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POhow to suspend a thread before another thread finishes its work
 

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  1. POhow to suspend a thread before another thread finishes its work
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    <p>hi there i'm working on POSIX threads and i have a work like</p> <ul> <li>We have 5 threads which each of them will print 'a','b','c','d,'e' separately with using same function</li> <li>Threads must be created in alphabetical order.</li> <li>Each character must be printed 50 times on screen</li> <li>'a' can only printed after all 'c's are printed</li> <li>'b' can only printed after all 'd's are printed</li> <li>'c' can only printed after all 'd's are printed</li> </ul> <p>so before i display my code i have to explain what i have done. first of all, i have 5 global variables (which are flags and all of them set to 1 initiallly ) and i assigned them to the value which pthread_create() function returns. and then in the main function i used if() conditions before i joined threads. but i guess i'm trying the wrong way. the issue is i coundnt handle with the process "before thread_a, thread_d must finish its work". i will appreciate if you can help and suggest some better ideas. and here is my code,</p> <pre><code>#include &lt;pthread.h&gt; #include &lt;stdlib.h&gt; #include &lt;unistd.h&gt; #include &lt;stdio.h&gt; int counter = 0; int flag_a = 1; int flag_b = 1; int flag_c = 1; int flag_d = 1; int flag_e = 1; pthread_mutex_t mymutex=PTHREAD_MUTEX_INITIALIZER; void* thread_function(void* str); void print_char(char* ch); int main(){ pthread_t thread_a, thread_b, thread_c, thread_d, thread_e; char* a = "a"; char* b = "b"; char* c = "c"; char* d = "d"; char* e = "e"; flag_a = pthread_create( &amp;thread_a, NULL, thread_function, (void*) a ); flag_b = pthread_create( &amp;thread_b, NULL, thread_function, (void*) b ); flag_c = pthread_create( &amp;thread_c, NULL, thread_function, (void*) c ); flag_d = pthread_create( &amp;thread_d, NULL, thread_function, (void*) d ); flag_e = pthread_create( &amp;thread_e, NULL, thread_function, (void*) e ); if(flag_c==0) pthread_join( thread_a, NULL ); pthread_join( thread_b, NULL ); if(flag_d==0) pthread_join( thread_c, NULL ); if(flag_d==0) pthread_join( thread_d, NULL ); pthread_join( thread_e, NULL ); printf("\nCounter = %d\n", counter); return 0; } void* thread_function(void* str) { int i; char* msg = (char*) str; for(i=0; i&lt;50; i++) { pthread_mutex_lock(&amp;mymutex); counter++; print_char(msg); pthread_mutex_unlock(&amp;mymutex); } } void print_char(char* ch){ int i; for(i=0; i&lt;1; i++) { printf("%s --&gt; ", ch); fflush(stdout); sleep(1); } } </code></pre> <p>edit: i found a solution which prints the characters properly but the issue i cant print them asynchronousnly. i mean whenever i run the code it has same output like:</p> <p>e-->d-->c-->b-->a (every character printed at 50 times )</p> <p>and this the editted part of thread_function()</p> <pre><code>void* thread_function(void* str) { int i; char* msg = (char*) str; while( (strcmp(msg,"a") == 0) &amp;&amp; (counter_c &lt; 5) ){ ;; } while( (strcmp(msg,"c") == 0) &amp;&amp; (counter_d &lt; 5) ){ ;; } while( (strcmp(msg,"b") == 0) &amp;&amp; (counter_d &lt; 5) ){ ;; } for(i=0; i&lt;5; i++) { pthread_mutex_lock(&amp;mymutex); counter++; if( strcmp(msg,"d") == 0 ) counter_d++; if( strcmp(msg,"c") == 0 ) counter_c++; print_char(msg); pthread_mutex_unlock(&amp;mymutex); } } </code></pre>
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    1. USquartaela
    1. USquartaela
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    1. COI don't know how to solve this problem, but what about reducing the problem to two characters only? Should be the same essentially
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      1. USstefan
    2. COwell logically we can try on at least 3 characters and just 'a' will be printed after all 'd' are printed.
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      1. USquartaela
    3. COIs there are spelling error becaue *'c' can only printed after all* **'D'***s are printed* or is it *'c' can only printed after all ***'E'***s are printed*
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      1. UStozka
 

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