svn commit: r219679 - head/sys/i386/include

[Bruce Evans]

On Wed, 16 Mar 2011, Maxim Dounin wrote:

> On Tue, Mar 15, 2011 at 09:45:10PM +0000, Jung-uk Kim wrote:
>
>> Author: jkim
>> Date: Tue Mar 15 21:45:10 2011
>> New Revision: 219679
>> URL: http://svn.freebsd.org/changeset/base/219679
>>
>> Log:
>>   Partially revert r219672.  After r198295, kernel need to seed randomness as
>> ...
>> Modified: head/sys/i386/include/cpu.h
>> ==============================================================================
>> --- head/sys/i386/include/cpu.h	Tue Mar 15 21:34:10 2011	(r219678)
>> +++ head/sys/i386/include/cpu.h	Tue Mar 15 21:45:10 2011	(r219679)
>> @@ -69,10 +69,14 @@ void	swi_vm(void *);
>>  static __inline uint64_t
>>  get_cyclecount(void)
>>  {
>> +#if defined(I486_CPU) || defined(KLD_MODULE)
>>  	struct bintime bt;
>>
>>  	binuptime(&bt);
>>  	return ((uint64_t)bt.sec << 56 | bt.frac >> 8);
>> +#else
>> +	return (rdtsc());
>> +#endif
>
> This isn't really different as long as GENERIC kernel used, as
> GENERIC defines I486_CPU.

Also, the KLD_MODULE case is broken.

This restores the ifdefs but not the tsc_present check in the old version.
The ifdefs are not sort of necessary, but they seem to have been bogus
in the old version.  Just checking a runtime variable like tsc_present
would have worked provided the variable existed.  tsc.c is standard so
the variable existed even if I486_CPU or KLD_MODULE was defined.  I
think TSC support was standard even when get_cyclecount() was first
committed and had an I386_CPU ifdef, so the ifdef was always bogus.  The
ifdef gave a micro-optimization in some cases, but it was a very tiny
one (avoid a perfectly predictable branch).

Bruce