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Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes: register/unregister probes.
- From: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- To: Peter Zijlstra <peterz at infradead dot org>
- Cc: Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, Linux-mm <linux-mm at kvack dot org>, Arnaldo Carvalho de Melo <acme at infradead dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Christoph Hellwig <hch at infradead dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Oleg Nesterov <oleg at redhat dot com>, Andrew Morton <akpm at linux-foundation dot org>, SystemTap <systemtap at sources dot redhat dot com>, Jim Keniston <jkenisto at linux dot vnet dot ibm dot com>, Frederic Weisbecker <fweisbec at gmail dot com>, Andi Kleen <andi at firstfloor dot org>, LKML <linux-kernel at vger dot kernel dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- Date: Wed, 26 Jan 2011 13:25:58 +0530
- Subject: Re: [RFC] [PATCH 2.6.37-rc5-tip 5/20] 5: Uprobes: register/unregister probes.
- References: <20101216095714.23751.52601.sendpatchset@localhost6.localdomain6> <20101216095817.23751.76989.sendpatchset@localhost6.localdomain6> <1295957744.28776.722.camel@laptop>
- Reply-to: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
> > +
> > + 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.
> > + if (list_empty(&tmp_list)) {
> > + ret = 0;
> > + goto consumers_add;
> > + }
> > + list_for_each_entry_safe(mm, tmpmm, &tmp_list, uprobes_list) {
> > + if (!install_uprobe(mm, uprobe))
> > + ret = 0;
> > + list_del(&mm->uprobes_list);
> > + mmput(mm);
> > + }
> > +
> > +consumers_add:
> > + add_consumer(uprobe, consumer);
> > + mutex_unlock(&uprobes_mutex);
> > + put_uprobe(uprobe);
> > + return ret;
> > +}
> > +
--
Thanks and Regards
Srikar