lk/linux-kernel-test
1
0
Fork 0
Code Issues Pull Requests Releases Wiki Activity

netfilter: get rid of atomic ops in fast path

Browse Source 
We currently use a percpu spinlock to 'protect' rule bytes/packets
counters, after various attempts to use RCU instead.

Lately we added a seqlock so that get_counters() can run without
blocking BH or 'writers'. But we really only need the seqcount in it.

Spinlock itself is only locked by the current/owner cpu, so we can
remove it completely.

This cleanups api, using correct 'writer' vs 'reader' semantic.

At replace time, the get_counters() call makes sure all cpus are done
using the old table.

Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Cc: Jan Engelhardt <jengelh@medozas.de>
Signed-off-by: Patrick McHardy <kaber@trash.net>
This commit is contained in:
Eric Dumazet
2011-04-04 17:04:03 +02:00
committed by Patrick McHardy
parent 8f7b01a178
commit 7f5c6d4f66
5 changed files with 82 additions and 92 deletions
Download Patch File Download Diff File Expand all files Collapse all files

19
net/ipv6/netfilter/ip6_tables.c
View File

@@ -340,6 +340,7 @@ ip6t_do_table(struct sk_buff *skb,
unsigned int *stackptr, origptr, cpu;
const struct xt_table_info *private;
struct xt_action_param acpar;
unsigned int addend;
/* Initialization */
indev = in ? in->name : nulldevname;
@@ -358,7 +359,8 @@ ip6t_do_table(struct sk_buff *skb,
IP_NF_ASSERT(table->valid_hooks & (1 << hook));
xt_info_rdlock_bh();
local_bh_disable();
addend = xt_write_recseq_begin();
private = table->private;
cpu = smp_processor_id();
table_base = private->entries[cpu];
@@ -442,7 +444,9 @@ ip6t_do_table(struct sk_buff *skb,
} while (!acpar.hotdrop);
*stackptr = origptr;
xt_info_rdunlock_bh();
xt_write_recseq_end(addend);
local_bh_enable();
#ifdef DEBUG_ALLOW_ALL
return NF_ACCEPT;
@@ -899,7 +903,7 @@ get_counters(const struct xt_table_info *t,
unsigned int i;
for_each_possible_cpu(cpu) {
seqlock_t *lock = &per_cpu(xt_info_locks, cpu).lock;
seqcount_t *s = &per_cpu(xt_recseq, cpu);
i = 0;
xt_entry_foreach(iter, t->entries[cpu], t->size) {
@@ -907,10 +911,10 @@ get_counters(const struct xt_table_info *t,
unsigned int start;
do {
start = read_seqbegin(lock);
start = read_seqcount_begin(s);
bcnt = iter->counters.bcnt;
pcnt = iter->counters.pcnt;
} while (read_seqretry(lock, start));
} while (read_seqcount_retry(s, start));
ADD_COUNTER(counters[i], bcnt, pcnt);
++i;
@@ -1325,6 +1329,7 @@ do_add_counters(struct net *net, const void __user *user, unsigned int len,
int ret = 0;
const void *loc_cpu_entry;
struct ip6t_entry *iter;
unsigned int addend;
#ifdef CONFIG_COMPAT
struct compat_xt_counters_info compat_tmp;
@@ -1381,13 +1386,13 @@ do_add_counters(struct net *net, const void __user *user, unsigned int len,
i = 0;
/* Choose the copy that is on our node */
curcpu = smp_processor_id();
xt_info_wrlock(curcpu);
addend = xt_write_recseq_begin();
loc_cpu_entry = private->entries[curcpu];
xt_entry_foreach(iter, loc_cpu_entry, private->size) {
ADD_COUNTER(iter->counters, paddc[i].bcnt, paddc[i].pcnt);
++i;
}
xt_info_wrunlock(curcpu);
xt_write_recseq_end(addend);
unlock_up_free:
local_bh_enable();