linux-kernel - [RFC PATCH 5/7] trace: Use early task context tracking if available

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Date:   Tue,  2 Apr 2019 22:03:57 +0200
From:   Daniel Bristot de Oliveira <bristot@...hat.com>
To:     linux-kernel@...r.kernel.org
Cc:     Steven Rostedt <rostedt@...dmis.org>,
        Arnaldo Carvalho de Melo <acme@...nel.org>,
        Ingo Molnar <mingo@...hat.com>,
        Andy Lutomirski <luto@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        Peter Zijlstra <peterz@...radead.org>,
        "H. Peter Anvin" <hpa@...or.com>,
        "Joel Fernandes (Google)" <joel@...lfernandes.org>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>,
        Romulo Silva de Oliveira <romulo.deoliveira@...c.br>,
        Clark Williams <williams@...hat.com>, x86@...nel.org
Subject: [RFC PATCH 5/7] trace: Use early task context tracking if available

Use the early task context tracking to detect the current context,
if the arch supports it.

Signed-off-by: Daniel Bristot de Oliveira <bristot@...hat.com>
Cc: Steven Rostedt <rostedt@...dmis.org>
Cc: Arnaldo Carvalho de Melo <acme@...nel.org>
Cc: Ingo Molnar <mingo@...hat.com>
Cc: Andy Lutomirski <luto@...nel.org>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Borislav Petkov <bp@...en8.de>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: "H. Peter Anvin" <hpa@...or.com>
Cc: "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Namhyung Kim <namhyung@...nel.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Tommaso Cucinotta <tommaso.cucinotta@...tannapisa.it>
Cc: Romulo Silva de Oliveira <romulo.deoliveira@...c.br>
Cc: Clark Williams <williams@...hat.com>
Cc: linux-kernel@...r.kernel.org
Cc: x86@...nel.org
---
 kernel/trace/trace.h | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/kernel/trace/trace.h b/kernel/trace/trace.h
index 09318748fab8..62ba4bd0e436 100644
--- a/kernel/trace/trace.h
+++ b/kernel/trace/trace.h
@@ -632,7 +632,18 @@ enum {
 	TRACE_CTX_NORMAL,
 	TRACE_CTX_MAX
 };
+#ifdef ARCH_HAS_TASK_CONTEXT
+static __always_inline int trace_get_context_bit(void)
+{
+	unsigned long tc = this_cpu_read(task_context);
 
+	if (tc)
+		return tc & TASK_CTX_NMI ? TRACE_CTX_NMI :
+			tc & TASK_CTX_IRQ ? TRACE_CTX_IRQ : TRACE_CTX_SOFTIRQ;
+	else
+		return TRACE_CTX_NORMAL;
+}
+#else /* ARCH_HAS_TASK_CONTEXT */
 static __always_inline int trace_get_context_bit(void)
 {
 	unsigned long pc = preempt_count();
@@ -643,6 +654,7 @@ static __always_inline int trace_get_context_bit(void)
 	else
 		return TRACE_CTX_NORMAL;
 }
+#endif /* ARCH_HAS_TASK_CONTEXT */
 
 static __always_inline int trace_test_and_set_recursion(int start, int max)
 {
-- 
2.20.1