On Tue, Jul 24, 2007 at 12:36:22PM +0200, John Sigler wrote: > Ankita Garg wrote: > > >This patch adds support to display captured -rt stats under > >/proc/schedstat. > > > >Signed-off-by: Ankita Garg <ankita@xxxxxxxxxx> > >-- > > sched_stats.h | 5 ++++- > > 1 file changed, 4 insertions(+), 1 deletion(-) > > > >Index: linux-2.6.22.1/kernel/sched_stats.h > >=================================================================== > >--- linux-2.6.22.1.orig/kernel/sched_stats.h 2007-07-23 > >18:15:57.000000000 +0530 > >+++ linux-2.6.22.1/kernel/sched_stats.h 2007-07-23 > >18:24:03.000000000 +0530 > >@@ -21,12 +21,15 @@ > > > > /* runqueue-specific stats */ > > seq_printf(seq, > >- "cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %llu %llu > >%lu", > >+ "cpu%d %lu %lu %lu %lu %lu %lu %lu %lu %lu %llu %lu %lu > >%lu %llu %lu", > > cpu, rq->yld_both_empty, > > rq->yld_act_empty, rq->yld_exp_empty, rq->yld_cnt, > > rq->sched_switch, rq->sched_cnt, rq->sched_goidle, > > rq->ttwu_cnt, rq->ttwu_local, > > rq->rq_sched_info.cpu_time, > >+#ifdef CONFIG_PREEMPT_RT > >+ rq->rto_schedule, rq->rto_wakeup, rq->rto_pulled, > >+#endif > > rq->rq_sched_info.run_delay, rq->rq_sched_info.pcnt); > > > > seq_printf(seq, "\n"); > > I know you've written a new patch that makes this one obsolete, but I > wanted to discuss this specific patch. > > Originally, there were 13 conversion specifications, and your patch > adds 3, for a total of 16 conversion specifications. > > However, if CONFIG_PREEMPT_RT is not defined, then seq_printf is > called with only 13 arguments. > > Is it safe to call seq_printf with too few arguments? So I tried to run the code disabling CONFIG_PREEMPT_RT, to see the behavior vsnprintf() on supplying fewer arguments. Arbit/garbage value is printed for conversion specifications that do not have a matching argument. It did not cause any issue at all beyond that point. But considering the correctness and quality of code, was going to post the updated patch (if the re-work had not happened)! > > Calling printf(3) with too few arguments leads to undefined behavior. > > seq_printf is a wrapper around vsnprintf() so there might be no issue? > > Regards. -- Regards, Ankita Garg (ankita@xxxxxxxxxx) Linux Technology Center IBM India Systems & Technology Labs, Bangalore, India - To unsubscribe from this list: send the line "unsubscribe linux-rt-users" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
