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[ Upstream commit 0870b0d8b393dde53106678a1e2cec9dfa52f9b7 ] Typically, busy-polling durations are below 100 usec. When/if the busy-poller thread migrates to another cpu, local_clock() can be off by +/-2msec or more for small values of HZ, depending on the platform. Use ktimer_get_ns() to ensure deterministic behavior, which is the whole point of busy-polling. Fixes:0602129286("net: add low latency socket poll") Fixes:9a3c71aa80("net: convert low latency sockets to sched_clock()") Fixes:3708983452("sched, net: Fixup busy_loop_us_clock()") Signed-off-by: Eric Dumazet <edumazet@google.com> Cc: Mina Almasry <almasrymina@google.com> Cc: Willem de Bruijn <willemb@google.com> Reviewed-by: Joe Damato <jdamato@fastly.com> Link: https://patch.msgid.link/20240827114916.223377-1-edumazet@google.com Signed-off-by: Jakub Kicinski <kuba@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>