• Alan Stern's avatar
    USB: move usbcore away from hcd->state · 9b37596a
    Alan Stern authored
    The hcd->state variable is a disaster.  It's not clearly owned by
    either usbcore or the host controller drivers, and they both change it
    from time to time, potentially stepping on each other's toes.  It's
    not protected by any locks.  And there's no mechanism to prevent it
    from going through an invalid transition.
    
    This patch (as1451) takes a first step toward fixing these problems.
    As it turns out, usbcore uses hcd->state for essentially only two
    things: checking whether the controller's root hub is running and
    checking whether the controller has died.  Therefore the patch adds
    two new atomic bitflags to the hcd structure, to store these pieces of
    information.  The new flags are used only by usbcore, and a private
    spinlock prevents invalid combinations (a dead controller's root hub
    cannot be running).
    
    The patch does not change the places where usbcore sets hcd->state,
    since HCDs may depend on them.  Furthermore, there is one place in
    usb_hcd_irq() where usbcore still must use hcd->state: An HCD's
    interrupt handler can implicitly indicate that the controller died by
    setting hcd->state to HC_STATE_HALT.  Nevertheless, the new code is a
    big improvement over the current code.
    
    The patch makes one other change.  The hcd_bus_suspend() and
    hcd_bus_resume() routines now check first whether the host controller
    has died; if it has then they return immediately without calling the
    HCD's bus_suspend or bus_resume methods.
    
    This fixes the major problem reported in Bugzilla #29902: The system
    fails to suspend after a host controller dies during system resume.
    Signed-off-by: default avatarAlan Stern <stern@rowland.harvard.edu>
    Tested-by: default avatarAlex Terekhov <a.terekhov@gmail.com>
    CC: <stable@kernel.org>
    Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@suse.de>
    9b37596a
hcd-pci.c 14.8 KB