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    SubjectRe: [REGRESSION][BISECTED] 3.10.26: net_dma: mark broken (b69ec589136c)
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    On Wed, Jan 29, 2014 at 4:41 AM, Stanislav Fomichev
    <stfomichev@yandex-team.ru> wrote:
    >> I wonder if we are simply racing the initialization of the completion
    >> vs when it is triggered by dma.
    > We have wmb() in the ioat2_tx_submit_unlock (before submitting work to dma,
    > but after init_completion), shouldn't it make race between interrupt handler
    > and our waiting thread impossible?
    >
    > I also believe I traced x->done in the do_wait_for_common
    > before and after 'timeout = action(timeout);' and it was as expected:
    > 0 - before and 1 - after.
    >
    >> I also think we need to be waiting
    >> for in-flight tasklet runs when stopping the channel.
    > Yes, I also thought that's the reason of the race, because tasklet is in
    > the queue, but it is disabled (on my weird trace I don't see the interrupt,
    > so I abandoned this idea).
    > But it seems to be possible only when we issue dma, wait_for_completion_timeout
    > waits and times out, we do cleanup (tasklet_disable), we get interrupt and
    > do tasklet_schedule. But (again) I don't see timeout and
    > interrupt on my trace (could it be corrupted?).
    >
    > Despite all this theory, the patch below (which just replaces tasklet_disable
    > with tasklet_kill in the cleanup routines) seems to be working (did about
    > 40 reboots and didn't see the issue).
    >
    > I think replacing tasklet_disable with tasklet_kill is reasonable anyway, so
    > should I send the patch rebased on 3.13 with comments or you'll take care
    > and merge it into mainline and stable yourself?

    I'll take it from here and I'll add your Reported-by and Tested-by.

    Thank you!

    --
    Dan

    >
    > ---
    > diff --git a/drivers/dma/ioat/dma.c b/drivers/dma/ioat/dma.c
    > index 17a2393b3e25..6c62f4de02c0 100644
    > --- a/drivers/dma/ioat/dma.c
    > +++ b/drivers/dma/ioat/dma.c
    > @@ -379,7 +379,7 @@ static void ioat1_dma_free_chan_resources(struct dma_chan *c)
    > if (ioat->desccount == 0)
    > return;
    >
    > - tasklet_disable(&chan->cleanup_task);
    > + tasklet_kill(&chan->cleanup_task);
    > del_timer_sync(&chan->timer);
    > ioat1_cleanup(ioat);
    >
    > diff --git a/drivers/dma/ioat/dma_v2.c b/drivers/dma/ioat/dma_v2.c
    > index b925e1b1d139..268e93d1af2d 100644
    > --- a/drivers/dma/ioat/dma_v2.c
    > +++ b/drivers/dma/ioat/dma_v2.c
    > @@ -809,7 +809,7 @@ void ioat2_free_chan_resources(struct dma_chan *c)
    > if (!ioat->ring)
    > return;
    >
    > - tasklet_disable(&chan->cleanup_task);
    > + tasklet_kill(&chan->cleanup_task);
    > del_timer_sync(&chan->timer);
    > device->cleanup_fn((unsigned long) c);
    > device->reset_hw(chan);
    > diff --git a/scripts/package/builddeb b/scripts/package/builddeb
    > index acb86507828a..94a5f04e114e 100644


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