diff options
| author | David S. Miller <davem@davemloft.net> | 2021-10-18 12:54:41 +0100 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2021-10-18 12:54:41 +0100 |
| commit | f8ba22a14268b432f685fd8463a958a3594b7fb6 (patch) | |
| tree | 6feb3ee12123611d1988813e9e139c4c81280aec /include/linux/netdevice.h | |
| parent | 254ec036db1123b10e23e1412c191a3cf70dce71 (diff) | |
| parent | 29cbcd85828372333aa87542c51f2b2b0fd4380c (diff) | |
Merge branch 'remove-qdisc-running-counter'
Sebastian Andrzej Siewior says:
====================
Try to simplify the gnet_stats and remove qdisc->running sequence counter.
The first few patches is a follow up to
https://lore.kernel.org/all/20211007175000.2334713-1-bigeasy@linutronix.de/
The remaining patches (#5+) remove the seqcount_t (Qdisc::running) from
the Qdisc. The statistics (Qdisc::bstats and Qdisc::cpu_bstats) use
u64_stats_t and the "running state" is now represented by a bit in
Qdisc::state.
By removing the seqcount_t from Qdisc and decoupling the bstats
statistics from the seqcount_t it is possible to query the statistics
even if the Qdisc is running instead of waiting until it is idle again.
The try-lock like usage of the seqcount_t in qdisc_run_begin() is
problematic on PREEMPT_RT. Inside the qdisc_run_begin/end() qdisc->running
sequence counter write sections, at sch_direct_xmit(), the seqcount write
serialization lock is released then re-acquired. This is fine for !RT, because
the writer is in a BH disabled region and there is a no in-IRQ reader. For RT
though, BH sections are preemptible. The earlier introduced seqcount_LOCKNAME_t
mechanism, which for RT the reader acquires then relesaes the write
serailization lock to avoid infinite spinning if it preempts a seqcount write
section, cannot work: the qdisc->running write serialization lock is already
intermittingly released inside the seqcount write section.
====================
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include/linux/netdevice.h')
| -rw-r--r-- | include/linux/netdevice.h | 4 |
1 files changed, 0 insertions, 4 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 173984414f38..f9cd6fea213f 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -1916,7 +1916,6 @@ enum netdev_ml_priv_type { * @sfp_bus: attached &struct sfp_bus structure. * * @qdisc_tx_busylock: lockdep class annotating Qdisc->busylock spinlock - * @qdisc_running_key: lockdep class annotating Qdisc->running seqcount * * @proto_down: protocol port state information can be sent to the * switch driver and used to set the phys state of the @@ -2250,7 +2249,6 @@ struct net_device { struct phy_device *phydev; struct sfp_bus *sfp_bus; struct lock_class_key *qdisc_tx_busylock; - struct lock_class_key *qdisc_running_key; bool proto_down; unsigned wol_enabled:1; unsigned threaded:1; @@ -2360,13 +2358,11 @@ static inline void netdev_for_each_tx_queue(struct net_device *dev, #define netdev_lockdep_set_classes(dev) \ { \ static struct lock_class_key qdisc_tx_busylock_key; \ - static struct lock_class_key qdisc_running_key; \ static struct lock_class_key qdisc_xmit_lock_key; \ static struct lock_class_key dev_addr_list_lock_key; \ unsigned int i; \ \ (dev)->qdisc_tx_busylock = &qdisc_tx_busylock_key; \ - (dev)->qdisc_running_key = &qdisc_running_key; \ lockdep_set_class(&(dev)->addr_list_lock, \ &dev_addr_list_lock_key); \ for (i = 0; i < (dev)->num_tx_queues; i++) \ |