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net_sched: sch_choke: implement lockless choke_dump()

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Instead of relying on RTNL, choke_dump() can use READ_ONCE()
annotations, paired with WRITE_ONCE() ones in choke_change().

v2: added a WRITE_ONCE(p->Scell_log, Scell_log)
    per Simon feedback in V1
    Removed the READ_ONCE(q->limit) in choke_enqueue()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <horms@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Eric Dumazet 2024-04-18 07:32:38 +00:00 committed by David S. Miller
parent 8eb54a421a
commit 7253c1d1e7
2 changed files with 17 additions and 16 deletions
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12
include/net/red.h
View File

@ -233,10 +233,10 @@ static inline void red_set_parms(struct red_parms *p,
int delta = qth_max - qth_min;
u32 max_p_delta;
p->qth_min = qth_min << Wlog;
p->qth_max = qth_max << Wlog;
p->Wlog = Wlog;
p->Plog = Plog;
WRITE_ONCE(p->qth_min, qth_min << Wlog);
WRITE_ONCE(p->qth_max, qth_max << Wlog);
WRITE_ONCE(p->Wlog, Wlog);
WRITE_ONCE(p->Plog, Plog);
if (delta <= 0)
delta = 1;
p->qth_delta = delta;
@ -244,7 +244,7 @@ static inline void red_set_parms(struct red_parms *p,
max_P = red_maxp(Plog);
max_P *= delta; /* max_P = (qth_max - qth_min)/2^Plog */
}
p->max_P = max_P;
WRITE_ONCE(p->max_P, max_P);
max_p_delta = max_P / delta;
max_p_delta = max(max_p_delta, 1U);
p->max_P_reciprocal = reciprocal_value(max_p_delta);
@ -257,7 +257,7 @@ static inline void red_set_parms(struct red_parms *p,
p->target_min = qth_min + 2*delta;
p->target_max = qth_min + 3*delta;
p->Scell_log = Scell_log;
WRITE_ONCE(p->Scell_log, Scell_log);
p->Scell_max = (255 << Scell_log);
if (stab)

21
net/sched/sch_choke.c
View File

@ -405,8 +405,8 @@ static int choke_change(struct Qdisc *sch, struct nlattr *opt,
} else
sch_tree_lock(sch);
q->flags = ctl->flags;
q->limit = ctl->limit;
WRITE_ONCE(q->flags, ctl->flags);
WRITE_ONCE(q->limit, ctl->limit);
red_set_parms(&q->parms, ctl->qth_min, ctl->qth_max, ctl->Wlog,
ctl->Plog, ctl->Scell_log,
@ -431,15 +431,16 @@ static int choke_init(struct Qdisc *sch, struct nlattr *opt,
static int choke_dump(struct Qdisc *sch, struct sk_buff *skb)
{
struct choke_sched_data *q = qdisc_priv(sch);
u8 Wlog = READ_ONCE(q->parms.Wlog);
struct nlattr *opts = NULL;
struct tc_red_qopt opt = {
.limit = q->limit,
.flags = q->flags,
.qth_min = q->parms.qth_min >> q->parms.Wlog,
.qth_max = q->parms.qth_max >> q->parms.Wlog,
.Wlog = q->parms.Wlog,
.Plog = q->parms.Plog,
.Scell_log = q->parms.Scell_log,
.limit = READ_ONCE(q->limit),
.flags = READ_ONCE(q->flags),
.qth_min = READ_ONCE(q->parms.qth_min) >> Wlog,
.qth_max = READ_ONCE(q->parms.qth_max) >> Wlog,
.Wlog = Wlog,
.Plog = READ_ONCE(q->parms.Plog),
.Scell_log = READ_ONCE(q->parms.Scell_log),
};
opts = nla_nest_start_noflag(skb, TCA_OPTIONS);
@ -447,7 +448,7 @@ static int choke_dump(struct Qdisc *sch, struct sk_buff *skb)
goto nla_put_failure;
if (nla_put(skb, TCA_CHOKE_PARMS, sizeof(opt), &opt) ||
nla_put_u32(skb, TCA_CHOKE_MAX_P, q->parms.max_P))
nla_put_u32(skb, TCA_CHOKE_MAX_P, READ_ONCE(q->parms.max_P)))
goto nla_put_failure;
return nla_nest_end(skb, opts);