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| /freebsd-11-stable/sys/dev/ath/ | ||
| H A D | if_ath_tx.c | diff 243786 Sun Dec 02 04:32:06 MST 2012 adrian Delete the per-TXQ locks and replace them with a single TX lock. I couldn't think of a way to maintain the hardware TXQ locks _and_ layer on top of that per-TXQ software queuing and any other kind of fine-grained locks (eg per-TID, or per-node locks.) So for now, to facilitate some further code refactoring and development as part of the final push to get software queue ps-poll and u-apsd handling into this driver, just do away with them entirely. I may eventually bring them back at some point, when it looks slightly more architectually cleaner to do so. But as it stands at the present, it's not really buying us much: * in order to properly serialise things and not get bitten by scheduling and locking interactions with things higher up in the stack, we need to wrap the whole TX path in a long held lock. Otherwise we can end up being pre-empted during frame handling, resulting in some out of order frame handling between sequence number allocation and encryption handling (ie, the seqno and the CCMP IV get out of sequence); * .. so whilst that's the case, holding the lock for that long means that we're acquiring and releasing the TXQ lock _inside_ that context; * And we also acquire it per-frame during frame completion, but we currently can't hold the lock for the duration of the TX completion as we need to call net80211 layer things with the locks _unheld_ to avoid LOR. * .. the other places were grab that lock are reset/flush, which don't happen often. My eventual aim is to change the TX path so all rejected frame transmissions and all frame completions result in any ieee80211_free_node() calls to occur outside of the TX lock; then I can cut back on the amount of locking that goes on here. There may be some LORs that occur when ieee80211_free_node() is called when the TX queue path fails; I'll begin to address these in follow-up commits. |
| H A D | if_ath.c | diff 243786 Sun Dec 02 04:32:06 MST 2012 adrian Delete the per-TXQ locks and replace them with a single TX lock. I couldn't think of a way to maintain the hardware TXQ locks _and_ layer on top of that per-TXQ software queuing and any other kind of fine-grained locks (eg per-TID, or per-node locks.) So for now, to facilitate some further code refactoring and development as part of the final push to get software queue ps-poll and u-apsd handling into this driver, just do away with them entirely. I may eventually bring them back at some point, when it looks slightly more architectually cleaner to do so. But as it stands at the present, it's not really buying us much: * in order to properly serialise things and not get bitten by scheduling and locking interactions with things higher up in the stack, we need to wrap the whole TX path in a long held lock. Otherwise we can end up being pre-empted during frame handling, resulting in some out of order frame handling between sequence number allocation and encryption handling (ie, the seqno and the CCMP IV get out of sequence); * .. so whilst that's the case, holding the lock for that long means that we're acquiring and releasing the TXQ lock _inside_ that context; * And we also acquire it per-frame during frame completion, but we currently can't hold the lock for the duration of the TX completion as we need to call net80211 layer things with the locks _unheld_ to avoid LOR. * .. the other places were grab that lock are reset/flush, which don't happen often. My eventual aim is to change the TX path so all rejected frame transmissions and all frame completions result in any ieee80211_free_node() calls to occur outside of the TX lock; then I can cut back on the amount of locking that goes on here. There may be some LORs that occur when ieee80211_free_node() is called when the TX queue path fails; I'll begin to address these in follow-up commits. |
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