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rcu: Make quiescent-state reporting use ->gp_seq

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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 <paulmck@linux.vnet.ibm.com>
This commit is contained in:
Paul E. McKenney 2018-04-27 14:54:46 -07:00
parent 78c5a67f17
commit c9a24e2d0c
1 changed files with 9 additions and 9 deletions
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18
kernel/rcu/tree.c
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@ -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 * 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 * leaf rcu_node structure, though it often will be). The gps parameter
* is the grace-period snapshot, which means that the quiescent states * 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. * must be held upon entry, and it is released before return.
*/ */
static void static void
@ -2257,7 +2257,7 @@ rcu_report_qs_rnp(unsigned long mask, struct rcu_state *rsp,
/* Walk up the rcu_node hierarchy. */ /* Walk up the rcu_node hierarchy. */
for (;;) { for (;;) {
if (!(rnp->qsmask & mask) || rnp->gpnum != gps) { if (!(rnp->qsmask & mask) || rnp->gp_seq != gps) {
/* /*
* Our bit has already been cleared, or the * Our bit has already been cleared, or the
@ -2335,8 +2335,8 @@ static void rcu_report_unblock_qs_rnp(struct rcu_state *rsp,
return; return;
} }
/* Report up the rest of the hierarchy, tracking current ->gpnum. */ /* Report up the rest of the hierarchy, tracking current ->gp_seq. */
gps = rnp->gpnum; gps = rnp->gp_seq;
mask = rnp->grpmask; mask = rnp->grpmask;
raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */
raw_spin_lock_rcu_node(rnp_p); /* irqs already 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; rnp = rdp->mynode;
raw_spin_lock_irqsave_rcu_node(rnp, flags); raw_spin_lock_irqsave_rcu_node(rnp, flags);
if (rdp->cpu_no_qs.b.norm || rdp->gpnum != rnp->gpnum || if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq ||
rnp->completed == rnp->gpnum || rdp->gpwrap) { rdp->gpwrap) {
/* /*
* The grace period in which this quiescent state was * 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); 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 */ /* ^^^ Released rnp->lock */
if (needwake) if (needwake)
rcu_gp_kthread_wake(rsp); 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) { if (mask != 0) {
/* Idle/offline CPUs, report (releases rnp->lock. */ /* Idle/offline CPUs, report (releases rnp->lock). */
rcu_report_qs_rnp(mask, rsp, rnp, rnp->gpnum, flags); rcu_report_qs_rnp(mask, rsp, rnp, rnp->gp_seq, flags);
} else { } else {
/* Nothing to do here, so just drop the lock. */ /* Nothing to do here, so just drop the lock. */
raw_spin_unlock_irqrestore_rcu_node(rnp, flags); raw_spin_unlock_irqrestore_rcu_node(rnp, flags);