| Message ID | 20211001145841.2308454-1-bigeasy@linutronix.de (mailing list archive) |
|---|---|
| State | Accepted |
| Commit | 20ab39d13e2e9f916cf570fc834f2cadd6e5dc4a |
| Delegated to: | Netdev Maintainers |
| Headers | show |
| Series | [net-next] net/core: disable NET_RX_BUSY_POLL on PREEMPT_RT | expand |
| Context | Check | Description |
|---|---|---|
| netdev/cover_letter | success | Link |
| netdev/fixes_present | success | Link |
| netdev/patch_count | success | Link |
| netdev/tree_selection | success | Clearly marked for net-next |
| netdev/subject_prefix | success | Link |
| netdev/cc_maintainers | success | CCed 3 of 3 maintainers |
| netdev/source_inline | success | Was 0 now: 0 |
| netdev/verify_signedoff | success | Link |
| netdev/module_param | success | Was 0 now: 0 |
| netdev/build_32bit | success | Errors and warnings before: 0 this patch: 0 |
| netdev/kdoc | success | Errors and warnings before: 0 this patch: 0 |
| netdev/verify_fixes | success | Link |
| netdev/checkpatch | success | total: 0 errors, 0 warnings, 0 checks, 8 lines checked |
| netdev/build_allmodconfig_warn | success | Errors and warnings before: 0 this patch: 0 |
| netdev/header_inline | success | Link |
Hello: This patch was applied to netdev/net-next.git (refs/heads/master): On Fri, 1 Oct 2021 16:58:41 +0200 you wrote: > 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. > > [...] Here is the summary with links: - [net-next] net/core: disable NET_RX_BUSY_POLL on PREEMPT_RT https://git.kernel.org/netdev/net-next/c/20ab39d13e2e You are awesome, thank you! -- Deet-doot-dot, I am a bot. https://korg.docs.kernel.org/patchwork/pwbot.html
diff --git a/net/Kconfig b/net/Kconfig index fb13460c6dab3..074472dfa94ae 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
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> --- net/Kconfig | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)