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    Subject[PATCH v8 11/16] 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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