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    Subject[tip:perf/core] printk/tracing: Add console output tracing
    Commit-ID:  95100358491abaa2e9a5483811370059bbca4645
    Gitweb: http://git.kernel.org/tip/95100358491abaa2e9a5483811370059bbca4645
    Author: Johannes Berg <johannes.berg@intel.com>
    AuthorDate: Thu, 24 Nov 2011 20:03:08 +0100
    Committer: Steven Rostedt <rostedt@goodmis.org>
    CommitDate: Mon, 13 Feb 2012 13:46:05 -0500

    printk/tracing: Add console output tracing

    Add a printk.console trace point to record any printk
    messages into the trace, regardless of the current
    console loglevel. This can help correlate (existing)
    printk debugging with other tracing.

    Link: http://lkml.kernel.org/r/1322161388.5366.54.camel@jlt3.sipsolutions.net

    Acked-by: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Christoph Hellwig <hch@infradead.org>
    Cc: Ingo Molnar <mingo@redhat.com>
    Acked-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Acked-by: Thomas Gleixner <tglx@linutronix.de>
    Signed-off-by: Johannes Berg <johannes.berg@intel.com>
    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    ---
    include/trace/events/printk.h | 41 +++++++++++++++++++++++++++++++++++++++++
    kernel/printk.c | 5 +++++
    2 files changed, 46 insertions(+), 0 deletions(-)

    diff --git a/include/trace/events/printk.h b/include/trace/events/printk.h
    new file mode 100644
    index 0000000..94ec79c
    --- /dev/null
    +++ b/include/trace/events/printk.h
    @@ -0,0 +1,41 @@
    +#undef TRACE_SYSTEM
    +#define TRACE_SYSTEM printk
    +
    +#if !defined(_TRACE_PRINTK_H) || defined(TRACE_HEADER_MULTI_READ)
    +#define _TRACE_PRINTK_H
    +
    +#include <linux/tracepoint.h>
    +
    +TRACE_EVENT_CONDITION(console,
    + TP_PROTO(const char *log_buf, unsigned start, unsigned end,
    + unsigned log_buf_len),
    +
    + TP_ARGS(log_buf, start, end, log_buf_len),
    +
    + TP_CONDITION(start != end),
    +
    + TP_STRUCT__entry(
    + __dynamic_array(char, msg, end - start + 1)
    + ),
    +
    + TP_fast_assign(
    + if ((start & (log_buf_len - 1)) > (end & (log_buf_len - 1))) {
    + memcpy(__get_dynamic_array(msg),
    + log_buf + (start & (log_buf_len - 1)),
    + log_buf_len - (start & (log_buf_len - 1)));
    + memcpy((char *)__get_dynamic_array(msg) +
    + log_buf_len - (start & (log_buf_len - 1)),
    + log_buf, end & (log_buf_len - 1));
    + } else
    + memcpy(__get_dynamic_array(msg),
    + log_buf + (start & (log_buf_len - 1)),
    + end - start);
    + ((char *)__get_dynamic_array(msg))[end - start] = 0;
    + ),
    +
    + TP_printk("%s", __get_str(msg))
    +);
    +#endif /* _TRACE_PRINTK_H */
    +
    +/* This part must be outside protection */
    +#include <trace/define_trace.h>
    diff --git a/kernel/printk.c b/kernel/printk.c
    index 13c0a11..cb8a6bd 100644
    --- a/kernel/printk.c
    +++ b/kernel/printk.c
    @@ -44,6 +44,9 @@

    #include <asm/uaccess.h>

    +#define CREATE_TRACE_POINTS
    +#include <trace/events/printk.h>
    +
    /*
    * Architectures can override it:
    */
    @@ -542,6 +545,8 @@ MODULE_PARM_DESC(ignore_loglevel, "ignore loglevel setting, to"
    static void _call_console_drivers(unsigned start,
    unsigned end, int msg_log_level)
    {
    + trace_console(&LOG_BUF(0), start, end, log_buf_len);
    +
    if ((msg_log_level < console_loglevel || ignore_loglevel) &&
    console_drivers && start != end) {
    if ((start & LOG_BUF_MASK) > (end & LOG_BUF_MASK)) {

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