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| /freebsd-11-stable/sys/dev/ath/ | ||
| H A D | if_ath.c | diff 232163 Sat Feb 25 17:22:51 MST 2012 adrian 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 |
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