2257,7 +2257,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp, /* Walk up the rcu_node hierarchy. */ for (;;) { - if (!(rnp->qsmask & mask) || rnp->gpnum != gps) { + if (!(rnp->qsmask & mask) || rnp->gp_seq != gps) { /* * Our bit has already been cleared, or the @@ -2335,8 +2335,8 @@ static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp, return; } - /* Report up the rest of the hierarchy, tracking current ->gpnum. */ - gps = rnp->gpnum; + /* Report up the rest of the hierarchy, tracking current ->gp_seq. */ + gps = rnp->gp_seq; mask = rnp->grpmask; raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ raw_spin_lock_rcu_node(rnp_p); /* irqs already disabled. */ @@ -2357,8 +2357,8 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) rnp = rdp->mynode; raw_spin_lock_irqsave_rcu_node(rnp, flags); - if (rdp->cpu_no_qs.b.norm || rdp->gpnum != rnp->gpnum || - rnp->completed == rnp->gpnum || rdp->gpwrap) { + if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq || + rdp->gpwrap) { /* * The grace period in which this quiescent state was @@ -2383,7 +2383,7 @@ rcu_report_qs_rdp(int cpu, struct rcu_state *rsp, struct rcu_data *rdp) */ needwake = rcu_accelerate_cbs(rsp, rnp, rdp); - rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); + rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags); /* ^^^ Released rnp->lock */ if (needwake) rcu_gp_kthread_wake(rsp); @@ -2688,8 +2688,8 @@ static void force_qs_rnp(struct rcu_state *rsp, int (*f)(struct rcu_data *rsp)) } } if (mask != 0) { - /* Idle/offline CPUs, report (releases rnp->lock. */ - rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); + /* Idle/offline CPUs, report (releases rnp->lock). */ + rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags); } else { /* Nothing to do here, so just drop the lock. */ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); -- 2.30.2