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SubjectRe: [PATCH 0/7] tracing: bug fixes for tracing/filters
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Date
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

> 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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