[RFC PATCH 10/11] powerpc/tm: Set failure summary

[Breno Leitao]

Hi Mikey,

On 09/18/2018 02:50 AM, Michael Neuling wrote:
> On Wed, 2018-09-12 at 16:40 -0300, Breno Leitao wrote:
>> Since the transaction will be doomed with treckpt., the TEXASR[FS]
>> should be set, to reflect that the transaction is a failure. This patch
>> ensures it before recheckpointing, and remove changes from other places
>> that were calling recheckpoint.
> 
> TEXASR[FS] should be set by the reclaim. 

Do you mean that the CPU should set TEXASR[FS] when treclaim is called, or,
that the tm_reclaim?

Looking at the ISA, I didn't see TEXASR[FS] being set automatically when a
reclaim happens, although, I see it needs TEXASR[FS] to be set when executing
a trecheckpoint, otherwise it will cause a TM Bad Thing.

That is why I am forcing TEXASR[FS]=1 to doom the transaction so we can
recheckpoint it, but it seems I understood this wrongly.

> I don't know why you'd need to set this
> explicitly in process.c. The only case is when the user supplies a bad signal
> context, but we should check that in the signals code, not process.c
> 
> Hence I think this patch is wrong.
> 
> Also, according to the architecture, TEXASR[FS] HAS TO BE SET on trecheckpoint
> otherwise you'll get a TM Bad Thing. You should say that rather than suggesting
> it's because the transaction is doomed. It's ilqlegal to not do it. That's why we
> have this check in arch/powerpc/kernel/tm.S.

When you say "HAS TO BE SET", do you mean that the hardware will set it and
we shouldn't care about this flag? Thus, if I am hitting EMIT_BUG_ENTRY, it
means my TEXASR was messed somehow?

Thank you