cvs commit: src/sys/kern uipc_sem.c

[Robert Watson]

rwatson     2005-02-25 19:10:51 UTC

  FreeBSD src repository

  Modified files:
    sys/kern             uipc_sem.c 
  Log:
  Add an exit hook, sem_forkhook(), which walks the list of POSIX semaphores
  owned by a process when it forks, and creates a matching set of references
  for the child process, as prescribed by POSIX.
  
  In order to avoid races with other threads in the parent process during
  fork(), it is necessary to allocate a temporary reference list while
  holding the sem_lock, then transfer those references to the new process
  once the sem_lock is released.  The implementation is inefficient but
  appears functional; in order to improve the efficiency, it will be
  necessary to modify the existing structures and logic, which generally
  rely on O(n) operations over the global set of semaphores.
  
  Revision  Changes    Path
  1.16      +113 -1    src/sys/kern/uipc_sem.c