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mac80211: fix scan race, simplify code 

The scan code has a race that Michael reported
he ran into, but it's easy to fix while at the
same time simplifying the code.

The race resulted in the following warning:

------------[ cut here ]------------
WARNING: at net/mac80211/scan.c:310 ieee80211_rx_bss_free+0x20c/0x4b8 [mac80211]()
Modules linked in: [...]
[<c0033edc>] (unwind_backtrace+0x0/0xe0) from [<c004f2a4>] (warn_slowpath_common+0x4c/0x64)
[... backtrace wasn't useful ...]

Reported-by: Michael Buesch <mb@bu3sch.de>
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Johannes Berg 2011-03-07 15:48:41 +01:00 committed by John W. Linville
parent 2a6672f2c4
commit d07bfd8b6f
1 changed files with 24 additions and 40 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

64
net/mac80211/scan.c
View File

@ -258,10 +258,12 @@ static bool ieee80211_prep_hw_scan(struct ieee80211_local *local)
return true;
}
static bool __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted,
static void __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted,
bool was_hw_scan)
{
struct ieee80211_local *local = hw_to_local(hw);
bool on_oper_chan;
bool enable_beacons = false;
lockdep_assert_held(&local->mtx);
@ -275,12 +277,12 @@ static bool __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted,
aborted = true;
if (WARN_ON(!local->scan_req))
return false;
return;
if (was_hw_scan && !aborted && ieee80211_prep_hw_scan(local)) {
int rc = drv_hw_scan(local, local->scan_sdata, local->hw_scan_req);
if (rc == 0)
return false;
return;
}
kfree(local->hw_scan_req);
@ -294,26 +296,11 @@ static bool __ieee80211_scan_completed(struct ieee80211_hw *hw, bool aborted,
local->scanning = 0;
local->scan_channel = NULL;
return true;
}
static void __ieee80211_scan_completed_finish(struct ieee80211_hw *hw,
bool was_hw_scan)
{
struct ieee80211_local *local = hw_to_local(hw);
bool on_oper_chan;
bool enable_beacons = false;
mutex_lock(&local->mtx);
on_oper_chan = ieee80211_cfg_on_oper_channel(local);
WARN_ON(local->scanning & (SCAN_SW_SCANNING | SCAN_HW_SCANNING));
if (was_hw_scan || !on_oper_chan) {
if (WARN_ON(local->scan_channel))
local->scan_channel = NULL;
if (was_hw_scan || !on_oper_chan)
ieee80211_hw_config(local, IEEE80211_CONF_CHANGE_CHANNEL);
} else
else
/* Set power back to normal operating levels. */
ieee80211_hw_config(local, 0);
@ -331,7 +318,6 @@ static void __ieee80211_scan_completed_finish(struct ieee80211_hw *hw,
}
ieee80211_recalc_idle(local);
mutex_unlock(&local->mtx);
ieee80211_mlme_notify_scan_completed(local);
ieee80211_ibss_notify_scan_completed(local);
@ -686,12 +672,14 @@ void ieee80211_scan_work(struct work_struct *work)
{
struct ieee80211_local *local =
container_of(work, struct ieee80211_local, scan_work.work);
struct ieee80211_sub_if_data *sdata = local->scan_sdata;
struct ieee80211_sub_if_data *sdata;
unsigned long next_delay = 0;
bool aborted, hw_scan, finish;
bool aborted, hw_scan;
mutex_lock(&local->mtx);
sdata = local->scan_sdata;
if (test_and_clear_bit(SCAN_COMPLETED, &local->scanning)) {
aborted = test_and_clear_bit(SCAN_ABORTED, &local->scanning);
goto out_complete;
@ -755,17 +743,11 @@ void ieee80211_scan_work(struct work_struct *work)
} while (next_delay == 0);
ieee80211_queue_delayed_work(&local->hw, &local->scan_work, next_delay);
mutex_unlock(&local->mtx);
return;
goto out;
out_complete:
hw_scan = test_bit(SCAN_HW_SCANNING, &local->scanning);
finish = __ieee80211_scan_completed(&local->hw, aborted, hw_scan);
mutex_unlock(&local->mtx);
if (finish)
__ieee80211_scan_completed_finish(&local->hw, hw_scan);
return;
__ieee80211_scan_completed(&local->hw, aborted, hw_scan);
out:
mutex_unlock(&local->mtx);
}
@ -835,7 +817,6 @@ int ieee80211_request_internal_scan(struct ieee80211_sub_if_data *sdata,
void ieee80211_scan_cancel(struct ieee80211_local *local)
{
bool abortscan;
bool finish = false;
/*
* We are only canceling software scan, or deferred scan that was not
@ -855,14 +836,17 @@ void ieee80211_scan_cancel(struct ieee80211_local *local)
mutex_lock(&local->mtx);
abortscan = local->scan_req && !test_bit(SCAN_HW_SCANNING, &local->scanning);
if (abortscan)
finish = __ieee80211_scan_completed(&local->hw, true, false);
mutex_unlock(&local->mtx);
if (abortscan) {
/* The scan is canceled, but stop work from being pending */
cancel_delayed_work_sync(&local->scan_work);
/*
* The scan is canceled, but stop work from being pending.
*
* If the work is currently running, it must be blocked on
* the mutex, but we'll set scan_sdata = NULL and it'll
* simply exit once it acquires the mutex.
*/
cancel_delayed_work(&local->scan_work);
/* and clean up */
__ieee80211_scan_completed(&local->hw, true, false);
}
if (finish)
__ieee80211_scan_completed_finish(&local->hw, false);
mutex_unlock(&local->mtx);
}