4.19-stable review patch. If anyone has any objections, please let me know.
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From: Eric Dumazet edumazet@google.com
[ 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: 060212928670 ("net: add low latency socket poll") Fixes: 9a3c71aa8024 ("net: convert low latency sockets to sched_clock()") Fixes: 37089834528b ("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 --- include/net/busy_poll.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/include/net/busy_poll.h b/include/net/busy_poll.h index 8f42f6f3af86f..c45253ee08c9f 100644 --- a/include/net/busy_poll.h +++ b/include/net/busy_poll.h @@ -73,7 +73,7 @@ static inline bool sk_can_busy_loop(struct sock *sk) static inline unsigned long busy_loop_current_time(void) { #ifdef CONFIG_NET_RX_BUSY_POLL - return (unsigned long)(local_clock() >> 10); + return (unsigned long)(ktime_get_ns() >> 10); #else return 0; #endif