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Attempt to catch scan cancellations at exactly the wrong time from occuring.

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The scan code unlocks the comlock and calls into the driver.  It then
assumes the state hasn't changed from underneath it.

Although I haven't seen this particular condition trigger, I'd like to
be informed if I or anyone else sees it.

What I'm thinking may occur:

* A cancellation comes in during the scan_end call;
* the cancel flag is set;
* but it's never checked, so scandone isn't updated;
* .. and the interface stays in the STA power save mode.

It's a subtle race, if it even exists.

PR:		kern/163318
This commit is contained in:
adrian 2012-03-02 02:53:43 +00:00
parent bdf6581a3a
commit 8aaa665509
1 changed files with 13 additions and 0 deletions
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13
sys/net80211/ieee80211_scan.c
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@ -959,6 +959,19 @@ scan_task(void *arg, int pending)
ic->ic_scan_end(ic); /* notify driver */
IEEE80211_LOCK(ic);
/*
* Since a cancellation may have occured during one of the
* driver calls (whilst unlocked), update scandone.
*/
if (scandone == 0 &&
((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) != 0)) {
/* XXX printf? */
if_printf(vap->iv_ifp,
"%s: OOPS! scan cancelled during driver call!\n",
__func__);
}
scandone |= ((SCAN_PRIVATE(ss)->ss_iflags & ISCAN_CANCEL) != 0);
/*
* Record scan complete time. Note that we also do
* this when canceled so any background scan will