Linux Kernel  3.7.1
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switch_to.h
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1 #ifndef _H8300_SWITCH_TO_H
2 #define _H8300_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, offset of tss in d1, and whether
28  * the mm structures are shared in d2 (to avoid atc flushing).
29  *
30  * H8/300 Porting 2002/09/04 Yoshinori Sato
31  */
32 
33 asmlinkage void resume(void);
34 #define switch_to(prev,next,last) { \
35  void *_last; \
36  __asm__ __volatile__( \
37  "mov.l %1, er0\n\t" \
38  "mov.l %2, er1\n\t" \
39  "mov.l %3, er2\n\t" \
40  "jsr @_resume\n\t" \
41  "mov.l er2,%0\n\t" \
42  : "=r" (_last) \
43  : "r" (&(prev->thread)), \
44  "r" (&(next->thread)), \
45  "g" (prev) \
46  : "cc", "er0", "er1", "er2", "er3"); \
47  (last) = _last; \
48 }
49 
50 #endif /* _H8300_SWITCH_TO_H */