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42 lines
1.7 KiB
Diff
42 lines
1.7 KiB
Diff
From: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Date: Mon, 25 Jan 2021 20:45:10 +0100
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Subject: [PATCH 3/4] tracing: Use in_serving_softirq() to deduct softirq
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status.
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PREEMPT_RT does not report "serving softirq" because the tracing core
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looks at the preemption counter while PREEMPT_RT does not update it
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while processing softirqs in order to remain preemptible. The
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information is stored somewhere else.
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The in_serving_softirq() macro and the SOFTIRQ_OFFSET define are still
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working but not on the preempt-counter.
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Use in_serving_softirq() macro which works on PREEMPT_RT. On !PREEMPT_RT
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the compiler (gcc-10 / clang-11) is smart enough to optimize the
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in_serving_softirq() related read of the preemption counter away.
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The only difference I noticed by using in_serving_softirq() on
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!PREEMPT_RT is that gcc-10 implemented tracing_gen_ctx_flags() as
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reading FLAG, jmp _tracing_gen_ctx_flags(). Without in_serving_softirq()
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it inlined _tracing_gen_ctx_flags() into tracing_gen_ctx_flags().
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Link: https://lkml.kernel.org/r/20210125194511.3924915-4-bigeasy@linutronix.de
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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Signed-off-by: Steven Rostedt (VMware) <rostedt@goodmis.org>
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Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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---
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kernel/trace/trace.c | 3 +--
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1 file changed, 1 insertion(+), 2 deletions(-)
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--- a/kernel/trace/trace.c
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+++ b/kernel/trace/trace.c
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@@ -2589,8 +2589,7 @@ unsigned int tracing_gen_ctx_irq_test(un
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trace_flags |= TRACE_FLAG_NMI;
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if (pc & HARDIRQ_MASK)
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trace_flags |= TRACE_FLAG_HARDIRQ;
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-
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- if (pc & SOFTIRQ_OFFSET)
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+ if (in_serving_softirq())
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trace_flags |= TRACE_FLAG_SOFTIRQ;
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if (tif_need_resched())
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