[GitHub] [incubator-nuttx] gustavonihei commented on a change in pull request #4779: libs/libc/wqueue/work_usrthread.c: Correct time calculation in work_p…

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gustavonihei commented on a change in pull request #4779:
URL: https://github.com/apache/incubator-nuttx/pull/4779#discussion_r741945947



##########
File path: libs/libc/wqueue/work_usrthread.c
##########
@@ -193,15 +193,18 @@ static void work_process(FAR struct usr_wqueue_s *wqueue)
     {
       struct timespec rqtp;
       time_t sec;
+      uint64_t nsec;
 
       /* Wait awhile to check the work list.  We will wait here until
        * either the time elapses or until we are awakened by a semaphore.
        * Interrupts will be re-enabled while we wait.
        */
 
-      sec          = next / 1000000;
-      rqtp.tv_sec  = sec;
-      rqtp.tv_nsec = (next - (sec * 1000000)) * 1000;
+      clock_gettime(CLOCK_REALTIME, &rqtp);
+      nsec = 1000 * TICK2USEC(next);
+      sec = nsec / (1000 * 1000 * 1000);
+      rqtp.tv_sec  += sec;
+      rqtp.tv_nsec += (uint32_t)(nsec - sec * 1000 * 1000 * 1000);

Review comment:
       ```suggestion
         clock_gettime(CLOCK_REALTIME, &rqtp);
         nsec = TICK2NSEC(next);
         sec = nsec / NSEC_PER_SEC;
         rqtp.tv_sec  += sec;
         rqtp.tv_nsec += nsec - sec * NSEC_PER_SEC;
   
         if (rqtp.tv_nsec >= NSEC_PER_SEC)
           {
             rqtp.tv_sec++;
             rqtp.tv_nsec -= NSEC_PER_SEC;
           }
   ```
   Some considerations here:
   1) Suggest using the nanoseconds macros for achieving cleaner code.
   2) The cast to `uint32_t` might end up narrowing the value on 64 bits architectures, since `tv_nsec` type is `long`.
   3) After incrementing `tv_nsec`, we still need to check if the final value is within the valid range of \[0, 1000000000\] (https://en.cppreference.com/w/c/chrono/timespec)




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