On Mon, Sep 23, 2019 at 04:09:35PM +0800, wangxu wrote: > From: Wang Xu <wangx...@huawei.com> > > For x86/ppc, hw_breakpoint is triggered after the instruction is > executed. > > For arm/arm64, which is triggered before the instruction executed. > Arm/arm64 skips the instruction by using single step. But it only > supports default overflow_handler.
Where is the recusion.. ? > This patch provides a chance to avoid sample hw_breakpoint recursion > for arm/arm64 by adding 'struct perf_event_attr.bp_step'. This patch also lacks justification for why this needs to come with ABI changes. There is also a distinct lack of comments. > Signed-off-by: Wang Xu <wangx...@huawei.com> > --- > include/linux/perf_event.h | 3 +++ > include/uapi/linux/perf_event.h | 3 ++- > samples/hw_breakpoint/data_breakpoint.c | 1 + > 3 files changed, 6 insertions(+), 1 deletion(-) > > diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h > index 61448c1..f270eb7 100644 > --- a/include/linux/perf_event.h > +++ b/include/linux/perf_event.h > @@ -1024,6 +1024,9 @@ extern int perf_event_output(struct perf_event *event, > return true; > if (unlikely(event->overflow_handler == perf_event_output_backward)) > return true; > + /* avoid sample hw_breakpoint recursion */ > + if (unlikely(event->attr.bp_step)) > + return true; This is just _wrong_.. it says that every event with bp_step set always is a 'default overflow handler', irrespective of what the overflow handler actually is. > return false; > } >
