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authorSebastian Andrzej Siewior <bigeasy@linutronix.de>2021-10-01 16:58:41 +0200
committerJakub Kicinski <kuba@kernel.org>2021-10-01 15:45:10 -0700
commit20ab39d13e2e9f916cf570fc834f2cadd6e5dc4a (patch)
treeab60af79e4689c98dc28042557aac8abcd586572 /net
parent05f1e35a13542bee0b3b83549a635560aaa94d90 (diff)
net/core: disable NET_RX_BUSY_POLL on PREEMPT_RT
napi_busy_loop() disables preemption and performs a NAPI poll. We can't acquire sleeping locks with disabled preemption which would be required while __napi_poll() invokes the callback of the driver. A threaded interrupt performing the NAPI-poll can be preempted on PREEMPT_RT. A RT thread on another CPU may observe NAPIF_STATE_SCHED bit set and busy-spin until it is cleared or its spin time runs out. Given it is the task with the highest priority it will never observe the NEED_RESCHED bit set. In this case the time is better spent by simply sleeping. The NET_RX_BUSY_POLL is disabled by default (the system wide sysctls for poll/read are set to zero). Disabling NET_RX_BUSY_POLL on PREEMPT_RT to avoid wrong locking context in case it is used. Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Link: https://lore.kernel.org/r/20211001145841.2308454-1-bigeasy@linutronix.de Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Diffstat (limited to 'net')
-rw-r--r--net/Kconfig2
1 files changed, 1 insertions, 1 deletions
diff --git a/net/Kconfig b/net/Kconfig
index fb13460c6dab..074472dfa94a 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -294,7 +294,7 @@ config CGROUP_NET_CLASSID
config NET_RX_BUSY_POLL
bool
- default y
+ default y if !PREEMPT_RT
config BQL
bool