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    SubjectRe: [PATCH] Make e100 suspend handler support PCI cards lacking PM capability

    On Sun, Jun 14, 2009 at 07:09:45PM +0200, Rafael J. Wysocki wrote:
    > On Sunday 14 June 2009, Andreas Mohr wrote:
    > > - why do we call netif_device_detach() _after_ doing hardware shutdown
    > > of the network controller? I'd guess this can cause huge issues?
    > > Someone told me he had rtnl lock issues upon S2D with e100
    > > (very similar to my rtnl issues during aborted .suspend),
    > > and that might possibly be the reason?
    > I think you're right, but I'm not a network driver expert.
    > Perhaps you can change the ordering and see if that fixes the rtnl issue
    > (since you're able to reproduce it without my patch, that should be easy to
    > verify).

    Well, I just moved netif_device_detach() above netif_running() check,
    but this didn't fix my network issues in case of a rejecting .suspend
    handler: after resume when unloading e100, that hangs, and I get tons of
    rtnl timeouts and locked rtnl mutex.
    This is most likely because upon e100 unload, a backtrace showed that I
    was hanging in e100_down -> msleep (somewhere at the very beginning of e100_down),
    which is most definitely the inlined napi_disable() call there:

    static inline void napi_disable(struct napi_struct *n)
    set_bit(NAPI_STATE_DISABLE, &n->state);
    while (test_and_set_bit(NAPI_STATE_SCHED, &n->state))
    clear_bit(NAPI_STATE_DISABLE, &n->state);

    IOW the .suspend seems to keep NAPI layer active, yet due to .suspend failure
    there's no .resume called, thus card is in an _inoperable_ state and
    NAPI cannot be processed any further, thus napi_disable() on driver unload
    locks up.

    BTW, in include/linux/napi.h, shouldn't napi_disable() make use of
    napi_synchronize() instead of C&P?
    (simply move napi_synchronize() above napi_disable() and use it there)
    Oh wait, there's the CONFIG_SMP complication:
    napi_synchronize() is implemented for SMP only, whereas napi_disable()
    checks the same thing _always_.
    (or is it a BUG that napi_disable() does the same check for non-SMP,


    Andreas Mohr

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