From 9bda91d805b02ba3d3a6481bee31f4569e3c2324 Mon Sep 17 00:00:00 2001 From: Felix Fietkau Date: Tue, 1 Jun 2021 23:19:48 +0200 Subject: kernel: backport fix for hang on napi_disable with threaded NAPI Signed-off-by: Felix Fietkau --- ...-hangup-on-napi_disable-for-threaded-napi.patch | 53 ++++++++++++++++++++++ 1 file changed, 53 insertions(+) create mode 100644 target/linux/generic/backport-5.10/604-v5.12-net-fix-hangup-on-napi_disable-for-threaded-napi.patch (limited to 'target/linux/generic/backport-5.10') diff --git a/target/linux/generic/backport-5.10/604-v5.12-net-fix-hangup-on-napi_disable-for-threaded-napi.patch b/target/linux/generic/backport-5.10/604-v5.12-net-fix-hangup-on-napi_disable-for-threaded-napi.patch new file mode 100644 index 0000000000..4b83641291 --- /dev/null +++ b/target/linux/generic/backport-5.10/604-v5.12-net-fix-hangup-on-napi_disable-for-threaded-napi.patch @@ -0,0 +1,53 @@ +From: Paolo Abeni +Date: Fri, 9 Apr 2021 17:24:17 +0200 +Subject: [PATCH] net: fix hangup on napi_disable for threaded napi + +napi_disable() is subject to an hangup, when the threaded +mode is enabled and the napi is under heavy traffic. + +If the relevant napi has been scheduled and the napi_disable() +kicks in before the next napi_threaded_wait() completes - so +that the latter quits due to the napi_disable_pending() condition, +the existing code leaves the NAPI_STATE_SCHED bit set and the +napi_disable() loop waiting for such bit will hang. + +This patch addresses the issue by dropping the NAPI_STATE_DISABLE +bit test in napi_thread_wait(). The later napi_threaded_poll() +iteration will take care of clearing the NAPI_STATE_SCHED. + +This also addresses a related problem reported by Jakub: +before this patch a napi_disable()/napi_enable() pair killed +the napi thread, effectively disabling the threaded mode. +On the patched kernel napi_disable() simply stops scheduling +the relevant thread. + +v1 -> v2: + - let the main napi_thread_poll() loop clear the SCHED bit + +Reported-by: Jakub Kicinski +Fixes: 29863d41bb6e ("net: implement threaded-able napi poll loop support") +Signed-off-by: Paolo Abeni +Reviewed-by: Eric Dumazet +Link: https://lore.kernel.org/r/883923fa22745a9589e8610962b7dc59df09fb1f.1617981844.git.pabeni@redhat.com +Signed-off-by: Jakub Kicinski +--- + +--- a/net/core/dev.c ++++ b/net/core/dev.c +@@ -6951,7 +6951,7 @@ static int napi_thread_wait(struct napi_ + + set_current_state(TASK_INTERRUPTIBLE); + +- while (!kthread_should_stop() && !napi_disable_pending(napi)) { ++ while (!kthread_should_stop()) { + /* Testing SCHED_THREADED bit here to make sure the current + * kthread owns this napi and could poll on this napi. + * Testing SCHED bit is not enough because SCHED bit might be +@@ -6969,6 +6969,7 @@ static int napi_thread_wait(struct napi_ + set_current_state(TASK_INTERRUPTIBLE); + } + __set_current_state(TASK_RUNNING); ++ + return -1; + } + -- cgit v1.2.3