Messages in this thread | | | Date | Fri, 20 Apr 2012 01:46:56 +0400 | From | Konstantin Khlebnikov <> | Subject | Re: + c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-update-after-mm- num_exe_file_vmas-removal.patch added to -mm tree |
| |
Oleg Nesterov wrote: > On 04/20, Cyrill Gorcunov wrote: >> >> On Thu, Apr 19, 2012 at 09:20:05PM +0200, Oleg Nesterov wrote: >>> On 04/19, Andrew Morton wrote: >>>> >>>> From: Konstantin Khlebnikov<khlebnikov@openvz.org> >>>> Subject: c/r: prctl: update prctl_set_mm_exe_file() after mm->num_exe_file_vmas removal >>>> >>>> [ fix for "c-r-prctl-add-ability-to-set-new-mm_struct-exe_file-v2" from mm tree ] >>>> >>>> After removing mm->num_exe_file_vmas kernel keeps mm->exe_file until final >>>> mmput(), it never becomes NULL while task is alive. >>>> >>>> We can check for other mapped files in mm instead of checking >>>> mm->num_exe_file_vmas, and mark mm with flag MMF_EXE_FILE_CHANGED in order >>>> to forbid second changing of mm->exe_file. >>> >>> I lost the track a long ago. >>> >>> Just one question, what does this "forbid second changing" actually mean? >> >> Heh :) Oleg, it was actually your idea to make this feature "one-shot". > > Heh, no ;) > > IIRC, I only asked you what do you actually want, > > Just one note for the record, prctl_set_mm_exe_file() does > > if (mm->num_exe_file_vmas) > return -EBUSY; > > We could do > > if (mm->exe_file) > return -EBUSY; > > This way "because this feature is a special to C/R" becomes > really true. IOW, you can't do PR_SET_MM_EXE_FILE twice. > > I am fine either way, just I want to ensure you really want > the current version. > > and only because it was documented as "feature is a special to C/R". > >> Once exe-file changed to a new value, it can't be changed again. The >> reason was to bring at least minimum disturbance in sysadmins life. > > You misunderstood. I am not arguing with "one-shot", I do not really > care. > > My question is: unless I missed something "it can't be changed again" > is not actually true. A task does PR_SET_MM_EXE_FILE, then it forks > the new child. The child can do PR_SET_MM_EXE_FILE again. Is this > by design? > > Oleg. >
I found more weird case: child thread (with CLONE_THREAD and without CLONE_VM) changes its exe_file...
| |