cvs commit: src/sys/dev/usb ehci.c ohci.c uhci.c usb_port.h
iedowse at FreeBSD.org
Tue Nov 9 20:51:33 GMT 2004
iedowse 2004-11-09 20:51:32 UTC
FreeBSD src repository
sys/dev/usb ehci.c ohci.c uhci.c usb_port.h
Attempt to fix a number of race conditions in the handling of
transfer timeouts that typically cause a transfer to be completed
twice, resulting in panics and page faults:
o A transfer completion interrupt could arrive while an abort_task
event was set up, so the transfer would be aborted after it had
completed. This is very easy to reproduce. Fix this by setting
the transfer status to USBD_TIMEOUT before scheduling the
abort_task so that the transfer completion code will ignore it.
o The transfer completion code could execute concurrently with the
timeout callout, leaving the callout blocked (e.g. waiting for
Giant) while the transfer completion code runs. In this case,
callout_stop() does not prevent the callout from running, so
again the timeout code would run after the transfer was complete.
Handle this case by checking the return value from callout_stop(),
and ignoring the transfer if the callout could not be removed.
o Finally, protect against a timeout callout occurring while a
transfer is being aborted by another process. Here we arrange
for the timeout processing to ignore the transfer, and use
callout_drain() to ensure that the callout has really gone before
completing the transfer.
This was tested by repeatedly performing USB transfers with a timeout
set to approximately the same as the normal transfer completion
time. In the PR below, apparently this occurred by accident with a
particular printer and the default timeout.
Revision Changes Path
1.18 +45 -19 src/sys/dev/usb/ehci.c
1.145 +39 -14 src/sys/dev/usb/ohci.c
1.157 +40 -16 src/sys/dev/usb/uhci.c
1.70 +1 -0 src/sys/dev/usb/usb_port.h
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