On Fri, Jun 19, 2020 at 08:19:54AM -0400, Steven Rostedt wrote:
> On Fri, 19 Jun 2020 15:28:59 +0800
> Ming Lei <ming.lei@xxxxxxxxxx> wrote:
>
> > >
> > > OK, then let's make events (for sure)
> > >
> > > root@devnote2:/sys/kernel/debug/tracing# echo p __blkdev_put >> kprobe_events
> > > root@devnote2:/sys/kernel/debug/tracing# echo r __blkdev_put >> kprobe_events
> > > root@devnote2:/sys/kernel/debug/tracing# echo p blkdev_put >> kprobe_events
>
> Hi Ming,
>
> Do you have the kprobe_events file?
>
> > > root@devnote2:/sys/kernel/debug/tracing# echo 1 > events/kprobes/enable
> >
> > I can't find 'events/kprobes' in my VM with upstream kernel, also not found
> > the dir under fedora31(5.5.15-200) & rhel8(v4.18 based).
>
> The events/kprobes directly will be created when you create a
> kprobe_event. It wont exist until then.
Hi Steven and Masami,
Got it, thanks for your help, now I can run the test, follows the steps
and results, and there is still one __blkdev_put probed.
And it is observed in my VM reliably with 5.7+ or Fedora kernel reliably,
kernel config is attached.
[root@ktest-01 tracing]# uname -a
Linux ktest-01 5.7.0+ #1900 SMP Fri Jun 19 16:26:47 CST 2020 x86_64 x86_64 x86_64 GNU/Linux
[root@ktest-01 tracing]#
[root@ktest-01 tracing]# cat kprobe_events
[root@ktest-01 tracing]#
[root@ktest-01 tracing]# echo p blkdev_put >> kprobe_events
[root@ktest-01 tracing]# echo p __blkdev_put >> kprobe_events
[root@ktest-01 tracing]# echo r __blkdev_put >> kprobe_events
[root@ktest-01 tracing]#
[root@ktest-01 tracing]# echo 1 > events/kprobes/enable
[root@ktest-01 tracing]# blockdev --getbsz /dev/sda1
4096
[root@ktest-01 tracing]# echo 0 > events/kprobes/enable
[root@ktest-01 tracing]# cat trace
# tracer: nop
#
# entries-in-buffer/entries-written: 3/3 #P:8
#
# _-----=> irqs-off
# / _----=> need-resched
# | / _---=> hardirq/softirq
# || / _--=> preempt-depth
# ||| / delay
# TASK-PID CPU# |||| TIMESTAMP FUNCTION
# | | | |||| | |
blockdev-970 [005] .... 17603.447236: p_blkdev_put_0: (blkdev_put+0x0/0xb4)
blockdev-970 [005] .... 17603.447244: p___blkdev_put_0: (__blkdev_put+0x0/0x19d)
blockdev-970 [005] d... 17603.447251: r___blkdev_put_0: (blkdev_close+0x22/0x25 <- __blkdev_put)
Thanks,
Ming
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