Re: [PATCH] IB/mad: Use ID allocator routines to allocate agent number

[HÃkon Bugge]

> On 29 May 2018, at 17:49, Jason Gunthorpe <jgg@xxxxxxxx> wrote:
> 
> On Tue, May 29, 2018 at 09:38:08AM +0200, Hans Westgaard Ry wrote:
>> The agent TID is a 64 bit value split in two dwords.  The least
>> significant dword is the TID running counter. The most significant
>> dword is the agent number. In the CX-3 shared port model, the mlx4
>> driver uses the most significant byte of the agent number to store the
>> slave number, making agent numbers greater and equal to 2^24 (3 bytes)
>> unusable.
> 
> There is no reason for this to be an ida, just do something like
> 
> mad_agent_priv->agent.hi_tid = atomic_inc_return(&ib_mad_client_id) & mad_agent_priv->ib_dev->tid_mask;
> 
> And have the driver set tid_mask to 3 bytes of 0xFF

The issue is that some of the mad agents are long-lived, so you will wrap and use the same TID twice.


Thxs, HÃkon


> 
> And no sysctl.
> 
> Jason
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