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29cbcd8582
The Qdisc::running sequence counter has two uses:
1. Reliably reading qdisc's tc statistics while the qdisc is running
(a seqcount read/retry loop at gnet_stats_add_basic()).
2. As a flag, indicating whether the qdisc in question is running
(without any retry loops).
For the first usage, the Qdisc::running sequence counter write section,
qdisc_run_begin() => qdisc_run_end(), covers a much wider area than what
is actually needed: the raw qdisc's bstats update. A u64_stats sync
point was thus introduced (in previous commits) inside the bstats
structure itself. A local u64_stats write section is then started and
stopped for the bstats updates.
Use that u64_stats sync point mechanism for the bstats read/retry loop
at gnet_stats_add_basic().
For the second qdisc->running usage, a __QDISC_STATE_RUNNING bit flag,
accessed with atomic bitops, is sufficient. Using a bit flag instead of
a sequence counter at qdisc_run_begin/end() and qdisc_is_running() leads
to the SMP barriers implicitly added through raw_read_seqcount() and
write_seqcount_begin/end() getting removed. All call sites have been
surveyed though, and no required ordering was identified.
Now that the qdisc->running sequence counter is no longer used, remove
it.
Note, using u64_stats implies no sequence counter protection for 64-bit
architectures. This can lead to the qdisc tc statistics "packets" vs.
"bytes" values getting out of sync on rare occasions. The individual
values will still be valid.
Signed-off-by: Ahmed S. Darwish <a.darwish@linutronix.de>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
84 lines
3 KiB
C
84 lines
3 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __NET_GEN_STATS_H
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#define __NET_GEN_STATS_H
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#include <linux/gen_stats.h>
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#include <linux/socket.h>
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#include <linux/rtnetlink.h>
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#include <linux/pkt_sched.h>
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/* Throughput stats.
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* Must be initialized beforehand with gnet_stats_basic_sync_init().
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*
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* If no reads can ever occur parallel to writes (e.g. stack-allocated
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* bstats), then the internal stat values can be written to and read
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* from directly. Otherwise, use _bstats_set/update() for writes and
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* gnet_stats_add_basic() for reads.
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*/
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struct gnet_stats_basic_sync {
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u64_stats_t bytes;
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u64_stats_t packets;
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struct u64_stats_sync syncp;
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} __aligned(2 * sizeof(u64));
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struct net_rate_estimator;
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struct gnet_dump {
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spinlock_t * lock;
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struct sk_buff * skb;
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struct nlattr * tail;
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/* Backward compatibility */
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int compat_tc_stats;
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int compat_xstats;
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int padattr;
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void * xstats;
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int xstats_len;
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struct tc_stats tc_stats;
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};
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void gnet_stats_basic_sync_init(struct gnet_stats_basic_sync *b);
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int gnet_stats_start_copy(struct sk_buff *skb, int type, spinlock_t *lock,
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struct gnet_dump *d, int padattr);
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int gnet_stats_start_copy_compat(struct sk_buff *skb, int type,
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int tc_stats_type, int xstats_type,
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spinlock_t *lock, struct gnet_dump *d,
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int padattr);
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int gnet_stats_copy_basic(struct gnet_dump *d,
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struct gnet_stats_basic_sync __percpu *cpu,
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struct gnet_stats_basic_sync *b, bool running);
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void gnet_stats_add_basic(struct gnet_stats_basic_sync *bstats,
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struct gnet_stats_basic_sync __percpu *cpu,
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struct gnet_stats_basic_sync *b, bool running);
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int gnet_stats_copy_basic_hw(struct gnet_dump *d,
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struct gnet_stats_basic_sync __percpu *cpu,
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struct gnet_stats_basic_sync *b, bool running);
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int gnet_stats_copy_rate_est(struct gnet_dump *d,
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struct net_rate_estimator __rcu **ptr);
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int gnet_stats_copy_queue(struct gnet_dump *d,
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struct gnet_stats_queue __percpu *cpu_q,
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struct gnet_stats_queue *q, __u32 qlen);
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void gnet_stats_add_queue(struct gnet_stats_queue *qstats,
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const struct gnet_stats_queue __percpu *cpu_q,
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const struct gnet_stats_queue *q);
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int gnet_stats_copy_app(struct gnet_dump *d, void *st, int len);
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int gnet_stats_finish_copy(struct gnet_dump *d);
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int gen_new_estimator(struct gnet_stats_basic_sync *bstats,
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struct gnet_stats_basic_sync __percpu *cpu_bstats,
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struct net_rate_estimator __rcu **rate_est,
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spinlock_t *lock,
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bool running, struct nlattr *opt);
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void gen_kill_estimator(struct net_rate_estimator __rcu **ptr);
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int gen_replace_estimator(struct gnet_stats_basic_sync *bstats,
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struct gnet_stats_basic_sync __percpu *cpu_bstats,
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struct net_rate_estimator __rcu **ptr,
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spinlock_t *lock,
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bool running, struct nlattr *opt);
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bool gen_estimator_active(struct net_rate_estimator __rcu **ptr);
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bool gen_estimator_read(struct net_rate_estimator __rcu **ptr,
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struct gnet_stats_rate_est64 *sample);
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#endif
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