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From: Ming Lei <ming.lei@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <mhiramat@kernel.org>,
	Ming Lei <tom.leiming@gmail.com>,
	"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>,
	linux-block <linux-block@vger.kernel.org>
Subject: Re: kprobe: __blkdev_put probe is missed
Date: Fri, 19 Jun 2020 21:32:40 +0800	[thread overview]
Message-ID: <20200619133240.GA351476@T590> (raw)
In-Reply-To: <20200619081954.3d72a252@oasis.local.home>

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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@redhat.com> 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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  reply	other threads:[~2020-06-19 13:33 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-17 10:30 krobe: __blkdev_put probe is missed Ming Lei
2020-06-18 12:54 ` kprobe: " 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 [this message]
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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