diff options
Diffstat (limited to 'debian/patches-rt/0001-net-Remove-conditional-threaded-NAPI-wakeup-based-on.patch')
| -rw-r--r-- | debian/patches-rt/0001-net-Remove-conditional-threaded-NAPI-wakeup-based-on.patch | 75 |
1 files changed, 75 insertions, 0 deletions
diff --git a/debian/patches-rt/0001-net-Remove-conditional-threaded-NAPI-wakeup-based-on.patch b/debian/patches-rt/0001-net-Remove-conditional-threaded-NAPI-wakeup-based-on.patch new file mode 100644 index 0000000000..ae507f979e --- /dev/null +++ b/debian/patches-rt/0001-net-Remove-conditional-threaded-NAPI-wakeup-based-on.patch @@ -0,0 +1,75 @@ +From: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +Date: Sat, 9 Mar 2024 10:05:09 +0100 +Subject: [PATCH 1/4] net: Remove conditional threaded-NAPI wakeup based on + task state. +Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/6.8/older/patches-6.8.2-rt11.tar.xz + +A NAPI thread is scheduled by first setting NAPI_STATE_SCHED bit. If +successful (the bit was not yet set) then the NAPI_STATE_SCHED_THREADED +is set but only if thread's state is not TASK_INTERRUPTIBLE (is +TASK_RUNNING) followed by task wakeup. + +If the task is idle (TASK_INTERRUPTIBLE) then the +NAPI_STATE_SCHED_THREADED bit is not set. The thread is no relying on +the bit but always leaving the wait-loop after returning from schedule() +because there must have been a wakeup. + +The smpboot-threads implementation for per-CPU threads requires an +explicit condition and does not support "if we get out of schedule() +then there must be something to do". + +Removing this optimisation simplifies the following integration. + +Set NAPI_STATE_SCHED_THREADED unconditionally on wakeup and rely on it +in the wait path by removing the `woken' condition. + +Acked-by: Jakub Kicinski <kuba@kernel.org> +Link: https://lore.kernel.org/r/20240309090824.2956805-2-bigeasy@linutronix.de +Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> +--- + net/core/dev.c | 14 ++------------ + 1 file changed, 2 insertions(+), 12 deletions(-) + +--- a/net/core/dev.c ++++ b/net/core/dev.c +@@ -4452,13 +4452,7 @@ static inline void ____napi_schedule(str + */ + thread = READ_ONCE(napi->thread); + if (thread) { +- /* Avoid doing set_bit() if the thread is in +- * INTERRUPTIBLE state, cause napi_thread_wait() +- * makes sure to proceed with napi polling +- * if the thread is explicitly woken from here. +- */ +- if (READ_ONCE(thread->__state) != TASK_INTERRUPTIBLE) +- set_bit(NAPI_STATE_SCHED_THREADED, &napi->state); ++ set_bit(NAPI_STATE_SCHED_THREADED, &napi->state); + wake_up_process(thread); + return; + } +@@ -6654,8 +6648,6 @@ 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()) { +@@ -6664,15 +6656,13 @@ static int napi_thread_wait(struct 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) { ++ if (test_bit(NAPI_STATE_SCHED_THREADED, &napi->state)) { + 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); |