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SubjectRE: [PATCH] HP iLO driver
Heikki Orsila wrote:
> On Thu, Jun 12, 2008 at 12:23:08PM -0600, David Altobelli wrote:
>> + volatile u64 fifobar[1];
>> +};
>
> Why do you need a volatile? What you probably want is atomic ops.
> Spinlocks will create memory barriers implicitly.

This points to a queue that is shared with hardware, and could
be modified outside of kernel control.

>> +static int fifo_enqueue(struct ilo_hwinfo *hw, char *fifobar, int
>> entry) +{ + struct fifo *Q = FIFOBARTOHANDLE(fifobar);
>> + int ret = 0;
>> +
>> + spin_lock(&hw->fifo_lock);
>> + if (!(Q->fifobar[(Q->tail + 1) & Q->imask] & ENTRY_MASK_O)) {
>> + Q->fifobar[Q->tail & Q->imask] |=
>> + ((entry & ENTRY_MASK_NOSTATE) | Q->merge); +
>> Q->tail += 1; + ret = 1;
>> + }
>> + spin_unlock(&hw->fifo_lock);
>> +
>> + return ret;
>> +}
>
> Is writing to Q->fifobar (u64 *) endian-safe?

No, this is not endian-safe. Good point. I think converting these
to readl() operations would let me remove the volatile and fix the
endian issue.


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