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Subject[PATCH v7 11/17] tracing: not trace mips_timecounter_read() for MIPS
Date
From: Wu Zhangjin <wuzhangjin@gmail.com>

We use mips_timecounter_read() to get the timestamp in MIPS, so, it's
better to not trace it and it's subroutines, otherwise, it will goto
recursion(hang) when using function graph tracer. we use the
__notrace_funcgraph annotation to indicate them not to be traced.

And there are two common functions called by mips_timecounter_read(), we
define the __time_notrace macro to ensure they are not to be traced
either.

Signed-off-by: Wu Zhangjin <wuzhangjin@gmail.com>
---
arch/mips/include/asm/ftrace.h | 6 ++++++
arch/mips/kernel/csrc-r4k.c | 5 +++--
2 files changed, 9 insertions(+), 2 deletions(-)
diff --git a/arch/mips/include/asm/ftrace.h b/arch/mips/include/asm/ftrace.h
index 7094a40..aa7c80b 100644
--- a/arch/mips/include/asm/ftrace.h
+++ b/arch/mips/include/asm/ftrace.h
@@ -28,6 +28,12 @@ static inline unsigned long ftrace_call_adjust(unsigned long addr)
struct dyn_arch_ftrace {
};
#endif /* CONFIG_DYNAMIC_FTRACE */
+
+/* not trace the timecounter_read* in kernel/time/clocksource.c */
+#ifdef CONFIG_FUNCTION_GRAPH_TRACER
+ #define __time_notrace notrace
+#endif
+
#endif /* __ASSEMBLY__ */
#endif /* CONFIG_FUNCTION_TRACER */
#endif /* _ASM_MIPS_FTRACE_H */
diff --git a/arch/mips/kernel/csrc-r4k.c b/arch/mips/kernel/csrc-r4k.c
index 4e7705f..0c1bf80 100644
--- a/arch/mips/kernel/csrc-r4k.c
+++ b/arch/mips/kernel/csrc-r4k.c
@@ -8,6 +8,7 @@
#include <linux/clocksource.h>
#include <linux/init.h>
#include <linux/sched.h>
+#include <linux/ftrace.h>

#include <asm/time.h>

@@ -42,7 +43,7 @@ static struct timecounter r4k_tc = {
.cc = NULL,
};

-static cycle_t r4k_cc_read(const struct cyclecounter *cc)
+static cycle_t __notrace_funcgraph r4k_cc_read(const struct cyclecounter *cc)
{
return read_c0_count();
}
@@ -66,7 +67,7 @@ int __init init_r4k_timecounter(void)
return 0;
}

-u64 r4k_timecounter_read(void)
+u64 __notrace_funcgraph r4k_timecounter_read(void)
{
u64 clock;

--
1.6.2.1


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