From: "Boehme, Markus" <markubo@amazon.de>
To: "Boehme, Markus" <markubo@amazon.de>,
"minyard@acm.org" <minyard@acm.org>
Cc: "openipmi-developer@lists.sourceforge.net"
<openipmi-developer@lists.sourceforge.net>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"Shah, Amit" <aams@amazon.de>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"arnd@arndb.de" <arnd@arndb.de>,
"Park, Seongjae" <sjpark@amazon.com>,
"Nuernberger, Stefan" <snu@amazon.de>
Subject: Re: [PATCH 3/3] ipmi: Add timeout waiting for channel information
Date: Thu, 10 Sep 2020 11:08:40 +0000 [thread overview]
Message-ID: <1599736120.29234.12.camel@amazon.de> (raw)
In-Reply-To: <20200908003412.GD15602@minyard.net>
Hey Corey, thanks for taking a look!
On Mon, 2020-09-07 at 19:34 -0500, Corey Minyard wrote:
> On Mon, Sep 07, 2020 at 06:25:37PM +0200, Markus Boehme wrote:
> >
> > We have observed hosts with misbehaving BMCs that receive a Get Channel
> > Info command but don't respond. This leads to an indefinite wait in the
> > ipmi_msghandler's __scan_channels function, showing up as hung task
> > messages for modprobe.
> >
> > Add a timeout waiting for the channel scan to complete. If the scan
> > fails to complete within that time, treat that like IPMI 1.0 and only
> > assume the presence of the primary IPMB channel at channel number 0.
> [...]
> While thinking about this, I realized an issue with these patches.
> There should be timers in the lower layers that detect that the BMC does
> not respond and should return an error response. This is supposed to be
> guaranteed by the lower layer, you shouldn't need timers here. In fact,
> if you abort with a timer here, you should get a lower layer reponds
> later, causing other issues.
>
> So, this is wrong. If you are never getting a response, there is a bug
> in the lower layer. If you are not getting the error response as
> quickly as you would like, I'm not sure what to do about that.
>
I see. I might not be able to get hold of more hosts behaving this way,
but if I do, I'll dig deeper into why the lower layer timeouts didn't
save us here. Thanks for the pointer.
> > Signed-off-by: Stefan Nuernberger <snu@amazon.com>
> > Signed-off-by: Markus Boehme <markubo@amazon.com>
> > ---
> > drivers/char/ipmi/ipmi_msghandler.c | 72 ++++++++++++++++++++-----------------
> > 1 file changed, 39 insertions(+), 33 deletions(-)
> >
> > diff --git a/drivers/char/ipmi/ipmi_msghandler.c b/drivers/char/ipmi/ipmi_msghandler.c
> > index 2a2e8b2..9de9ba6 100644
> > --- a/drivers/char/ipmi/ipmi_msghandler.c
> > +++ b/drivers/char/ipmi/ipmi_msghandler.c
> > @@ -3315,46 +3315,52 @@ channel_handler(struct ipmi_smi *intf, struct ipmi_recv_msg *msg)
> > */
> > static int __scan_channels(struct ipmi_smi *intf, struct ipmi_device_id *id)
> > {
> > - int rv;
> > + long rv;
> > + unsigned int set;
> >
> > - if (ipmi_version_major(id) > 1
> > - || (ipmi_version_major(id) == 1
> > - && ipmi_version_minor(id) >= 5)) {
> > - unsigned int set;
> > + if (ipmi_version_major(id) == 1 && ipmi_version_minor(id) < 5) {
> This is incorrect, it will not correctly handle IPMI 0.x BMCs. Yes,
> they exist.
Interesting! I wasn't aware of those. Searching the web doesn't turn up
much and the spec doesn't mention them either. Are these pre-release
implementations of the IPMI 1.0 spec or some kind of "IPMI light"?
Markus
Amazon Development Center Germany GmbH
Krausenstr. 38
10117 Berlin
Geschaeftsfuehrung: Christian Schlaeger, Jonathan Weiss
Eingetragen am Amtsgericht Charlottenburg unter HRB 149173 B
Sitz: Berlin
Ust-ID: DE 289 237 879
next prev parent reply other threads:[~2020-09-10 11:13 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-07 16:25 [PATCH 1/3] ipmi: Reset response handler when failing to send the command Markus Boehme
2020-09-07 16:25 ` [PATCH 2/3] ipmi: Add timeout waiting for device GUID Markus Boehme
2020-09-08 0:07 ` Corey Minyard
2020-09-07 16:25 ` [PATCH 3/3] ipmi: Add timeout waiting for channel information Markus Boehme
2020-09-08 0:34 ` Corey Minyard
2020-09-10 11:08 ` Boehme, Markus [this message]
2020-10-07 18:42 ` [Openipmi-developer] " Corey Minyard
2020-09-08 0:03 ` [PATCH 1/3] ipmi: Reset response handler when failing to send the command Corey Minyard
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