On Tue, Sep 29, 2020 at 09:50:51AM +0800, [email protected] wrote: > From: Quanyang Wang <[email protected]> > > Since sched_clock_read_begin and sched_clock_read_retry are called > by notrace function sched_clock, they shouldn't be traceable either, > or else ftrace_graph_caller will run into a dead loop on the path > as below (arm for instance): > > ftrace_graph_caller > prepare_ftrace_return > function_graph_enter > ftrace_push_return_trace > trace_clock_local > sched_clock > sched_clock_read_begin/retry > > Fixes: 1b86abc1c645 ("sched_clock: Expose struct clock_read_data") > Signed-off-by: Quanyang Wang <[email protected]> > --- > Changes: > V2: Add notrace to sched_clock_read_retry according to Peter's suggestion. > > kernel/time/sched_clock.c | 4 ++-- > 1 file changed, 2 insertions(+), 2 deletions(-) > > diff --git a/kernel/time/sched_clock.c b/kernel/time/sched_clock.c > index 1c03eec6ca9b..f629e3f5afbe 100644 > --- a/kernel/time/sched_clock.c > +++ b/kernel/time/sched_clock.c > @@ -68,13 +68,13 @@ static inline u64 notrace cyc_to_ns(u64 cyc, u32 mult, > u32 shift) > return (cyc * mult) >> shift; > } > > -struct clock_read_data *sched_clock_read_begin(unsigned int *seq) > +notrace struct clock_read_data *sched_clock_read_begin(unsigned int *seq) > { > *seq = raw_read_seqcount_latch(&cd.seq); > return cd.read_data + (*seq & 1); > } > > -int sched_clock_read_retry(unsigned int seq) > +int notrace sched_clock_read_retry(unsigned int seq) > { > return read_seqcount_retry(&cd.seq, seq); > }
You're inconsistent in the placement of notrace, I prefer the first, the second read like notrace is the return type instead of a qualifier. In any case, Acked-by: Peter Zijlstra (Intel) <[email protected]>
