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appeared to rely on all kinds of non-guaranteed behaviours: the transfer abort code assumed that TDs with no interrupt timeout configured would end up on the done queue within 20ms, the done queue processing assumed that all TDs from a transfer would appear at the same time, and there were access-after-free bugs triggered on failed transfers. Attempt to fix these problems by the following changes: - Use a maximum (6-frame) interrupt delay instead of no interrupt delay to ensure that the 20ms wait in ohci_abort_xfer() is enough for the TDs to have been taken off the hardware done queue. - Defer cancellation of timeouts and freeing of TDs until we either hit an error or reach the final TD. - Remove TDs from the done queue before freeing them so that it is safe to continue traversing the done queue. This appears to fix a hang that was reproducable with revision 1.67 or 1.68 of ulpt.c (earlier revisions had a different transfer pattern). With certain HP printers, the command "true > /dev/ulpt0" would cause ohci_add_done() to spin because the done queue had a loop. The list corruption was caused by a 3-TD transfer where the first TD completed but remained on the internal host controller done queue because it had no interrupt timeout. When the transfer timed out, the TD got freed and reused, so it caused a loop in the done queue when it was inserted a second time from a different transfer. Reported by: Alex Pivovarov MFC after: 1 week
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