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charset="UTF-8" X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 8FF8F140003 X-Rspam-User: X-Stat-Signature: 6jh33hjk765qyyxfkfeb8ah1ycdu6i8s X-HE-Tag: 1674006792-231669 X-HE-Meta: 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 9/rd1A3/ mawdC4O0qKD8WaG0= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000777, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Jan 17, 2023 at 7:42 AM 'Michal Hocko' via kernel-team wrote: > > On Mon 09-01-23 12:53:21, Suren Baghdasaryan wrote: > > Assert there are no holders of VMA lock for reading when it is about to be > > destroyed. > > > > Signed-off-by: Suren Baghdasaryan > > --- > > include/linux/mm.h | 8 ++++++++ > > kernel/fork.c | 2 ++ > > 2 files changed, 10 insertions(+) > > > > diff --git a/include/linux/mm.h b/include/linux/mm.h > > index 594e835bad9c..c464fc8a514c 100644 > > --- a/include/linux/mm.h > > +++ b/include/linux/mm.h > > @@ -680,6 +680,13 @@ static inline void vma_assert_write_locked(struct vm_area_struct *vma) > > VM_BUG_ON_VMA(vma->vm_lock_seq != READ_ONCE(vma->vm_mm->mm_lock_seq), vma); > > } > > > > +static inline void vma_assert_no_reader(struct vm_area_struct *vma) > > +{ > > + VM_BUG_ON_VMA(rwsem_is_locked(&vma->lock) && > > + vma->vm_lock_seq != READ_ONCE(vma->vm_mm->mm_lock_seq), > > + vma); > > Do we really need to check for vm_lock_seq? rwsem_is_locked should tell > us something is wrong on its own, no? This could be somebody racing with > the vma destruction and using the write lock. Unlikely but I do not see > why to narrow debugging scope. I wanted to ensure there are no page fault handlers (read-lockers) when we are destroying the VMA and rwsem_is_locked(&vma->lock) alone could trigger if someone is concurrently calling vma_write_lock(). But I don't think we expect someone to be write-locking the VMA while we are destroying it, so you are right, I'm overcomplicating things here. I think I can get rid of vma_assert_no_reader() and add VM_BUG_ON_VMA(rwsem_is_locked(&vma->lock)) directly in __vm_area_free(). WDYT? > -- > Michal Hocko > SUSE Labs > > -- > To unsubscribe from this group and stop receiving emails from it, send an email to kernel-team+unsubscribe@android.com. >