On Fri, Nov 5, 2021 at 5:03 PM Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> On Fri, 5 Nov 2021 14:16:13 +0200
> "Tzvetomir Stoyanov (VMware)" <tz.stoyanov@xxxxxxxxx> wrote:
>
> > +static void init_devent_desc(void)
> > +{
> > + int i;
> > +
> > + BUILD_BUG_ON(ARRAY_SIZE(dynevents) != max_dyn_index);
> > +
> > + /* Use ftrace dynamic_events, if available */
> > + if (tracefs_file_exists(NULL, DYNEVENTS_EVENTS)) {
> > + for (i = 0; i < max_dyn_index; i++)
> > + dynevents[i].file = DYNEVENTS_EVENTS;
> > + return;
> > + }
> > +
> > + if (tracefs_file_exists(NULL, KPROBE_EVENTS)) {
> > + dynevents[ffs(TRACEFS_DYNEVENT_KPROBE) - 1].file = KPROBE_EVENTS;
> > + dynevents[ffs(TRACEFS_DYNEVENT_KRETPROBE) - 1].file = KPROBE_EVENTS;
> > + }
> > + if (tracefs_file_exists(NULL, UPROBE_EVENTS)) {
> > + dynevents[ffs(TRACEFS_DYNEVENT_UPROBE) - 1].file = UPROBE_EVENTS;
> > + dynevents[ffs(TRACEFS_DYNEVENT_URETPROBE) - 1].file = UPROBE_EVENTS;
> > + }
> > + if (tracefs_file_exists(NULL, SYNTH_EVENTS)) {
> > + dynevents[ffs(TRACEFS_DYNEVENT_SYNTH) - 1].file = SYNTH_EVENTS;
> > + dynevents[ffs(TRACEFS_DYNEVENT_SYNTH) - 1].prefix = "";
> > + }
> > +}
> > +
>
> I would have kept your bit_index() function to simplify the above. I just
> meant to use ffs in that function.
>
> static inline bit_index(unsigned int bits)
> {
> return ffs(bits) - 1;
> }
>
> -- Steve
>
The problem with that function is that it cannot be used to initialise
constant variables, gcc complains about that. The ffs() API has no
such problem
--
Tzvetomir (Ceco) Stoyanov
VMware Open Source Technology Center
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