kernel/linux.git/include/net/sch_generic.h, branch v5.15.89

net: sched: delete duplicate cleanup of backlog and qlen

2022-10-29T08:12:57+00:00

[ Upstream commit c19d893fbf3f2f8fa864ae39652c7fee939edde2 ] qdisc_reset() is clearing qdisc->q.qlen and qdisc->qstats.backlog _after_ calling qdisc->ops->reset. There is no need to clear them again in the specific reset function. Signed-off-by: Zhengchao Shao Link: https://lore.kernel.org/r/20220824005231.345727-1-shaozhengchao@huawei.com Signed-off-by: Paolo Abeni Stable-dep-of: 2a3fc78210b9 ("net: sched: sfb: fix null pointer access issue when sfb_init() fails") Signed-off-by: Sasha Levin

net: sched: add barrier to fix packet stuck problem for lockless qdisc

2022-06-14T16:36:12+00:00

[ Upstream commit 2e8728c955ce0624b958eee6e030a37aca3a5d86 ] In qdisc_run_end(), the spin_unlock() only has store-release semantic, which guarantees all earlier memory access are visible before it. But the subsequent test_bit() has no barrier semantics so may be reordered ahead of the spin_unlock(). The store-load reordering may cause a packet stuck problem. The concurrent operations can be described as below, CPU 0 | CPU 1 qdisc_run_end() | qdisc_run_begin() . | . ----> /* may be reorderd here */ | . | . | . | spin_unlock() | set_bit() | . | smp_mb__after_atomic() ---- test_bit() | spin_trylock() . | . Consider the following sequence of events: CPU 0 reorder test_bit() ahead and see MISSED = 0 CPU 1 calls set_bit() CPU 1 calls spin_trylock() and return fail CPU 0 executes spin_unlock() At the end of the sequence, CPU 0 calls spin_unlock() and does nothing because it see MISSED = 0. The skb on CPU 1 has beed enqueued but no one take it, until the next cpu pushing to the qdisc (if ever ...) will notice and dequeue it. This patch fix this by adding one explicit barrier. As spin_unlock() and test_bit() ordering is a store-load ordering, a full memory barrier smp_mb() is needed here. Fixes: a90c57f2cedd ("net: sched: fix packet stuck problem for lockless qdisc") Signed-off-by: Guoju Fang Link: https://lore.kernel.org/r/20220528101628.120193-1-gjfang@linux.alibaba.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: sched: fixed barrier to prevent skbuff sticking in qdisc backlog

2022-06-14T16:36:10+00:00

[ Upstream commit a54ce3703613e41fe1d98060b62ec09a3984dc28 ] In qdisc_run_begin(), smp_mb__before_atomic() used before test_bit() does not provide any ordering guarantee as test_bit() is not an atomic operation. This, added to the fact that the spin_trylock() call at the beginning of qdisc_run_begin() does not guarantee acquire semantics if it does not grab the lock, makes it possible for the following statement : if (test_bit(__QDISC_STATE_MISSED, &qdisc->state)) to be executed before an enqueue operation called before qdisc_run_begin(). As a result the following race can happen : CPU 1 CPU 2 qdisc_run_begin() qdisc_run_begin() /* true */ set(MISSED) . /* returns false */ . . /* sees MISSED = 1 */ . /* so qdisc not empty */ . __qdisc_run() . . . pfifo_fast_dequeue() ----> /* may be done here */ . | . clear(MISSED) | . . | . smp_mb __after_atomic(); | . . | . /* recheck the queue */ | . /* nothing => exit */ | enqueue(skb1) | . | qdisc_run_begin() | . | spin_trylock() /* fail */ | . | smp_mb__before_atomic() /* not enough */ | . ---- if (test_bit(MISSED)) return false; /* exit */ In the above scenario, CPU 1 and CPU 2 both try to grab the qdisc->seqlock at the same time. Only CPU 2 succeeds and enters the bypass code path, where it emits its skb then calls __qdisc_run(). CPU1 fails, sets MISSED and goes down the traditionnal enqueue() + dequeue() code path. But when executing qdisc_run_begin() for the second time, after enqueuing its skbuff, it sees the MISSED bit still set (by itself) and consequently chooses to exit early without setting it again nor trying to grab the spinlock again. Meanwhile CPU2 has seen MISSED = 1, cleared it, checked the queue and found it empty, so it returned. At the end of the sequence, we end up with skb1 enqueued in the backlog, both CPUs out of __dev_xmit_skb(), the MISSED bit not set, and no __netif_schedule() called made. skb1 will now linger in the qdisc until somebody later performs a full __qdisc_run(). Associated to the bypass capacity of the qdisc, and the ability of the TCP layer to avoid resending packets which it knows are still in the qdisc, this can lead to serious traffic "holes" in a TCP connection. We fix this by replacing the smp_mb__before_atomic() / test_bit() / set_bit() / smp_mb__after_atomic() sequence inside qdisc_run_begin() by a single test_and_set_bit() call, which is more concise and enforces the needed memory barriers. Fixes: 89837eb4b246 ("net: sched: add barrier to ensure correct ordering for lockless qdisc") Signed-off-by: Vincent Ray Signed-off-by: Eric Dumazet Link: https://lore.kernel.org/r/20220526001746.2437669-1-eric.dumazet@gmail.com Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net_sched: restore "mpu xxx" handling

2022-01-27T10:05:40+00:00

commit fb80445c438c78b40b547d12b8d56596ce4ccfeb upstream. commit 56b765b79e9a ("htb: improved accuracy at high rates") broke "overhead X", "linklayer atm" and "mpu X" attributes. "overhead X" and "linklayer atm" have already been fixed. This restores the "mpu X" handling, as might be used by DOCSIS or Ethernet shaping: tc class add ... htb rate X overhead 4 mpu 64 The code being fixed is used by htb, tbf and act_police. Cake has its own mpu handling. qdisc_calculate_pkt_len still uses the size table containing values adjusted for mpu by user space. iproute2 tc has always passed mpu into the kernel via a tc_ratespec structure, but the kernel never directly acted on it, merely stored it so that it could be read back by `tc class show`. Rather, tc would generate length-to-time tables that included the mpu (and linklayer) in their construction, and the kernel used those tables. Since v3.7, the tables were no longer used. Along with "mpu", this also broke "overhead" and "linklayer" which were fixed in 01cb71d2d47b ("net_sched: restore "overhead xxx" handling", v3.10) and 8a8e3d84b171 ("net_sched: restore "linklayer atm" handling", v3.11). "overhead" was fixed by simply restoring use of tc_ratespec::overhead - this had originally been used by the kernel but was initially omitted from the new non-table-based calculations. "linklayer" had been handled in the table like "mpu", but the mode was not originally passed in tc_ratespec. The new implementation was made to handle it by getting new versions of tc to pass the mode in an extended tc_ratespec, and for older versions of tc the table contents were analysed at load time to deduce linklayer. As "mpu" has always been given to the kernel in tc_ratespec, accompanying the mpu-based table, we can restore system functionality with no userspace change by making the kernel act on the tc_ratespec value. Fixes: 56b765b79e9a ("htb: improved accuracy at high rates") Signed-off-by: Kevin Bracey Cc: Eric Dumazet Cc: Jiri Pirko Cc: Vimalkumar Link: https://lore.kernel.org/r/20220112170210.1014351-1-kevin@bracey.fi Signed-off-by: Jakub Kicinski Signed-off-by: Greg Kroah-Hartman

net/sched: Extend qdisc control block with tc control block

2022-01-05T11:42:33+00:00

[ Upstream commit ec624fe740b416fb68d536b37fb8eef46f90b5c2 ] BPF layer extends the qdisc control block via struct bpf_skb_data_end and because of that there is no more room to add variables to the qdisc layer control block without going over the skb->cb size. Extend the qdisc control block with a tc control block, and move all tc related variables to there as a pre-step for extending the tc control block with additional members. Signed-off-by: Paul Blakey Signed-off-by: Jakub Kicinski Signed-off-by: Sasha Levin

net: sched: update default qdisc visibility after Tx queue cnt changes

2021-11-18T18:16:10+00:00

[ Upstream commit 1e080f17750d1083e8a32f7b350584ae1cd7ff20 ] mq / mqprio make the default child qdiscs visible. They only do so for the qdiscs which are within real_num_tx_queues when the device is registered. Depending on order of calls in the driver, or if user space changes config via ethtool -L the number of qdiscs visible under tc qdisc show will differ from the number of queues. This is confusing to users and potentially to system configuration scripts which try to make sure qdiscs have the right parameters. Add a new Qdisc_ops callback and make relevant qdiscs TTRT. Note that this uncovers the "shortcut" created by commit 1f27cde313d7 ("net: sched: use pfifo_fast for non real queues") The default child qdiscs beyond initial real_num_tx are always pfifo_fast, no matter what the sysfs setting is. Fixing this gets a little tricky because we'd need to keep a reference on whatever the default qdisc was at the time of creation. In practice this is likely an non-issue the qdiscs likely have to be configured to non-default settings, so whatever user space is doing such configuration can replace the pfifos... now that it will see them. Reported-by: Matthew Massey Reviewed-by: Dave Taht Signed-off-by: Jakub Kicinski Signed-off-by: David S. Miller Signed-off-by: Sasha Levin

net_sched: refactor TC action init API

2021-08-02T09:24:38+00:00

TC action ->init() API has 10 parameters, it becomes harder to read. Some of them are just boolean and can be replaced by flags. Similarly for the internal API tcf_action_init() and tcf_exts_validate(). This patch converts them to flags and fold them into the upper 16 bits of "flags", whose lower 16 bits are still reserved for user-space. More specifically, the following kernel flags are introduced: TCA_ACT_FLAGS_POLICE replace 'name' in a few contexts, to distinguish whether it is compatible with policer. TCA_ACT_FLAGS_BIND replaces 'bind', to indicate whether this action is bound to a filter. TCA_ACT_FLAGS_REPLACE replaces 'ovr' in most contexts, means we are replacing an existing action. TCA_ACT_FLAGS_NO_RTNL replaces 'rtnl_held' but has the opposite meaning, because we still hold RTNL in most cases. The only user-space flag TCA_ACT_FLAGS_NO_PERCPU_STATS is untouched and still stored as before. I have tested this patch with tdc and I do not see any failure related to this patch. Tested-by: Vlad Buslov Acked-by: Jamal Hadi Salim Cc: Jiri Pirko Signed-off-by: Cong Wang Signed-off-by: David S. Miller

Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

2021-06-29T22:45:27+00:00

Trivial conflict in net/netfilter/nf_tables_api.c. Duplicate fix in tools/testing/selftests/net/devlink_port_split.py - take the net-next version. skmsg, and L4 bpf - keep the bpf code but remove the flags and err params. Signed-off-by: Jakub Kicinski

net: sched: remove qdisc->empty for lockless qdisc

2021-06-23T19:17:35+00:00

As MISSED and DRAINING state are used to indicate a non-empty qdisc, qdisc->empty is not longer needed, so remove it. Acked-by: Jakub Kicinski Tested-by: Vladimir Oltean # flexcan Signed-off-by: Yunsheng Lin Signed-off-by: David S. Miller

net: sched: implement TCQ_F_CAN_BYPASS for lockless qdisc

2021-06-23T19:17:35+00:00

Currently pfifo_fast has both TCQ_F_CAN_BYPASS and TCQ_F_NOLOCK flag set, but queue discipline by-pass does not work for lockless qdisc because skb is always enqueued to qdisc even when the qdisc is empty, see __dev_xmit_skb(). This patch calls sch_direct_xmit() to transmit the skb directly to the driver for empty lockless qdisc, which aviod enqueuing and dequeuing operation. As qdisc->empty is not reliable to indicate a empty qdisc because there is a time window between enqueuing and setting qdisc->empty. So we use the MISSED state added in commit a90c57f2cedd ("net: sched: fix packet stuck problem for lockless qdisc"), which indicate there is lock contention, suggesting that it is better not to do the qdisc bypass in order to avoid packet out of order problem. In order to make MISSED state reliable to indicate a empty qdisc, we need to ensure that testing and clearing of MISSED state is within the protection of qdisc->seqlock, only setting MISSED state can be done without the protection of qdisc->seqlock. A MISSED state testing is added without the protection of qdisc->seqlock to aviod doing unnecessary spin_trylock() for contention case. As the enqueuing is not within the protection of qdisc->seqlock, there is still a potential data race as mentioned by Jakub [1]: thread1 thread2 thread3 qdisc_run_begin() # true qdisc_run_begin(q) set(MISSED) pfifo_fast_dequeue clear(MISSED) # recheck the queue qdisc_run_end() enqueue skb1 qdisc empty # true qdisc_run_begin() # true sch_direct_xmit() # skb2 qdisc_run_begin() set(MISSED) When above happens, skb1 enqueued by thread2 is transmited after skb2 is transmited by thread3 because MISSED state setting and enqueuing is not under the qdisc->seqlock. If qdisc bypass is disabled, skb1 has better chance to be transmited quicker than skb2. This patch does not take care of the above data race, because we view this as similar as below: Even at the same time CPU1 and CPU2 write the skb to two socket which both heading to the same qdisc, there is no guarantee that which skb will hit the qdisc first, because there is a lot of factor like interrupt/softirq/cache miss/scheduling afffecting that. There are below cases that need special handling: 1. When MISSED state is cleared before another round of dequeuing in pfifo_fast_dequeue(), and __qdisc_run() might not be able to dequeue all skb in one round and call __netif_schedule(), which might result in a non-empty qdisc without MISSED set. In order to avoid this, the MISSED state is set for lockless qdisc and __netif_schedule() will be called at the end of qdisc_run_end. 2. The MISSED state also need to be set for lockless qdisc instead of calling __netif_schedule() directly when requeuing a skb for a similar reason. 3. For netdev queue stopped case, the MISSED case need clearing while the netdev queue is stopped, otherwise there may be unnecessary __netif_schedule() calling. So a new DRAINING state is added to indicate this case, which also indicate a non-empty qdisc. 4. As there is already netif_xmit_frozen_or_stopped() checking in dequeue_skb() and sch_direct_xmit(), which are both within the protection of qdisc->seqlock, but the same checking in __dev_xmit_skb() is without the protection, which might cause empty indication of a lockless qdisc to be not reliable. So remove the checking in __dev_xmit_skb(), and the checking in the protection of qdisc->seqlock seems enough to avoid the cpu consumption problem for netdev queue stopped case. 1. https://lkml.org/lkml/2021/5/29/215 Acked-by: Jakub Kicinski Tested-by: Vladimir Oltean # flexcan Signed-off-by: Yunsheng Lin Signed-off-by: David S. Miller