From: Philp Prindeville <philipp@redfish-solutions.com>
To: Feng Gao <gfree.wind@gmail.com>
Cc: Gao Feng <fgao@48lvckh6395k16k5.yundunddos.com>,
paulus@samba.org, linux-ppp@vger.kernel.org,
Linux Kernel Network Developers <netdev@vger.kernel.org>
Subject: Re: [PATCH 1/1] ppp: Fix one deadlock issue of PPP when send frame
Date: Thu, 18 Aug 2016 16:48:27 +0000 [thread overview]
Message-ID: <fcdca34b-cfbb-4536-b857-843218645b82@redfish-solutions.com> (raw)
In-Reply-To: <CA+6hz4rUGeqohKCiTbeqp9NwkH5w_JKjqD8VEiQC4DyVL7Q7JA@mail.gmail.com>
On 08/18/2016 09:05 AM, Feng Gao wrote:
> On Thu, Aug 18, 2016 at 10:11 PM, Philp Prindeville
> <philipp@redfish-solutions.com> wrote:
>> >Feng,
>> >
>> >If the CPU can already be holding the lock, that implies re-entrancy.
>> >What's to stop the first flow of code which acquired the lock from releasing
>> >it again before the 2nd flow is done? Is the 2nd flow running at a higher
>> >priority or with interrupts disabled?
> There is no preemption happened. It is caused by wrong route policy by l2tp.
> For example, the cpu0 get the spinlock of channel1, then the channel1
> is selected again after route. As a result, cpu0 tries to get the same
> spinlock again.
>
> The call flow is like this.
> ppp_write->ppp_channel_push->start_xmit->select inappropriate route
> .... -> dev_hard_start_xmit->ppp_start_xmit->ppp_xmit_process->
> ppp_push. Now ppp_push tries to get the same spinlock which is held
> in ppp_channel_push.
>
> Regards
> Feng
>
If we're detecting (through the fact that the lock has already been
acquired) that the wrong route is being applied, why don't we just punt
the packet instead?
-Philip
next prev parent reply other threads:[~2016-08-18 16:48 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-08-16 11:05 [PATCH 1/1] ppp: Fix one deadlock issue of PPP when send frame fgao
2016-08-16 11:36 ` Feng Gao
2016-08-18 14:11 ` Philp Prindeville
2016-08-18 15:05 ` Feng Gao
2016-08-18 16:48 ` Philp Prindeville [this message]
2016-08-18 22:53 ` Feng Gao
2016-08-19 22:47 ` Guillaume Nault
2016-08-19 15:16 ` [PATCH 1/1] ppp: Fix one deadlock issue of PPP when reentrant fgao
2016-08-19 21:48 ` Guillaume Nault
2016-08-20 6:40 ` Feng Gao
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=fcdca34b-cfbb-4536-b857-843218645b82@redfish-solutions.com \
--to=philipp@redfish-solutions.com \
--cc=fgao@48lvckh6395k16k5.yundunddos.com \
--cc=gfree.wind@gmail.com \
--cc=linux-ppp@vger.kernel.org \
--cc=netdev@vger.kernel.org \
--cc=paulus@samba.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).