Dave Hansen <dave@xxxxxxxxxxxxxxxxxx> writes: > 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). We probably should. Historically read_lock(&tasklist_lock) implies rcu_read_lock(). And the tasklist lock is what we hold when it is safe. But if you look at find_vpid we should be holding just the rcu lock there. Eric _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers