Commit fadbe52b authored by Jakub Kicinski's avatar Jakub Kicinski
Browse files

Merge branch 'net-sysfs-remove-the-rtnl_trylock-restart_syscall-construction' 

Antoine Tenart says:

====================
net-sysfs: remove the rtnl_trylock/restart_syscall construction

The series initially aimed at improving spins (and thus delays) while
accessing net sysfs under rtnl lock contention[1]. The culprit was the
trylock/restart_syscall constructions. There wasn't much interest at the
time but it got traction recently for other reasons (lowering the rtnl
lock pressure).

Since v1[2]:

- Do not export rtnl_lock_interruptible [Stephen].
- Add netdev_warn_once messages in rx_queue_add_kobject [Jakub].

Since the RFC[1]:

- Limit the breaking of the sysfs protection to sysfs_rtnl_lock() only
  as this is not needed in the whole rtnl locking section thanks to the
  additional check on dev_isalive(). This simplifies error handling as
  well as the unlocking path.
- Used an interruptible version of rtnl_lock, as done by Jakub in
  his experiments.
- Removed a WARN_ONCE_ONCE [Greg].
- Removed explicit inline markers [Stephen].

Most of the reasoning is explained in comments added in patch 1. This
was tested by stress-testing net sysfs attributes (read/write ops) while
adding/removing queues and adding/removing veths, all in parallel. I
also used an OCP single node cluster, spawning lots of pods.

[1] https://lore.kernel.org/all/20231018154804.420823-1-atenart@kernel.org/T/
[2] https://lore.kernel.org/all/20250117102612.132644-1-atenart@kernel.org/T/
====================

Link: https://patch.msgid.link/20250204170314.146022-1-atenart@kernel.org


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parents 0bea93fd b0b6fcfa

include/linux/netdevice.h

+1 −0
Original line number Diff line number Diff line
@@ -658,6 +658,7 @@ struct netdev_queue { 
	struct Qdisc __rcu	*qdisc_sleeping;

#ifdef CONFIG_SYSFS

	struct kobject		kobj;

	const struct attribute_group	**groups;

#endif

	unsigned long		tx_maxrate;

	/*

include/linux/rtnetlink.h

+1 −0
Original line number Diff line number Diff line
@@ -43,6 +43,7 @@ extern void rtnl_lock(void); 
extern void rtnl_unlock(void);

extern int rtnl_trylock(void);

extern int rtnl_is_locked(void);

extern int rtnl_lock_interruptible(void);

extern int rtnl_lock_killable(void);

extern bool refcount_dec_and_rtnl_lock(refcount_t *r);

include/net/netdev_rx_queue.h

+1 −0
Original line number Diff line number Diff line
@@ -16,6 +16,7 @@ struct netdev_rx_queue { 
	struct rps_dev_flow_table __rcu	*rps_flow_table;

#endif

	struct kobject			kobj;

	const struct attribute_group	**groups;

	struct net_device		*dev;

	netdevice_tracker		dev_tracker;

net/core/net-sysfs.c

+275 −117

File changed.

Preview size limit exceeded, changes collapsed.

net/core/rtnetlink.c

+5 −0
Original line number Diff line number Diff line
@@ -80,6 +80,11 @@ void rtnl_lock(void) 
}

EXPORT_SYMBOL(rtnl_lock);



int rtnl_lock_interruptible(void)

{

	return mutex_lock_interruptible(&rtnl_mutex);

}



int rtnl_lock_killable(void)

{

	return mutex_lock_killable(&rtnl_mutex);