tcp/dccp: bypass empty buckets in inet_twsk_purge()

[ Upstream commit 50e2907e ]

TCP ehash table is often sparsely populated.

inet_twsk_purge() spends too much time calling cond_resched().

This patch can reduce time spent in inet_twsk_purge() by 20x.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Reviewed-by: Kuniyuki Iwashima <kuniyu@amazon.com>
Link: https://lore.kernel.org/r/20240327191206.508114-1-edumazet@google.com


Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Stable-dep-of: 565d121b ("tcp: prevent concurrent execution of tcp_sk_exit_batch")
Signed-off-by: Sasha Levin <sashal@kernel.org>