On Wed, 1 May 2024 16:12:37 -0700 "Paul E. McKenney" <paul...@kernel.org> wrote:
> Note that the immediate pressure for this patch should be relieved by the > NAPI patch series [1], but this sort of problem could easily arise again. > > When running heavy test workloads with KASAN enabled, RCU Tasks grace > periods can extend for many tens of seconds, significantly slowing > trace registration. Therefore, make the registration-side RCU Tasks > grace period be asynchronous via call_rcu_tasks(). > Good catch! AFAICS, there is no reason to wait for synchronization when adding a new direct trampoline. This looks good to me. Reviewed-by: Masami Hiramatsu (Google) <mhira...@kernel.org> Thank you, > [1] https://lore.kernel.org/all/cover.1710877680.git....@cloudflare.com/ > > Reported-by: Jakub Kicinski <k...@kernel.org> > Reported-by: Alexei Starovoitov <a...@kernel.org> > Reported-by: Chris Mason <c...@fb.com> > Signed-off-by: Paul E. McKenney <paul...@kernel.org> > Cc: Steven Rostedt <rost...@goodmis.org> > Cc: Masami Hiramatsu <mhira...@kernel.org> > Cc: Mark Rutland <mark.rutl...@arm.com> > Cc: Mathieu Desnoyers <mathieu.desnoy...@efficios.com> > Cc: <linux-trace-ker...@vger.kernel.org> > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 6c96b30f3d63b..32ea92934268c 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -5365,6 +5365,13 @@ static void remove_direct_functions_hash(struct > ftrace_hash *hash, unsigned long > } > } > > +static void register_ftrace_direct_cb(struct rcu_head *rhp) > +{ > + struct ftrace_hash *fhp = container_of(rhp, struct ftrace_hash, rcu); > + > + free_ftrace_hash(fhp); > +} > + > /** > * register_ftrace_direct - Call a custom trampoline directly > * for multiple functions registered in @ops > @@ -5463,10 +5470,8 @@ int register_ftrace_direct(struct ftrace_ops *ops, > unsigned long addr) > out_unlock: > mutex_unlock(&direct_mutex); > > - if (free_hash && free_hash != EMPTY_HASH) { > - synchronize_rcu_tasks(); > - free_ftrace_hash(free_hash); > - } > + if (free_hash && free_hash != EMPTY_HASH) > + call_rcu_tasks(&free_hash->rcu, register_ftrace_direct_cb); > > if (new_hash) > free_ftrace_hash(new_hash); -- Masami Hiramatsu (Google) <mhira...@kernel.org>
