Eric Dumazet 131287ff83 once: add DO_ONCE_SLOW() for sleepable contexts
[ Upstream commit 62c07983bef9d3e78e71189441e1a470f0d1e653 ]

Christophe Leroy reported a ~80ms latency spike
happening at first TCP connect() time.

This is because __inet_hash_connect() uses get_random_once()
to populate a perturbation table which became quite big
after commit 4c2c8f03a5ab ("tcp: increase source port perturb table to 2^16")

get_random_once() uses DO_ONCE(), which block hard irqs for the duration
of the operation.

This patch adds DO_ONCE_SLOW() which uses a mutex instead of a spinlock
for operations where we prefer to stay in process context.

Then __inet_hash_connect() can use get_random_slow_once()
to populate its perturbation table.

Fixes: 4c2c8f03a5ab ("tcp: increase source port perturb table to 2^16")
Fixes: 190cc82489f4 ("tcp: change source port randomizarion at connect() time")
Reported-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Link: https://lore.kernel.org/netdev/CANn89iLAEYBaoYajy0Y9UmGFff5GPxDUoG-ErVB2jDdRNQ5Tug@mail.gmail.com/T/#t
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Willy Tarreau <w@1wt.eu>
Tested-by: Christophe Leroy <christophe.leroy@csgroup.eu>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
2022-10-26 13:22:27 +02:00
..
2022-05-18 09:47:25 +02:00
2021-09-15 09:47:29 +02:00
2018-08-22 10:52:48 -07:00
2018-10-12 09:17:46 +02:00
2019-07-25 15:47:37 +02:00
2018-08-16 12:14:42 -07:00
2018-08-22 10:52:48 -07:00
2017-02-24 17:46:57 -08:00
2022-07-12 16:30:49 +02:00
2021-05-07 10:51:37 +02:00
2018-10-16 13:45:44 +02:00
2020-11-05 11:43:22 +01:00
2019-07-11 15:17:41 -07:00
2020-10-01 13:18:23 +02:00
2018-06-27 18:58:49 +03:00
2018-10-15 16:31:29 -04:00
2019-05-06 11:12:09 -07:00
2017-08-15 09:02:07 -07:00