This is a note to let you know that I've just added the patch titled
net: busy-poll: use ktime_get_ns() instead of local_clock()
to the 4.19-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
net-busy-poll-use-ktime_get_ns-instead-of-local_cloc.patch
and it can be found in the queue-4.19 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
commit ad0c4aaa1be78795cdf1914532e0664f425757e0
Author: Eric Dumazet <edumazet@xxxxxxxxxx>
Date: Tue Aug 27 11:49:16 2024 +0000
net: busy-poll: use ktime_get_ns() instead of local_clock()
[ 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@xxxxxxxxxx>
Cc: Mina Almasry <almasrymina@xxxxxxxxxx>
Cc: Willem de Bruijn <willemb@xxxxxxxxxx>
Reviewed-by: Joe Damato <jdamato@xxxxxxxxxx>
Link: https://patch.msgid.link/20240827114916.223377-1-edumazet@xxxxxxxxxx
Signed-off-by: Jakub Kicinski <kuba@xxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
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
