This is the mail archive of the
systemtap@sourceware.org
mailing list for the systemtap project.
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: Stephen Wilson <wilsons at start dot ca>
- 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 14:52:47 +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> <20110314180914.GA18855@fibrous.localdomain>
- Reply-to: Srikar Dronamraju <srikar at linux dot vnet dot ibm dot com>
* Stephen Wilson <wilsons@start.ca> [2011-03-14 14:09:14]:
> On Mon, Mar 14, 2011 at 07:05:22PM +0530, 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);
> > + tsk = mm->owner;
> > + if (!tsk)
> > + return ret;
>
> I think you need to check that tsk != NULL before calling
> get_task_struct()...
>
Guess checking for tsk != NULL would only help if and only if we are doing
within rcu. i.e we have to change to something like this
rcu_read_lock()
if (mm->owner) {
get_task_struct(mm->owner)
tsk = mm->owner;
}
rcu_read_unlock()
if (!tsk)
return ret;
Agree?