Commit 3ed66e91 authored by Christoph Lameter's avatar Christoph Lameter Committed by Linus Torvalds
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net: replace __this_cpu_inc in route.c with raw_cpu_inc

The RT_CACHE_STAT_INC macro triggers the new preemption checks
for __this_cpu ops.

I do not see any other synchronization that would allow the use of a
__this_cpu operation here however in commit dbd2915c ("[IPV4]:
RT_CACHE_STAT_INC() warning fix") Andrew justifies the use of
raw_smp_processor_id() here because "we do not care" about races.  In
the past we agreed that the price of disabling interrupts here to get
consistent counters would be too high.  These counters may be inaccurate
due to race conditions.

The use of __this_cpu op improves the situation already from what commit

 did since the single instruction emitted on x86 does not
allow the race to occur anymore.  However, non x86 platforms could still
experience a race here.


  __this_cpu_add operation in preemptible [00000000] code: avahi-daemon/1193
  caller is __this_cpu_preempt_check+0x38/0x60
  CPU: 1 PID: 1193 Comm: avahi-daemon Tainted: GF            3.12.0-rc4+ #187
  Call Trace:

Signed-off-by: default avatarChristoph Lameter <>
Acked-by: default avatarDavid S. Miller <>
Acked-by: default avatarIngo Molnar <>
Cc: Eric Dumazet <>
Cc: Tejun Heo <>
Signed-off-by: default avatarAndrew Morton <>
Signed-off-by: default avatarLinus Torvalds <>
parent 08f141d3
......@@ -188,7 +188,7 @@ const __u8 ip_tos2prio[16] = {
static DEFINE_PER_CPU(struct rt_cache_stat, rt_cache_stat);
#define RT_CACHE_STAT_INC(field) __this_cpu_inc(rt_cache_stat.field)
#define RT_CACHE_STAT_INC(field) raw_cpu_inc(rt_cache_stat.field)
static void *rt_cache_seq_start(struct seq_file *seq, loff_t *pos)
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