Hi,
The note above __switch_to macro in i386/kernel/process.c says that we no
more use hardware context switching as some problems in recovering from
saved state that is no longer valid. (I am peeking into 2.2 kernel). Now I have
following questions
1) What exactly is meant by ' stale segment register values' in the note.
2) In the above macro, I think we recover gracefully from error condition while
recovering fs and gs segment registers . The loadsegment(fs,next->tss.fs) and
loadsegment(gs,next->tss.gs) does it. I am not able to understand loadsegment
macro. The macro is as under
/** Load a segment. Fall back on loading a zero segment if something goes wrong
**/
#define loadsegment(seg,value) \
asm volatile("\n" \
"1:\t" \
"movl %0,%%" #seg "\n" \
"2:\n" \
"3:\t" \
"pushl $0\n\t" \
"jmp 2b\n" \
".previous\n" \
".section __ex_table,\"a\"\n\t \
"/align 4\n\t" \
".long 1b,3b\n" \
".previous" \
: :"m" (*(unsigned int *)&(value)))
I also want to know what is 'something' in the comment above the macro
Thanks in advance
Amol
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