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scan: Allow scan_cancel for finished requests

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scan_request_failed and scan_finished remove the finished scan_request
from the request queue right away, before calling the callback.  This
breaks those clients that rely on scan_cancel working on such requests
(i.e. to force the destroy callback to be invoked synchronously, see
a0911ca778 ("station: Make sure roam_scan_id is always canceled").

Fix this by removing the scan_request from the request queue after
invoking the callback.  Also provide a re-entrancy guard that will make
sure that the scan_request isn't removed in scan_cancel itself.
This commit is contained in:
Denis Kenzior 2022-01-19 14:39:27 -06:00
parent bef550df81
commit 62978ef0fb
1 changed files with 37 additions and 17 deletions
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54
src/scan.c
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@ -93,6 +93,7 @@ struct scan_request {
* be false when the scan is complete and GET_SCAN is pending.
*/
bool triggered : 1;
bool in_callback : 1; /* Scan request complete, re-entrancy guard */
struct l_queue *cmds;
/* The time the current scan was started. Reported in TRIGGER_SCAN */
uint64_t start_time_tsf;
@ -164,13 +165,15 @@ static void scan_request_free(struct wiphy_radio_work_item *item)
static void scan_request_failed(struct scan_context *sc,
struct scan_request *sr, int err)
{
l_queue_remove(sc->requests, sr);
sr->in_callback = true;
if (sr->trigger)
sr->trigger(err, sr->userdata);
else if (sr->callback)
sr->callback(err, NULL, NULL, sr->userdata);
sr->in_callback = false;
l_queue_remove(sc->requests, sr);
wiphy_radio_work_done(sc->wiphy, sr->work.id);
}
@ -815,23 +818,30 @@ bool scan_cancel(uint64_t wdev_id, uint32_t id)
if (!sr)
return false;
/* We're in the callback and about to be removed, invoke destroy now */
if (sr->in_callback)
goto call_destroy;
/* If already triggered, just zero out the callback */
if (sr == l_queue_peek_head(sc->requests) && sr->triggered) {
l_debug("Scan is at the top of the queue and triggered");
if (sr->triggered) {
l_debug("Scan has been triggered, wait for it to complete");
sr->callback = NULL;
if (sr->destroy) {
sr->destroy(sr->userdata);
sr->destroy = NULL;
}
return true;
goto call_destroy;
}
/* If we already sent the trigger command, cancel the scan */
if (sr == l_queue_peek_head(sc->requests)) {
l_debug("Scan is at the top of the queue, but not triggered");
/*
* Takes care of the following cases:
* 1. If TRIGGER_SCAN is in flight
* 2. TRIGGER_SCAN sent but bounced with -EBUSY
* 3. Scan request is done but GET_SCAN is still pending
*
* For case 3, we can easily cancel the command and proceed with the
* other pending requests. For case 1 & 2, the subsequent pending
* request might bounce off with an -EBUSY.
*/
if (wiphy_radio_work_is_running(sc->wiphy, sr->work.id)) {
l_debug("Scan is already started");
/* l_genl_family_cancel will trigger destroy callbacks */
sr->canceled = true;
@ -843,12 +853,20 @@ bool scan_cancel(uint64_t wdev_id, uint32_t id)
l_genl_family_cancel(nl80211, sc->get_scan_cmd_id);
sc->start_cmd_id = 0;
l_queue_remove(sc->requests, sr);
} else
l_queue_remove(sc->requests, sr);
sc->get_scan_cmd_id = 0;
}
l_queue_remove(sc->requests, sr);
wiphy_radio_work_done(sc->wiphy, sr->work.id);
return true;
call_destroy:
if (sr->destroy) {
sr->destroy(sr->userdata);
sr->destroy = NULL;
}
return true;
}
@ -1710,7 +1728,7 @@ static void scan_finished(struct scan_context *sc,
discover_hidden_network_bsses(sc, bss_list);
if (sr)
l_queue_remove(sc->requests, sr);
sr->in_callback = true;
if (callback)
new_owner = callback(err, bss_list, freqs, userdata);
@ -1728,6 +1746,8 @@ static void scan_finished(struct scan_context *sc,
* SCAN_FINISHED or SCAN_ABORTED handler would have taken care of
* sending the next command for a new or ongoing scan.
*/
sr->in_callback = false;
l_queue_remove(sc->requests, sr);
wiphy_radio_work_done(sc->wiphy, sr->work.id);
}