The netlink connector uses its own workqueue to relay the datas sent
from userspace to the appropriate callback. If you launch the test
from Documentation/connector and change it a bit to send a high flow
of data, you will see thousands of events coming to the "cqueue"
workqueue by looking at the workqueue tracer.
This flow of events can be sent very quickly. So, to not encumber the
kevent workqueue and delay other jobs, the "cqueue" workqueue should
remain.
But this workqueue is pointless most of the time, it will always be
created (assuming you have built it of course) although only
developpers with specific needs will use it.
So avoid this "most of the time useless task", this patch proposes to
create this workqueue only when needed once. The first jobs to be
sent to connector callbacks will be sent to kevent while the "cqueue"
thread creation will be scheduled to kevent too.
The following jobs will continue to be scheduled to keventd until the
cqueue workqueue is created, and then the rest of the jobs will
continue to perform as usual, through this dedicated workqueue.
Each time I tested this patch, only the first event was sent to
keventd, the rest has been sent to cqueue which have been created
quickly.
Also, this patch fixes some trailing whitespaces on the connector files.
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Evgeniy Polyakov <zbr@ioremap.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
From: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
We don't need one cqueue thread for each CPU. cqueue is used for
receiving userspace datagrams, which are very rare and thus will
happily live with a single queue.
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
- 'cb' is a fake struct member. In a previous patch struct cn_callback
was renamed to cn_callback_id, so 'cb' should have been deleted at that
time.
- 'nls' isn't used and is redundant, we can retrieve this data through
cn_callback_entry.pdev->nls.
- 'seq' and 'group' should be u32, as they are declared to be u32 in
other places.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Struct member netlink_groups is never used, and I don't see how it can
be useful.
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
cn_queue_free_callback() will touch 'dev'(i.e. cbq->pdev), so it
should be called before atomic_dec(&dev->refcnt).
Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
cn_queue.c:130: warning: value computed is not used
There is no point in testing the atomic value if the result is thrown
away.
From Evgeniy:
It was created to put implicit smp barrier, but it is not needed there.
Signed-off-by: Andreas Schwab <schwab@suse.de>
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
If input message rate from userspace is too high, do not drop them,
but try to deliver using work queue allocation.
Failing there is some kind of congestion control.
It also removes warn_on on this condition, which scares people.
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: David S. Miller <davem@davemloft.net>
Kernel connector - new userspace <-> kernel space easy to use
communication module which implements easy to use bidirectional
message bus using netlink as it's backend. Connector was created to
eliminate complex skb handling both in send and receive message bus
direction.
Connector driver adds possibility to connect various agents using as
one of it's backends netlink based network. One must register
callback and identifier. When driver receives special netlink message
with appropriate identifier, appropriate callback will be called.
From the userspace point of view it's quite straightforward:
socket();
bind();
send();
recv();
But if kernelspace want to use full power of such connections, driver
writer must create special sockets, must know about struct sk_buff
handling... Connector allows any kernelspace agents to use netlink
based networking for inter-process communication in a significantly
easier way:
int cn_add_callback(struct cb_id *id, char *name, void (*callback) (void *));
void cn_netlink_send(struct cn_msg *msg, u32 __groups, int gfp_mask);
struct cb_id
{
__u32 idx;
__u32 val;
};
idx and val are unique identifiers which must be registered in
connector.h for in-kernel usage. void (*callback) (void *) - is a
callback function which will be called when message with above idx.val
will be received by connector core.
Using connector completely hides low-level transport layer from it's
users.
Connector uses new netlink ability to have many groups in one socket.
[ Incorporating many cleanups and fixes by myself and
Andrew Morton -DaveM ]
Signed-off-by: Evgeniy Polyakov <johnpol@2ka.mipt.ru>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
