On Tue, 15 Nov 2022 17:48:47 -0300 "Guilherme G. Piccoli" <gpiccoli@xxxxxxxxxx> wrote: > The function match_records() may take a while due to a large > number of string comparisons, so when in PREEMPT_VOLUNTARY > kernels we could face RCU stalls due to that. > > Add a cond_resched() to prevent that. > > Suggested-by: Steven Rostedt <rostedt@xxxxxxxxxxx> > Acked-by: Paul E. McKenney <paulmck@xxxxxxxxxx> # from RCU CPU stall warning perspective > Cc: Masami Hiramatsu <mhiramat@xxxxxxxxxx> > Cc: Mark Rutland <mark.rutland@xxxxxxx> > Signed-off-by: Guilherme G. Piccoli <gpiccoli@xxxxxxxxxx> This looks good to me. Acked-by: Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx> Thanks! > --- > > Hi Steve / Paul, thanks for the discussions on the first thread [0], > much appreciated! Here is the "official" version. > > Steve: lemme know if it's good for you, and in case you prefer to > send it yourself (since you proposed it on IRC), fine by me! > > Paul: kept your ACK (thanks for that BTW) even though I changed the > place of cond_resched() to align with Steve's preference. Lemme know > in case you want to drop this ACK. > > Cheers, > > Guilherme > > > [0] https://lore.kernel.org/lkml/1ef5fe19-a82f-835e-fda5-455e9c2b94b4@xxxxxxxxxx/ > > > kernel/trace/ftrace.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/kernel/trace/ftrace.c b/kernel/trace/ftrace.c > index 7dc023641bf1..80639bdb85f6 100644 > --- a/kernel/trace/ftrace.c > +++ b/kernel/trace/ftrace.c > @@ -4192,6 +4192,7 @@ match_records(struct ftrace_hash *hash, char *func, int len, char *mod) > } > found = 1; > } > + cond_resched(); > } while_for_each_ftrace_rec(); > out_unlock: > mutex_unlock(&ftrace_lock); > -- > 2.38.0 > -- Masami Hiramatsu (Google) <mhiramat@xxxxxxxxxx>
