Subj : How to ensure that a thread runs while another is doing I/O
To   : comp.programming.threads
From : Anant Padmanath Mudambi
Date : Sun Jan 09 2005 07:56 pm

Hi all,
Consider this psuedo code:

M1,M2 : mutexes    C: condition variable

thread_1
{
  mutex_lock(M1);
  mutex_lock(M2);
  create thread_2;
  cond_wait(C, M1);
  mutex_unlock(M1);
  mutex_unlock(M2);
  big write to a file on disk;
  join(thread_2);
}

thread_2
{
  mutex_lock(M1);
  CPU-bound work #1;
  mutex_unlock(M1);
  cond_signal(C);
  mutex_lock(M2);
  CPU-bound work #2;
}

By putting printf()s in this code I saw that after thread_2 signals C,
sometimes the "CPU-bound work #2" executes while thread_1 is waiting for
the file write to finish and sometimes it executes AFTER the whole file
write finishes.

How can I ensure that thread_2 always continues to execute as soon as
possible without waiting for the whole file write in thread_1 to finish?
Assume these are the only 2 user threads on the system.

Thank you,
Anant.

.