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authorWen Gu2021-11-13 15:33:35 +0800
committerDavid S. Miller2021-11-15 13:27:02 +0000
commit2153bd1e3d3dbf6a3403572084ef6ed31c53c5f0 (patch)
tree95fa9765abacc50090186f7a8c06c37b9ca629f4 /net/smc
parentae32bd420b91070a9743c996993559d086a6c80c (diff)
net/smc: Transfer remaining wait queue entries during fallback
The SMC fallback is incomplete currently. There may be some wait queue entries remaining in smc socket->wq, which should be removed to clcsocket->wq during the fallback. For example, in nginx/wrk benchmark, this issue causes an all-zeros test result: server: nginx -g 'daemon off;' client: smc_run wrk -c 1 -t 1 -d 5 http://11.200.15.93/index.html Running 5s test @ http://11.200.15.93/index.html 1 threads and 1 connections Thread Stats Avg Stdev Max ± Stdev Latency 0.00us 0.00us 0.00us -nan% Req/Sec 0.00 0.00 0.00 -nan% 0 requests in 5.00s, 0.00B read Requests/sec: 0.00 Transfer/sec: 0.00B The reason for this all-zeros result is that when wrk used SMC to replace TCP, it added an eppoll_entry into smc socket->wq and expected to be notified if epoll events like EPOLL_IN/ EPOLL_OUT occurred on the smc socket. However, once a fallback occurred, wrk switches to use clcsocket. Now it is clcsocket->wq instead of smc socket->wq which will be woken up. The eppoll_entry remaining in smc socket->wq does not work anymore and wrk stops the test. This patch fixes this issue by removing remaining wait queue entries from smc socket->wq to clcsocket->wq during the fallback. Link: https://www.spinics.net/lists/netdev/msg779769.html Signed-off-by: Wen Gu <guwen@linux.alibaba.com> Reviewed-by: Tony Lu <tonylu@linux.alibaba.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/smc')
-rw-r--r--net/smc/af_smc.c14
1 files changed, 14 insertions, 0 deletions
diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c
index 59284da9116d..b61c802e3bf3 100644
--- a/net/smc/af_smc.c
+++ b/net/smc/af_smc.c
@@ -566,6 +566,10 @@ static void smc_stat_fallback(struct smc_sock *smc)
static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code)
{
+ wait_queue_head_t *smc_wait = sk_sleep(&smc->sk);
+ wait_queue_head_t *clc_wait = sk_sleep(smc->clcsock->sk);
+ unsigned long flags;
+
smc->use_fallback = true;
smc->fallback_rsn = reason_code;
smc_stat_fallback(smc);
@@ -575,6 +579,16 @@ static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code)
smc->clcsock->file->private_data = smc->clcsock;
smc->clcsock->wq.fasync_list =
smc->sk.sk_socket->wq.fasync_list;
+
+ /* There may be some entries remaining in
+ * smc socket->wq, which should be removed
+ * to clcsocket->wq during the fallback.
+ */
+ spin_lock_irqsave(&smc_wait->lock, flags);
+ spin_lock(&clc_wait->lock);
+ list_splice_init(&smc_wait->head, &clc_wait->head);
+ spin_unlock(&clc_wait->lock);
+ spin_unlock_irqrestore(&smc_wait->lock, flags);
}
}