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There were crashes reported in this code, and the timer_shutdown()
warning in one of the previous patches indicates that the timeout
timer for the AP response (addba_resp_timer) is still armed while
we're stopping the aggregation session.
After a very long deliberation of the code, so far the only way I
could find that might cause this would be the following sequence:
- session start requested
- session start indicated to driver, but driver returns
IEEE80211_AMPDU_TX_START_DELAY_ADDBA
- session stop requested, sets HT_AGG_STATE_WANT_STOP
- session stop worker runs ___ieee80211_stop_tx_ba_session(),
sets HT_AGG_STATE_STOPPING
From here on, the order doesn't matter exactly, but:
1. driver calls ieee80211_start_tx_ba_cb_irqsafe(),
setting HT_AGG_STATE_START_CB
2. driver calls ieee80211_stop_tx_ba_cb_irqsafe(),
setting HT_AGG_STATE_STOP_CB
3. the worker will run ieee80211_start_tx_ba_cb() for
HT_AGG_STATE_START_CB
4. the worker will run ieee80211_stop_tx_ba_cb() for
HT_AGG_STATE_STOP_CB
(the order could also be 1./3./2./4.)
This will cause ieee80211_start_tx_ba_cb() to send out the AddBA
request frame to the AP and arm the timer, but we're already in
the middle of stopping and so the ieee80211_stop_tx_ba_cb() will
no longer assume it needs to stop anything.
Prevent this by checking for WANT_STOP/STOPPING in the start CB,
and warn if we're sending a frame on a stopping session.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: Gregory Greenman <gregory.greenman@intel.com>
Link: https://lore.kernel.org/r/20230618214436.e5b52777462a.I0b2ed6658e81804279f5d7c9c1918cb1f6626bf2@changeid
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
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Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.