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    SubjectRe: [PATCH 2/3] scsi: arcmsr: Fix suspend/resume of ACB_ADAPTER_TYPE_B part 2
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    On Thu, 2019-01-17 at 12:16 +0300, Dan Carpenter wrote:
    > On Thu, Jan 17, 2019 at 04:47:07PM +0800, Ching Huang wrote:
    > > On Thu, 2019-01-17 at 10:59 +0300, Dan Carpenter wrote:
    > > > On Thu, Jan 17, 2019 at 11:45:03AM +0800, Ching Huang wrote:
    > > > > >From Ching Huang <ching2048@areca.com.tw>
    > > > >
    > > > > Fix suspend/resume of ACB_ADAPTER_TYPE_B part 2.
    > > > >
    > > >
    > > > What does this look like from a user perspective? Does it fail every
    > > > time or does it only fail sometimes?
    > > >
    > > > What's the bug exactly?
    > > >
    > > > There is no Fixes tag...
    > > >From user's perspective, hibernate/resume are OK.
    > > But following IO may cause 'isr get an illegal ccb command' in
    > > log/messages sometime.
    > > >
    >
    >
    > You will need to resend with that information included in the commit
    > message.
    OK. I will resend this patch later.
    >
    > > > > Signed-off-by: Ching Huang <ching2048@areca.com.tw>
    > > > > ---
    > > > >
    > > > > diff --git a/drivers/scsi/arcmsr/arcmsr.h b/drivers/scsi/arcmsr/arcmsr.h
    > > > > index a94c513..b98c632 100755
    > > > > --- a/drivers/scsi/arcmsr/arcmsr.h
    > > > > +++ b/drivers/scsi/arcmsr/arcmsr.h
    > > > > @@ -508,9 +508,9 @@ struct MessageUnit_A
    > > > > struct MessageUnit_B
    > > > > {
    > > > > uint32_t post_qbuffer[ARCMSR_MAX_HBB_POSTQUEUE];
    > > > > - uint32_t done_qbuffer[ARCMSR_MAX_HBB_POSTQUEUE];
    > > > > + volatile uint32_t done_qbuffer[ARCMSR_MAX_HBB_POSTQUEUE];
    > > >
    > > > There is a well known rule of thumb that when someone uses "volatile"
    > > > in the kernel it means there is a locking problem... Is this __iomem or
    > > > something?
    > > The done_qbuffer was a command completion queue, it was an area written
    > > by IO processor and read by device driver. So, ...
    >
    > I'm not totally positive I understand this sentence. I can find a bunch
    > of places which read from this buffer, but I haven't immediately found
    > which place writes to it. Can you give me a function name that I should
    > read?
    Well, we allocate memory for struct MessageUnit_B in
    arcmsr_alloc_ccb_pool(), by assign to acb->dma_coherent_handle2.
    Then we tell IO controller its DMA address in arcmsr_iop_confirm().
    When a command was completed, controller's firmware program will write a
    completion ccb in done_qbuffer through DMA. So, you can't see any driver
    funtion write to it.
    >
    > > >
    > > > > uint32_t postq_index;
    > > > > - uint32_t doneq_index;
    > > > > + volatile uint32_t doneq_index;
    >
    > The volatile here is not right. It's just normal memory.
    Right. this volatile is not necessary.
    >
    > regards,
    > dan carpenter


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