On Sat, Apr 22, 2017 at 12:52 AM, Jason Gunthorpe
<jgunthorpe@xxxxxxxxxxxxxxxxxxxx> wrote:
> On Fri, Apr 21, 2017 at 02:57:08PM -0400, Devesh Sharma wrote:
>
>> +static void bnxt_re_ring_db(struct bnxt_re_dpi *dpi,
>> + struct bnxt_re_db_hdr *hdr)
>> +{
>> + __le64 *dbval;
>> +
>> + pthread_spin_lock(&dpi->db_lock);
>> + dbval = (__le64 *)&hdr->indx;
>> + udma_to_device_barrier();
>> + iowrite64(dpi->dbpage, dbval);
>> + pthread_spin_unlock(&dpi->db_lock);
>> +}
>
> What are you expecting this db_lock to do?
>
> Is 'dbpage' UC or WC memory?
Driver re-maps it as "UC-" where strong ordering is guaranteed. How
system would handle 64-bit writes will it issue two 32-bit consecutive
writes on the bus?
>
> If this is UC memory then writing 64 bit values concurrently from
> multiple threads is OK and this lock does nothing.
>
> If this is WC memory then you need to use mmio_wc_spinlock /
> mmio_wc_spinunlock instead, or the lock doesn't work right.
>
> Jason
--
To unsubscribe from this list: send the line "unsubscribe linux-rdma" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
