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srcu: Make srcu_funnel_gp_start() cache ->mynode in snp_leaf

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Currently, the srcu_funnel_gp_start() walks its local variable snp up the
tree and reloads sdp->mynode whenever it is necessary to check whether
it is still at the leaf srcu_node level.  This works, but is a bit more
obtuse than absolutely necessary.  In addition, upcoming commits will
dynamically size srcu_struct structures, in which case sdp->mynode will
no longer necessarily be a constant, and this commit helps prepare for
that dynamic sizing.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Paul E. McKenney 2022-01-20 13:39:33 -08:00
parent 95ebe80d99
commit 7b9e9b5856
1 changed files with 7 additions and 6 deletions
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13
kernel/rcu/srcutree.c
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@ -632,20 +632,21 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp,
{
unsigned long flags;
int idx = rcu_seq_ctr(s) % ARRAY_SIZE(sdp->mynode->srcu_have_cbs);
struct srcu_node *snp = sdp->mynode;
struct srcu_node *snp;
struct srcu_node *snp_leaf = sdp->mynode;
unsigned long snp_seq;
/* Each pass through the loop does one level of the srcu_node tree. */
for (; snp != NULL; snp = snp->srcu_parent) {
if (rcu_seq_done(&ssp->srcu_gp_seq, s) && snp != sdp->mynode)
for (snp = snp_leaf; snp != NULL; snp = snp->srcu_parent) {
if (rcu_seq_done(&ssp->srcu_gp_seq, s) && snp != snp_leaf)
return; /* GP already done and CBs recorded. */
spin_lock_irqsave_rcu_node(snp, flags);
if (ULONG_CMP_GE(snp->srcu_have_cbs[idx], s)) {
snp_seq = snp->srcu_have_cbs[idx];
if (snp == sdp->mynode && snp_seq == s)
if (snp == snp_leaf && snp_seq == s)
snp->srcu_data_have_cbs[idx] |= sdp->grpmask;
spin_unlock_irqrestore_rcu_node(snp, flags);
if (snp == sdp->mynode && snp_seq != s) {
if (snp == snp_leaf && snp_seq != s) {
srcu_schedule_cbs_sdp(sdp, do_norm
? SRCU_INTERVAL
: 0);
@ -656,7 +657,7 @@ static void srcu_funnel_gp_start(struct srcu_struct *ssp, struct srcu_data *sdp,
return;
}
snp->srcu_have_cbs[idx] = s;
if (snp == sdp->mynode)
if (snp == snp_leaf)
snp->srcu_data_have_cbs[idx] |= sdp->grpmask;
if (!do_norm && ULONG_CMP_LT(snp->srcu_gp_seq_needed_exp, s))
WRITE_ONCE(snp->srcu_gp_seq_needed_exp, s);