From 4a79c32fee81aba5ae3a7efda9db7819a66ac838 Mon Sep 17 00:00:00 2001 From: Felix Fietkau Date: Sun, 14 Mar 2021 23:53:35 +0100 Subject: kernel: replace threaded NAPI implementation in 5.10 with upstream backport This uses a kthread per NAPI instance instead of the workqueue approach Signed-off-by: Felix Fietkau --- ...e-between-napi-kthread-mode-and-busy-poll.patch | 93 ++++++++++++++++++++++ 1 file changed, 93 insertions(+) create mode 100644 target/linux/generic/backport-5.10/603-v5.12-net-fix-race-between-napi-kthread-mode-and-busy-poll.patch (limited to 'target/linux/generic/backport-5.10/603-v5.12-net-fix-race-between-napi-kthread-mode-and-busy-poll.patch') diff --git a/target/linux/generic/backport-5.10/603-v5.12-net-fix-race-between-napi-kthread-mode-and-busy-poll.patch b/target/linux/generic/backport-5.10/603-v5.12-net-fix-race-between-napi-kthread-mode-and-busy-poll.patch new file mode 100644 index 0000000000..e0fd09b012 --- /dev/null +++ b/target/linux/generic/backport-5.10/603-v5.12-net-fix-race-between-napi-kthread-mode-and-busy-poll.patch @@ -0,0 +1,93 @@ +From: Wei Wang +Date: Mon, 1 Mar 2021 17:21:13 -0800 +Subject: [PATCH] net: fix race between napi kthread mode and busy poll + +Currently, napi_thread_wait() checks for NAPI_STATE_SCHED bit to +determine if the kthread owns this napi and could call napi->poll() on +it. However, if socket busy poll is enabled, it is possible that the +busy poll thread grabs this SCHED bit (after the previous napi->poll() +invokes napi_complete_done() and clears SCHED bit) and tries to poll +on the same napi. napi_disable() could grab the SCHED bit as well. +This patch tries to fix this race by adding a new bit +NAPI_STATE_SCHED_THREADED in napi->state. This bit gets set in +____napi_schedule() if the threaded mode is enabled, and gets cleared +in napi_complete_done(), and we only poll the napi in kthread if this +bit is set. This helps distinguish the ownership of the napi between +kthread and other scenarios and fixes the race issue. + +Fixes: 29863d41bb6e ("net: implement threaded-able napi poll loop support") +Reported-by: Martin Zaharinov +Suggested-by: Jakub Kicinski +Signed-off-by: Wei Wang +Cc: Alexander Duyck +Cc: Eric Dumazet +Cc: Paolo Abeni +Cc: Hannes Frederic Sowa +--- + +--- a/include/linux/netdevice.h ++++ b/include/linux/netdevice.h +@@ -359,6 +359,7 @@ enum { + NAPI_STATE_NO_BUSY_POLL,/* Do not add in napi_hash, no busy polling */ + NAPI_STATE_IN_BUSY_POLL,/* sk_busy_loop() owns this NAPI */ + NAPI_STATE_THREADED, /* The poll is performed inside its own thread*/ ++ NAPI_STATE_SCHED_THREADED, /* Napi is currently scheduled in threaded mode */ + }; + + enum { +@@ -370,6 +371,7 @@ enum { + NAPIF_STATE_NO_BUSY_POLL = BIT(NAPI_STATE_NO_BUSY_POLL), + NAPIF_STATE_IN_BUSY_POLL = BIT(NAPI_STATE_IN_BUSY_POLL), + NAPIF_STATE_THREADED = BIT(NAPI_STATE_THREADED), ++ NAPIF_STATE_SCHED_THREADED = BIT(NAPI_STATE_SCHED_THREADED), + }; + + enum gro_result { +--- a/net/core/dev.c ++++ b/net/core/dev.c +@@ -4275,6 +4275,8 @@ static inline void ____napi_schedule(str + */ + thread = READ_ONCE(napi->thread); + if (thread) { ++ if (thread->state != TASK_INTERRUPTIBLE) ++ set_bit(NAPI_STATE_SCHED_THREADED, &napi->state); + wake_up_process(thread); + return; + } +@@ -6495,7 +6497,8 @@ bool napi_complete_done(struct napi_stru + + WARN_ON_ONCE(!(val & NAPIF_STATE_SCHED)); + +- new = val & ~(NAPIF_STATE_MISSED | NAPIF_STATE_SCHED); ++ new = val & ~(NAPIF_STATE_MISSED | NAPIF_STATE_SCHED | ++ NAPIF_STATE_SCHED_THREADED); + + /* If STATE_MISSED was set, leave STATE_SCHED set, + * because we will call napi->poll() one more time. +@@ -6931,16 +6934,25 @@ static int napi_poll(struct napi_struct + + static int napi_thread_wait(struct napi_struct *napi) + { ++ bool woken = false; ++ + set_current_state(TASK_INTERRUPTIBLE); + + while (!kthread_should_stop() && !napi_disable_pending(napi)) { +- if (test_bit(NAPI_STATE_SCHED, &napi->state)) { ++ /* 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 ++ * set by some other busy poll thread or by napi_disable(). ++ */ ++ if (test_bit(NAPI_STATE_SCHED_THREADED, &napi->state) || woken) { + WARN_ON(!list_empty(&napi->poll_list)); + __set_current_state(TASK_RUNNING); + return 0; + } + + schedule(); ++ /* woken being true indicates this thread owns this napi. */ ++ woken = true; + set_current_state(TASK_INTERRUPTIBLE); + } + __set_current_state(TASK_RUNNING); -- cgit v1.2.3