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Demystified code

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git-svn-id: svn://svn.rockbox.org/rockbox/trunk@1183 a1c6a512-1295-4272-9138-f99709370657
This commit is contained in:
Björn Stenberg 2002-06-25 12:04:23 +00:00
parent ef15d9983a
commit 3f9c7c2ab5
2 changed files with 31 additions and 42 deletions
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59
firmware/thread.c
View file

@ -18,9 +18,7 @@
****************************************************************************/
#include "thread.h"
typedef union
{
struct regs_t
struct regs
{
unsigned int r[7]; /* Registers r8 thru r14 */
void *sp; /* Stack pointer (r15) */
@ -28,23 +26,17 @@ typedef union
unsigned int macl;
unsigned int sr; /* Status register */
void* pr; /* Procedure register */
} regs;
} ctx_t;
};
typedef struct
{
int num_threads;
int current;
ctx_t ctx[MAXTHREADS];
} thread_t;
static thread_t threads;
static int num_threads;
static int current_thread;
static struct regs thread_contexts[MAXTHREADS];
/*---------------------------------------------------------------------------
* Store non-volatile context.
*---------------------------------------------------------------------------
*/
static inline void stctx(void* addr)
static inline void store_context(void* addr)
{
asm volatile ("add #48, %0\n\t"
"sts.l pr, @-%0\n\t"
@ -65,7 +57,7 @@ static inline void stctx(void* addr)
* Load non-volatile context.
*---------------------------------------------------------------------------
*/
static inline void ldctx(void* addr)
static inline void load_context(void* addr)
{
asm volatile ("mov.l @%0+,r8\n\t"
"mov.l @%0+,r9\n\t"
@ -89,16 +81,15 @@ static inline void ldctx(void* addr)
*/
void switch_thread(void)
{
int ct;
int nt;
thread_t* t = &threads;
int current;
int next;
nt = ct = t->current;
if (++nt >= t->num_threads)
nt = 0;
t->current = nt;
stctx(&t->ctx[ct]);
ldctx(&t->ctx[nt]);
next = current = current_thread;
if (++next >= num_threads)
next = 0;
current_thread = next;
store_context(&thread_contexts[current]);
load_context(&thread_contexts[next]);
}
/*---------------------------------------------------------------------------
@ -106,27 +97,25 @@ void switch_thread(void)
* Return 0 if context area could be allocated, else -1.
*---------------------------------------------------------------------------
*/
int create_thread(void* fp, void* sp, int stk_size)
int create_thread(void* function, void* stack, int stack_size)
{
thread_t* t = &threads;
if (t->num_threads >= MAXTHREADS)
if (num_threads >= MAXTHREADS)
return -1;
else
{
ctx_t* ctxp = &t->ctx[t->num_threads++];
stctx(ctxp);
struct regs* regs = &thread_contexts[num_threads++];
store_context(regs);
/* Subtract 4 to leave room for the PR push in ldctx()
Align it on an even 32 bit boundary */
ctxp->regs.sp = (void*)(((unsigned int)sp + stk_size - 4) & ~3);
ctxp->regs.sr = 0;
ctxp->regs.pr = fp;
regs->sp = (void*)(((unsigned int)stack + stack_size - 4) & ~3);
regs->sr = 0;
regs->pr = function;
}
return 0;
}
void init_threads(void)
{
threads.num_threads = 1; /* We have 1 thread to begin with */
threads.current = 0; /* The current thread is number 0 */
num_threads = 1; /* We have 1 thread to begin with */
current_thread = 0; /* The current thread is number 0 */
}

2
firmware/thread.h
View file

@ -21,7 +21,7 @@
#define MAXTHREADS 16
int create_thread(void* fp, void* sp, int stk_size);
int create_thread(void* function, void* stack, int stack_size);
void switch_thread(void);
void init_threads(void);