From 7d8021c967648accd1b78e5e1ddaad655cd2c61f Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Tue, 30 Jun 2015 11:25:54 -0400 Subject: [PATCH 1/1] USB: OHCI: Fix race between ED unlink and URB submission This patch fixes a bug introduced by commit 977dcfdc6031 ("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 Reported-by: Heiko Przybyl Tested-by: Heiko Przybyl Fixes: 977dcfdc60311e7aa571cabf6f39c36dde13339e CC: Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ohci-q.c | 7 +------ 1 file changed, 1 insertion(+), 6 deletions(-) diff --git a/drivers/usb/host/ohci-q.c b/drivers/usb/host/ohci-q.c index f7d561ed3c23..d029bbe9eb36 100644 --- a/drivers/usb/host/ohci-q.c +++ b/drivers/usb/host/ohci-q.c @@ -981,10 +981,6 @@ rescan_all: int completed, modified; __hc32 *prev; - /* Is this ED already invisible to the hardware? */ - if (ed->state == ED_IDLE) - goto ed_idle; - /* only take off EDs that the HC isn't using, accounting for * frame counter wraps and EDs with partially retired TDs */ @@ -1012,12 +1008,10 @@ skip_ed: } /* ED's now officially unlinked, hc doesn't see */ - ed->state = ED_IDLE; ed->hwHeadP &= ~cpu_to_hc32(ohci, ED_H); ed->hwNextED = 0; wmb(); ed->hwINFO &= ~cpu_to_hc32(ohci, ED_SKIP | ED_DEQUEUE); -ed_idle: /* reentrancy: if we drop the schedule lock, someone might * have modified this list. normally it's just prepending @@ -1088,6 +1082,7 @@ rescan_this: if (list_empty(&ed->td_list)) { *last = ed->ed_next; ed->ed_next = NULL; + ed->state = ED_IDLE; list_del(&ed->in_use_list); } else if (ohci->rh_state == OHCI_RH_RUNNING) { *last = ed->ed_next; -- 2.39.2