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    SubjectRe: [PATCH 0/7] tracing: bug fixes for tracing/filters
    On Sat, Apr 11, 2009 at 04:48:33PM +0200, Frederic Weisbecker wrote:
    > On Sat, Apr 11, 2009 at 04:30:48AM -0500, Tom Zanussi wrote:
    > > Hi,
    > >
    > > On Sat, 2009-04-11 at 15:52 +0800, Li Zefan wrote:
    > > > This patchset fixes some bugs in tracing/filters. Most of the change
    > > > goes to the last patch, and others are small ones.
    > > >
    > >
    > > At first glance, they look good and fix real problems - thanks for
    > > fixing them. Re patch 7, there's been some discussion about using rcu
    > > for this. See:
    > >
    > > http://lkml.org/lkml/2009/4/5/46
    > >
    > > >From that discussion, it seems some non-trivial changes to rcu would be
    > > needed for this. I'm playing around with a different idea now to
    > > hopefully avoid the need for that, or the other approach mentioned, of
    > > temporarily stopping tracing while removing/changing the filters.
    > >
    > > Basically my thought is to avoid the problem by not allocating or
    > > destroying the preds when removing filters but instead switch out the
    > > pred->fns with a nop version while keeping the fields intact for awhile.
    > > I think that will work for removing filters, but I still need to think
    > > about how it would (or would not) work for replacing them.
    > >
    > > Tom
    >
    > It would be sort of reinventing rcu :-)
    > Well, Paul proposed something recently, hmm I should double check
    > this discussion.

    I am actually thinking about doing this. Please do take a look at:

    http://lkml.org/lkml/2009/4/6/332
    http://lkml.org/lkml/2009/4/6/496

    What I need from you is to tell me whether or not the proposed placement
    of rcu_idle(), rcu_idle_start(), and rcu_idle_end() makes sense from a
    tracing viewpoint.

    Thanx, Paul

    > Anyway, the fixes from Li (other than 4 and 7 for which we have comments)
    > look very good!
    >
    > Frederic.
    >
    >
    >
    > >
    > > > Maybe 3rd to 6th patches can be regarded as small enhancements instead
    > > > of bug fixes? But they are behavioural changes.
    > > >
    > > >
    > > > [PATCH 1/7] tracing/filters: NUL-terminate user input filter
    > > > [PATCH 2/7] tracing/filters: fix NULL pointer dereference
    > > > [PATCH 3/7] tracing/filters: allow user input integer to be oct or hex
    > > > [PATCH 4/7] tracing/filters: allow user to specify a filter val to be string
    > > > [PATCH 5/7] tracing/filters: disallow newline as delimeter
    > > > [PATCH 6/7] tracing/filters: return proper error code when writing filter file
    > > > [PATCH 7/7] tracing/filters: make filter preds RCU safe
    > > >
    > > > kernel/trace/trace.h | 6 +-
    > > > kernel/trace/trace_events.c | 16 +++--
    > > > kernel/trace/trace_events_filter.c | 131 ++++++++++++++++++++++++++---------
    > > > kernel/trace/trace_events_stage_3.h | 10 +++-
    > > > 4 files changed, 121 insertions(+), 42 deletions(-)
    > > > ---
    > >
    >
    > --
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