Commit Graph

3191 Commits

Author SHA1 Message Date
David S. Miller
0808dc8093 netfilter: Fix extra semi-colon in skb_walk_frags() changes.
Noticed by Jesper Dangaard Brouer

Signed-off-by: David S. Miller <davem@davemloft.net>
2009-06-09 18:05:28 -07:00
David S. Miller
343a99724e netfilter: Use frag list abstraction interfaces.
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-06-09 00:23:58 -07:00
David S. Miller
d7fcf1a5ca ipv4: Use frag list abstraction interfaces.
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-06-09 00:19:37 -07:00
Rami Rosen
2307f866f5 ipv4: remove ip_mc_drop_socket() declaration from af_inet.c.
ip_mc_drop_socket() method is declared in linux/igmp.h, which
is included anyhow in af_inet.c. So there is no need for this declaration.
This patch removes it from af_inet.c.

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-06-03 21:43:26 -07:00
Eric Dumazet
adf30907d6 net: skb->dst accessors
Define three accessors to get/set dst attached to a skb

struct dst_entry *skb_dst(const struct sk_buff *skb)

void skb_dst_set(struct sk_buff *skb, struct dst_entry *dst)

void skb_dst_drop(struct sk_buff *skb)
This one should replace occurrences of :
dst_release(skb->dst)
skb->dst = NULL;

Delete skb->dst field

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-06-03 02:51:04 -07:00
Eric Dumazet
511c3f92ad net: skb->rtable accessor
Define skb_rtable(const struct sk_buff *skb) accessor to get rtable from skb

Delete skb->rtable field

Setting rtable is not allowed, just set dst instead as rtable is an alias.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-06-03 02:51:02 -07:00
David S. Miller
b2f8f7525c Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
Conflicts:
	drivers/net/forcedeth.c
2009-06-03 02:43:41 -07:00
Nivedita Singhvi
f771bef980 ipv4: New multicast-all socket option
After some discussion offline with Christoph Lameter and David Stevens
regarding multicast behaviour in Linux, I'm submitting a slightly
modified patch from the one Christoph submitted earlier.

This patch provides a new socket option IP_MULTICAST_ALL.

In this case, default behaviour is _unchanged_ from the current
Linux standard. The socket option is set by default to provide
original behaviour. Sockets wishing to receive data only from
multicast groups they join explicitly will need to clear this
socket option.

Signed-off-by: Nivedita Singhvi <niv@us.ibm.com>
Signed-off-by: Christoph Lameter<cl@linux.com>
Acked-by: David Stevens <dlstevens@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-06-02 00:45:24 -07:00
Eric Dumazet
4d52cfbef6 net: ipv4/ip_sockglue.c cleanups
Pure cleanups

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-06-02 00:42:16 -07:00
Ilpo Järvinen
2df9001edc tcp: fix loop in ofo handling code and reduce its complexity
Somewhat luckily, I was looking into these parts with very fine
comb because I've made somewhat similar changes on the same
area (conflicts that arose weren't that lucky though). The loop
was very much overengineered recently in commit 915219441d
(tcp: Use SKB queue and list helpers instead of doing it
by-hand), while it basically just wants to know if there are
skbs after 'skb'.

Also it got broken because skb1 = skb->next got translated into
skb1 = skb1->next (though abstracted) improperly. Note that
'skb1' is pointing to previous sk_buff than skb or NULL if at
head. Two things went wrong:
- We'll kfree 'skb' on the first iteration instead of the
  skbuff following 'skb' (it would require required SACK reneging
  to recover I think).
- The list head case where 'skb1' is NULL is checked too early
  and the loop won't execute whereas it previously did.

Conclusion, mostly revert the recent changes which makes the
cset very messy looking but using proper accessor in the
previous-like version.

The effective changes against the original can be viewed with:
  git-diff 915219441d566f1da0caa0e262be49b666159e17^ \
		net/ipv4/tcp_input.c | sed -n -e '57,70 p'

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-29 15:02:29 -07:00
Eric Dumazet
108bfa895c net: unset IFF_XMIT_DST_RELEASE in ipgre_tunnel_setup()
ipgre_tunnel_xmit() might need skb->dst, so tell dev_hard_start_xmit()
to no release it.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-29 01:46:29 -07:00
Eric Dumazet
28e72216d7 net: unset IFF_XMIT_DST_RELEASE in ipip_tunnel_setup()
ipip_tunnel_xmit() might need skb->dst, so tell dev_hard_start_xmit()
to no release it.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-29 01:46:27 -07:00
David S. Miller
915219441d tcp: Use SKB queue and list helpers instead of doing it by-hand.
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-28 21:35:47 -07:00
Herbert Xu
a2a804cddf tcp: Do not check flush when comparing options for GRO
There is no need to repeatedly check flush when comparing TCP
options for GRO as it will be false 99% of the time where it
matters.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-27 03:26:05 -07:00
Herbert Xu
1075f3f65d ipv4: Use 32-bit loads for ID and length in GRO
This patch optimises the IPv4 GRO code by using 32-bit loads
(instead of 16-bit ones) on the ID and length checks in the receive
function.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-27 03:26:02 -07:00
Herbert Xu
a5b1cf288d gro: Avoid unnecessary comparison after skb_gro_header
For the overwhelming majority of cases, skb_gro_header's return
value cannot be NULL.  Yet we must check it because of its current
form.  This patch splits it up into multiple functions in order
to avoid this.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-27 03:26:01 -07:00
Herbert Xu
30a3ae30c7 tcp: Optimise len/mss comparison
Instead of checking len > mss || len == 0, we can accomplish
both by checking (len - 1) > mss using the unsigned wraparound.
At nearly a million times a second, this might just help.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-27 03:26:00 -07:00
Herbert Xu
4a9a2968a1 tcp: Remove unnecessary window comparisons for GRO
The window has already been checked as part of the flag word
so there is no need to check it explicitly.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-27 03:25:59 -07:00
Herbert Xu
745898eaf0 tcp: Optimise GRO port comparisons
Instead of doing two 16-bit operations for the source/destination
ports, we can do one 32-bit operation to take care both.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-27 03:25:57 -07:00
Doug Leith
c80a5cdfc5 tcp: tcp_vegas ssthresh bugfix
This patch fixes ssthresh accounting issues in tcp_vegas when cwnd decreases

Signed-off-by: Doug Leith <doug.leith@nuim.ie>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-25 22:44:59 -07:00
David S. Miller
c649c0e31d Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
Conflicts:
	drivers/net/wireless/ath/ath5k/phy.c
	drivers/net/wireless/iwlwifi/iwl-agn.c
	drivers/net/wireless/iwlwifi/iwl3945-base.c
2009-05-25 01:42:21 -07:00
Robert Olsson
3ed18d76d9 ipv4: Fix oops with FIB_TRIE
It seems we can fix this by disabling preemption while we re-balance the 
trie. This is with the CONFIG_CLASSIC_RCU. It's been stress-tested at high 
loads continuesly taking a full BGP table up/down via iproute -batch.

Note. fib_trie is not updated for CONFIG_PREEMPT_RCU

Reported-by: Andrei Popa
Signed-off-by: Robert Olsson <robert.olsson@its.uu.se>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-21 15:20:59 -07:00
Rami Rosen
04af8cf6f3 net: Remove unused parameter from fill method in fib_rules_ops.
The netlink message header (struct nlmsghdr) is an unused parameter in
fill method of fib_rules_ops struct.  This patch removes this
parameter from this method and fixes the places where this method is
called.

(include/net/fib_rules.h)

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-20 17:26:23 -07:00
Eric Dumazet
1ddbcb005c net: fix rtable leak in net/ipv4/route.c
Alexander V. Lukyanov found a regression in 2.6.29 and made a complete
analysis found in http://bugzilla.kernel.org/show_bug.cgi?id=13339
Quoted here because its a perfect one :

begin_of_quotation
 2.6.29 patch has introduced flexible route cache rebuilding. Unfortunately the
 patch has at least one critical flaw, and another problem.

 rt_intern_hash calculates rthi pointer, which is later used for new entry
 insertion. The same loop calculates cand pointer which is used to clean the
 list. If the pointers are the same, rtable leak occurs, as first the cand is
 removed then the new entry is appended to it.

 This leak leads to unregister_netdevice problem (usage count > 0).

 Another problem of the patch is that it tries to insert the entries in certain
 order, to facilitate counting of entries distinct by all but QoS parameters.
 Unfortunately, referencing an existing rtable entry moves it to list beginning,
 to speed up further lookups, so the carefully built order is destroyed.

 For the first problem the simplest patch it to set rthi=0 when rthi==cand, but
 it will also destroy the ordering.
end_of_quotation

Problematic commit is 1080d709fb
(net: implement emergency route cache rebulds when gc_elasticity is exceeded)

Trying to keep dst_entries ordered is too complex and breaks the fact that
order should depend on the frequency of use for garbage collection.

A possible fix is to make rt_intern_hash() simpler, and only makes
rt_check_expire() a litle bit smarter, being able to cope with an arbitrary
entries order. The added loop is running on cache hot data, while cpu
is prefetching next object, so should be unnoticied.

Reported-and-analyzed-by: Alexander V. Lukyanov <lav@yar.ru>
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-20 17:18:02 -07:00
Eric Dumazet
cf8da764fc net: fix length computation in rt_check_expire()
rt_check_expire() computes average and standard deviation of chain lengths,
but not correclty reset length to 0 at beginning of each chain.
This probably gives overflows for sum2 (and sum) on loaded machines instead
of meaningful results.

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Acked-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-20 17:18:01 -07:00
Chris Friesen
9643f45512 ipv4: teach ipconfig about the MTU option in DHCP
The DHCP spec allows the server to specify the MTU.  This can be useful
for netbooting with UDP-based NFS-root on a network using jumbo frames.
This patch allows the kernel IP autoconfiguration to handle this option
correctly.

It would be possible to use initramfs and add a script to set the MTU,
but that seems like a complicated solution if no initramfs is otherwise
necessary, and would bloat the kernel image more than this code would.

This patch was originally submitted to LKML in 2003 by Hans-Peter Jansen.

Signed-off-by: Chris Friesen <cfriesen@nortel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-19 15:36:17 -07:00
Eric W. Biederman
9b8adb5ea0 net: Fix devinet_sysctl_forward
sysctls are unregistered with the rntl_lock held making
it unsafe to unconditionally grab the the rtnl_lock.  Instead
we need to call rtnl_trylock and restart the system call
if we can not grab it.  Otherwise we could deadlock at unregistration
time.

Signed-off-by: Eric W. Biederman <ebiederm@aristanetworks.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-18 22:15:58 -07:00
Frans Pop
bc8a539743 ipv4: make default for INET_LRO consistent with help text
Commit e81963b1 ("ipv4: Make INET_LRO a bool instead of tristate.")
changed this config from tristate to bool.  Add default so that it is
consistent with the help text.

Signed-off-by: Frans Pop <elendil@planet.nl>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-18 21:48:38 -07:00
David S. Miller
bb803cfbec Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
Conflicts:
	drivers/scsi/fcoe/fcoe.c
2009-05-18 21:08:20 -07:00
Rami Rosen
d23a9b5baa ipv4: cleanup: remove unnecessary include.
There is no need for net/icmp.h header in net/ipv4/fib_frontend.c.
This patch removes the #include net/icmp.h from it.

Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-18 15:16:38 -07:00
Rami Rosen
e204a345a0 ipv4: cleanup - remove two unused parameters from fib_semantic_match().
Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-18 15:16:37 -07:00
Ilpo Järvinen
7752731318 tcp: fix MSG_PEEK race check
Commit 518a09ef11 (tcp: Fix recvmsg MSG_PEEK influence of
blocking behavior) lets the loop run longer than the race check
did previously expect, so we need to be more careful with this
check and consider the work we have been doing.

I tried my best to deal with urg hole madness too which happens
here:
	if (!sock_flag(sk, SOCK_URGINLINE)) {
		++*seq;
		...
by using additional offset by one but I certainly have very
little interest in testing that part.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Tested-by: Frans Pop <elendil@planet.nl>
Tested-by: Ian Zimmermann <itz@buug.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-18 15:05:40 -07:00
Chris Friesen
2513dfb83f ipconfig: handle case of delayed DHCP server
If a DHCP server is delayed, it's possible for the client to receive the 
DHCPOFFER after it has already sent out a new DHCPDISCOVER message from 
a second interface.  The client then sends out a DHCPREQUEST from the 
second interface, but the server doesn't recognize the device and 
rejects the request.

This patch simply tracks the current device being configured and throws 
away the OFFER if it is not intended for the current device.  A more 
sophisticated approach would be to put the OFFER information into the 
struct ic_device rather than storing it globally.

Signed-off-by: Chris Friesen <cfriesen@nortel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-17 20:39:33 -07:00
Rami Rosen
8b3521eeb7 ipv4: remove an unused parameter from configure method of fib_rules_ops.
Signed-off-by: Rami Rosen <ramirose@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-17 11:59:45 -07:00
David S. Miller
e81963b180 ipv4: Make INET_LRO a bool instead of tristate.
This code is used as a library by several device drivers,
which select INET_LRO.

If some are modules and some are statically built into the
kernel, we get build failures if INET_LRO is modular.

Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-08 12:45:26 -07:00
David S. Miller
22f6dacdfc Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
Conflicts:
	include/net/tcp.h
2009-05-08 02:48:30 -07:00
Arnaldo Carvalho de Melo
4dbc8ef7e1 net: Make inet_twsk_put similar to sock_put
By separating the freeing code from the refcounting decrementing.
Probably reducing icache pressure when we still have reference counts to
go.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-06 16:50:52 -07:00
Shan Wei
ae8d7f884a tcp:fix the code indent
Signed-off-by: Shan Wei<shanwei@cn.fujitsu.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-05 12:29:47 -07:00
Satoru SATOH
0c266898b4 tcp: Fix tcp_prequeue() to get correct rto_min value
tcp_prequeue() refers to the constant value (TCP_RTO_MIN) regardless of
the actual value might be tuned. The following patches fix this and make
tcp_prequeue get the actual value returns from tcp_rto_min().

Signed-off-by: Satoru SATOH <satoru.satoh@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-04 11:11:01 -07:00
Ilpo Järvinen
255cac91c3 tcp: extend ECN sysctl to allow server-side only ECN
This should be very safe compared with full enabled, so I see
no reason why it shouldn't be done right away. As ECN can only
be negotiated if the SYN sending party is also supporting it,
somebody in the loop probably knows what he/she is doing. If
SYN does not ask for ECN, the server side SYN-ACK is identical
to what it is without ECN. Thus it's quite safe.

The chosen value is safe w.r.t to existing configs which
choose to currently set manually either 0 or 1 but
silently upgrades those who have not explicitly requested
ECN off.

Whether to just enable both sides comes up time to time but
unless that gets done now we can at least make the servers
aware of ECN already. As there are some known problems to occur
if ECN is enabled, it's currently questionable whether there's
any real gain from enabling clients as servers mostly won't
support it anyway (so we'd hit just the negative sides). After
enabling the servers and getting that deployed, the client end
enable really has some potential gain too.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-05-04 11:07:36 -07:00
David S. Miller
aba7453037 Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
Conflicts:
	Documentation/isdn/00-INDEX
	drivers/net/wireless/iwlwifi/iwl-scan.c
	drivers/net/wireless/rndis_wlan.c
	net/mac80211/main.c
2009-04-29 20:30:35 -07:00
Stephen Hemminger
942e4a2bd6 netfilter: revised locking for x_tables
The x_tables are organized with a table structure and a per-cpu copies
of the counters and rules. On older kernels there was a reader/writer 
lock per table which was a performance bottleneck. In 2.6.30-rc, this
was converted to use RCU and the counters/rules which solved the performance
problems for do_table but made replacing rules much slower because of
the necessary RCU grace period.

This version uses a per-cpu set of spinlocks and counters to allow to
table processing to proceed without the cache thrashing of a global
reader lock and keeps the same performance for table updates.

Signed-off-by: Stephen Hemminger <shemminger@vyatta.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-04-28 22:36:33 -07:00
Arnaldo Carvalho de Melo
ac5978e7f8 inet_diag: Remove dup assignments
These are later assigned to other values without being used meanwhile.

Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-04-28 08:03:26 -07:00
Herbert Xu
36e7b1b8da gro: Fix COMPLETE checksum handling
On a brand new GRO skb, we cannot call ip_hdr since the header
may lie in the non-linear area.  This patch adds the helper
skb_gro_network_header to handle this.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-04-27 05:44:45 -07:00
Anton Blanchard
c9503e0fe0 ipv4: Limit size of route cache hash table
Right now we have no upper limit on the size of the route cache hash table.
On a 128GB POWER6 box it ends up as 32MB:

    IP route cache hash table entries: 4194304 (order: 9, 33554432 bytes)

It would be nice to cap this for memory consumption reasons, but a massive
hashtable also causes a significant spike when measuring OS jitter.

With a 32MB hashtable and 4 million entries, rt_worker_func is taking
5 ms to complete. On another system with more memory it's taking 14 ms.
Even though rt_worker_func does call cond_sched() to limit its impact,
in an HPC environment we want to keep all sources of OS jitter to a minimum.

With the patch applied we limit the number of entries to 512k which
can still be overriden by using the rt_entries boot option:

    IP route cache hash table entries: 524288 (order: 6, 4194304 bytes)

With this patch rt_worker_func now takes 0.460 ms on the same system.

Signed-off-by: Anton Blanchard <anton@samba.org>
Acked-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-04-27 05:42:24 -07:00
Neil Horman
edf391ff17 snmp: add missing counters for RFC 4293
The IP MIB (RFC 4293) defines stats for InOctets, OutOctets, InMcastOctets and
OutMcastOctets:
http://tools.ietf.org/html/rfc4293
But it seems we don't track those in any way that easy to separate from other
protocols.  This patch adds those missing counters to the stats file. Tested
successfully by me

With help from Eric Dumazet.

Signed-off-by: Neil Horman <nhorman@tuxdriver.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-04-27 02:45:02 -07:00
David S. Miller
e5e9743bb7 Merge branch 'master' of master.kernel.org:/pub/scm/linux/kernel/git/davem/net-2.6
Conflicts:
	net/core/dev.c
2009-04-21 01:32:26 -07:00
Florian Westphal
a0f82f64e2 syncookies: remove last_synq_overflow from struct tcp_sock
last_synq_overflow eats 4 or 8 bytes in struct tcp_sock, even
though it is only used when a listening sockets syn queue
is full.

We can (ab)use rx_opt.ts_recent_stamp to store the same information;
it is not used otherwise as long as a socket is in listen state.

Move linger2 around to avoid splitting struct mtu_probe
across cacheline boundary on 32 bit arches.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-04-20 02:25:26 -07:00
Ilpo Järvinen
52cf3cc8ac tcp: fix mid-wq adjustment helper
Just noticed while doing some new work that the recent
mid-wq adjustment logic will misbehave when FACK is not
in use (happens either due sysctl'ed off or auto-detected
reordering) because I forgot the relevant TCPCB tagbit.

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-04-20 02:15:00 -07:00
Eric Dumazet
573636cbaf [PATCH] net: remove superfluous call to synchronize_net()
inet_register_protosw() function is responsible for adding a new
inet protocol into a global table (inetsw[]) that is used with RCU rules.

As soon as the store of the pointer is done, other cpus might see
this new protocol in inetsw[], so we have to make sure new protocol
is ready for use. All pending memory updates should thus be committed
to memory before setting the pointer.
This is correctly done using rcu_assign_pointer()

synchronize_net() is typically used at unregister time, after
unsetting the pointer, to make sure no other cpu is still using
the object we want to dismantle. Using it at register time
is only adding an artificial delay that could hide a real bug,
and this bug could popup if/when synchronize_rcu() can proceed
faster than now.

This saves about 13 ms on boot time on a HZ=1000 8 cpus machine  ;) 
(4 calls to inet_register_protosw(), and about 3200 us per call)

Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2009-04-17 04:52:48 -07:00