On Mon, Jan 27, 2020 at 05:31:09PM -0500, Steven Rostedt wrote:
> On Mon, 27 Jan 2020 14:36:24 -0500
> Steven Rostedt <rostedt@xxxxxxxxxxx> wrote:
>
> > On Mon, 27 Jan 2020 13:19:28 -0600
> > Tom Zanussi <zanussi@xxxxxxxxxx> wrote:
> >
> > > It does fix the issue for me and passes the selftests. Remember that
> > > 4.19 doesn't have the .trace() hist action - you need to use the event
> > > name e.g. .first()
> >
> > Yeah I did that, but it was still clearing out the start variable when
> > I tried. I'll test the full commits next, right after I fix my git repo
> > that got corrupted because it had an alternative based on a repo that
> > rebased :-(
> >
>
> Finally got my repo fixed. Yes, after applying the two commits, this
> failed patch applies fine, and it does fix the issue. The test I did:
>
> # mount -t tracefs nodev /sys/kernel/tracing
> # cd /sys/kernel/tracing
> # echo 'first u64 start_time u64 end_time pid_t pid u64 delta' >> synthetic_events
> # echo 'hist:keys=pid:start=common_timestamp' > events/sched/sched_waking/trigger
> # echo 'hist:keys=next_pid:delta=common_timestamp-$start,start2=$start:onmatch(sched.sched_waking).first($start2,common_timestamp,next_pid,$delta)' > events/sched/sched_switch/trigger
> # cat events/sched/sched_switch/hist
>
> And make sure there were events:
>
> # cat events/sched/sched_switch/hist
> # event histogram
> #
> # trigger info: hist:keys=next_pid:vals=hitcount:delta=common_timestamp-$start,start2=$start:sort=hitcount:size=2048:clock=global:onmatch(sched.sched_waking).first($start2,common_timestamp,next_pid,$delta) [active]
> #
>
> { next_pid: 1246 } hitcount: 1
> { next_pid: 153 } hitcount: 1
> { next_pid: 21 } hitcount: 1
> { next_pid: 26 } hitcount: 1
> { next_pid: 1245 } hitcount: 1
> { next_pid: 1613 } hitcount: 1
> { next_pid: 1303 } hitcount: 1
> { next_pid: 1375 } hitcount: 1
> { next_pid: 67 } hitcount: 1
> { next_pid: 41 } hitcount: 1
> { next_pid: 12 } hitcount: 1
> { next_pid: 31 } hitcount: 1
> { next_pid: 46 } hitcount: 1
> { next_pid: 36 } hitcount: 1
> { next_pid: 16 } hitcount: 1
> { next_pid: 606 } hitcount: 3
> { next_pid: 102 } hitcount: 3
> { next_pid: 936 } hitcount: 3
> { next_pid: 13 } hitcount: 6
> { next_pid: 10 } hitcount: 7
> { next_pid: 1584 } hitcount: 13
> { next_pid: 1579 } hitcount: 27
> { next_pid: 145 } hitcount: 30
> { next_pid: 1417 } hitcount: 33
>
> Totals:
> Hits: 140
> Entries: 24
> Dropped: 0
>
> Greg,
>
> This patch is dependent on commits
> 656fe2ba85e81d00e4447bf77b8da2be3c47acb2 and
> de40f033d4e84e843d6a12266e3869015ea9097c
>
> Can you backport them as well to 4.19 and then apply this fix?
Will do, thanks!
greg k-h
