On Tue, May 24, 2016 at 11:06:52AM -0700, Paul E. McKenney wrote: > On Mon, May 23, 2016 at 12:35:35PM +0800, Boqun Feng wrote: > > On Sun, May 22, 2016 at 08:28:06AM -0700, Paul E. McKenney wrote: > > > On Sun, May 22, 2016 at 02:26:49PM +0800, Boqun Feng wrote: > > > > Hi Paul, > > > > > > > > On Sat, May 21, 2016 at 10:24:22PM -0700, Paul E. McKenney wrote: > > > > > On Sun, May 22, 2016 at 10:36:00AM +0800, kernel test robot wrote: > > > > > > Greetings, > > > > > > > > > > > > 0day kernel testing robot got the below dmesg and the first bad > > > > > > commit is > > > > > > > > > > > > https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git > > > > > > master > > > > > > > > > > > > commit 8704baab9bc848b58c129fed6b591bb84ec02f41 > > > > > > Author: Paul E. McKenney <paul...@linux.vnet.ibm.com> > > > > > > AuthorDate: Thu Dec 31 18:33:22 2015 -0800 > > > > > > Commit: Paul E. McKenney <paul...@linux.vnet.ibm.com> > > > > > > CommitDate: Thu Mar 31 13:37:38 2016 -0700 > > > > > > > > > > > > rcutorture: Add RCU grace-period performance tests > > > > > > > > > > > > This commit adds a new rcuperf module that carries out simple > > > > > > performance > > > > > > tests of RCU grace periods. > > > > > > > > > > > > Signed-off-by: Paul E. McKenney <paul...@linux.vnet.ibm.com> > > > > > > > > > > ??? > > > > > > > > > > This commit adds a default-n performance-test module. I don't believe > > > > > > > > I think the robot was using a !SMP && CONFIG_TORTURE_TEST=y && > > > > CONFIG_RCU_PERF_TEST=y configuration ;-) > > > > > > > > > that this would result in boot failures. False bisection? > > > > > > > > > > > > > The code triggering the warning is: > > > > > > > > WARN_ON(rcu_gp_is_normal() && gp_exp); > > > > > > > > , so rcu_gp_is_normal() is true because we are using TINY RCU, moreover > > > > the default value of gp_exp for *rcuperf* is also true (whereas the one > > > > for rcutorture is false). That's why the warnning was triggered. > > > > > > > > It happened in the boot progress because rcu_perf_writer threads were > > > > created and ran via module init function rcu_perf_init(). > > > > > > > > Maybe we'd better change the defaut value of gp_exp for rcuperf? > > > > > > Or make the default depend on CONFIG_TINY_RCU. Or downgrade the > > > WARN_ON() to soething that results in torture-test failure but does > > > not cause 0day to complain. Or... > > > > > > > So I think a better is we > > > > 1. set the default value to false (to align with rcutorture) > > > > and > > > > 2. downgrade the WARN_ON() to torture-test failures, because those > > are not kernel bugs. > > > > Here is a patch for further discussion: > > This patch looks good to me, given a little editing of the commit log. > (See below for error string suggestion.) >
Those are better (shorter and more accurate), thank you! I will send out a standalone patch with the modification. Regards, Boqun > Other thoughts? > > Thanx, Paul > > > ------------------------->8 > > Subject: [PATCH] rcuperf: Don't treat gp_exp mis-setting as a kernel warning > > > > 0day found a boot warning triggered in rcu_perf_writer() on !SMP kernel: > > > > WARN_ON(rcu_gp_is_normal() && gp_exp); > > > > , which turned out to be caused by the default value of gp_exp. > > > > However, the reason of the warning is only mis-setting, which should be > > handled inside rcuperf module rather than treated as a kernel warning. > > > > Therefore this patch moves the WARN_ON from rcu_perf_writer() and > > handles those checkings in rcu_perf_init(), which could also save the > > checkings for each writer. > > > > 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. > > > > Signed-off-by: Boqun Feng <boqun.f...@gmail.com> > > Fixes: > > http://lkml.kernel.org/r/57411b10.mfvg0+agcrmxgtcj%fengguang...@intel.com > > --- > > 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..1dc2bd1de4b6 100644 > > --- a/kernel/rcu/rcuperf.c > > +++ b/kernel/rcu/rcuperf.c > > @@ -58,7 +58,7 @@ MODULE_AUTHOR("Paul E. McKenney > > <paul...@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("try to measure normal grace periods > > when all the grace periods are expedited"); > > "All grace periods expedited, no normal ones to measure!" > > > + firsterr = -EINVAL; > > + goto unwind; > > + } > > + if (rcu_gp_is_normal() && gp_exp) { > > + VERBOSE_PERFOUT_ERRSTRING("try to measure expedited grace > > periods when all the expedited ones fall back to the normal ones"); > > "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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