• Daniel Drake's avatar
    shell-app: remove child_setup from app launching · 4b522a02
    Daniel Drake authored
    When the amount of free memory on the system is somewhat low, gnome-shell
    will sometimes fail to launch apps, reporting the error:
      fork(): Cannot allocate memory
    
    fork() is failing here because while cloning the process virtual address
    space, Linux worries that the thread being forked may end up COWing the
    entire address space of the parent process (gnome-shell, which is
    memory-hungry), and there is not enough free memory to permit that to
    happen. This check is somewhat irrelevant because we are only forking
    to immediately exec(), which will discard the whole virtual address
    space anyway.
    
    This issue can be avoided by using a new optimized gspawn codepath in
    the latest glib development version, which uses posix_spawn() internally.
    
    For the optimized codepath to be used, we must not pass a child_setup
    function, so the the file descriptor management is reimplemented here
    using new glib API to pass fds to the child process. The old API will
    continue to be used on older glib versions.
    
    We must also change the spawn flags for this code path to be hit.
    I checked that gnome-shell's open file descriptors are all CLOEXEC
    so using G_SPAWN_LEAVE_DESCRIPTORS_OPEN should be safe.
    
    This will result in more resilient app launching when memory is low,
    since the optimized spawn path avoids cloning the virtual address
    space of the parent process (gnome-shell) and avoids the irrelevant
    memory overcommit check.
    
    !132
    4b522a02
config.h.meson 829 Bytes