Messages in this thread | | | Date | Thu, 19 Apr 2012 23:12:16 +0200 | From | Oleg Nesterov <> | 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 |
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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.
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