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update comments for check_sync.c in lab7&lab7_result

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chyyuu 8 years ago
parent
commit
dbc1819174
2 changed files with 61 additions and 1 deletions
  1. +60
    -0
      labcodes/lab7/kern/sync/check_sync.c
  2. +1
    -1
      labcodes_answer/lab7_result/kern/sync/check_sync.c

+ 60
- 0
labcodes/lab7/kern/sync/check_sync.c View File

@ -13,6 +13,66 @@
#define TIMES 4 /* 吃4次饭 */
#define SLEEP_TIME 10
//-----------------philosopher problem using monitor ------------
/*PSEUDO CODE :philosopher problem using semaphore
system DINING_PHILOSOPHERS
VAR
me: semaphore, initially 1; # for mutual exclusion
s[5]: semaphore s[5], initially 0; # for synchronization
pflag[5]: {THINK, HUNGRY, EAT}, initially THINK; # philosopher flag
# As before, each philosopher is an endless cycle of thinking and eating.
procedure philosopher(i)
{
while TRUE do
{
THINKING;
take_chopsticks(i);
EATING;
drop_chopsticks(i);
}
}
# The take_chopsticks procedure involves checking the status of neighboring
# philosophers and then declaring one's own intention to eat. This is a two-phase
# protocol; first declaring the status HUNGRY, then going on to EAT.
procedure take_chopsticks(i)
{
DOWN(me); # critical section
pflag[i] := HUNGRY;
test[i];
UP(me); # end critical section
DOWN(s[i]) # Eat if enabled
}
void test(i) # Let phil[i] eat, if waiting
{
if ( pflag[i] == HUNGRY
&& pflag[i-1] != EAT
&& pflag[i+1] != EAT)
then
{
pflag[i] := EAT;
UP(s[i])
}
}
# Once a philosopher finishes eating, all that remains is to relinquish the
# resources---its two chopsticks---and thereby release waiting neighbors.
void drop_chopsticks(int i)
{
DOWN(me); # critical section
test(i-1); # Let phil. on left eat if possible
test(i+1); # Let phil. on rght eat if possible
UP(me); # up critical section
}
*/
//---------- philosophers problem using semaphore ----------------------
int state_sema[N]; /* 记录每个人状态的数组 */
/* 信号量是一个特殊的整型变量 */

+ 1
- 1
labcodes_answer/lab7_result/kern/sync/check_sync.c View File

@ -167,7 +167,7 @@ int philosopher_using_semaphore(void * arg) /* i:哲学家号码,从0到N-1
struct proc_struct *philosopher_proc_condvar[N]; // N philosopher
int state_condvar[N]; // the philosopher's state: EATING, HUNGARY, THINKING
monitor_t mt, *mtp=&mt; // mp is mutex semaphore for monitor's procedures
monitor_t mt, *mtp=&mt; // monitor
void phi_test_condvar (i) {
if(state_condvar[i]==HUNGRY&&state_condvar[LEFT]!=EATING

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