From f0bcb9dfe5ca2c9140a79df84aa35e5fd130abd0 Mon Sep 17 00:00:00 2001 From: Sebastian Andrzej Siewior Date: Wed, 3 Feb 2021 11:05:25 -0500 Subject: [PATCH 078/323] tracing: Use in_serving_softirq() to deduct softirq status. Origin: https://www.kernel.org/pub/linux/kernel/projects/rt/5.10/older/patches-5.10.215-rt107.tar.xz PREEMPT_RT does not report "serving softirq" because the tracing core looks at the preemption counter while PREEMPT_RT does not update it while processing softirqs in order to remain preemptible. The information is stored somewhere else. The in_serving_softirq() macro and the SOFTIRQ_OFFSET define are still working but not on the preempt-counter. Use in_serving_softirq() macro which works on PREEMPT_RT. On !PREEMPT_RT the compiler (gcc-10 / clang-11) is smart enough to optimize the in_serving_softirq() related read of the preemption counter away. The only difference I noticed by using in_serving_softirq() on !PREEMPT_RT is that gcc-10 implemented tracing_gen_ctx_flags() as reading FLAG, jmp _tracing_gen_ctx_flags(). Without in_serving_softirq() it inlined _tracing_gen_ctx_flags() into tracing_gen_ctx_flags(). Link: https://lkml.kernel.org/r/20210125194511.3924915-4-bigeasy@linutronix.de Signed-off-by: Sebastian Andrzej Siewior Signed-off-by: Steven Rostedt (VMware) Signed-off-by: Sebastian Andrzej Siewior --- kernel/trace/trace.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index 4145776513273..db3b3b2455894 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2614,8 +2614,7 @@ unsigned int tracing_gen_ctx_irq_test(unsigned int irqs_status) trace_flags |= TRACE_FLAG_NMI; if (pc & HARDIRQ_MASK) trace_flags |= TRACE_FLAG_HARDIRQ; - - if (pc & SOFTIRQ_OFFSET) + if (in_serving_softirq()) trace_flags |= TRACE_FLAG_SOFTIRQ; if (tif_need_resched()) -- 2.44.0