From 361aabf395e4a23cf554cf4ec0c0c6963b8beb01 Mon Sep 17 00:00:00 2001 From: Alan Stern Date: Wed, 11 Jul 2012 11:22:57 -0400 Subject: [PATCH] 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 Signed-off-by: Greg Kroah-Hartman --- drivers/usb/host/ehci-hcd.c | 13 ++++++++++--- drivers/usb/host/ehci.h | 3 ++- 2 files changed, 12 insertions(+), 4 deletions(-) diff --git a/drivers/usb/host/ehci-hcd.c b/drivers/usb/host/ehci-hcd.c index 74ffd20edff8..f6cf1d178107 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. diff --git a/drivers/usb/host/ehci.h b/drivers/usb/host/ehci.h index 303c36cc99c9..c462d52ac575 100644 --- a/drivers/usb/host/ehci.h +++ b/drivers/usb/host/ehci.h @@ -113,7 +113,8 @@ struct ehci_hcd { /* one per controller */ enum ehci_rh_state rh_state; /* general schedule support */ - unsigned scanning:1; + bool scanning:1; + bool need_rescan:1; bool intr_unlinking:1; bool async_unlinking:1; -- 2.34.1