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enable_fpu_exception() - only write cr0 if bit isn't already on.

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(NMI profiling results indicate this both is relatively expensive and
happens a lot unnecessarily if the fpu is in use.)
This commit is contained in:
Ben Gras 2010-09-22 14:31:06 +00:00
parent b0572bfd1e
commit 82d576c9ca
1 changed files with 3 additions and 1 deletions
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4
kernel/arch/i386/exception.c
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@ -285,7 +285,9 @@ PUBLIC void proc_stacktrace(struct proc *whichproc)
PUBLIC void enable_fpu_exception(void) PUBLIC void enable_fpu_exception(void)
{ {
write_cr0(read_cr0() | I386_CR0_TS); u32_t cr0 = read_cr0();
if(!(cr0 & I386_CR0_TS))
write_cr0(cr0 | I386_CR0_TS);
} }
PUBLIC void disable_fpu_exception(void) PUBLIC void disable_fpu_exception(void)