42 lines
1.5 KiB
C
42 lines
1.5 KiB
C
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#ifndef _M68K_SWITCH_TO_H
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#define _M68K_SWITCH_TO_H
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/*
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* switch_to(n) should switch tasks to task ptr, first checking that
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* ptr isn't the current task, in which case it does nothing. This
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* also clears the TS-flag if the task we switched to has used the
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* math co-processor latest.
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*/
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/*
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* switch_to() saves the extra registers, that are not saved
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* automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and
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* a0-a1. Some of these are used by schedule() and its predecessors
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* and so we might get see unexpected behaviors when a task returns
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* with unexpected register values.
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*
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* syscall stores these registers itself and none of them are used
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* by syscall after the function in the syscall has been called.
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*
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* Beware that resume now expects *next to be in d1 and the offset of
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* tss to be in a1. This saves a few instructions as we no longer have
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* to push them onto the stack and read them back right after.
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*
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* 02/17/96 - Jes Sorensen (jds@kom.auc.dk)
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*
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* Changed 96/09/19 by Andreas Schwab
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* pass prev in a0, next in a1
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*/
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asmlinkage void resume(void);
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#define switch_to(prev,next,last) do { \
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register void *_prev __asm__ ("a0") = (prev); \
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register void *_next __asm__ ("a1") = (next); \
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register void *_last __asm__ ("d1"); \
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__asm__ __volatile__("jbsr resume" \
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: "=a" (_prev), "=a" (_next), "=d" (_last) \
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: "0" (_prev), "1" (_next) \
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: "d0", "d2", "d3", "d4", "d5"); \
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(last) = _last; \
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} while (0)
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#endif /* _M68K_SWITCH_TO_H */
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