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Date: Wed, 26 Jan 2011 20:44:18 +0530
From: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@elte.hu>, Steven Rostedt <rostedt@goodmis.org>,
        Linux-mm <linux-mm@kvack.org>,
        Arnaldo Carvalho de Melo <acme@infradead.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Ananth N Mavinakayanahalli <ananth@in.ibm.com>,
        Christoph Hellwig <hch@infradead.org>,
        Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
        Oleg Nesterov <oleg@redhat.com>, LKML <linux-kernel@vger.kernel.org>,
        SystemTap <systemtap@sources.redhat.com>,
        Jim Keniston <jkenisto@linux.vnet.ibm.com>,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Andi Kleen <andi@firstfloor.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Subject: Re: [RFC] [PATCH 2.6.37-rc5-tip 14/20] 14: uprobes: Handing int3
 and singlestep exception.
Message-ID: <20110126151418.GL19725@linux.vnet.ibm.com>
Reply-To: Srikar Dronamraju <srikar@linux.vnet.ibm.com>
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* Peter Zijlstra <peterz@infradead.org> [2011-01-26 11:17:11]:

> On Wed, 2011-01-26 at 14:22 +0530, Srikar Dronamraju wrote:
> > * Peter Zijlstra <peterz@infradead.org> [2011-01-25 14:56:19]:
> > 
> > > On Thu, 2010-12-16 at 15:29 +0530, Srikar Dronamraju wrote:
> > > > +               down_read(&mm->mmap_sem);
> > > > +               for (vma = mm->mmap; vma; vma = vma->vm_next) {
> > > > +                       if (!valid_vma(vma))
> > > > +                               continue;
> > > > +                       if (probept < vma->vm_start || probept > vma->vm_end)
> > > > +                               continue;
> > > > +                       u = find_uprobe(vma->vm_file->f_mapping->host,
> > > > +                                       probept - vma->vm_start);
> > > > +                       if (u)
> > > > +                               break;
> > > > +               }
> > > > +               up_read(&mm->mmap_sem); 
> > > 
> > > One has to ask, what's wrong with find_vma() ?
> > 
> > Are you looking for something like this.
> > 
> >        down_read(&mm->mmap_sem);
> > 	for (vma = find_vma(mm, probept); ; vma = vma->vm_next) {
> > 	       if (!valid_vma(vma))
> > 		       continue;
> > 	       u = find_uprobe(vma->vm_file->f_mapping->host,
> > 			       probept - vma->vm_start);
> > 	       if (u)
> > 		       break;
> >        }
> >        up_read(&mm->mmap_sem); 
> 
> How could you ever need to iterate here? There is only a single vma that
> covers the probe point, if that doesn't find a uprobe, there isn't any.

Agree.
So it simplifies to 

        down_read(&mm->mmap_sem);
 	vma = find_vma(mm, probept);
        if (valid_vma(vma)) {
 	       u = find_uprobe(vma->vm_file->f_mapping->host,
 			       probept - vma->vm_start);
        }
        up_read(&mm->mmap_sem); 

-- 
Thanks and Regards
Srikar