Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757378Ab1DZSYU (ORCPT ); Tue, 26 Apr 2011 14:24:20 -0400 Received: from e1.ny.us.ibm.com ([32.97.182.141]:46557 "EHLO e1.ny.us.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751467Ab1DZSYR (ORCPT ); Tue, 26 Apr 2011 14:24:17 -0400 Date: Tue, 26 Apr 2011 08:42:55 -0700 From: "Paul E. McKenney" To: sedat.dilek@gmail.com Cc: Stephen Rothwell , linux-next@vger.kernel.org, LKML , peterz@infradead.org Subject: Re: linux-next: Tree for April 14 (Call-traces: RCU/ACPI/WQ related?) Message-ID: <20110426154255.GA2135@linux.vnet.ibm.com> Reply-To: paulmck@linux.vnet.ibm.com References: <20110424062728.GM2628@linux.vnet.ibm.com> <20110424164331.GN2628@linux.vnet.ibm.com> <20110426050612.GA7651@linux.vnet.ibm.com> <20110426124256.GI4308@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/1.5.20 (2009-06-14) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 8469 Lines: 206 On Tue, Apr 26, 2011 at 02:50:25PM +0200, Sedat Dilek wrote: > On Tue, Apr 26, 2011 at 2:42 PM, Paul E. McKenney > wrote: > > On Tue, Apr 26, 2011 at 01:45:31PM +0200, Sedat Dilek wrote: > >> On Tue, Apr 26, 2011 at 7:06 AM, Paul E. McKenney > >> wrote: > >> > On Sun, Apr 24, 2011 at 09:43:31AM -0700, Paul E. McKenney wrote: > >> >> On Sun, Apr 24, 2011 at 11:36:44AM +0200, Sedat Dilek wrote: > >> >> > On Sun, Apr 24, 2011 at 8:27 AM, Paul E. McKenney > >> >> > wrote: > >> >> > >> >> [ . . . ] > >> >> > >> >> > > OK, this looks unrelated, but just in case, could you please try it > >> >> > > again with the following patch? ?(Not mainlinable, debug only.) > >> >> > > > >> >> > > Also, it does look like you are still seeing a grace-period hang. > >> >> > > Could you please send the output of the script? ?Same one as last time. > >> >> > > > >> >> > > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Thanx, Paul > >> >> > > > >> >> > > ------------------------------------------------------------------------ > >> >> > > > >> >> > > ?debugobjects.c | ? ?8 +++++--- > >> >> > > ?1 file changed, 5 insertions(+), 3 deletions(-) > >> >> > > > >> >> > > diff --git a/lib/debugobjects.c b/lib/debugobjects.c > >> >> > > index 9d86e45..10a7c7a 100644 > >> >> > > --- a/lib/debugobjects.c > >> >> > > +++ b/lib/debugobjects.c > >> >> > > @@ -289,10 +289,12 @@ static void debug_object_is_on_stack(void *addr, int onstack) > >> >> > > ? ? ? ? ? ? ? ?return; > >> >> > > > >> >> > > ? ? ? ?limit++; > >> >> > > - ? ? ? if (is_on_stack) > >> >> > > + ? ? ? if (is_on_stack) { > >> >> > > + ? ? ? ? ? ? ? struct rcu_head *p = (struct rcu_head *)addr; > >> >> > > ? ? ? ? ? ? ? ?printk(KERN_WARNING > >> >> > > - ? ? ? ? ? ? ? ? ? ? ?"ODEBUG: object is on stack, but not annotated\n"); > >> >> > > - ? ? ? else > >> >> > > + ? ? ? ? ? ? ? ? ? ? ?"ODEBUG: object is on stack, but not annotated: %p\n", > >> >> > > + ? ? ? ? ? ? ? ? ? ? ?p->func); > >> >> > > + ? ? ? } else > >> >> > > ? ? ? ? ? ? ? ?printk(KERN_WARNING > >> >> > > ? ? ? ? ? ? ? ? ? ? ? "ODEBUG: object is not on stack, but annotated\n"); > >> >> > > ? ? ? ?WARN_ON(1); > >> >> > > > >> >> > > >> >> > Somehow your attached patch was not applicable. > >> >> > As the changes were a few lines I applied it by myself. > >> >> > Attached are log, dmesg and patches (orig + mine) > >> >> > >> >> Hmmm... ?Does 0xc10231a1 correspond to a function in your build? ?If so, > >> >> could you please let me know which one? > >> >> > >> >> OK, so according to "ps" the per-CPU kthread is runnable, but it appears > >> >> to never run. ?You only have one CPU, so it cannot be waiting due to > >> >> running on the wrong CPU. ?The only other loop is in wait_event(), and > >> >> that code looks good -- besides, if wait_event() was broken, we would > >> >> be seeing breakage everywhere. > >> >> > >> >> Peter, any thoughts on what I might have done wrong to get the scheduler > >> >> into a state where it was ignoring a runnable realtime task? > >> > > >> > Hello, Sedat, > >> > > >> > Here is a diagnostic patch to apply on top of sedat.2011.04.23a from > >> > the -rcu git tree. ?Could you please try it out, let me know what > >> > happens, and run the last collectdebugfs.sh during the test? > >> > > >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Thanx, Paul > >> > > >> > ------------------------------------------------------------------------ > >> > > >> > diff --git a/kernel/rcutree.c b/kernel/rcutree.c > >> > index 6cf6e47..65ae701 100644 > >> > --- a/kernel/rcutree.c > >> > +++ b/kernel/rcutree.c > >> > @@ -1524,9 +1524,9 @@ static void rcu_cpu_kthread_setrt(int cpu, int to_rt) > >> > ? ? ? ? ? ? ? ?return; > >> > ? ? ? ?if (to_rt) { > >> > ? ? ? ? ? ? ? ?policy = SCHED_NORMAL; > >> > - ? ? ? ? ? ? ? sp.sched_priority = RCU_KTHREAD_PRIO; > >> > + ? ? ? ? ? ? ? sp.sched_priority = 0; > >> > ? ? ? ?} else { > >> > - ? ? ? ? ? ? ? policy = SCHED_FIFO; > >> > + ? ? ? ? ? ? ? policy = SCHED_NORMAL; > >> > ? ? ? ? ? ? ? ?sp.sched_priority = 0; > >> > ? ? ? ?} > >> > ? ? ? ?sched_setscheduler_nocheck(t, policy, &sp); > >> > @@ -1566,8 +1566,8 @@ static void rcu_yield(void (*f)(unsigned long), unsigned long arg) > >> > ? ? ? ?sp.sched_priority = 0; > >> > ? ? ? ?sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp); > >> > ? ? ? ?schedule(); > >> > - ? ? ? sp.sched_priority = RCU_KTHREAD_PRIO; > >> > - ? ? ? sched_setscheduler_nocheck(current, SCHED_FIFO, &sp); > >> > + ? ? ? sp.sched_priority = 0; > >> > + ? ? ? sched_setscheduler_nocheck(current, SCHED_NORMAL, &sp); > >> > ? ? ? ?del_timer(&yield_timer); > >> > ?} > >> > > >> > @@ -1671,8 +1671,8 @@ static int __cpuinit rcu_spawn_one_cpu_kthread(int cpu) > >> > ? ? ? ?WARN_ON_ONCE(per_cpu(rcu_cpu_kthread_task, cpu) != NULL); > >> > ? ? ? ?per_cpu(rcu_cpu_kthread_task, cpu) = t; > >> > ? ? ? ?wake_up_process(t); > >> > - ? ? ? sp.sched_priority = RCU_KTHREAD_PRIO; > >> > - ? ? ? sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); > >> > + ? ? ? sp.sched_priority = 0; > >> > + ? ? ? sched_setscheduler_nocheck(t, SCHED_NORMAL, &sp); > >> > ? ? ? ?return 0; > >> > ?} > >> > > >> > @@ -1713,8 +1713,8 @@ static int rcu_node_kthread(void *arg) > >> > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?continue; > >> > ? ? ? ? ? ? ? ? ? ? ? ?} > >> > ? ? ? ? ? ? ? ? ? ? ? ?per_cpu(rcu_cpu_has_work, cpu) = 1; > >> > - ? ? ? ? ? ? ? ? ? ? ? sp.sched_priority = RCU_KTHREAD_PRIO; > >> > - ? ? ? ? ? ? ? ? ? ? ? sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); > >> > + ? ? ? ? ? ? ? ? ? ? ? sp.sched_priority = 0; > >> > + ? ? ? ? ? ? ? ? ? ? ? sched_setscheduler_nocheck(t, SCHED_NORMAL, &sp); > >> > ? ? ? ? ? ? ? ? ? ? ? ?preempt_enable(); > >> > ? ? ? ? ? ? ? ?} > >> > ? ? ? ?} > >> > diff --git a/kernel/rcutree_plugin.h b/kernel/rcutree_plugin.h > >> > index a21413d..baee185 100644 > >> > --- a/kernel/rcutree_plugin.h > >> > +++ b/kernel/rcutree_plugin.h > >> > @@ -1307,8 +1307,8 @@ static int __cpuinit rcu_spawn_one_boost_kthread(struct rcu_state *rsp, > >> > ? ? ? ?rnp->boost_kthread_task = t; > >> > ? ? ? ?raw_spin_unlock_irqrestore(&rnp->lock, flags); > >> > ? ? ? ?wake_up_process(t); > >> > - ? ? ? sp.sched_priority = RCU_KTHREAD_PRIO; > >> > - ? ? ? sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); > >> > + ? ? ? sp.sched_priority = 0; > >> > + ? ? ? sched_setscheduler_nocheck(t, SCHED_NORMAL, &sp); > >> > ? ? ? ?return 0; > >> > ?} > >> > > >> > > >> > >> Hi Paul, > >> > >> I have tested with your patch and kept the kernel-config file from > >> previous tests (don't get confused by the new name). > >> Hope this helps you. > >> > >> I have some questions to k-c options espcially X86_UP and > >> CONFIG_RCU_FANOUT=32 options. > >> To what extent can they influence our RCU issue? > >> The below options were not set for this round of testing, but I would > >> like to have a feedback. > >> Thanks in advance. > >> > >> Would these settings be more optimal for a UP-machine? > >> > >> # CONFIG_SMP is not set > >> # CONFIG_M486 is not set > >> CONFIG_M686=y > >> CONFIG_NR_CPUS=1 > > > > These should be fine. > > > >> CONFIG_X86_UP_APIC=y > >> CONFIG_X86_UP_IOAPIC=y > > > > These I don't know about. > > > >> CONFIG_HIGHMEM4G=y > > > > This one seems good for allowing the system to go as long as possible. > > > >> Is CONFIG_RCU_FANOUT=32 OK? > > > > On a UP system, this one doesn't matter. > > > >> With reverting commit 687d7a960aea46e016182c7ce346d62c4dbd0366 ("rcu: > >> restrict TREE_RCU to SMP builds with !PREEMPT"). > > > > Thank you for trying this one out! > > > > I don't see any sign of a grace-period hang. ?Did your test complete > > correctly? > > > > ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ? ?Thanx, Paul > > > > Thanks for the comments. > > I let run the script very long (approx. one hour) and did parallelly > my daily work. > Then booted into a known as working kernel. > Did I miss something, should I stress more? I wouldn't know -- I never have been able to reproduce this. For the moment, I will do my inspections assuming that the bug has something to do with realtime priority. Thank you again for your testing! Thanx, Paul -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/