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From: Ming Lei <tom.leiming@gmail.com>
To: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>,
	Anil S Keshavamurthy <anil.s.keshavamurthy@intel.com>,
	Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
	"David S. Miller" <davem@davemloft.net>,
	Masami Hiramatsu <mhiramat@kernel.org>
Cc: Steven Rostedt <rostedt@goodmis.org>,
	linux-block <linux-block@vger.kernel.org>
Subject: krobe: __blkdev_put probe is missed
Date: Wed, 17 Jun 2020 18:30:39 +0800	[thread overview]
Message-ID: <CACVXFVO5saamQXs0naLamTKJfXZMW+p446weeqJK=9+V34UM0g@mail.gmail.com> (raw)

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 only special thing about __blkdev_put() is that the function will call into
itself. However, no such issue on __blkdev_get() which calls itself too.


Thanks,
Ming Lei

             reply	other threads:[~2020-06-17 10:30 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-17 10:30 Ming Lei [this message]
2020-06-18 12:54 ` kprobe: __blkdev_put probe is missed Ming Lei
2020-06-18 13:56   ` Masami Hiramatsu
2020-06-18 23:19     ` Ming Lei
2020-06-19  5:12       ` Masami Hiramatsu
2020-06-19  7:28         ` Ming Lei
2020-06-19 12:19           ` Steven Rostedt
2020-06-19 13:32             ` Ming Lei
2020-06-19 15:35               ` Masami Hiramatsu
2020-06-19 23:28                 ` Ming Lei
2020-06-20  0:59                   ` Steven Rostedt
2020-06-20  1:37                   ` Masami Hiramatsu
2020-06-22  0:27                     ` Ming Lei
2020-06-22  1:34                       ` Masami Hiramatsu
2020-06-22 13:01                       ` Steven Rostedt
2020-06-22 23:47                         ` Masami Hiramatsu
2020-06-23  0:38                           ` Masami Hiramatsu
2020-06-23  5:28                             ` Masami Hiramatsu

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