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3d4405226d
linux/net
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Hannes Frederic Sowa 3d4405226d net: avoid dependency of net_get_random_once on nop patching 
net_get_random_once depends on the static keys infrastructure to patch up
the branch to the slow path during boot. This was realized by abusing the
static keys api and defining a new initializer to not enable the call
site while still indicating that the branch point should get patched
up. This was needed to have the fast path considered likely by gcc.

The static key initialization during boot up normally walks through all
the registered keys and either patches in ideal nops or enables the jump
site but omitted that step on x86 if ideal nops where already placed at
static_key branch points. Thus net_get_random_once branches not always
became active.

This patch switches net_get_random_once to the ordinary static_key
api and thus places the kernel fast path in the - by gcc considered -
unlikely path.  Microbenchmarks on Intel and AMD x86-64 showed that
the unlikely path actually beats the likely path in terms of cycle cost
and that different nop patterns did not make much difference, thus this
switch should not be noticeable.

Fixes: a48e42920f ("net: introduce new macro net_get_random_once")
Reported-by: Tuomas Räsänen <tuomasjjrasanen@tjjr.fi>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
2014-05-14 00:37:34 -04:00
..
9p A bunch of updates and cleanup within the transport layer, 2014-04-11 14:14:57 -07:00
802 neigh: use NEIGH_VAR_INIT in ndo_neigh_setup functions. 2014-01-16 11:31:58 -08:00
8021q vlan: Fix lockdep warning when vlan dev handle notification 2014-04-18 17:48:30 -04:00
appletalk appletalk: fix checkpatch error with indent 2014-02-14 16:18:32 -05:00
atm net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
ax25 net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
batman-adv batman-adv: fix removing neigh_ifinfo 2014-05-11 09:10:58 +02:00
bluetooth Bluetooth: Fix redundant encryption request for reauthentication 2014-04-25 09:47:15 +03:00
bridge bridge: superfluous skb->nfct check in br_nf_dev_queue_xmit 2014-05-05 16:05:43 +02:00
caif net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
can net: Use netlink_ns_capable to verify the permisions of netlink messages 2014-04-24 13:44:54 -04:00
ceph Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client 2014-05-05 15:17:02 -07:00
core net: avoid dependency of net_get_random_once on nop patching 2014-05-14 00:37:34 -04:00
dcb net: Use netlink_ns_capable to verify the permisions of netlink messages 2014-04-24 13:44:54 -04:00
dccp ipv4: add a sock pointer to ip_queue_xmit() 2014-04-15 12:58:34 -04:00
decnet net: Use netlink_ns_capable to verify the permisions of netlink messages 2014-04-24 13:44:54 -04:00
dns_resolver net/*: Fix FSF address in file headers 2013-12-06 12:37:57 -05:00
dsa dsa: Use ether_addr_copy 2014-01-21 18:13:05 -08:00
ethernet net: eth_type_trans() should use skb_header_pointer() 2014-01-16 15:30:31 -08:00
hsr hsr: replace del_timer by del_timer_sync 2014-03-27 15:28:06 -04:00
ieee802154 mac802154: make csma/cca parameters per-wpan 2014-04-01 16:25:51 -04:00
ipv4 Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf 2014-05-09 13:17:30 -04:00
ipv6 ip6_tunnel: fix potential NULL pointer dereference 2014-05-13 00:27:19 -04:00
ipx ipx: implement shutdown() 2014-02-12 19:26:32 -05:00
irda net: add build-time checks for msg->msg_name size 2014-01-18 23:04:16 -08:00
iucv net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
key net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
l2tp ipv4: add a sock pointer to ip_queue_xmit() 2014-04-15 12:58:34 -04:00
lapb net/lapb: re-send packets on timeout 2013-09-23 16:52:45 -04:00
llc llc: remove noisy WARN from llc_mac_hdr_init 2014-01-28 18:01:32 -08:00
mac80211 mac80211: fix nested rtnl locking on ieee80211_reconfig 2014-05-05 15:14:58 +02:00
mac802154 mac802154: fix duplicate #include headers 2014-04-07 13:18:44 -04:00
mpls ipip: add GSO/TSO support 2013-10-19 19:36:19 -04:00
netfilter netfilter: nfnetlink: Fix use after free when it fails to process batch 2014-05-04 15:14:08 +02:00
netlabel netlabel: Fix FSF address in file headers 2013-12-06 12:37:56 -05:00
netlink net: Use netlink_ns_capable to verify the permisions of netlink messages 2014-04-24 13:44:54 -04:00
netrom net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
nfc net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
openvswitch ipv4: add a sock pointer to dst->output() path. 2014-04-15 13:47:15 -04:00
packet net: Use netlink_ns_capable to verify the permisions of netlink messages 2014-04-24 13:44:54 -04:00
phonet net: Use netlink_ns_capable to verify the permisions of netlink messages 2014-04-24 13:44:54 -04:00
rds net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
rfkill net: rfkill: move poll work to power efficient workqueue 2014-02-04 21:58:16 +01:00
rose net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
rxrpc net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
sched net: sched: lock imbalance in hhf qdisc 2014-05-04 19:41:45 -04:00
sctp net: sctp: Don't transition to PF state when transport has exhausted 'Path.Max.Retrans'. 2014-04-27 23:41:14 -04:00
sunrpc Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-04-12 17:31:22 -07:00
tipc net: Use netlink_ns_capable to verify the permisions of netlink messages 2014-04-24 13:44:54 -04:00
unix net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
vmw_vsock vsock: Make transport the proto owner 2014-05-05 13:13:50 -04:00
wimax wimax: remove dead code 2013-11-21 13:09:42 -05:00
wireless cfg80211: add cfg80211_sched_scan_stopped_rtnl 2014-05-05 15:14:57 +02:00
x25 net: Fix use after free by removing length arg from sk_data_ready callbacks. 2014-04-11 16:15:36 -04:00
xfrm net: Use netlink_ns_capable to verify the permisions of netlink messages 2014-04-24 13:44:54 -04:00
compat.c net/compat: convert to COMPAT_SYSCALL_DEFINE with changing parameter types 2014-03-06 16:30:45 +01:00
Kconfig Merge branch 'for-3.15' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup 2014-04-03 13:05:42 -07:00
Makefile net: move 6lowpan compression code to separate module 2014-01-15 15:36:38 -08:00
nonet.c
socket.c net: use SYSCALL_DEFINEx for sys_recv 2014-04-16 15:15:05 -04:00
sysctl_net.c net: Update the sysctl permissions handler to test effective uid/gid 2013-10-07 15:57:56 -04:00