Author: adrian
Date: Sat Feb 25 19:12:54 2012
New Revision: 232163
URL: http://svn.freebsd.org/changeset/base/232163
Log:
Attempt to further fix some of the concurrency/reset issues that occur.
* ath_reset() is being called in softclock context, which may have the
thing sleep on a lock. To avoid this, since we really _shouldn't_
be sleeping on any locks, break out the no-loss reset path into a tasklet
and call that from:
+ ath_calibrate()
+ ath_watchdog()
This has the added advantage that it'll end up also doing the frame
RX cleanup from within the taskqueue context, rather than the softclock
context.
* Shuffle around the taskqueue_block() call to be before we grab the lock
and disable interrupts.
The trouble here is that taskqueue_block() doesn't block currently
queued (but not yet running) tasks so calling it doesn't guarantee
no further tasks (that weren't running on _A_ CPU at the time of this
call) will complete. Calling taskqueue_drain() on these tasks won't
work because if any _other_ thread calls taskqueue_enqueue() for whatever
reason, everything gets very angry and stops working.
This slightly changes the race condition enough to let ath_rx_tasklet()
run before we try disabling it, and thus quietens the warnings a bit.
The (more) true solution will be doing something like the following:
* having a taskqueue_blocked mask in ath_softc;
* having an interrupt_blocked mask in ath_softc;
* only calling taskqueue_drain() on each individual task _after_ the
lock has been acquired - that way no further tasklet scheduling
is going to occur.
* Then once the tasks have been blocked _and_ the interrupt has been
disabled, call taskqueue_drain() on each, ensuring that anything
that _was_ scheduled or running is removed.
The trouble is if something calls taskqueue_enqueue() on a task
after taskqueue_blocked() has been called but BEFORE taskqueue_drain()
has been called, ta_pending will be set to 1 and taskqueue_drain()
will sit there stuck in msleep() until you hard-kill the machine.
PR: kern/165382
PR: kern/165220
Modified:
head/sys/dev/ath/if_ath.c
head/sys/dev/ath/if_athvar.h
Modified: head/sys/dev/ath/if_ath.c
==============================================================================
--- head/sys/dev/ath/if_ath.c Sat Feb 25 18:48:06 2012 (r232162)
+++ head/sys/dev/ath/if_ath.c Sat Feb 25 19:12:54 2012 (r232163)
@@ -159,6 +159,7 @@ static void ath_beacon_proc(void *, int)
static struct ath_buf *ath_beacon_generate(struct ath_softc *,
struct ieee80211vap *);
static void ath_bstuck_proc(void *, int);
+static void ath_reset_proc(void *, int);
static void ath_beacon_return(struct ath_softc *, struct ath_buf *);
static void ath_beacon_free(struct ath_softc *);
static void ath_beacon_config(struct ath_softc *, struct ieee80211vap *);
@@ -392,6 +393,7 @@ ath_attach(u_int16_t devid, struct ath_s
TASK_INIT(&sc->sc_rxtask, 0, ath_rx_tasklet, sc);
TASK_INIT(&sc->sc_bmisstask, 0, ath_bmiss_proc, sc);
TASK_INIT(&sc->sc_bstucktask,0, ath_bstuck_proc, sc);
+ TASK_INIT(&sc->sc_resettask,0, ath_reset_proc, sc);
/*
* Allocate hardware transmit queues: one queue for
@@ -1910,9 +1912,6 @@ ath_txrx_stop_locked(struct ath_softc *s
ATH_UNLOCK_ASSERT(sc);
ATH_PCU_LOCK_ASSERT(sc);
- /* Stop any new TX/RX from occuring */
- taskqueue_block(sc->sc_tq);
-
/*
* Sleep until all the pending operations have completed.
*
@@ -2050,6 +2049,9 @@ ath_reset(struct ifnet *ifp, ATH_RESET_T
ATH_PCU_UNLOCK_ASSERT(sc);
ATH_UNLOCK_ASSERT(sc);
+ /* Try to (stop any further TX/RX from occuring */
+ taskqueue_block(sc->sc_tq);
+
ATH_PCU_LOCK(sc);
ath_hal_intrset(ah, 0); /* disable interrupts */
ath_txrx_stop_locked(sc); /* Ensure TX/RX is stopped */
@@ -3163,6 +3165,23 @@ ath_beacon_start_adhoc(struct ath_softc
}
/*
+ * Reset the hardware, with no loss.
+ *
+ * This can't be used for a general case reset.
+ */
+static void
+ath_reset_proc(void *arg, int pending)
+{
+ struct ath_softc *sc = arg;
+ struct ifnet *ifp = sc->sc_ifp;
+
+#if 0
+ if_printf(ifp, "%s: resetting\n", __func__);
+#endif
+ ath_reset(ifp, ATH_RESET_NOLOSS);
+}
+
+/*
* Reset the hardware after detecting beacons have stopped.
*/
static void
@@ -5387,6 +5406,12 @@ ath_chan_set(struct ath_softc *sc, struc
int ret = 0;
/* Treat this as an interface reset */
+ ATH_PCU_UNLOCK_ASSERT(sc);
+ ATH_UNLOCK_ASSERT(sc);
+
+ /* (Try to) stop TX/RX from occuring */
+ taskqueue_block(sc->sc_tq);
+
ATH_PCU_LOCK(sc);
ath_hal_intrset(ah, 0); /* Stop new RX/TX completion */
ath_txrx_stop_locked(sc); /* Stop pending RX/TX completion */
@@ -5526,18 +5551,10 @@ ath_calibrate(void *arg)
DPRINTF(sc, ATH_DEBUG_CALIBRATE,
"%s: rfgain change\n", __func__);
sc->sc_stats.ast_per_rfgain++;
- /*
- * Drop lock - we can't hold it across the
- * ath_reset() call. Instead, we'll drop
- * out here, do a reset, then reschedule
- * the callout.
- */
- callout_reset(&sc->sc_cal_ch, 1, ath_calibrate, sc);
sc->sc_resetcal = 0;
sc->sc_doresetcal = AH_TRUE;
- ATH_UNLOCK(sc);
- ath_reset(ifp, ATH_RESET_NOLOSS);
- ATH_LOCK(sc);
+ taskqueue_enqueue(sc->sc_tq, &sc->sc_resettask);
+ callout_reset(&sc->sc_cal_ch, 1, ath_calibrate, sc);
return;
}
/*
@@ -6187,11 +6204,12 @@ ath_watchdog(void *arg)
/*
* We can't hold the lock across the ath_reset() call.
+ *
+ * And since this routine can't hold a lock and sleep,
+ * do the reset deferred.
*/
if (do_reset) {
- ATH_UNLOCK(sc);
- ath_reset(sc->sc_ifp, ATH_RESET_NOLOSS);
- ATH_LOCK(sc);
+ taskqueue_enqueue(sc->sc_tq, &sc->sc_resettask);
}
callout_schedule(&sc->sc_wd_ch, hz);
Modified: head/sys/dev/ath/if_athvar.h
==============================================================================
--- head/sys/dev/ath/if_athvar.h Sat Feb 25 18:48:06 2012
(r232162)
+++ head/sys/dev/ath/if_athvar.h Sat Feb 25 19:12:54 2012
(r232163)
@@ -501,6 +501,7 @@ struct ath_softc {
struct ath_txq *sc_cabq; /* tx q for cab frames */
struct task sc_bmisstask; /* bmiss int processing */
struct task sc_bstucktask; /* stuck beacon processing */
+ struct task sc_resettask; /* interface reset task */
enum {
OK, /* no change needed */
UPDATE, /* update pending */
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