kernel/linux.git/net/core/gen_stats.c, branch v6.12.80

net: Remove the obsolte u64_stats_fetch_*_irq() users (net).

2022-10-29T03:13:54+00:00

Now that the 32bit UP oddity is gone and 32bit uses always a sequence count, there is no need for the fetch_irq() variants anymore. Convert to the regular interface. Signed-off-by: Thomas Gleixner Signed-off-by: Sebastian Andrzej Siewior Acked-by: Peter Zijlstra (Intel) Signed-off-by: Jakub Kicinski

net: sched: fix misuse of qcpu->backlog in gnet_stats_add_queue_cpu

2022-08-17T02:38:20+00:00

In the gnet_stats_add_queue_cpu function, the qstats->qlen statistics are incorrectly set to qcpu->backlog. Fixes: 448e163f8b9b ("gen_stats: Add gnet_stats_add_queue()") Signed-off-by: Zhengchao Shao Link: https://lore.kernel.org/r/20220815030848.276746-1-shaozhengchao@huawei.com Signed-off-by: Jakub Kicinski

net: stats: Read the statistics in ___gnet_stats_copy_basic() instead of adding.

2021-10-21T11:47:56+00:00

Since the rework, the statistics code always adds up the byte and packet value(s). On 32bit architectures a seqcount_t is used in gnet_stats_basic_sync to ensure that the 64bit values are not modified during the read since two 32bit loads are required. The usage of a seqcount_t requires a lock to ensure that only one writer is active at a time. This lock leads to disabled preemption during the update. The lack of disabling preemption is now creating a warning as reported by Naresh since the query done by gnet_stats_copy_basic() is in preemptible context. For ___gnet_stats_copy_basic() there is no need to disable preemption since the update is performed on stack and can't be modified by another writer. Instead of disabling preemption, to avoid the warning, simply create a read function to just read the values and return as u64. Reported-by: Naresh Kamboju Fixes: 67c9e6270f301 ("net: sched: Protect Qdisc::bstats with u64_stats") Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

net: sched: Allow statistics reads from softirq.

2021-10-19T12:07:35+00:00

Eric reported that the rate estimator reads statics from the softirq which in turn triggers a warning introduced in the statistics rework. The warning is too cautious. The updates happen in the softirq context so reads from softirq are fine since the writes can not be preempted. The updates/writes happen during qdisc_run() which ensures one writer and the softirq context. The remaining bad context for reading statistics remains in hard-IRQ because it may preempt a writer. Fixes: 29cbcd8582837 ("net: sched: Remove Qdisc::running sequence counter") Reported-by: Eric Dumazet Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

net: sched: Remove Qdisc::running sequence counter

2021-10-18T11:54:41+00:00

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 Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

net: sched: Merge Qdisc::bstats and Qdisc::cpu_bstats data types

2021-10-18T11:54:41+00:00

The only factor differentiating per-CPU bstats data type (struct gnet_stats_basic_cpu) from the packed non-per-CPU one (struct gnet_stats_basic_packed) was a u64_stats sync point inside the former. The two data types are now equivalent: earlier commits added a u64_stats sync point to the latter. Combine both data types into "struct gnet_stats_basic_sync". This eliminates redundancy and simplifies the bstats read/write APIs. Use u64_stats_t for bstats "packets" and "bytes" data types. On 64-bit architectures, u64_stats sync points do not use sequence counter protection. Signed-off-by: Ahmed S. Darwish Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

net: sched: Use _bstats_update/set() instead of raw writes

2021-10-18T11:54:41+00:00

The Qdisc::running sequence counter, used to protect Qdisc::bstats reads from parallel writes, is in the process of being removed. Qdisc::bstats read/writes will synchronize using an internal u64_stats sync point instead. Modify all bstats writes to use _bstats_update(). This ensures that the internal u64_stats sync point is always acquired and released as appropriate. Signed-off-by: Ahmed S. Darwish Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

net: sched: Protect Qdisc::bstats with u64_stats

2021-10-18T11:54:41+00:00

The not-per-CPU variant of qdisc tc (traffic control) statistics, Qdisc::gnet_stats_basic_packed bstats, is protected with Qdisc::running sequence counter. This sequence counter is used for reliably protecting bstats reads from parallel writes. Meanwhile, the seqcount's write section covers a much wider area than bstats update: qdisc_run_begin() => qdisc_run_end(). That read/write section asymmetry can lead to needless retries of the read section. To prepare for removing the Qdisc::running sequence counter altogether, introduce a u64_stats sync point inside bstats instead. Modify _bstats_update() to start/end the bstats u64_stats write section. For bisectability, and finer commits granularity, the bstats read section is still protected with a Qdisc::running read/retry loop and qdisc_run_begin/end() still starts/ends that seqcount write section. Once all call sites are modified to use _bstats_update(), the Qdisc::running seqcount will be removed and bstats read/retry loop will be modified to utilize the internal u64_stats sync point. Note, using u64_stats implies no sequence counter protection for 64-bit architectures. This can lead to the statistics "packets" vs. "bytes" values getting out of sync on rare occasions. The individual values will still be valid. [bigeasy: Minor commit message edits, init all gnet_stats_basic_packed.] Signed-off-by: Ahmed S. Darwish Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

gen_stats: Move remaining users to gnet_stats_add_queue().

2021-10-18T11:54:41+00:00

The gnet_stats_queue::qlen member is only used in the SMP-case. qdisc_qstats_qlen_backlog() needs to add qdisc_qlen() to qstats.qlen to have the same value as that provided by qdisc_qlen_sum(). gnet_stats_copy_queue() needs to overwritte the resulting qstats.qlen field whith the caller submitted qlen value. It might be differ from the submitted value. Let both functions use gnet_stats_add_queue() and remove unused __gnet_stats_copy_queue(). Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller

gen_stats: Add gnet_stats_add_queue().

2021-10-18T11:54:41+00:00

This function will replace __gnet_stats_copy_queue(). It reads all arguments and adds them into the passed gnet_stats_queue argument. In contrast to __gnet_stats_copy_queue() it also copies the qlen member. Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: David S. Miller