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    SubjectRe: [PATCH AUTOSEL 4.18 27/48] sound: enable interrupt after dma buffer initialization
    On Fri, Oct 05, 2018 at 12:14:03PM -0400, Sasha Levin wrote:
    > From: Yu Zhao <yuzhao@google.com>
    >
    > [ Upstream commit b61749a89f826eb61fc59794d9e4697bd246eb61 ]
    >
    > In snd_hdac_bus_init_chip(), we enable interrupt before
    > snd_hdac_bus_init_cmd_io() initializing dma buffers. If irq has
    > been acquired and irq handler uses the dma buffer, kernel may crash
    > when interrupt comes in.

    CCing Takashi who's the maintainer here for review.

    >
    > Fix the problem by postponing enabling irq after dma buffer
    > initialization. And warn once on null dma buffer pointer during the
    > initialization.
    >
    > Reviewed-by: Takashi Iwai <tiwai@suse.de>
    > Signed-off-by: Yu Zhao <yuzhao@google.com>
    > Signed-off-by: Mark Brown <broonie@kernel.org>
    > Signed-off-by: Sasha Levin <alexander.levin@microsoft.com>
    > ---
    > sound/hda/hdac_controller.c | 8 ++++++--
    > 1 file changed, 6 insertions(+), 2 deletions(-)
    >
    > diff --git a/sound/hda/hdac_controller.c b/sound/hda/hdac_controller.c
    > index 560ec0986e1a..11057d9f84ec 100644
    > --- a/sound/hda/hdac_controller.c
    > +++ b/sound/hda/hdac_controller.c
    > @@ -40,6 +40,8 @@ static void azx_clear_corbrp(struct hdac_bus *bus)
    > */
    > void snd_hdac_bus_init_cmd_io(struct hdac_bus *bus)
    > {
    > + WARN_ON_ONCE(!bus->rb.area);
    > +
    > spin_lock_irq(&bus->reg_lock);
    > /* CORB set up */
    > bus->corb.addr = bus->rb.addr;
    > @@ -479,13 +481,15 @@ bool snd_hdac_bus_init_chip(struct hdac_bus *bus, bool full_reset)
    > /* reset controller */
    > azx_reset(bus, full_reset);
    >
    > - /* initialize interrupts */
    > + /* clear interrupts */
    > azx_int_clear(bus);
    > - azx_int_enable(bus);
    >
    > /* initialize the codec command I/O */
    > snd_hdac_bus_init_cmd_io(bus);
    >
    > + /* enable interrupts after CORB/RIRB buffers are initialized above */
    > + azx_int_enable(bus);
    > +
    > /* program the position buffer */
    > if (bus->use_posbuf && bus->posbuf.addr) {
    > snd_hdac_chip_writel(bus, DPLBASE, (u32)bus->posbuf.addr);
    > --
    > 2.17.1
    >
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