USB: OHCI: Fix race between ED unlink and URB submission
This patch fixes a bug introduced by commit977dcfdc60
("USB: OHCI: don't lose track of EDs when a controller dies"). The commit changed ed_state from ED_UNLINK to ED_IDLE too early, before finish_urb() had been called. The user-visible consequence is that the driver occasionally crashes or locks up when an URB is submitted while another URB for the same endpoint is being unlinked. This patch moves the ED state change later, to the right place. The drawback is that now we may unnecessarily execute some instructions multiple times when a controller dies. Since controllers dying is an exceptional occurrence, a little wasted time won't matter. Signed-off-by: Alan Stern <stern@rowland.harvard.edu> Reported-by: Heiko Przybyl <lil_tux@web.de> Tested-by: Heiko Przybyl <lil_tux@web.de> Fixes:977dcfdc60
CC: <stable@vger.kernel.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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@ -981,10 +981,6 @@ rescan_all:
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int completed, modified;
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__hc32 *prev;
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/* Is this ED already invisible to the hardware? */
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if (ed->state == ED_IDLE)
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goto ed_idle;
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/* only take off EDs that the HC isn't using, accounting for
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* frame counter wraps and EDs with partially retired TDs
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*/
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@ -1012,12 +1008,10 @@ skip_ed:
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}
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/* ED's now officially unlinked, hc doesn't see */
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ed->state = ED_IDLE;
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ed->hwHeadP &= ~cpu_to_hc32(ohci, ED_H);
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ed->hwNextED = 0;
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wmb();
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ed->hwINFO &= ~cpu_to_hc32(ohci, ED_SKIP | ED_DEQUEUE);
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ed_idle:
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/* reentrancy: if we drop the schedule lock, someone might
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* have modified this list. normally it's just prepending
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@ -1088,6 +1082,7 @@ rescan_this:
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if (list_empty(&ed->td_list)) {
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*last = ed->ed_next;
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ed->ed_next = NULL;
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ed->state = ED_IDLE;
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list_del(&ed->in_use_list);
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} else if (ohci->rh_state == OHCI_RH_RUNNING) {
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*last = ed->ed_next;
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