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Pavel Emelyanov cf7b708c8d Make access to task's nsproxy lighter ... When someone wants to deal with some other taks's namespaces it has to lock the task and then to get the desired namespace if the one exists. This is slow on read-only paths and may be impossible in some cases. E.g. Oleg recently noticed a race between unshare() and the (sent for review in cgroups) pid namespaces - when the task notifies the parent it has to know the parent's namespace, but taking the task_lock() is impossible there - the code is under write locked tasklist lock. On the other hand switching the namespace on task (daemonize) and releasing the namespace (after the last task exit) is rather rare operation and we can sacrifice its speed to solve the issues above. The access to other task namespaces is proposed to be performed like this: rcu_read_lock(); nsproxy = task_nsproxy(tsk); if (nsproxy != NULL) { / * * work with the namespaces here * e.g. get the reference on one of them * / } / * * NULL task_nsproxy() means that this task is * almost dead (zombie) * / rcu_read_unlock(); This patch has passed the review by Eric and Oleg :) and, of course, tested. [clg@fr.ibm.com: fix unshare()] [ebiederm@xmission.com: Update get_net_ns_by_pid] Signed-off-by: Pavel Emelyanov <xemul@openvz.org> Signed-off-by: Eric W. Biederman <ebiederm@xmission.com> Cc: Oleg Nesterov <oleg@tv-sign.ru> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Serge Hallyn <serue@us.ibm.com> Signed-off-by: Cedric Le Goater <clg@fr.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>		18 years ago
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Makefile	[NET]: Fix running without sysfs	18 years ago
datagram.c	[NET]: Do not dereference iov if length is zero	18 years ago
dev.c	[NET]: Avoid copying TCP packets unnecessarily	18 years ago
dev_mcast.c	[NETNS]: Move some code into __init section when CONFIG_NET_NS=n	18 years ago
dst.c	[NET]: Make the loopback device per network namespace.	18 years ago
ethtool.c	[ETHTOOL] Provide default behaviors for a few ethtool sub-ioctls	18 years ago
fib_rules.c	[IPV4/IPV6/DECNET]: Small cleanup for fib rules.	18 years ago
filter.c	[NET]: Fix the race between sk_filter_(de|at)tach and sk_clone()	18 years ago
flow.c	…
gen_estimator.c	…
gen_stats.c	…
iovec.c	…
kmap_skb.h	…
link_watch.c	…
neighbour.c	sysctl: fix neighbour table sysctls.	18 years ago
net-sysfs.c	Driver core: change add_uevent_var to use a struct	18 years ago
net_namespace.c	[NETNS]: Don't memset() netns to zero manually	18 years ago
netevent.c	…
netpoll.c	[NET]: Wrap netdevice hardware header creation.	18 years ago
pktgen.c	[IPSEC]: Rename mode to outer_mode and add inner_mode	18 years ago
request_sock.c	…
rtnetlink.c	Make access to task's nsproxy lighter	18 years ago
scm.c	[NET]: sparse warning fixes	18 years ago
skbuff.c	[NET]: Fix csum_start update in pskb_expand_head	18 years ago
sock.c	[NET]: Move the filter releasing into a separate call	18 years ago
stream.c	…
sysctl_net_core.c	…
user_dma.c	…
utils.c	…