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    Subject[34-longterm 001/179] ftrace: Only update the function code on write to filter files
    Date
    From: Steven Rostedt <srostedt@redhat.com>

    -------------------
    This is a commit scheduled for the next v2.6.34 longterm release.
    http://git.kernel.org/?p=linux/kernel/git/paulg/longterm-queue-2.6.34.git
    If you see a problem with using this for longterm, please comment.
    -------------------

    commit 058e297d34a404caaa5ed277de15698d8dc43000 upstream.

    If function tracing is enabled, a read of the filter files will
    cause the call to stop_machine to update the function trace sites.
    It should only call stop_machine on write.

    Signed-off-by: Steven Rostedt <rostedt@goodmis.org>
    Signed-off-by: Paul Gortmaker <paul.gortmaker@windriver.com>
    ---
    kernel/trace/ftrace.c | 12 +++++++-----
    1 file changed, 7 insertions(+), 5 deletions(-)

    diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c
    index e28af02..7dd746c 100644
    --- a/kernel/trace/ftrace.c
    +++ b/kernel/trace/ftrace.c
    @@ -2355,14 +2355,16 @@ ftrace_regex_release(struct inode *inode, struct file *file, int enable)
    ftrace_match_records(parser->buffer, parser->idx, enable);
    }

    - mutex_lock(&ftrace_lock);
    - if (ftrace_start_up && ftrace_enabled)
    - ftrace_run_update_code(FTRACE_ENABLE_CALLS);
    - mutex_unlock(&ftrace_lock);
    -
    trace_parser_put(parser);
    kfree(iter);

    + if (file->f_mode & FMODE_WRITE) {
    + mutex_lock(&ftrace_lock);
    + if (ftrace_start_up && ftrace_enabled)
    + ftrace_run_update_code(FTRACE_ENABLE_CALLS);
    + mutex_unlock(&ftrace_lock);
    + }
    +
    mutex_unlock(&ftrace_regex_lock);
    return 0;
    }
    --
    1.7.9.6


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