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Re: [RFC] [PATCH 2.6.37-rc5-tip 4/20] 4: uprobes: Adding and remove a uprobe in a rb tree.
- From: Peter Zijlstra <peterz at infradead dot org>
- To: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- Cc: Ingo Molnar <mingo at elte dot hu>, Steven Rostedt <rostedt at goodmis dot org>, Arnaldo Carvalho de Melo <acme at infradead dot org>, Linus Torvalds <torvalds at linux-foundation dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Christoph Hellwig <hch at infradead dot org>, Andi Kleen <andi at firstfloor dot org>, Oleg Nesterov <oleg at redhat dot com>, LKML <linux-kernel at vger dot kernel 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>, Ananth N Mavinakayanahalli <ananth at in dot ibm dot com>, Andrew Morton <akpm at linux-foundation dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- Date: Wed, 26 Jan 2011 11:13:21 +0100
- Subject: Re: [RFC] [PATCH 2.6.37-rc5-tip 4/20] 4: uprobes: Adding and remove a uprobe in a rb tree.
- References: <20101216095714.23751.52601.sendpatchset@localhost6.localdomain6> <20101216095803.23751.41491.sendpatchset@localhost6.localdomain6> <1295957742.28776.720.camel@laptop> <20110126084103.GE19725@linux.vnet.ibm.com>
On Wed, 2011-01-26 at 14:11 +0530, Srikar Dronamraju wrote:
> * Peter Zijlstra <peterz@infradead.org> [2011-01-25 13:15:42]:
>
> > On Thu, 2010-12-16 at 15:28 +0530, Srikar Dronamraju wrote:
> > > +/* Should be called lock-less */
> > > +static void put_uprobe(struct uprobe *uprobe)
> > > +{
> > > + if (atomic_dec_and_test(&uprobe->ref))
> > > + kfree(uprobe);
> > > +}
> >
> > Since this instantly frees the uprobe once ref hits 0, the
> > atomic_inc_not_zero() in find_uprobe() doesn't really make sense does
> > it?
>
> Okay, I can move the atomic_inc_not_zero() in find_uprobe() to
> atomic_inc().
>
> Do you see any side-effects of using atomic_inc_not_zero?
No, its just slower, once you want to start doing RCU lookups in the
probe tree you'll need it through.