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From: Avery Pennarun <apenwarr@gmail.com>
To: Johannes Berg <johannes@sipsolutions.net>
Cc: ath9k-devel <ath9k-devel@lists.ath9k.org>,
	linux-wireless <linux-wireless@vger.kernel.org>,
	Felix Fietkau <nbd@nbd.name>
Subject: Re: [PATCH] mac80211: debugfs var for the default aggregation timeout.
Date: Thu, 7 Apr 2016 21:32:57 -0400	[thread overview]
Message-ID: <CAHqTa-3VtwYWLUHQuFyqtmMwPE2XQYJD4-U+-1PqXKtmTFrEgA@mail.gmail.com> (raw)
In-Reply-To: <1459928436.17504.11.camel@sipsolutions.net>

On Wed, Apr 6, 2016 at 3:40 AM, Johannes Berg <johannes@sipsolutions.net> wrote:
> On Tue, 2016-04-05 at 19:46 -0400, Avery Pennarun wrote:
>
>> This test was with backports-20150525 on ath9k.  (We have newer
>> versions in the queue, but they haven't rolled out to our customers
>> yet.  Anyway, earlier in this thread, I was able to trigger the race
>> condition on much newer backports.  Unfortunately the current fix
>> makes my reproducible test case go away, but I don't know any reason
>> to assume the race condition is fixed.)
>
> Well, we know that the timeout is likely unrelated to the issue (other
> than not triggering the broken code path that frequently), so you can
> revert the timeout change for the test case.

Yes.  And I can make it happen more often by making it timeout the
aggregation agreement much more frequently than usual.

>> While we're here, unfortunately it turns out that just observing the
>> agg_status file can cause crashes (though not very often... except
>> for a few unlucky customers), probably due to a different race
>> condition.
>> Any suggestions about this one?  Stack trace attached below.  (I
>> think the stack trace suggests a mac80211 problem?)
>
> That has to be a mac80211 problem, yeah.
> (Side note: I'm a bit surprised this is a 32-bit system?)

We're going for all of good, fast, and cheap here.  That should end well :)

> Looks like we use RCU protection to get the data. Can I get the
> mac80211.ko binary (with debug data) corresponding to the crash below?

Yes.  Here it is:
http://apenwarr.ca/tmp/mac80211-agg-status-crash.ko

Thanks for your help!

WARNING: multiple messages have this Message-ID (diff)
From: Avery Pennarun <apenwarr@gmail.com>
To: ath9k-devel@lists.ath9k.org
Subject: [ath9k-devel] [PATCH] mac80211: debugfs var for the default aggregation timeout.
Date: Thu, 7 Apr 2016 21:32:57 -0400	[thread overview]
Message-ID: <CAHqTa-3VtwYWLUHQuFyqtmMwPE2XQYJD4-U+-1PqXKtmTFrEgA@mail.gmail.com> (raw)
In-Reply-To: <1459928436.17504.11.camel@sipsolutions.net>

On Wed, Apr 6, 2016 at 3:40 AM, Johannes Berg <johannes@sipsolutions.net> wrote:
> On Tue, 2016-04-05 at 19:46 -0400, Avery Pennarun wrote:
>
>> This test was with backports-20150525 on ath9k.  (We have newer
>> versions in the queue, but they haven't rolled out to our customers
>> yet.  Anyway, earlier in this thread, I was able to trigger the race
>> condition on much newer backports.  Unfortunately the current fix
>> makes my reproducible test case go away, but I don't know any reason
>> to assume the race condition is fixed.)
>
> Well, we know that the timeout is likely unrelated to the issue (other
> than not triggering the broken code path that frequently), so you can
> revert the timeout change for the test case.

Yes.  And I can make it happen more often by making it timeout the
aggregation agreement much more frequently than usual.

>> While we're here, unfortunately it turns out that just observing the
>> agg_status file can cause crashes (though not very often... except
>> for a few unlucky customers), probably due to a different race
>> condition.
>> Any suggestions about this one?  Stack trace attached below.  (I
>> think the stack trace suggests a mac80211 problem?)
>
> That has to be a mac80211 problem, yeah.
> (Side note: I'm a bit surprised this is a 32-bit system?)

We're going for all of good, fast, and cheap here.  That should end well :)

> Looks like we use RCU protection to get the data. Can I get the
> mac80211.ko binary (with debug data) corresponding to the crash below?

Yes.  Here it is:
http://apenwarr.ca/tmp/mac80211-agg-status-crash.ko

Thanks for your help!

  reply	other threads:[~2016-04-08  1:33 UTC|newest]

Thread overview: 36+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-11-04  5:03 ath9k(?): AP stops sending traffic to iPhone 4S until another 802.11n-capable STA joins Avery Pennarun
2016-02-16 21:28 ` Avery Pennarun
2016-02-16 21:28   ` [PATCH] mac80211: debugfs var for the default aggregation timeout Avery Pennarun
2016-02-16 21:44     ` Johannes Berg
2016-02-17  2:05     ` Sujith Manoharan
2016-02-23 10:14     ` Johannes Berg
2016-02-23 18:43       ` Avery Pennarun
2016-02-23 20:05         ` Johannes Berg
2016-04-05 23:46           ` Avery Pennarun
2016-04-05 23:46             ` [ath9k-devel] " Avery Pennarun
2016-04-06  7:40             ` Johannes Berg
2016-04-06  7:40               ` [ath9k-devel] " Johannes Berg
2016-04-08  1:32               ` Avery Pennarun [this message]
2016-04-08  1:32                 ` Avery Pennarun
2016-04-08  6:56                 ` Johannes Berg
2016-04-08  6:56                   ` [ath9k-devel] " Johannes Berg
2016-04-08  7:01                   ` Johannes Berg
2016-04-08  7:01                     ` [ath9k-devel] " Johannes Berg
2016-04-08  7:15                     ` Johannes Berg
2016-04-08  7:15                       ` [ath9k-devel] " Johannes Berg
2016-04-08  8:31                       ` Avery Pennarun
2016-04-08  8:31                         ` [ath9k-devel] " Avery Pennarun
2016-04-09  1:27                         ` Avery Pennarun
2016-04-09  1:27                           ` [ath9k-devel] " Avery Pennarun
2016-04-09  4:56                           ` Johannes Berg
2016-04-09  4:56                             ` [ath9k-devel] " Johannes Berg
2016-04-10  0:31                             ` Adrian Chadd
2016-04-10  0:31                               ` [ath9k-devel] " Adrian Chadd
2016-04-10  1:59                               ` bruce m beach
2016-04-10  2:12                                 ` [ath9k-devel] " bruce m beach
2016-04-19  1:29                                 ` Avery Pennarun
2016-04-19  1:29                                   ` [ath9k-devel] " Avery Pennarun
2016-02-16 22:05   ` ath9k(?): AP stops sending traffic to iPhone 4S until another 802.11n-capable STA joins Johannes Berg
2016-02-17  4:32     ` Avery Pennarun
2016-02-17  6:23       ` Krishna Chaitanya
2016-02-17  7:05         ` Avery Pennarun

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