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Re: [PATCH v2 2.6.38-rc8-tip 7/20] 7: uprobes: store/restore original instruction.
- From: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
- To: Thomas Gleixner <tglx at linutronix dot de>
- Cc: Peter Zijlstra <peterz at infradead dot org>, 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>, Andi Kleen <andi at firstfloor dot org>, Masami Hiramatsu <masami dot hiramatsu dot pt at hitachi dot com>, Oleg Nesterov <oleg at redhat dot com>, LKML <linux-kernel at vger dot kernel dot org>, Jim Keniston <jkenisto at linux dot vnet dot ibm dot com>, Roland McGrath <roland at hack dot frob dot com>, SystemTap <systemtap at sources dot redhat dot com>, Andrew Morton <akpm at linux-foundation dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>
- Date: Tue, 15 Mar 2011 21:55:08 +0530
- Subject: Re: [PATCH v2 2.6.38-rc8-tip 7/20] 7: uprobes: store/restore original instruction.
- References: <20110314133403.27435.7901.sendpatchset@localhost6.localdomain6> <20110314133522.27435.45121.sendpatchset@localhost6.localdomain6> <alpine.LFD.2.00.1103151538200.2787@localhost6.localdomain6>
- Reply-to: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
* Thomas Gleixner <tglx@linutronix.de> [2011-03-15 15:41:20]:
> On Mon, 14 Mar 2011, Srikar Dronamraju wrote:
> > static int install_uprobe(struct mm_struct *mm, struct uprobe *uprobe)
> > {
> > - int ret = 0;
> > + struct task_struct *tsk;
> > + int ret = -EINVAL;
> >
> > - /*TODO: install breakpoint */
> > - if (!ret)
> > + get_task_struct(mm->owner);
>
> Increment task ref before checking for NULL ?
In response to earlier comments/suggestions from Stephen Wilson, we
resolved to handle it this way
static uprobes_get_mm_owner() {
struct task_struct *tsk;
rcu_read_lock()
tsk = rcu_dereference(mm->owner);
if (tsk)
get_task_struct(tsk);
rcu_read_unlock();
return tsk;
}
Both install_uprobe and remove_uprobe will end up calling uprobes_get_mm_owner().
--
Thanks and Regards
Srikar