[PATCH v4 05/13] powerpc/rtas: Facilitate high-level call sequences

[Nathan Lynch]

Michael Ellerman <mpe at ellerman.id.au> writes:

> Nathan Lynch via B4 Relay <devnull+nathanl.linux.ibm.com at kernel.org>
> writes:
>> From: Nathan Lynch <nathanl at linux.ibm.com>
>>
>> On RTAS platforms there is a general restriction that the OS must not
>> enter RTAS on more than one CPU at a time. This low-level
>> serialization requirement is satisfied by holding a spin
>> lock (rtas_lock) across most RTAS function invocations.
> ...
>> diff --git a/arch/powerpc/kernel/rtas.c b/arch/powerpc/kernel/rtas.c
>> index 1fc0b3fffdd1..52f2242d0c28 100644
>> --- a/arch/powerpc/kernel/rtas.c
>> +++ b/arch/powerpc/kernel/rtas.c
>> @@ -581,6 +652,28 @@ static const struct rtas_function *rtas_token_to_function(s32 token)
>>  	return NULL;
>>  }
>>  
>> +static void __rtas_function_lock(struct rtas_function *func)
>> +{
>> +	if (func && func->lock)
>> +		mutex_lock(func->lock);
>> +}
>
> This is obviously going to defeat most static analysis tools.

I guess it's not that obvious to me :-) Is it because the mutex_lock()
is conditional? I'll improve this if it's possible.

> I assume lockdep is OK with it though?

Seems to be, yes.