[PATCH RFC 00/25] Replacing net_mutex with rw_semaphore

Kirill Tkhai
2017-11-17T18:27:13Z

Hi,

this is continuation of discussion from here:

https://lkml.org/lkml/2017/11/14/298

The plan has changed a little bit, so I'd be happy to hear
people's comments, before I dived into all 400+ pernet subsys
and devices.

The patch set adds pernet sys list ahead of subsys and device,
and it's used for pernet_operations, which may be executed
in parallel with any other pernet_operations methods. Also,
some high-priority ops converted (up to registered using
postcore_initcall(), and some subsys_initcall()) in order
of appearance. The sequence in setup_net() is following:

1)execute all the callbacks from pernet_sys list
2)lock net_mutex
3)execute all the callbacks from pernet_subsys list
4)execute all the callbacks from pernet_device list
5)unlock net_mutex

There was not pernet_operations, requiring additional
synchronization, yet, but I've bumped in another problem.
The problem is that some drivers may be compiled as modules
and as kernel-image part. They register pernet_operations
from device_initcall() for example. This initcall executes
in different time comparing to in-kernel built-in only
drivers.

Imagine, we have three state driverA, and boolean driverB.
driverA registers pernet_subsys from subsys_initcall().
driverB registers pernet_subsys from fs_initcall().
So, here we have two cases:

driverA is module driverA is built-in
-------------------- -------------------
register driverB ops register driverA ops
register driverA ops register driverB ops

So, the order is different. When converting driver one-by-one,
it's impossible to make the order true for all .config
states, because of the above. So, the bisect won't work.

And it seems, it's just the same as to convert pernet_operations
from all the files in file alphabetical order. What do you
think about this? (Note, the patches has no such a problem
at the moment, as there are all in-kernel early core drivers).

Maybe there are another comments on the code.
---

Kirill Tkhai (25):
net: Assign net to net_namespace_list in setup_net()
net: Cleanup copy_net_ns()
net: Introduce net_sem for protection of pernet_list
net: Move mutex_unlock() in cleanup_net() up
net: Add primitives to update heads of pernet_list sublists
net: Add pernet sys and registration functions
net: Make sys sublist pernet_operations executed out of net_mutex
net: Move proc_net_ns_ops to pernet_sys list
net: Move net_ns_ops to pernet_sys list
net: Move sysctl_pernet_ops to pernet_sys list
net: Move netfilter_net_ops to pernet_sys list
net: Move nf_log_net_ops to pernet_sys list
net: Move net_inuse_ops to pernet_sys list
net: Move net_defaults_ops to pernet_sys list
net: Move netlink_net_ops to pernet_sys list
net: Move rtnetlink_net_ops to pernet_sys list
net: Move audit_net_ops to pernet_sys list
net: Move uevent_net_ops to pernet_sys list
net: Move proto_net_ops to pernet_sys list
net: Move pernet_subsys, registered via net_dev_init(), to pernet_sys list
net: Move fib_* pernet_operations, registered via subsys_initcall(), to pernet_sys list
net: Move subsys_initcall() registered pernet_operations from net/sched to pernet_sys list
net: Move genl_pernet_ops to pernet_sys list
net: Move wext_pernet_ops to pernet_sys list
net: Move sysctl_core_ops to pernet_sys list

fs/proc/proc_net.c | 2
include/linux/rtnetlink.h | 1
include/net/net_namespace.h | 2
kernel/audit.c | 2
lib/kobject_uevent.c | 2
net/core/dev.c | 2
net/core/fib_notifier.c | 2
net/core/fib_rules.c | 2
net/core/net-procfs.c | 4 -
net/core/net_namespace.c | 203 +++++++++++++++++++++++++++++++++----------
net/core/rtnetlink.c | 6 +
net/core/sock.c | 4 -
net/core/sysctl_net_core.c | 2
net/netfilter/core.c | 2
net/netfilter/nf_log.c | 2
net/netlink/af_netlink.c | 2
net/netlink/genetlink.c | 2
net/sched/act_api.c | 2
net/sched/sch_api.c | 2
net/sysctl_net.c | 2
net/wireless/wext-core.c | 2
21 files changed, 183 insertions(+), 67 deletions(-)

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