lkml.org 
[lkml]   [2008]   [Dec]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH 2/3] ftrace: use struct pid

On Thu, 4 Dec 2008, Dave Hansen wrote:

> On Thu, 2008-12-04 at 04:56 -0800, Dave Hansen wrote:
> > On Thu, 2008-12-04 at 04:42 -0800, Eric W. Biederman wrote:
> > >
> > > > +static void clear_ftrace_pid_task(struct pid **pid)
> > > > +{
> > > > + struct task_struct *p;
> > > > +
> > > rcu_read_lock();
> > >
> > > > + do_each_pid_task(*pid, PIDTYPE_PID, p) {
> > > > + clear_tsk_trace_trace(p);
> > > > + } while_each_pid_task(*pid, PIDTYPE_PID, p);
> > > rcu_read_unlock()
> > >
> > > > + put_pid(*pid);
> > > > +
> > > > + *pid = NULL;
> > > > +}
> >
> > Could we get away with sticking the rcu_read_{un}lock() inside those
> > macros? Those are going to get used in pretty high level code and we're
> > allowed to nest rcu_read_lock(). No danger of deadlocks or lock
> > inversions.
>
> Why don't any of the other users of do_each_pid_task() use
> rcu_read_lock()? They all seem to be under read_lock(&tasklist_lock)
> (except one is under a write lock of the same).

Well, if the pid hashes are traversal safe (rcu style), then we only worry
about a node or task being freed. I'm assuming that the node is protected
via RCU as tasks are, then using only rcu_read_lock should be sufficient.

-- Steve



\
 
 \ /
  Last update: 2008-12-04 15:31    [from the cache]
©2003-2011 Jasper Spaans