嵌入式操作系统内核原理和开发（抢占式优先级调度）

$d&|7gJ^6@0int find_next_thread()
.?DL?%@S0{51Testing软件测试网+AX6Z9ij5s,yc1[]
    int index;
Ii'j6H]1cO0S0    int choice = THREAD_MAX_NUMBER -1;
i_"C8t0KGc0    int value = gAllTask[choice].time_slice;51Testing软件测试网y@@6D0gVp_

-N:AT#`"M9Cs%f0    for(index = choice -1; index >= 0; index --)
-S5Q8Jn,a/t8^8|o0    {51Testing软件测试网n`4LWdE
        if(value < gAllTask[index].time_slice)

m_$pZ(Swu-A0        {51Testing软件测试网d,_l5q4s
            choice = index;51Testing软件测试网 __8A\.u5l
            value = gAllTask[index].time_slice;
w$IN"Uy&W#_d0        }
"D3d K.Q{uP0    }51Testing软件测试网:ZwLAb

1e,Z9v}%ke!~ \,y9D0    if(0 == value)
Ul:]XhN_3U0        choice = -1;

C!@D
l.Y0    return choice;     
&z,{7Z3c1[D!y0}51Testing软件测试网GYp#hOM~*Q

-t9C,YLP7D4el0#include <stdio.h>
R N[3JVcJ%r0#include <time.h>
&@D#mwU)`6eE0#include <stdlib.h>51Testing软件测试网WY&bI)G-gTJ
#include <signal.h>
"t2^"M eVR!YE,Q|0#include <assert.h>51Testing软件测试网i"w+H+I|
#include <string.h>51Testing软件测试网!cU7o5c]0g.e
#include <sys/time.h>

!xIkm
AV0OK`J"S0#define UINT32 unsigned         int
{1E/^6q(Xb0#define STACK_LENGTH            51251Testing软件测试网EG2{L3F+N
#define THREAD_MAX_NUMBER       10
I Bv;pDY;O\6m0#define TIME_ROUND_SCHEDULE     0
hptia4V0#define HARD_PRIORITY_SCHEDULE  0
~ X:a `2o
A?iy0#define SOFT_PRIORITY_SCHEDULE  1 

typedef struct _TASK_INFO
X7K@+zV,k%F9c`r0{
8D*MMW0NPj!X;A0    UINT32 id;51Testing软件测试网2r1J.w$?j4_.G1y@$u
    UINT32* stack;51Testing软件测试网 }8{-x.Le
    UINT32 size;
tL;gOs+y"hA%mQ0    UINT32 context;51Testing软件测试网 vE2VFK&E6p#{3SS/`1f
    UINT32 priority;
*@-Wy6P_/S D4P(q$n_0    UINT32 time_slice;51Testing软件测试网9fO%h.}6pu
    void (*func)();51Testing软件测试网$PC.HV%R\m

}TASK_INFO;

X*{%Tk"H0static struct itimerval oldtv;
7FLK&B3Pg0UINT32 old   = 0;51Testing软件测试网*M"jUUC
UINT32 count = 0;
?;K'f5Ingx a/y6y@0UINT32 task_stack[THREAD_MAX_NUMBER][STACK_LENGTH] = {0};
6_J
OA!Z-u a9]S0TASK_INFO gAllTask[THREAD_MAX_NUMBER] = {0};51Testing软件测试网q6N;e8h%x)s`*c
UINT32 current_thread_id = 0;51Testing软件测试网,?;]+]8l%X|aQ2y

void set_timer()51Testing软件测试网0l'kYQj~[h
{
JuES2CJ0        struct itimerval itv;
Z$}o'DO
z2I B0        itv.it_interval.tv_sec = 1;51Testing软件测试网"kh b
M#D|,L
        itv.it_interval.tv_usec = 0;51Testing软件测试网s3|i
z_6^}nZ reRR
        itv.it_value.tv_sec = 1;51Testing软件测试网eC${| @/_-q,F
        itv.it_value.tv_usec = 0;
?O4Y4ov'P0        setitimer(ITIMER_REAL, &itv, &oldtv);
UF*d|l"a7^0}51Testing软件测试网)[H%v}4YDx

d9H A"j/v0void swap(UINT32* prev, UINT32* next)
.ocE%U\q*IV0{
$g;Hl;K/YI0    __asm("push %%eax\n\t"51Testing软件测试网/Z0auz bY6sHYXFj
          "push %%ebx\n\t"51Testing软件测试网t[h"F&filk
          "push %%ecx\n\t"
'@.iIU7\] XJM)U0          "push %%edx\n\t"51Testing软件测试网M
?&F z1| Ol-@
          "push %%esi\n\t"51Testing软件测试网H:gcmz A
          "push %%edi\n\t"51Testing软件测试网VAElB?{SA
          "push %%ebp\n\t"51Testing软件测试网*n!mx+KUco8Rg
          "push %%esp\n\t"
's R;g9h7k0          "lea 0x8(%%ebp), %%eax\n\t"51Testing软件测试网
f!\ W{f:Rb
          "mov (%%eax), %%eax\n\t"51Testing软件测试网{:j.?k)y.J(kJ
          "mov %%esp, (%%eax)\n\t"

Q6CaK`+s*{K)b;b0          "lea 0xc(%%ebp), %%eax\n\t"51Testing软件测试网1G)^ ^ f!\c$E7X/Rl9|
          "mov (%%eax), %%eax\n\t"51Testing软件测试网eh4tL@8aD
          "mov (%%eax), %%esp\n\t"51Testing软件测试网@/R.n{c+H|*Y%aP8f
          "pop %%esp\n\t"51Testing软件测试网;[`5N"iK
          "pop %%ebp\n\t"

aG/Xoi:[:lu~d0          "pop %%edi\n\t"51Testing软件测试网p[6orI0D
_3S-[
          "pop %%esi\n\t"51Testing软件测试网b^Q&VE8Py.[i
          "pop %%edx\n\t"
v8^lN,s$kJxS0          "pop %%ecx\n\t"51Testing软件测试网a \*}g.sPL1ks
          "pop %%ebx\n\t"51Testing软件测试网:E&j~$M|A
Bi
          "pop %%eax\n\t"51Testing软件测试网s ZSm6ACaP
          ::);
})g4odze.ux m0}

void hello()51Testing软件测试网IQ8nNL
{
O#{y,k ~-M{0        int temp = 0;51Testing软件测试网4j8U:nb+K:zJ

        while(1) {
b1j5V jGx0            printf("id = %d, temp = %d, count = %d in thread!\n",current_thread_id,  temp ++, count ++);51Testing软件测试网6LQ|f[C
F
            swap(&gAllTask[current_thread_id].context, &old);

"Qj3Y{7x cJs]0            printf("id = %d, temp = %d, count = %d in thread!\n",current_thread_id,  temp ++, count ++);
r+T x.}i0            swap(&gAllTask[current_thread_id].context, &old);
My3Rr'eqgT0        }51Testing软件测试网"} |
Tmi2~8^*y
l
}51Testing软件测试网?[Y |p*i0H

#if HARD_PRIORITY_SCHEDULE51Testing软件测试网B*^ krP
int find_next_thread()
1w)[-N8I9W0{
.zt[Vz:v}L5E'Uv'G0    int index;51Testing软件测试网:gN0~Y eA$j2z!Y

    for(index = THREAD_MAX_NUMBER -1; index >=0; index --)
Js(E,x/v
~0    {51Testing软件测试网c(sCgc1w4_
        if(0 != gAllTask[index].time_slice)
8e8n e3s_)w R6Fi0            break;51Testing软件测试网{[1f4kM,u
    }

Ha!]
wG0    return index;     
w3YX&wVh%T*G0}51Testing软件测试网7X%GJ9yI

^,w6W3qf0#endif

51Testing软件测试网jI,Qk![
#if SOFT_PRIORITY_SCHEDULE51Testing软件测试网&{ZQ7K vI ]e
int find_next_thread()51Testing软件测试网't6[,C#}`h7V2k
{51Testing软件测试网
R3W!k7c-b1c(\
    int index;51Testing软件测试网dZx2_3j)h*E C9z
    int choice = THREAD_MAX_NUMBER -1;51Testing软件测试网0C_/@8h g?m{
    int value = gAllTask[choice].time_slice;

}R*V6LN^0@&|
q|0    for(index = choice -1; index >= 0; index --)
-{-R1jMh1Y'gTc-H0    {51Testing软件测试网R7GNQ-ju\1O
        if(value < gAllTask[index].time_slice)
3DH%p&p)Tk:v0        {51Testing软件测试网i H4qV[,Bt{S@(j
            choice = index;51Testing软件测试网H `
i(t)H#UE*W[
            value = gAllTask[index].time_slice;51Testing软件测试网j9@p0B9L:[
        }
t\7Mz3}E(k;Z!R0    }

'VzTo0~[0    if(0 == value)51Testing软件测试网!T p1zBO*B7z
        choice = -1;

    return choice;     
eo1ZN3j f7K+`0}51Testing软件测试网/ZM(W/D)c*GTZ

#endif

void reset_time_slice ()
U0@9Ba'Rx
w0{
EY-b{ B0    int index;51Testing软件测试网#h!^9Z`"L'h6w

    for(index = 0; index < THREAD_MAX_NUMBER; index++)
$|)i,o;S1ij3^0        gAllTask[index].time_slice = gAllTask[index].priority + 1;
`:ER
t@D/i|0}

void task_init(int index)
[1Zc4V$Dp8fi`0{51Testing软件测试网Soa}(lK
        UINT32 unit = gAllTask[index].size;
qvIW,f3Hi0        UINT32* pData = gAllTask[index].stack;

jCe!L%j'dq U1}0        memset((void*)pData,(int) 0, unit * sizeof(UINT32));51Testing软件测试网0g5ae gG0}AaZ
        pData[unit -1] = (UINT32) gAllTask[index].func;51Testing软件测试网5N7D
Q$a^c$s(G3R
        pData[unit -2] = 0;51Testing软件测试网0M.UC+O].e;u"j
        pData[unit -3] = 0;51Testing软件测试网CE?E F(|
~B
        pData[unit -4] = 0;51Testing软件测试网.cNvw7Q~c l
        pData[unit -5] = 0;51Testing软件测试网0@-?@q+?B:I
        pData[unit -6] = 0;
+M0}'Lc O-y O$j0        pData[unit -7] = 0;51Testing软件测试网qZ[{ w,hs
        pData[unit -8] = 0;51Testing软件测试网o{Z l0r ^
        pData[unit -9] = 0;51Testing软件测试网0~:E1_.omLK
        pData[unit -10] = (UINT32) &pData[unit - 9];
L)UDt_(~0        gAllTask[index].context = (UINT32) &pData[unit -10];
Tm;BN6F0}51Testing软件测试网.Qxi,m.[hoW7H

#if TIME_ROUND_SCHEDULE
7n"[C&Z~:OY]D0void signal_handler(int m)51Testing软件测试网@0O E@t*Nt/e\
{
$h"M?y]En9V0        current_thread_id = current_thread_id % THREAD_MAX_NUMBER;
cM`j2}3eNVg0        swap(&old, &gAllTask[current_thread_id].context);
m;MZ6l7a+s9h;I0        current_thread_id ++;
"Fg/M@a3cF
b0}

9@?'UC4|1^qYR M5VR0#else51Testing软件测试网/Guo(h7|G
void signal_handler(int m)51Testing软件测试网_A^N1GEc
{51Testing软件测试网$LTjOCL\B
        int index;51Testing软件测试网o-@%a/A.r

O Cg Y+U1[e1E"X%LWx0start:
;P L.zh
@&?"o0        index = find_next_thread();
i6ff
mL9c u_'JO0        if(-1 == index)51Testing软件测试网/i6^aga\l
        {51Testing软件测试网K!OA'lN%E.J`.X
            reset_time_slice();51Testing软件测试网,Cul-c
K,ed/{)t
            goto start;51Testing软件测试网P
@S?7jU
        }

-J AZ&N%Z u*['FH0        gAllTask[index].time_slice --;
juF'`_C0        current_thread_id = index;51Testing软件测试网9R_ir5tgT
        swap(&old, &gAllTask[current_thread_id].context);
+|hu3|%d.T0}51Testing软件测试网Q*v4S6KO$d$o&|6n8]5kR
#endif51Testing软件测试网,A*hJwg

jnH*e4KLO!T051Testing软件测试网IJhT?k
void set_all_task() 
ht$k}_3tp~:UM8oe0{51Testing软件测试网m3n U+kt
        int index;
BMR(H(j!S3t3X&K0        memset(gAllTask, 0, sizeof(gAllTask));

0EmRcRU0        for(index = 0; index < THREAD_MAX_NUMBER; index ++)51Testing软件测试网1]9\]Y%gVOEPZ
        {51Testing软件测试网-h5pE4x6Zf5S9A
            gAllTask[index].id = index;51Testing软件测试网4DW|:xTLF
            gAllTask[index].stack = task_stack[index];51Testing软件测试网 wg[N1e)C7[!u
            gAllTask[index].size = STACK_LENGTH;51Testing软件测试网hCF#V.^
F
            gAllTask[index].context = 0;
D)g!qH$f2]YR0            gAllTask[index].func = hello;
,R J[`s2DB3e-X8d0            gAllTask[index].priority = index;51Testing软件测试网Y9V!qRrJo6t
            gAllTask[index].time_slice = index + 1;

            task_init(index);
W8\0i;iaTK9q0        }
L{\J\ Ue
xaQ*r+o0}51Testing软件测试网,l.h&n1~7p6X)c!?2q+O(P

6\j5R Avh%`6v[%G9P0int main()51Testing软件测试网8jdx
h0Fh'm{
{51Testing软件测试网)i#iJ$R8~Z8l
        char val;

e-U.ZUzD+h0        set_all_task();51Testing软件测试网 P.p Du [)P
        set_timer();
-p
?8Wx
W,Xtw!F'L0        signal(SIGALRM, signal_handler);51Testing软件测试网5u+A5rE:@|

p7K w~R h!z
| U9?0        while(1)51Testing软件测试网
\V;LFJ w
        {51Testing软件测试网0O)t"e$g8\2E2^"@n+x
            scanf("%c", &val);51Testing软件测试网-CQ0c+L#XM6T |&K*p
        }51Testing软件测试网?w
X.c)q0n1Jr7Uaw

f*Zt&W E4Hyb&Zk0        exit(0);51Testing软件测试网|{(plxf4W
        return 1;51Testing软件测试网0@-Rg6M j qZ
}