Re: [PATCH RFC] r8152: Ensure that napi_schedule() is handled
From: Peter Zijlstra <peterz@infradead.org>
Date: 2021-05-15 13:10:20
Also in:
linux-usb, lkml
On Sat, May 15, 2021 at 01:23:02AM +0200, Thomas Gleixner wrote:
We can make that work but sure I'm not going to argue when you decide to just go for raise_softirq_irqsoff(). I just hacked that check up which is actually useful beyond NAPI. It's straight forward except for that flush_smp_call_function_from_idle() oddball, which immeditately triggered that assert because block mq uses __raise_softirq_irqsoff() in a smp function call... See below. Peter might have opinions though :)
Yeah, lovely stuff :-)
+#define lockdep_assert_softirq_raise_ok() \
+do { \
+ WARN_ON_ONCE(__lockdep_enabled && \
+ !current->softirq_raise_safe && \
+ !(softirq_count() | hardirq_count())); \
+} while (0)quoted hunk ↗ jump to hunk
--- a/kernel/smp.c +++ b/kernel/smp.c@@ -691,7 +691,9 @@ void flush_smp_call_function_from_idle(v cfd_seq_store(this_cpu_ptr(&cfd_seq_local)->idle, CFD_SEQ_NOCPU, smp_processor_id(), CFD_SEQ_IDLE); local_irq_save(flags); + lockdep_set_softirq_raise_safe(); flush_smp_call_function_queue(true); + lockdep_clear_softirq_raise_safe(); if (local_softirq_pending()) do_softirq();
I think it might make more sense to raise hardirq_count() in/for flush_smp_call_function_queue() callers that aren't already from hardirq context. That's this site and smpcfd_dying_cpu(). Then we can do away with this new special case.