On Wed, 10 Apr 2019 21:34:25 -0500 Josh Poimboeuf <jpoim...@redhat.com> wrote:
> > --- a/kernel/trace/trace_stack.c > > +++ b/kernel/trace/trace_stack.c > > @@ -18,8 +18,7 @@ > > > > #include "trace.h" > > > > -static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES+1] = > > - { [0 ... (STACK_TRACE_ENTRIES)] = ULONG_MAX }; > > +static unsigned long stack_dump_trace[STACK_TRACE_ENTRIES + 1]; > > Is the "+ 1" still needed? AFAICT, accesses to this array never go past > nr_entries. Probably not. But see this for an explanation: http://lkml.kernel.org/r/20180620110758.crunhd5bfep7zuiz@kili.mountain > > Also I've been staring at the code but I can't figure out why > max_entries is "- 1". > > struct stack_trace stack_trace_max = { > .max_entries = STACK_TRACE_ENTRIES - 1, > .entries = &stack_dump_trace[0], > }; > Well, it had a reason in the past, but there doesn't seem to be a reason today. Looking at git history, that code was originally: .max_entries = STACK_TRACE_ENTRIES - 1, .entries = &stack_dump_trace[1], Where we had to make max_entries -1 as we started at the first index into the array. I'll have to take a new look into this code. After Thomas's clean up here, I'm sure we can simplify it a bit more. -- Steve