I am beginning to enjoy the Prepare Future program on Linux internal and\u00a0\u00a0 driver development. Today’s class was about pthreads. I had some prior experience on pthreads library while at CUSAT.\u00a0\u00a0 It was refreshed today.<\/p>\n
Pthreads is a user space library for\u00a0 manipulating threads.<\/p>\n
Here is what we did today.\u00a0 First we wrote a small program which created a thread.<\/p>\n
It is here.<\/p>\n
#include<stdio.h>
\n#include <sys\/types.h>
\n#include <pthread.h><\/p>\n
void * thread_function ( void *arg)
\n{
\nprintf(“In Thread\\n”);
\npthread_exit(“Success”);
\n}<\/p>\n
int main()
\n{
\npthread_t tid;
\nvoid * ret_status;
\npthread_create( &tid,NULL, &thread_function,NULL);<\/p>\n
printf(“In Main\\n”);<\/p>\n
pthread_join(tid ,&ret_status);<\/p>\n
return (0);<\/p>\n
}<\/p>\n
For compiling this I used.<\/p>\n
$gcc -D_REENTRANT -o pt1 pt1.c -l pthread<\/p>\n
Then\u00a0 i tried out \u00a0 semaphore and mutex in pthread library.<\/p>\n
The important semaphore operations are<\/p>\n
sem_init\u00a0 –\u00a0\u00a0 int sem_init(sem_t *sem, int pshared, unsigned int value);<\/p>\n
sem_ wait\u00a0 \u00a0 int sem_wait(sem_t *sem);<\/p>\n
sem_post\u00a0\u00a0\u00a0 \u00a0\u00a0\u00a0\u00a0 int sem_post(sem_t *sem);<\/p>\n
sem_destroy\u00a0\u00a0 int sem_destroy(sem_t *sem);<\/p>\n
I was forced to RTFM the manual. \ud83d\ude00<\/p>\n
I wrote this then.<\/p>\n
#include<stdio.h>
\n#include <sys\/types.h>
\n#include <pthread.h>
\n#include <semaphore.h><\/p>\n
int y=0;
\nsem_t sigsem;<\/p>\n
void * thread1 ( void *arg)
\n{
\nint x;
\nsem_wait(&sigsem);<\/p>\n
x=y+3;<\/p>\n
printf(“In Thread1\\n”);
\nprintf(” x is %d\\n”,x);<\/p>\n
pthread_exit(“Success thread1 “);
\n}<\/p>\n
void * thread2 ( void *arg)
\n{
\ny=45;
\nsem_post(&sigsem);
\nprintf(“In Thread2\\n”);
\nprintf(” y is %d\\n”,y);
\npthread_exit(“Success thread2”);
\n}<\/p>\n
int main()
\n{
\npthread_t tid1,tid2;
\nvoid * ret_status;<\/p>\n
sem_init( &sigsem,0,0);<\/p>\n
pthread_create( &tid1,NULL, &thread1,NULL);
\npthread_create( &tid2,NULL, &thread2,NULL);
\nprintf(“In Main\\n”);<\/p>\n
pthread_join(tid1 ,&ret_status);
\npthread_join(tid2 ,&ret_status);<\/p>\n
sem_destroy(&sigsem);<\/p>\n
return (0);<\/p>\n
}
\nThis was followed by producer consumer problem as below.<\/p>\n
#include<stdio.h>
\n#include <sys\/types.h>
\n#include <pthread.h><\/p>\n
\/\/sem_t sigsem;
\nint buffer[10];<\/p>\n
void * producer ( void *arg)
\n{
\nint i,index;
\nindex=0;<\/p>\n
for (i =0;i<40 ;++i)
\n{<\/p>\n
printf(“Producer\u00a0 trying to produce an item……….\\n”);<\/p>\n
buffer[index] =i;<\/p>\n
printf (“producer put\u00a0 %d\u00a0 at buffer [%d]\\n”, i,index);<\/p>\n
index++;
\nif (index==10)
\nindex=0;
\n}<\/p>\n
pthread_exit(“Producer ends”);
\n}<\/p>\n
void * consumer ( void *arg)
\n{
\nint i,index=0;
\nfor (i=0;i<40;++i)
\n{
\nprintf(” Consumer\u00a0 trying to consume\u00a0 an item ……….\\n”);
\nprintf ( ” Consumer ate\u00a0 %d from buffer[%d]\\n”, buffer [index] ,index);<\/p>\n
index++;
\nif (index==10)
\nindex=0;
\n}<\/p>\n
pthread_exit(“Consumer ends”);
\n}<\/p>\n
int main()
\n{
\npthread_t tid1,tid2;
\nvoid * ret_status;
\npthread_create( &tid1,NULL, &producer,NULL);
\npthread_create( &tid2,NULL, &consumer,NULL);<\/p>\n
pthread_join(tid1 ,&ret_status);
\npthread_join(tid2 ,&ret_status);<\/p>\n
return (0);<\/p>\n
}
\nThe mutex in it\u00a0 was then rewritten with pthread_mutex functions. Again lot of RTFM.<\/p>\n
Then as an assignment we did the readers and writers problem.<\/p>\n
#include<stdio.h>
\n#include <sys\/types.h>
\n#include <pthread.h>
\n#include <semaphore.h><\/p>\n
sem_t\u00a0 mutex,rcmutex;
\nint reader_count=0;
\nint buffer=10;<\/p>\n
void reader_action(int r )
\n{<\/p>\n
printf ( “\\nReader %d\u00a0 buffer is %d “,r, buffer);
\n}<\/p>\n
void\u00a0 write_action (int i)
\n{
\nint j;
\nbuffer+=10;
\nfor (j=0;j<10;++j) ; \/\/Waste some time<\/p>\n
printf ( “\\n Writing for %d time buffer is %d “,i, buffer);<\/p>\n
}<\/p>\n
void * reader1 ( void *arg)
\n{<\/p>\n
sem_wait(&rcmutex);
\nreader_count++;
\nif(reader_count==1)
\nsem_wait(&mutex);
\nsem_post(&rcmutex);<\/p>\n
reader_action(1);<\/p>\n
sem_wait(&rcmutex);<\/p>\n
reader_count–;
\nif ( reader_count==0)
\nsem_post(&mutex);<\/p>\n
sem_post(&rcmutex);<\/p>\n
pthread_exit(“Success reader1 “);
\n}<\/p>\n
void * reader2 ( void *arg)
\n{<\/p>\n
sem_wait(&rcmutex);
\nreader_count++;
\nif(reader_count==1)
\nsem_wait(&mutex);
\nsem_post(&rcmutex);<\/p>\n
reader_action(2);<\/p>\n
sem_wait(&rcmutex);<\/p>\n
reader_count–;
\nif ( reader_count==0)
\nsem_post(&mutex);<\/p>\n
sem_post(&rcmutex);<\/p>\n
pthread_exit(“Success reader2 “);
\n}<\/p>\n
void * writer ( void *arg)
\n{
\nint i;
\nfor (i=0 ; i<10;++i)
\n{<\/p>\n
sem_wait (&mutex);
\nwrite_action(i);
\nsem_post(&mutex);
\n}
\npthread_exit(“Success writer”);
\n}<\/p>\n
int main()
\n{
\npthread_t tid1,tid2,tid3,tid4,tid5,tid6;
\nvoid * ret_status;<\/p>\n
sem_init( &mutex,0,1);
\nsem_init( &rcmutex,0,1);<\/p>\n
pthread_create( &tid1,NULL, &reader1,NULL);
\npthread_create( &tid2,NULL, &writer,NULL);
\npthread_create( &tid3,NULL, &reader2,NULL);
\npthread_create( &tid4,NULL, &reader1,NULL);
\npthread_create( &tid5,NULL, &reader2,NULL);
\npthread_create( &tid6,NULL, &reader1,NULL);<\/p>\n
pthread_join(tid1 , &ret_status);
\npthread_join(tid2 ,&ret_status);
\npthread_join(tid3 ,&ret_status);
\npthread_join(tid4 , &ret_status);
\npthread_join(tid5 , &ret_status);
\npthread_join(tid6 , &ret_status);<\/p>\n
sem_destroy(&mutex);
\nsem_destroy(&rcmutex);
\nreturn (0);<\/p>\n
}
\nThe course is progressing smoothly. and looks interesting several fellow participants are also stimulating.<\/p>\n
I forgot to take the card reader, so I am unable to post photos.\u00a0 I had a walk around the JNTU campus in the morning and took several photos. May be I will beautify these blog enties with\u00a0 photos and proper code snippets ( and build \u00a0 proper pthread tutorial) \u00a0 when I return.<\/p>\n","protected":false},"excerpt":{"rendered":"
I am beginning to enjoy the Prepare Future program on Linux internal and\u00a0\u00a0 driver development. Today’s class was about pthreads. I had some prior experience on pthreads library while at CUSAT.\u00a0\u00a0 It was refreshed today. Pthreads is a user space library for\u00a0 manipulating threads. Here is what we did today.\u00a0 First we wrote a small… Continue reading Learning Pthreads<\/span><\/a><\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[5,6],"tags":[52,53],"_links":{"self":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts\/250"}],"collection":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=250"}],"version-history":[{"count":3,"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts\/250\/revisions"}],"predecessor-version":[{"id":530,"href":"https:\/\/brainstorms.in\/index.php?rest_route=\/wp\/v2\/posts\/250\/revisions\/530"}],"wp:attachment":[{"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=250"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=250"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/brainstorms.in\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=250"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}