From: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
To: "Dorau, Lukasz" <lukasz.dorau@intel.com>
Cc: Ananth N Mavinakayanahalli <ananth@linux.vnet.ibm.com>,
"Keshavamurthy, Anil S" <anil.s.keshavamurthy@intel.com>,
"David S. Miller" <davem@davemloft.net>,
Masami Hiramatsu <mhiramat@kernel.org>,
linux-trace-users@vger.kernel.org, "Slusarz,
Marcin" <marcin.slusarz@intel.com>,
"Jelinek, Sarah" <sarah.jelinek@intel.com>,
"Chernookyi, Vitalii" <vitalii.chernookyi@intel.com>,
"Buella, Gabor" <gabor.buella@intel.com>
Subject: Re: Why return probes of some syscalls sometimes are not called?
Date: Thu, 9 Mar 2017 13:58:29 +0000 (UTC) [thread overview]
Message-ID: <253263641.1274.1489067909121.JavaMail.zimbra@efficios.com> (raw)
In-Reply-To: <D9FFE20C522965449E182ACE73889AEB4868177B@irsmsx105.ger.corp.intel.com>
----- On Mar 9, 2017, at 8:44 AM, Dorau, Lukasz lukasz.dorau@intel.com wrote:
> Hi,
>
> Could someone explain me why return probes of some syscalls (for example: futex,
> poll, epoll_wait) sometimes are not called?
>
> It can be reproduced using the following bash script:
> https://gist.github.com/ldorau/c439d9ec7635409a5016c42e3a9121ec
>
> Here are results gathered from 60 seconds test run on kernel 4.9.12 (Fedora 24):
>
> futex: p 56904 r 5489 (90% did not return (51415))
> poll: p 43466 r 7703 (82% did not return (35763))
> epoll_wait: p 73366 r 23551 (67% did not return (49815))
Most likely scenario: those processes are still blocked on those
system calls when your tracing ends.
AFAIU, another possible (less frequent) scenario: a process gets
killed with SIGKILL while blocked on the signal.
Thanks,
Mathieu
>
> The whole log is attached below.
>
> Lukasz
>
> ---
> # ./test_kprobes.sh 60
>
> Will trace using following kprobe_events:
> r:kprobes/r_futex sys_futex
> p:kprobes/p_futex sys_futex
> r:kprobes/r_poll sys_poll
> p:kprobes/p_poll sys_poll
> r:kprobes/r_epoll_wait sys_epoll_wait
> p:kprobes/p_epoll_wait sys_epoll_wait
> r:kprobes/r_select sys_select
> p:kprobes/p_select sys_select
> r:kprobes/r_fork sys_fork
> p:kprobes/p_fork sys_fork
> r:kprobes/r_vfork sys_vfork
> p:kprobes/p_vfork sys_vfork
> r:kprobes/r_mmap sys_mmap
> p:kprobes/p_mmap sys_mmap
> r:kprobes/r_open sys_open
> p:kprobes/p_open sys_open
> r:kprobes/r_close sys_close
> p:kprobes/p_close sys_close
> r:kprobes/r_write sys_write
> p:kprobes/p_write sys_write
> r:kprobes/r_read sys_read
> p:kprobes/p_read sys_read
>
> Results (60 sec):
> futex: p 56904 r 5489 (90% did not return (51415))
> poll: p 43466 r 7703 (82% did not return (35763))
> epoll_wait: p 73366 r 23551 (67% did not return (49815))
> select: p 13355 r 13351 (0% did not return (4))
> fork: p 0 r 0 (OK)
> vfork: p 0 r 0 (OK)
> mmap: p 4328 r 4328 (OK)
> open: p 4579 r 4579 (OK)
> close: p 7163 r 7163 (OK)
> write: p 22769 r 22769 (OK)
> read: p 40014 r 40014 (OK)
>
> --
> To unsubscribe from this list: send the line "unsubscribe linux-trace-users" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at http://vger.kernel.org/majordomo-info.html
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com
next prev parent reply other threads:[~2017-03-09 13:58 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-09 13:44 Why return probes of some syscalls sometimes are not called? Dorau, Lukasz
2017-03-09 13:58 ` Mathieu Desnoyers [this message]
2017-03-09 14:44 ` Steven Rostedt
2017-03-09 14:57 ` Steven Rostedt
[not found] ` <1231722663.1343.1489071698914.JavaMail.zimbra@efficios.com>
2017-03-09 15:20 ` Steven Rostedt
[not found] ` <D9FFE20C522965449E182ACE73889AEB486818F2@irsmsx105.ger.corp.intel.com>
2017-03-09 15:38 ` Steven Rostedt
2017-03-09 17:00 ` Masami Hiramatsu
2017-03-09 18:19 ` Chernookyi, Vitalii
2017-03-10 10:51 ` Masami Hiramatsu
2017-03-13 9:09 ` Dorau, Lukasz
2017-03-16 10:01 ` Masami Hiramatsu
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