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Groups > linux.kernel > #1727477

Re: hung task in mac80211

From Johannes Berg <johannes@sipsolutions.net>
Newsgroups linux.kernel
Subject Re: hung task in mac80211
Date 2017-09-06 15:40 +0200
Message-ID <umIIF-2qh-11@gated-at.bofh.it> (permalink)
References (1 earlier) <umHWi-1Qd-15@gated-at.bofh.it> <umHWi-1Qd-13@gated-at.bofh.it> <umIpk-2iw-13@gated-at.bofh.it> <umIz3-2mH-41@gated-at.bofh.it> <umIz3-2mH-39@gated-at.bofh.it>
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On Wed, 2017-09-06 at 15:27 +0200, Stefano Brivio wrote:
> 
> Yes, that was based on the assumption that the initial part of
> __ieee80211_start_rx_ba_session() can't really affect the AMPDU
> state-machine in any way.

That's not really the point, if that changes that function would have
to move the locking around, and nothing else.

The point is more that code in ieee80211_ba_session_work() could assume
the lock is held across the entire loop, since that's the way it's
written and looks like even with your patch.

So for example replacing the loop of tid = 0..NUM_TIDS-1 with a
list_for_each_entry() would already be unsafe with the dropping if the
list were to require the mutex for locking.

johannes

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Thread

hung task in mac80211 Matteo Croce <mcroce@redhat.com> - 2017-09-06 14:00 +0200
  Re: hung task in mac80211 Christian Lamparter <chunkeey@googlemail.com> - 2017-09-06 14:30 +0200
  Re: hung task in mac80211 Stefano Brivio <sbrivio@redhat.com> - 2017-09-06 14:50 +0200
    Re: hung task in mac80211 Johannes Berg <johannes@sipsolutions.net> - 2017-09-06 14:50 +0200
      Re: hung task in mac80211 Johannes Berg <johannes@sipsolutions.net> - 2017-09-06 15:10 +0200
        Re: hung task in mac80211 Sebastian Gottschall <s.gottschall@dd-wrt.com> - 2017-09-06 15:30 +0200
      Re: hung task in mac80211 Stefano Brivio <sbrivio@redhat.com> - 2017-09-06 15:20 +0200
        Re: hung task in mac80211 Stefano Brivio <sbrivio@redhat.com> - 2017-09-06 15:30 +0200
          Re: hung task in mac80211 Johannes Berg <johannes@sipsolutions.net> - 2017-09-06 15:40 +0200
            Re: hung task in mac80211 Stefano Brivio <sbrivio@redhat.com> - 2017-09-06 15:50 +0200
        Re: hung task in mac80211 Johannes Berg <johannes@sipsolutions.net> - 2017-09-06 15:30 +0200
    Re: hung task in mac80211 Matteo Croce <mcroce@redhat.com> - 2017-09-06 15:10 +0200
  Re: hung task in mac80211 Johannes Berg <johannes@sipsolutions.net> - 2017-09-06 15:00 +0200
    Re: hung task in mac80211 Stefano Brivio <sbrivio@redhat.com> - 2017-09-06 16:30 +0200
      Re: hung task in mac80211 Johannes Berg <johannes@sipsolutions.net> - 2017-09-06 16:40 +0200
    Re: hung task in mac80211 Matteo Croce <mcroce@redhat.com> - 2017-09-06 17:10 +0200
      Re: hung task in mac80211 Johannes Berg <johannes@sipsolutions.net> - 2017-09-06 17:20 +0200
      Re: hung task in mac80211 Sebastian Gottschall <s.gottschall@dd-wrt.com> - 2017-09-06 17:50 +0200

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