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SubjectRe: [RFC PATCH 3/3] kernel tracing prototype
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On Tue, 2008-12-02 at 16:26 -0800, Jiaying Zhang wrote:
> Refer to the previous email
> "[RFC PATCH 0/3] A couple of feature requests to the unified trace
> buffer".
>
> A kernel tracing prototype that uses the unified trace buffer to keep
> the collected trace data.
>

> Index: linux-2.6.26.2/include/linux/ktrace.h
> ===================================================================
> --- /dev/null 1970-01-01 00:00:00.000000000 +0000
> +++ linux-2.6.26.2/include/linux/ktrace.h 2008-11-25
> 11:32:37.000000000 -0800
> @@ -0,0 +1,73 @@
> +#ifndef _LINUX_KTRACE_H
> +#define _LINUX_KTRACE_H
> +
> +#include <linux/types.h>
> +
> +struct kernel_trace;
> +
> +typedef void ktrace_probe_func(struct kernel_trace *, void *,
> size_t);
> +
> +struct kernel_trace {
> + const char *name;
> + const char *format; /* format string describing variable
> list */
> + u32 enabled:1, event_id:31;
> + ktrace_probe_func *func; /* probe function */
> + struct list_head list; /* list head linked to the hash table
> entry */
> +} __attribute__((aligned(8)));
> +
> +extern int ktrace_enabled;
> +
> +/*
> + * Make sure the alignment of the structure in the __ktrace section
> will
> + * not add unwanted padding between the beginning of the section and
> the
> + * structure. Force alignment to the same alignment as the section
> start.
> + */
> +
> +#define DEFINE_KTRACE_STRUCT(name) struct ktrace_struct_##name
> +
> +#ifdef CONFIG_KTRACE
> +#define DO_TRACE(name, format, args...)
> \
> + do {
> \
> + static const char __kstrtab_##name[]
> \
> + __attribute__((section("__ktrace_strings")))
> \
> + = #name "\0" format;
> \
> + static struct kernel_trace __ktrace_##name
> \
> + __attribute__((section("__ktrace"), aligned(8))) =
> \
> + { __kstrtab_##name, &__kstrtab_##name[sizeof(#name)],
> \
> + 0, 0, NULL, LIST_HEAD_INIT(__ktrace_##name.list) };
> \
> + __ktrace_check_format(format, ## args);
> \
> + if (unlikely(ktrace_enabled) &&
> \
> + unlikely(__ktrace_##name.enabled))
> { \
> + struct ktrace_struct_##name karg = { args };
> \
> + (*__ktrace_##name.func)
> \
> + (&__ktrace_##name, &karg, sizeof(karg));
> \
> + }
> \

This looks like another form of markers/trace-points. Why not use them?

> + } while (0)
> +
> +#else /* !CONFIG_KTRACE */
> +#define DO_TRACE(name, format, args...)
> +#endif
> +

-- Steve




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