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authorKurt Kanzenbach <kurt@linutronix.de>2023-05-23 14:15:18 +0300
committerDavid S. Miller <davem@davemloft.net>2023-05-26 10:51:26 +0300
commitc857946a4e262e0f798fe7625fadf85bf1190fc4 (patch)
treec0418a73bcaad880157f11215788da9aa9a5ebbc /net/Kconfig
parentd6f1e0bfe532b2ec725d9f768ca305af7aa1029a (diff)
downloadlinux-c857946a4e262e0f798fe7625fadf85bf1190fc4.tar.xz
net/core: Enable socket busy polling on -RT
Busy polling is currently not allowed on PREEMPT_RT, because it disables preemption while invoking the NAPI callback. It is not possible to acquire sleeping locks with disabled preemption. For details see commit 20ab39d13e2e ("net/core: disable NET_RX_BUSY_POLL on PREEMPT_RT"). However, strict cyclic and/or low latency network applications may prefer busy polling e.g., using AF_XDP instead of interrupt driven communication. The preempt_disable() is used in order to prevent the poll_owner and NAPI owner to be preempted while owning the resource to ensure progress. Netpoll performs busy polling in order to acquire the lock. NAPI is locked by setting the NAPIF_STATE_SCHED flag. There is no busy polling if the flag is set and the "owner" is preempted. Worst case is that the task owning NAPI gets preempted and NAPI processing stalls. This is can be prevented by properly prioritising the tasks within the system. Allow RX_BUSY_POLL on PREEMPT_RT if NETPOLL is disabled. Don't disable preemption on PREEMPT_RT within the busy poll loop. Tested on x86 hardware with v6.1-RT and v6.3-RT on Intel i225 (igc) with AF_XDP/ZC sockets configured to run in busy polling mode. Suggested-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Kurt Kanzenbach <kurt@linutronix.de> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/Kconfig')
-rw-r--r--net/Kconfig2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/Kconfig b/net/Kconfig
index 7d39c1773eb4..2fb25b534df5 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -324,7 +324,7 @@ config CGROUP_NET_CLASSID
config NET_RX_BUSY_POLL
bool
- default y if !PREEMPT_RT
+ default y if !PREEMPT_RT || (PREEMPT_RT && !NETCONSOLE)
config BQL
bool