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 _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers