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| author | Eric Dumazet <edumazet@google.com> | 2023-06-06 07:41:15 +0000 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2023-06-14 11:09:43 +0200 |
| commit | dad7417db765da7068b3c96447520bd0a9d10cff (patch) | |
| tree | 485e27e1ed4415537fd06f5d666d93eb4edff083 | |
| parent | c62ca9d03777c81b4c69895cf2955a31012594c7 (diff) | |
| download | linux-dad7417db765da7068b3c96447520bd0a9d10cff.tar.gz linux-dad7417db765da7068b3c96447520bd0a9d10cff.tar.bz2 linux-dad7417db765da7068b3c96447520bd0a9d10cff.zip | |
rfs: annotate lockless accesses to RFS sock flow table
[ Upstream commit 5c3b74a92aa285a3df722bf6329ba7ccf70346d6 ]
Add READ_ONCE()/WRITE_ONCE() on accesses to the sock flow table.
This also prevents a (smart ?) compiler to remove the condition in:
if (table->ents[index] != newval)
table->ents[index] = newval;
We need the condition to avoid dirtying a shared cache line.
Fixes: fec5e652e58f ("rfs: Receive Flow Steering")
Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
| -rw-r--r-- | include/linux/netdevice.h | 7 | ||||
| -rw-r--r-- | net/core/dev.c | 6 |
2 files changed, 9 insertions, 4 deletions
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h index 9ef63bc14b00..24fe2cd4b0e8 100644 --- a/include/linux/netdevice.h +++ b/include/linux/netdevice.h @@ -744,8 +744,11 @@ static inline void rps_record_sock_flow(struct rps_sock_flow_table *table, /* We only give a hint, preemption can change CPU under us */ val |= raw_smp_processor_id(); - if (table->ents[index] != val) - table->ents[index] = val; + /* The following WRITE_ONCE() is paired with the READ_ONCE() + * here, and another one in get_rps_cpu(). + */ + if (READ_ONCE(table->ents[index]) != val) + WRITE_ONCE(table->ents[index], val); } } diff --git a/net/core/dev.c b/net/core/dev.c index 29e6e11c481c..f4aad9b00cc9 100644 --- a/net/core/dev.c +++ b/net/core/dev.c @@ -4385,8 +4385,10 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb, u32 next_cpu; u32 ident; - /* First check into global flow table if there is a match */ - ident = sock_flow_table->ents[hash & sock_flow_table->mask]; + /* First check into global flow table if there is a match. + * This READ_ONCE() pairs with WRITE_ONCE() from rps_record_sock_flow(). + */ + ident = READ_ONCE(sock_flow_table->ents[hash & sock_flow_table->mask]); if ((ident ^ hash) & ~rps_cpu_mask) goto try_rps; |