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Message-ID: <20240418073248.2952954-2-edumazet@google.com>
Date: Thu, 18 Apr 2024 07:32:35 +0000
From: Eric Dumazet <edumazet@...gle.com>
To: "David S . Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>,
Paolo Abeni <pabeni@...hat.com>
Cc: Jamal Hadi Salim <jhs@...atatu.com>, Simon Horman <horms@...nel.org>,
"Toke Høiland-Jørgensen" <toke@...hat.com>, Cong Wang <xiyou.wangcong@...il.com>,
Jiri Pirko <jiri@...nulli.us>, netdev@...r.kernel.org, eric.dumazet@...il.com,
Eric Dumazet <edumazet@...gle.com>
Subject: [PATCH v2 net-next 01/14] net_sched: sch_fq: implement lockless fq_dump()
Instead of relying on RTNL, fq_dump() can use READ_ONCE()
annotations, paired with WRITE_ONCE() in fq_change()
v2: Addressed Simon feedback in V1: https://lore.kernel.org/netdev/20240416181915.GT2320920@kernel.org/
Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
net/sched/sch_fq.c | 108 +++++++++++++++++++++++++++++----------------
1 file changed, 69 insertions(+), 39 deletions(-)
diff --git a/net/sched/sch_fq.c b/net/sched/sch_fq.c
index cdf23ff16f40bf244bb822e76016fde44e0c439b..238974725679327b0a0d483c011e15fc94ab0878 100644
--- a/net/sched/sch_fq.c
+++ b/net/sched/sch_fq.c
@@ -106,6 +106,8 @@ struct fq_perband_flows {
int quantum; /* based on band nr : 576KB, 192KB, 64KB */
};
+#define FQ_PRIO2BAND_CRUMB_SIZE ((TC_PRIO_MAX + 1) >> 2)
+
struct fq_sched_data {
/* Read mostly cache line */
@@ -122,7 +124,7 @@ struct fq_sched_data {
u8 rate_enable;
u8 fq_trees_log;
u8 horizon_drop;
- u8 prio2band[(TC_PRIO_MAX + 1) >> 2];
+ u8 prio2band[FQ_PRIO2BAND_CRUMB_SIZE];
u32 timer_slack; /* hrtimer slack in ns */
/* Read/Write fields. */
@@ -159,7 +161,7 @@ struct fq_sched_data {
/* return the i-th 2-bit value ("crumb") */
static u8 fq_prio2band(const u8 *prio2band, unsigned int prio)
{
- return (prio2band[prio / 4] >> (2 * (prio & 0x3))) & 0x3;
+ return (READ_ONCE(prio2band[prio / 4]) >> (2 * (prio & 0x3))) & 0x3;
}
/*
@@ -888,7 +890,7 @@ static int fq_resize(struct Qdisc *sch, u32 log)
fq_rehash(q, old_fq_root, q->fq_trees_log, array, log);
q->fq_root = array;
- q->fq_trees_log = log;
+ WRITE_ONCE(q->fq_trees_log, log);
sch_tree_unlock(sch);
@@ -927,11 +929,15 @@ static const struct nla_policy fq_policy[TCA_FQ_MAX + 1] = {
static void fq_prio2band_compress_crumb(const u8 *in, u8 *out)
{
const int num_elems = TC_PRIO_MAX + 1;
+ u8 tmp[FQ_PRIO2BAND_CRUMB_SIZE];
int i;
- memset(out, 0, num_elems / 4);
+ memset(tmp, 0, sizeof(tmp));
for (i = 0; i < num_elems; i++)
- out[i / 4] |= in[i] << (2 * (i & 0x3));
+ tmp[i / 4] |= in[i] << (2 * (i & 0x3));
+
+ for (i = 0; i < FQ_PRIO2BAND_CRUMB_SIZE; i++)
+ WRITE_ONCE(out[i], tmp[i]);
}
static void fq_prio2band_decompress_crumb(const u8 *in, u8 *out)
@@ -958,7 +964,7 @@ static int fq_load_weights(struct fq_sched_data *q,
}
}
for (i = 0; i < FQ_BANDS; i++)
- q->band_flows[i].quantum = weights[i];
+ WRITE_ONCE(q->band_flows[i].quantum, weights[i]);
return 0;
}
@@ -1011,16 +1017,18 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt,
err = -EINVAL;
}
if (tb[TCA_FQ_PLIMIT])
- sch->limit = nla_get_u32(tb[TCA_FQ_PLIMIT]);
+ WRITE_ONCE(sch->limit,
+ nla_get_u32(tb[TCA_FQ_PLIMIT]));
if (tb[TCA_FQ_FLOW_PLIMIT])
- q->flow_plimit = nla_get_u32(tb[TCA_FQ_FLOW_PLIMIT]);
+ WRITE_ONCE(q->flow_plimit,
+ nla_get_u32(tb[TCA_FQ_FLOW_PLIMIT]));
if (tb[TCA_FQ_QUANTUM]) {
u32 quantum = nla_get_u32(tb[TCA_FQ_QUANTUM]);
if (quantum > 0 && quantum <= (1 << 20)) {
- q->quantum = quantum;
+ WRITE_ONCE(q->quantum, quantum);
} else {
NL_SET_ERR_MSG_MOD(extack, "invalid quantum");
err = -EINVAL;
@@ -1028,7 +1036,8 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt,
}
if (tb[TCA_FQ_INITIAL_QUANTUM])
- q->initial_quantum = nla_get_u32(tb[TCA_FQ_INITIAL_QUANTUM]);
+ WRITE_ONCE(q->initial_quantum,
+ nla_get_u32(tb[TCA_FQ_INITIAL_QUANTUM]));
if (tb[TCA_FQ_FLOW_DEFAULT_RATE])
pr_warn_ratelimited("sch_fq: defrate %u ignored.\n",
@@ -1037,17 +1046,19 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt,
if (tb[TCA_FQ_FLOW_MAX_RATE]) {
u32 rate = nla_get_u32(tb[TCA_FQ_FLOW_MAX_RATE]);
- q->flow_max_rate = (rate == ~0U) ? ~0UL : rate;
+ WRITE_ONCE(q->flow_max_rate,
+ (rate == ~0U) ? ~0UL : rate);
}
if (tb[TCA_FQ_LOW_RATE_THRESHOLD])
- q->low_rate_threshold =
- nla_get_u32(tb[TCA_FQ_LOW_RATE_THRESHOLD]);
+ WRITE_ONCE(q->low_rate_threshold,
+ nla_get_u32(tb[TCA_FQ_LOW_RATE_THRESHOLD]));
if (tb[TCA_FQ_RATE_ENABLE]) {
u32 enable = nla_get_u32(tb[TCA_FQ_RATE_ENABLE]);
if (enable <= 1)
- q->rate_enable = enable;
+ WRITE_ONCE(q->rate_enable,
+ enable);
else
err = -EINVAL;
}
@@ -1055,7 +1066,8 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt,
if (tb[TCA_FQ_FLOW_REFILL_DELAY]) {
u32 usecs_delay = nla_get_u32(tb[TCA_FQ_FLOW_REFILL_DELAY]) ;
- q->flow_refill_delay = usecs_to_jiffies(usecs_delay);
+ WRITE_ONCE(q->flow_refill_delay,
+ usecs_to_jiffies(usecs_delay));
}
if (!err && tb[TCA_FQ_PRIOMAP])
@@ -1065,21 +1077,26 @@ static int fq_change(struct Qdisc *sch, struct nlattr *opt,
err = fq_load_weights(q, tb[TCA_FQ_WEIGHTS], extack);
if (tb[TCA_FQ_ORPHAN_MASK])
- q->orphan_mask = nla_get_u32(tb[TCA_FQ_ORPHAN_MASK]);
+ WRITE_ONCE(q->orphan_mask,
+ nla_get_u32(tb[TCA_FQ_ORPHAN_MASK]));
if (tb[TCA_FQ_CE_THRESHOLD])
- q->ce_threshold = (u64)NSEC_PER_USEC *
- nla_get_u32(tb[TCA_FQ_CE_THRESHOLD]);
+ WRITE_ONCE(q->ce_threshold,
+ (u64)NSEC_PER_USEC *
+ nla_get_u32(tb[TCA_FQ_CE_THRESHOLD]));
if (tb[TCA_FQ_TIMER_SLACK])
- q->timer_slack = nla_get_u32(tb[TCA_FQ_TIMER_SLACK]);
+ WRITE_ONCE(q->timer_slack,
+ nla_get_u32(tb[TCA_FQ_TIMER_SLACK]));
if (tb[TCA_FQ_HORIZON])
- q->horizon = (u64)NSEC_PER_USEC *
- nla_get_u32(tb[TCA_FQ_HORIZON]);
+ WRITE_ONCE(q->horizon,
+ (u64)NSEC_PER_USEC *
+ nla_get_u32(tb[TCA_FQ_HORIZON]));
if (tb[TCA_FQ_HORIZON_DROP])
- q->horizon_drop = nla_get_u8(tb[TCA_FQ_HORIZON_DROP]);
+ WRITE_ONCE(q->horizon_drop,
+ nla_get_u8(tb[TCA_FQ_HORIZON_DROP]));
if (!err) {
@@ -1160,13 +1177,13 @@ static int fq_init(struct Qdisc *sch, struct nlattr *opt,
static int fq_dump(struct Qdisc *sch, struct sk_buff *skb)
{
struct fq_sched_data *q = qdisc_priv(sch);
- u64 ce_threshold = q->ce_threshold;
struct tc_prio_qopt prio = {
.bands = FQ_BANDS,
};
- u64 horizon = q->horizon;
struct nlattr *opts;
+ u64 ce_threshold;
s32 weights[3];
+ u64 horizon;
opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
if (opts == NULL)
@@ -1174,35 +1191,48 @@ static int fq_dump(struct Qdisc *sch, struct sk_buff *skb)
/* TCA_FQ_FLOW_DEFAULT_RATE is not used anymore */
+ ce_threshold = READ_ONCE(q->ce_threshold);
do_div(ce_threshold, NSEC_PER_USEC);
+
+ horizon = READ_ONCE(q->horizon);
do_div(horizon, NSEC_PER_USEC);
- if (nla_put_u32(skb, TCA_FQ_PLIMIT, sch->limit) ||
- nla_put_u32(skb, TCA_FQ_FLOW_PLIMIT, q->flow_plimit) ||
- nla_put_u32(skb, TCA_FQ_QUANTUM, q->quantum) ||
- nla_put_u32(skb, TCA_FQ_INITIAL_QUANTUM, q->initial_quantum) ||
- nla_put_u32(skb, TCA_FQ_RATE_ENABLE, q->rate_enable) ||
+ if (nla_put_u32(skb, TCA_FQ_PLIMIT,
+ READ_ONCE(sch->limit)) ||
+ nla_put_u32(skb, TCA_FQ_FLOW_PLIMIT,
+ READ_ONCE(q->flow_plimit)) ||
+ nla_put_u32(skb, TCA_FQ_QUANTUM,
+ READ_ONCE(q->quantum)) ||
+ nla_put_u32(skb, TCA_FQ_INITIAL_QUANTUM,
+ READ_ONCE(q->initial_quantum)) ||
+ nla_put_u32(skb, TCA_FQ_RATE_ENABLE,
+ READ_ONCE(q->rate_enable)) ||
nla_put_u32(skb, TCA_FQ_FLOW_MAX_RATE,
- min_t(unsigned long, q->flow_max_rate, ~0U)) ||
+ min_t(unsigned long,
+ READ_ONCE(q->flow_max_rate), ~0U)) ||
nla_put_u32(skb, TCA_FQ_FLOW_REFILL_DELAY,
- jiffies_to_usecs(q->flow_refill_delay)) ||
- nla_put_u32(skb, TCA_FQ_ORPHAN_MASK, q->orphan_mask) ||
+ jiffies_to_usecs(READ_ONCE(q->flow_refill_delay))) ||
+ nla_put_u32(skb, TCA_FQ_ORPHAN_MASK,
+ READ_ONCE(q->orphan_mask)) ||
nla_put_u32(skb, TCA_FQ_LOW_RATE_THRESHOLD,
- q->low_rate_threshold) ||
+ READ_ONCE(q->low_rate_threshold)) ||
nla_put_u32(skb, TCA_FQ_CE_THRESHOLD, (u32)ce_threshold) ||
- nla_put_u32(skb, TCA_FQ_BUCKETS_LOG, q->fq_trees_log) ||
- nla_put_u32(skb, TCA_FQ_TIMER_SLACK, q->timer_slack) ||
+ nla_put_u32(skb, TCA_FQ_BUCKETS_LOG,
+ READ_ONCE(q->fq_trees_log)) ||
+ nla_put_u32(skb, TCA_FQ_TIMER_SLACK,
+ READ_ONCE(q->timer_slack)) ||
nla_put_u32(skb, TCA_FQ_HORIZON, (u32)horizon) ||
- nla_put_u8(skb, TCA_FQ_HORIZON_DROP, q->horizon_drop))
+ nla_put_u8(skb, TCA_FQ_HORIZON_DROP,
+ READ_ONCE(q->horizon_drop)))
goto nla_put_failure;
fq_prio2band_decompress_crumb(q->prio2band, prio.priomap);
if (nla_put(skb, TCA_FQ_PRIOMAP, sizeof(prio), &prio))
goto nla_put_failure;
- weights[0] = q->band_flows[0].quantum;
- weights[1] = q->band_flows[1].quantum;
- weights[2] = q->band_flows[2].quantum;
+ weights[0] = READ_ONCE(q->band_flows[0].quantum);
+ weights[1] = READ_ONCE(q->band_flows[1].quantum);
+ weights[2] = READ_ONCE(q->band_flows[2].quantum);
if (nla_put(skb, TCA_FQ_WEIGHTS, sizeof(weights), &weights))
goto nla_put_failure;
--
2.44.0.683.g7961c838ac-goog
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