net/sched: sch_htb: annotate data-races (II)

htb_dump_class_stats() will soon run locklessly.
(no RTNL, not qdisc spinlock).

Remove cl->xstats and replace it with two fields:

-	xstats_lends
-	xstats_borrows

Then use READ_ONCE()/WRITE_ONCE() annotations on them, and change
htb_dump_class_stats to use a private struct tc_htb_xstats.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Link: https://patch.msgid.link/20260514095935.3926276-4-edumazet@google.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

diff --git a/net/sched/sch_htb.c b/net/sched/sch_htb.c
index 5bf1889bc0300e8e3a61d56ddcf1bb1402955107..353467eb7611be45c6a9c92a0dcd4357d136a232 100644 (file)
--- a/net/sched/sch_htb.c
+++ b/net/sched/sch_htb.c
@@ -114,7 +114,8 @@ struct htb_class {
         */
        struct gnet_stats_basic_sync bstats;
        struct gnet_stats_basic_sync bstats_bias;
-       struct tc_htb_xstats    xstats; /* our special stats */
+       u32                     xstats_lends;
+       u32                     xstats_borrows;
 
        /* token bucket parameters */
        s64                     tokens, ctokens;/* current number of tokens */
@@ -707,10 +708,10 @@ static void htb_charge_class(struct htb_sched *q, struct htb_class *cl,
                diff = min_t(s64, q->now - cl->t_c, cl->mbuffer);
                if (cl->level >= level) {
                        if (cl->level == level)
-                               cl->xstats.lends++;
+                               WRITE_ONCE(cl->xstats_lends, cl->xstats_lends + 1);
                        htb_accnt_tokens(cl, bytes, diff);
                } else {
-                       cl->xstats.borrows++;
+                       WRITE_ONCE(cl->xstats_borrows, cl->xstats_borrows + 1);
                        cl->tokens += diff;     /* we moved t_c; update tokens */
                }
                htb_accnt_ctokens(cl, bytes, diff);
@@ -1319,6 +1320,10 @@ htb_dump_class_stats(struct Qdisc *sch, unsigned long arg, struct gnet_dump *d)
 {
        struct htb_class *cl = (struct htb_class *)arg;
        struct htb_sched *q = qdisc_priv(sch);
+       struct tc_htb_xstats xstats = {
+               .lends = READ_ONCE(cl->xstats_lends),
+               .borrows = READ_ONCE(cl->xstats_borrows),
+       };
        struct gnet_stats_queue qs = {
                .drops = cl->drops,
                .overlimits = cl->overlimits,
@@ -1328,10 +1333,10 @@ htb_dump_class_stats(struct Qdisc *sch, unsigned long arg, struct gnet_dump *d)
        if (!cl->level && cl->leaf.q)
                qdisc_qstats_qlen_backlog(cl->leaf.q, &qlen, &qs.backlog);
 
-       cl->xstats.tokens = clamp_t(s64, PSCHED_NS2TICKS(cl->tokens),
-                                   INT_MIN, INT_MAX);
-       cl->xstats.ctokens = clamp_t(s64, PSCHED_NS2TICKS(cl->ctokens),
-                                    INT_MIN, INT_MAX);
+       xstats.tokens = clamp_t(s64, PSCHED_NS2TICKS(cl->tokens),
+                               INT_MIN, INT_MAX);
+       xstats.ctokens = clamp_t(s64, PSCHED_NS2TICKS(cl->ctokens),
+                                INT_MIN, INT_MAX);
 
        if (q->offload) {
                if (!cl->level) {
@@ -1352,7 +1357,7 @@ htb_dump_class_stats(struct Qdisc *sch, unsigned long arg, struct gnet_dump *d)
            gnet_stats_copy_queue(d, NULL, &qs, qlen) < 0)
                return -1;
 
-       return gnet_stats_copy_app(d, &cl->xstats, sizeof(cl->xstats));
+       return gnet_stats_copy_app(d, &xstats, sizeof(xstats));
 }
 
 static struct netdev_queue *