Linux Kernel  3.7.1
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switch_to.h
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1 #ifndef _M68K_SWITCH_TO_H
2 #define _M68K_SWITCH_TO_H
3 
4 /*
5  * switch_to(n) should switch tasks to task ptr, first checking that
6  * ptr isn't the current task, in which case it does nothing. This
7  * also clears the TS-flag if the task we switched to has used the
8  * math co-processor latest.
9  */
10 /*
11  * switch_to() saves the extra registers, that are not saved
12  * automatically by SAVE_SWITCH_STACK in resume(), ie. d0-d5 and
13  * a0-a1. Some of these are used by schedule() and its predecessors
14  * and so we might get see unexpected behaviors when a task returns
15  * with unexpected register values.
16  *
17  * syscall stores these registers itself and none of them are used
18  * by syscall after the function in the syscall has been called.
19  *
20  * Beware that resume now expects *next to be in d1 and the offset of
21  * tss to be in a1. This saves a few instructions as we no longer have
22  * to push them onto the stack and read them back right after.
23  *
24  * 02/17/96 - Jes Sorensen ([email protected])
25  *
26  * Changed 96/09/19 by Andreas Schwab
27  * pass prev in a0, next in a1
28  */
29 asmlinkage void resume(void);
30 #define switch_to(prev,next,last) do { \
31  register void *_prev __asm__ ("a0") = (prev); \
32  register void *_next __asm__ ("a1") = (next); \
33  register void *_last __asm__ ("d1"); \
34  __asm__ __volatile__("jbsr resume" \
35  : "=a" (_prev), "=a" (_next), "=d" (_last) \
36  : "0" (_prev), "1" (_next) \
37  : "d0", "d2", "d3", "d4", "d5"); \
38  (last) = _last; \
39 } while (0)
40 
41 #endif /* _M68K_SWITCH_TO_H */