diff options
| author | Alan Stern <stern@rowland.harvard.edu> | 2012-07-11 11:22:57 -0400 |
|---|---|---|
| committer | Greg Kroah-Hartman <gregkh@linuxfoundation.org> | 2012-07-16 16:56:47 -0700 |
| commit | 361aabf395e4a23cf554cf4ec0c0c6963b8beb01 (patch) | |
| tree | 607f8e039f47905713b7634a663dccd6998d8135 /drivers/usb/host/ehci-hcd.c | |
| parent | 32830f207691176234b4c4dd17f0d7ab6d87d94b (diff) | |
USB: EHCI: don't lose events during a scan
This patch (as1584) fixes a minor bug that has been present in
ehci-hcd since the beginning.
Scanning the schedules for URB completions is single-threaded. If a
completion interrupt occurs while an URB is being given back, the
interrupt handler realizes that a scan is in progress on another CPU
and avoids starting a new one.
This means that completion events can be lost. If an URB completes
after it has been scanned but while a scan is still in progress, the
driver won't notice and won't rescan the completed URB.
The patch fixes the problem by adding a new flag to indicate that
another scan is needed after the current scan is done. The flag gets
set whenever a completion interrupt occurs while a scan is in
progress. The rescan will see the completion, thus preventing it from
getting lost.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Diffstat (limited to 'drivers/usb/host/ehci-hcd.c')
| -rw-r--r-- | drivers/usb/host/ehci-hcd.c | 13 |
1 files changed, 10 insertions, 3 deletions
diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index 74ffd20edff..f6cf1d17810 100644 --- a/drivers/usb/host/ehci-hcd.c +++ b/drivers/usb/host/ehci-hcd.c @@ -400,14 +400,21 @@ static void ehci_work (struct ehci_hcd *ehci) * it reports urb completions. this flag guards against bogus * attempts at re-entrant schedule scanning. */ - if (ehci->scanning) + if (ehci->scanning) { + ehci->need_rescan = true; return; - ehci->scanning = 1; + } + ehci->scanning = true; + + rescan: + ehci->need_rescan = false; if (ehci->async_count) scan_async(ehci); if (ehci->next_uframe != -1) scan_periodic (ehci); - ehci->scanning = 0; + if (ehci->need_rescan) + goto rescan; + ehci->scanning = false; /* the IO watchdog guards against hardware or driver bugs that * misplace IRQs, and should let us run completely without IRQs. |