Messages in this thread | | | Date | Tue, 24 May 2016 19:26:23 -0700 | From | "Paul E. McKenney" <> | Subject | Re: [PATCH] rcuperf: Don't treat gp_exp mis-setting as a WARN |
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On Wed, May 25, 2016 at 09:25:33AM +0800, Boqun Feng wrote: > 0day found a boot warning triggered in rcu_perf_writer() on !SMP kernel: > > WARN_ON(rcu_gp_is_normal() && gp_exp); > > , the root cause of which is trying to measure expedited grace > periods(by setting gp_exp to true by default) when all the grace periods > are normal(TINY RCU only has normal grace periods). > > However, such a mis-setting would only result in failing to measure the > performance for a specific kind of grace periods, therefore using a > WARN_ON to check this is a little overkilling. We could handle this > inside rcuperf module via some error messages to tell users about the > mis-settings. > > Therefore this patch removes the WARN_ON in rcu_perf_writer() and > handles those checkings in rcu_perf_init() with plain if() code. > > Moreover, this patch changes the default value of gp_exp to 1) align > with rcutorture tests and 2) make the default setting work for all RCU > implementations by default. > > Suggested-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> > Signed-off-by: Boqun Feng <boqun.feng@gmail.com> > Fixes: http://lkml.kernel.org/r/57411b10.mFvG0+AgcrMXGtcj%fengguang.wu@intel.com
Queued for review and testing, thank you!
Thanx, Paul
> --- > kernel/rcu/rcuperf.c | 14 +++++++++++--- > 1 file changed, 11 insertions(+), 3 deletions(-) > > diff --git a/kernel/rcu/rcuperf.c b/kernel/rcu/rcuperf.c > index 3cee0d8393ed..8ce4eecff319 100644 > --- a/kernel/rcu/rcuperf.c > +++ b/kernel/rcu/rcuperf.c > @@ -58,7 +58,7 @@ MODULE_AUTHOR("Paul E. McKenney <paulmck@linux.vnet.ibm.com>"); > #define VERBOSE_PERFOUT_ERRSTRING(s) \ > do { if (verbose) pr_alert("%s" PERF_FLAG "!!! %s\n", perf_type, s); } while (0) > > -torture_param(bool, gp_exp, true, "Use expedited GP wait primitives"); > +torture_param(bool, gp_exp, false, "Use expedited GP wait primitives"); > torture_param(int, holdoff, 10, "Holdoff time before test start (s)"); > torture_param(int, nreaders, -1, "Number of RCU reader threads"); > torture_param(int, nwriters, -1, "Number of RCU updater threads"); > @@ -363,8 +363,6 @@ rcu_perf_writer(void *arg) > u64 *wdpp = writer_durations[me]; > > VERBOSE_PERFOUT_STRING("rcu_perf_writer task started"); > - WARN_ON(rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp); > - WARN_ON(rcu_gp_is_normal() && gp_exp); > WARN_ON(!wdpp); > set_cpus_allowed_ptr(current, cpumask_of(me % nr_cpu_ids)); > sp.sched_priority = 1; > @@ -631,6 +629,16 @@ rcu_perf_init(void) > firsterr = -ENOMEM; > goto unwind; > } > + if (rcu_gp_is_expedited() && !rcu_gp_is_normal() && !gp_exp) { > + VERBOSE_PERFOUT_ERRSTRING("All grace periods expedited, no normal ones to measure!"); > + firsterr = -EINVAL; > + goto unwind; > + } > + if (rcu_gp_is_normal() && gp_exp) { > + VERBOSE_PERFOUT_ERRSTRING("All grace periods normal, no expedited ones to measure!"); > + firsterr = -EINVAL; > + goto unwind; > + } > for (i = 0; i < nrealwriters; i++) { > writer_durations[i] = > kcalloc(MAX_MEAS, sizeof(*writer_durations[i]), > -- > 2.8.2 >
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