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
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