Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes:register/unregister probes.
From: Srikar Dronamraju
Date: Wed Jan 26 2011 - 10:37:34 EST
* Peter Zijlstra <peterz@xxxxxxxxxxxxx> [2011-01-26 11:11:48]:
> On Wed, 2011-01-26 at 13:25 +0530, Srikar Dronamraju wrote:
> > > > +
> > > > + list_add(&mm->uprobes_list, &tmp_list);
> > > > + mm->uprobes_vaddr = vma->vm_start + offset;
> > > > + }
> > > > + spin_unlock(&mapping->i_mmap_lock);
> > >
> > > Both this and unregister are racy, what is to say:
> > > - the vma didn't get removed from the mm
> > > - no new matching vma got added
> > >
> > register_uprobe, unregister_uprobe, uprobe_mmap are all synchronized by
> > uprobes_mutex. So I dont see one unregister_uprobe getting thro when
> > another register_uprobe is working with a vma.
> > If I am missing something elementary, please explain a bit more.
> afaict you're not holding the mmap_sem, so userspace can simply unmap
> the vma.
When we do the actual insert/remove of the breakpoint we hold the
mmap_sem. During the actual insertion/removal, if the vma for the
specific inode is not found, we just come out without doing the
Thanks and Regards
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