On Wed, Jun 17, 2020 at 06:30:39PM +0800, Ming Lei wrote: > Hello Guys, > > I found probe on __blkdev_put is missed, which can be observed > via bcc/perf reliably: > > 1) start trace > - perf probe __blkdev_put > - perf trace -a -e probe:__blkdev_put > > or > > /usr/share/bcc/tools/stackcount __blkdev_put > > 2) run the following command: > blockdev --getbsz /dev/sda1 > > 3) 'perf trace' or stackcount just dumps one trace event, and it > should have been two > __blkdev_put() traces, since one __blkdev_put() is called for > partition(/dev/sda1), > and another is for disk(/dev/sda). If trace_printk() is added in > __blkdev_put(), > two events will be captured from ftrace. >
The issue can be shown by loading a kprobe module which registers on __blkdev_put(), just by replacing _do_fork with __blkdev_put on samples/kprobes/kprobe_example.c. So the issue is really in kprobe code. Thanks, Ming
