Messages in this thread | | | Subject | Re: [v3 PATCH] mm: introduce arg_lock to protect arg_start|end and env_start|end in mm_struct | From | Yang Shi <> | Date | Tue, 10 Apr 2018 09:21:19 -0700 |
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On 4/10/18 5:28 AM, Cyrill Gorcunov wrote: > On Tue, Apr 10, 2018 at 01:10:01PM +0200, Michal Hocko wrote: >>> Because do_brk does vma manipulations, for this reason it's >>> running under down_write_killable(&mm->mmap_sem). Or you >>> mean something else? >> Yes, all we need the new lock for is to get a consistent view on brk >> values. I am simply asking whether there is something fundamentally >> wrong by doing the update inside the new lock while keeping the original >> mmap_sem locking in the brk path. That would allow us to drop the >> mmap_sem lock in the proc path when looking at brk values. > Michal gimme some time. I guess we might do so, but I need some > spare time to take more precise look into the code, hopefully today > evening. Also I've a suspicion that we've wracked check_data_rlimit > with this new lock in prctl. Need to verify it again.
I see you guys points. We might be able to move the drop of mmap_sem before setting mm->brk in sys_brk since mmap_sem should be used to protect vma manipulation only, then protect the value modify with the new arg_lock. Then we can eliminate mmap_sem stuff in prctl path, and it also prevents from wrecking check_data_rlimit.
At the first glance, it looks feasible to me. Will look into deeper later.
Thanks, Yang
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