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    SubjectRe: [PATCH 0/5][GIT PULL][2.6.34] tracing: urgent fixes

    * Steven Rostedt <rostedt@goodmis.org> wrote:

    > Ingo,
    >
    > Li Zefan and Lai Jiangshan told me they were finding various bugs
    > with running a stress test. I asked for this test, and Li sent it
    > to me. Running the test I was also able to trigger the same bugs that
    > they were seeing. Unfortunately, these bugs were very hard to figure
    > out and it took me most of the week to fix them.
    >
    > These bugs would most likely not happen in normal use, since they
    > all require multiple users writing to the control files of ftrace.
    > This stress test does just that, it creates several processes that
    > each write to a different part of a ftrace control system. One resizes
    > the ring buffer, the other enables and disables various options,
    > another changes the ftrace plugins, another enables and disables
    > various events, another enables and disables the tracer, etc.
    >
    > Normal use generally has a single user that would only do one of these
    > actions at a time. But that is no excuse for not fixing the issues
    > that this test uncovered, so I took this very seriously.
    >
    > Even the fix "tracing: Disable buffer switching when starting or
    > stopping trace" may look like it could happen if wakeup tracer is running,
    > but since opening the trace file would cause the wakeup tracer to stop,
    > it actually required another task to change the current tracer to
    > the wakeup tracer while the trace file was being read.
    >
    > In any event, I've been running Li's ftrace_stress_test for a few
    > hours now, and it seems pretty stable with these patches. I'll continue
    > to run it to see if it finds anything else.
    >
    > All of these patches I consider urgent and have also Cc'd stable on them.
    >
    > Please pull the latest tip/tracing/urgent tree, which can be found at:
    >
    > git://git.kernel.org/pub/scm/linux/kernel/git/rostedt/linux-2.6-trace.git
    > tip/tracing/urgent
    >
    >
    > Lai Jiangshan (1):
    > ring-buffer: Move disabled check into preempt disable section
    >
    > Steven Rostedt (4):
    > function-graph: Init curr_ret_stack with ret_stack
    > tracing: Use same local variable when resetting the ring buffer
    > tracing: Disable buffer switching when starting or stopping trace
    > tracing: Do not record user stack trace from NMI context
    >
    > ----
    > kernel/trace/ftrace.c | 2 +-
    > kernel/trace/ring_buffer.c | 12 ++++++------
    > kernel/trace/trace.c | 24 ++++++++++++++++++++----
    > 3 files changed, 27 insertions(+), 11 deletions(-)

    Pulled, thanks a lot Steve!

    Ingo


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