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Groups > linux.kernel > #1333438 > unrolled thread

[PATCH v2 1/2] tracing/mm: don't trace kfree on offline CPUs

Started byDenis Kirjanov <kda@linux-powerpc.org>
First post2016-02-14 08:00 +0100
Last post2016-02-16 01:50 +0100
Articles 4 — 2 participants

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  [PATCH v2 1/2] tracing/mm: don't trace kfree on offline CPUs Denis Kirjanov <kda@linux-powerpc.org> - 2016-02-14 08:00 +0100
    [PATCH v2 2/2] tracing/rcu: don't trace rcu_callback on offline CPUs Denis Kirjanov <kda@linux-powerpc.org> - 2016-02-14 08:00 +0100
      Re: [PATCH v2 2/2] tracing/rcu: don't trace rcu_callback on offline  CPUs "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-15 07:10 +0100
        Re: [PATCH v2 2/2] tracing/rcu: don't trace rcu_callback on offline  CPUs "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-02-16 01:50 +0100

#1333438 — [PATCH v2 1/2] tracing/mm: don't trace kfree on offline CPUs

FromDenis Kirjanov <kda@linux-powerpc.org>
Date2016-02-14 08:00 +0100
Subject[PATCH v2 1/2] tracing/mm: don't trace kfree on offline CPUs
Message-ID<r1YP0-7Co-3@gated-at.bofh.it>
Tracepoints use RCU for protection and they must not be called on
offline CPUS. So make this tracepoint conditional.

INFO: suspicious RCU usage. ]
[   99.749382] 4.4.0-00006-g0fe53e8-dirty #34 Tainted: G S
[   99.749383] -------------------------------
[   99.749385] include/trace/events/kmem.h:141 suspicious rcu_dereference_check() usage!
[   99.749385]
other info that might help us debug this:

[   99.749387]
RCU used illegally from offline CPU!
rcu_scheduler_active = 1, debug_locks = 1
[   99.749388] no locks held by swapper/8/0.
[   99.749388]
stack backtrace:
[   99.749390] CPU: 8 PID: 0 Comm: swapper/8 Tainted: G S              4.4.0-00006-g0fe53e8-dirty #34
[   99.749391] Call Trace:
[   99.749399] [c0000005b76c78d0] [c0000000008b9540] .dump_stack+0x98/0xd4 (unreliable)
[   99.749402] [c0000005b76c7950] [c00000000010c898] .lockdep_rcu_suspicious+0x108/0x170
[   99.749405] [c0000005b76c79e0] [c00000000029adc0] .kfree+0x390/0x440
[   99.749409] [c0000005b76c7a80] [c000000000055f74] .destroy_context+0x44/0x100
[   99.749412] [c0000005b76c7b00] [c0000000000934a0] .__mmdrop+0x60/0x150
[   99.749415] [c0000005b76c7b90] [c0000000000e3ff0] .idle_task_exit+0x130/0x140
[   99.749417] [c0000005b76c7c20] [c000000000075804] .pseries_mach_cpu_die+0x64/0x310
[   99.749420] [c0000005b76c7cd0] [c000000000043e7c] .cpu_die+0x3c/0x60
[   99.749423] [c0000005b76c7d40] [c0000000000188d8] .arch_cpu_idle_dead+0x28/0x40
[   99.749426] [c0000005b76c7db0] [c000000000101e6c] .cpu_startup_entry+0x50c/0x560
[   99.749428] [c0000005b76c7ed0] [c000000000043bd8] .start_secondary+0x328/0x360
[   99.749431] [c0000005b76c7f90] [c000000000008a6c] start_secondary_prolog+0x10/0x14

Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
---
 include/trace/events/kmem.h | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/include/trace/events/kmem.h b/include/trace/events/kmem.h
index f7554fd..9473c2d 100644
--- a/include/trace/events/kmem.h
+++ b/include/trace/events/kmem.h
@@ -133,11 +133,22 @@ DECLARE_EVENT_CLASS(kmem_free,
 	TP_printk("call_site=%lx ptr=%p", __entry->call_site, __entry->ptr)
 );
 
-DEFINE_EVENT(kmem_free, kfree,
+DEFINE_EVENT_CONDITION(kmem_free, kfree,
 
 	TP_PROTO(unsigned long call_site, const void *ptr),
 
-	TP_ARGS(call_site, ptr)
+	TP_ARGS(call_site, ptr),
+
+	/*
+	 * This trace can be potentially called from an offlined cpu.
+	 * Since trace points use RCU and RCU should not be used from
+	 * offline cpus, filter such calls out.
+	 * While this trace can be called from a preemptable section,
+	 * it has no impact on the condition since tasks can migrate
+	 * only from online cpus to other online cpus. Thus its safe
+	 * to use raw_smp_processor_id.
+	 */
+	TP_CONDITION(cpu_online(raw_smp_processor_id()))
 );
 
 DEFINE_EVENT_CONDITION(kmem_free, kmem_cache_free,
-- 
2.4.0

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#1333440 — [PATCH v2 2/2] tracing/rcu: don't trace rcu_callback on offline CPUs

FromDenis Kirjanov <kda@linux-powerpc.org>
Date2016-02-14 08:00 +0100
Subject[PATCH v2 2/2] tracing/rcu: don't trace rcu_callback on offline CPUs
Message-ID<r1YP0-7Co-5@gated-at.bofh.it>
In reply to#1333438
Tracepoints use RCU for protection and they must not be called on
offline CPUS. So make this tracepoint conditional.

NFO: suspicious RCU usage. ]
[  413.344670] 4.4.0-00006-g0fe53e8-dirty #33 Tainted: G S
[  413.344672] -------------------------------
[  413.344673] include/trace/events/rcu.h:457 suspicious rcu_dereference_check() usage!
[  413.344674]
other info that might help us debug this:

[  413.344676]
RCU used illegally from offline CPU!
rcu_scheduler_active = 1, debug_locks = 1
[  413.344678] no locks held by swapper/4/0.
[  413.344679]
stack backtrace:
[  413.344682] CPU: 4 PID: 0 Comm: swapper/4 Tainted: G S              4.4.0-00006-g0fe53e8-dirty #33
[  413.344683] Call Trace:
[  413.344692] [c0000005b76b7800] [c0000000008bb080] .dump_stack+0x98/0xd4 (unreliable)
[  413.344698] [c0000005b76b7880] [c00000000010c8b8] .lockdep_rcu_suspicious+0x108/0x170
[  413.344703] [c0000005b76b7910] [c00000000013b9e4] .__call_rcu.constprop.60+0x264/0x600
[  413.344708] [c0000005b76b79e0] [c0000000002bceec] .put_object+0x5c/0x80
[  413.344712] [c0000005b76b7a60] [c00000000029a368] .kmem_cache_free+0x298/0x450
[  413.344716] [c0000005b76b7b00] [c000000000093494] .__mmdrop+0x54/0x150
[  413.344720] [c0000005b76b7b90] [c0000000000e4010] .idle_task_exit+0x130/0x140
[  413.344725] [c0000005b76b7c20] [c000000000075804] .pseries_mach_cpu_die+0x64/0x310
[  413.344730] [c0000005b76b7cd0] [c000000000043e7c] .cpu_die+0x3c/0x60
[  413.344734] [c0000005b76b7d40] [c0000000000188d8] .arch_cpu_idle_dead+0x28/0x40
[  413.344738] [c0000005b76b7db0] [c000000000101e8c] .cpu_startup_entry+0x50c/0x560
[  413.344741] [c0000005b76b7ed0] [c000000000043bd8] .start_secondary+0x328/0x360
[  413.344746] [c0000005b76b7f90] [c000000000008a6c] start_secondary_prolog+0x10/0x14

Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
---

v2: Fix the build error that was made
while sending the pacthes from another machine

 include/trace/events/rcu.h | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
index ef72c4a..793d306b 100644
--- a/include/trace/events/rcu.h
+++ b/include/trace/events/rcu.h
@@ -428,13 +428,15 @@ TRACE_EVENT(rcu_prep_idle,
  * number of lazy callbacks queued, and the fourth element is the
  * total number of callbacks queued.
  */
-TRACE_EVENT(rcu_callback,
+TRACE_EVENT_CONDITION(rcu_callback,
 
 	TP_PROTO(const char *rcuname, struct rcu_head *rhp, long qlen_lazy,
 		 long qlen),
 
 	TP_ARGS(rcuname, rhp, qlen_lazy, qlen),
 
+	TP_CONDITION(cpu_online(raw_smp_processor_id())),
+
 	TP_STRUCT__entry(
 		__field(const char *, rcuname)
 		__field(void *, rhp)
-- 
2.4.0

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#1334174 — Re: [PATCH v2 2/2] tracing/rcu: don't trace rcu_callback on offline CPUs

From"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Date2016-02-15 07:10 +0100
SubjectRe: [PATCH v2 2/2] tracing/rcu: don't trace rcu_callback on offline CPUs
Message-ID<r2kw9-5tY-9@gated-at.bofh.it>
In reply to#1333440
On Sun, Feb 14, 2016 at 09:50:18AM +0300, Denis Kirjanov wrote:
> Tracepoints use RCU for protection and they must not be called on
> offline CPUS. So make this tracepoint conditional.

Good catch!  Queued for review and testing.

							Thanx, Paul

> NFO: suspicious RCU usage. ]
> [  413.344670] 4.4.0-00006-g0fe53e8-dirty #33 Tainted: G S
> [  413.344672] -------------------------------
> [  413.344673] include/trace/events/rcu.h:457 suspicious rcu_dereference_check() usage!
> [  413.344674]
> other info that might help us debug this:
> 
> [  413.344676]
> RCU used illegally from offline CPU!
> rcu_scheduler_active = 1, debug_locks = 1
> [  413.344678] no locks held by swapper/4/0.
> [  413.344679]
> stack backtrace:
> [  413.344682] CPU: 4 PID: 0 Comm: swapper/4 Tainted: G S              4.4.0-00006-g0fe53e8-dirty #33
> [  413.344683] Call Trace:
> [  413.344692] [c0000005b76b7800] [c0000000008bb080] .dump_stack+0x98/0xd4 (unreliable)
> [  413.344698] [c0000005b76b7880] [c00000000010c8b8] .lockdep_rcu_suspicious+0x108/0x170
> [  413.344703] [c0000005b76b7910] [c00000000013b9e4] .__call_rcu.constprop.60+0x264/0x600
> [  413.344708] [c0000005b76b79e0] [c0000000002bceec] .put_object+0x5c/0x80
> [  413.344712] [c0000005b76b7a60] [c00000000029a368] .kmem_cache_free+0x298/0x450
> [  413.344716] [c0000005b76b7b00] [c000000000093494] .__mmdrop+0x54/0x150
> [  413.344720] [c0000005b76b7b90] [c0000000000e4010] .idle_task_exit+0x130/0x140
> [  413.344725] [c0000005b76b7c20] [c000000000075804] .pseries_mach_cpu_die+0x64/0x310
> [  413.344730] [c0000005b76b7cd0] [c000000000043e7c] .cpu_die+0x3c/0x60
> [  413.344734] [c0000005b76b7d40] [c0000000000188d8] .arch_cpu_idle_dead+0x28/0x40
> [  413.344738] [c0000005b76b7db0] [c000000000101e8c] .cpu_startup_entry+0x50c/0x560
> [  413.344741] [c0000005b76b7ed0] [c000000000043bd8] .start_secondary+0x328/0x360
> [  413.344746] [c0000005b76b7f90] [c000000000008a6c] start_secondary_prolog+0x10/0x14
> 
> Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
> ---
> 
> v2: Fix the build error that was made
> while sending the pacthes from another machine
> 
>  include/trace/events/rcu.h | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
> index ef72c4a..793d306b 100644
> --- a/include/trace/events/rcu.h
> +++ b/include/trace/events/rcu.h
> @@ -428,13 +428,15 @@ TRACE_EVENT(rcu_prep_idle,
>   * number of lazy callbacks queued, and the fourth element is the
>   * total number of callbacks queued.
>   */
> -TRACE_EVENT(rcu_callback,
> +TRACE_EVENT_CONDITION(rcu_callback,
> 
>  	TP_PROTO(const char *rcuname, struct rcu_head *rhp, long qlen_lazy,
>  		 long qlen),
> 
>  	TP_ARGS(rcuname, rhp, qlen_lazy, qlen),
> 
> +	TP_CONDITION(cpu_online(raw_smp_processor_id())),
> +
>  	TP_STRUCT__entry(
>  		__field(const char *, rcuname)
>  		__field(void *, rhp)
> -- 
> 2.4.0
>

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#1334891 — Re: [PATCH v2 2/2] tracing/rcu: don't trace rcu_callback on offline CPUs

From"Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Date2016-02-16 01:50 +0100
SubjectRe: [PATCH v2 2/2] tracing/rcu: don't trace rcu_callback on offline CPUs
Message-ID<r2C01-aC-15@gated-at.bofh.it>
In reply to#1334174
On Sun, Feb 14, 2016 at 10:05:22PM -0800, Paul E. McKenney wrote:
> On Sun, Feb 14, 2016 at 09:50:18AM +0300, Denis Kirjanov wrote:
> > Tracepoints use RCU for protection and they must not be called on
> > offline CPUS. So make this tracepoint conditional.
> 
> Good catch!  Queued for review and testing.

And I dequeued this in favor of Steven's more recent patch.

But there is one other hitch...  It is currently not legal to invoke
call_rcu() from an offline CPU.  You can get away with it during a
short window towards the end of the offline process, but shortly after
the outgoing CPU hits the idle loop, call_rcu() will splat and leak
the callback.

So what exactly is the purpose of invoking call_rcu() from an offline CPU?
(Yes, I could probably make it work, but there needs to be a good reason.)

							Thanx, Paul

> > NFO: suspicious RCU usage. ]
> > [  413.344670] 4.4.0-00006-g0fe53e8-dirty #33 Tainted: G S
> > [  413.344672] -------------------------------
> > [  413.344673] include/trace/events/rcu.h:457 suspicious rcu_dereference_check() usage!
> > [  413.344674]
> > other info that might help us debug this:
> > 
> > [  413.344676]
> > RCU used illegally from offline CPU!
> > rcu_scheduler_active = 1, debug_locks = 1
> > [  413.344678] no locks held by swapper/4/0.
> > [  413.344679]
> > stack backtrace:
> > [  413.344682] CPU: 4 PID: 0 Comm: swapper/4 Tainted: G S              4.4.0-00006-g0fe53e8-dirty #33
> > [  413.344683] Call Trace:
> > [  413.344692] [c0000005b76b7800] [c0000000008bb080] .dump_stack+0x98/0xd4 (unreliable)
> > [  413.344698] [c0000005b76b7880] [c00000000010c8b8] .lockdep_rcu_suspicious+0x108/0x170
> > [  413.344703] [c0000005b76b7910] [c00000000013b9e4] .__call_rcu.constprop.60+0x264/0x600
> > [  413.344708] [c0000005b76b79e0] [c0000000002bceec] .put_object+0x5c/0x80
> > [  413.344712] [c0000005b76b7a60] [c00000000029a368] .kmem_cache_free+0x298/0x450
> > [  413.344716] [c0000005b76b7b00] [c000000000093494] .__mmdrop+0x54/0x150
> > [  413.344720] [c0000005b76b7b90] [c0000000000e4010] .idle_task_exit+0x130/0x140
> > [  413.344725] [c0000005b76b7c20] [c000000000075804] .pseries_mach_cpu_die+0x64/0x310
> > [  413.344730] [c0000005b76b7cd0] [c000000000043e7c] .cpu_die+0x3c/0x60
> > [  413.344734] [c0000005b76b7d40] [c0000000000188d8] .arch_cpu_idle_dead+0x28/0x40
> > [  413.344738] [c0000005b76b7db0] [c000000000101e8c] .cpu_startup_entry+0x50c/0x560
> > [  413.344741] [c0000005b76b7ed0] [c000000000043bd8] .start_secondary+0x328/0x360
> > [  413.344746] [c0000005b76b7f90] [c000000000008a6c] start_secondary_prolog+0x10/0x14
> > 
> > Signed-off-by: Denis Kirjanov <kda@linux-powerpc.org>
> > ---
> > 
> > v2: Fix the build error that was made
> > while sending the pacthes from another machine
> > 
> >  include/trace/events/rcu.h | 4 +++-
> >  1 file changed, 3 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/trace/events/rcu.h b/include/trace/events/rcu.h
> > index ef72c4a..793d306b 100644
> > --- a/include/trace/events/rcu.h
> > +++ b/include/trace/events/rcu.h
> > @@ -428,13 +428,15 @@ TRACE_EVENT(rcu_prep_idle,
> >   * number of lazy callbacks queued, and the fourth element is the
> >   * total number of callbacks queued.
> >   */
> > -TRACE_EVENT(rcu_callback,
> > +TRACE_EVENT_CONDITION(rcu_callback,
> > 
> >  	TP_PROTO(const char *rcuname, struct rcu_head *rhp, long qlen_lazy,
> >  		 long qlen),
> > 
> >  	TP_ARGS(rcuname, rhp, qlen_lazy, qlen),
> > 
> > +	TP_CONDITION(cpu_online(raw_smp_processor_id())),
> > +
> >  	TP_STRUCT__entry(
> >  		__field(const char *, rcuname)
> >  		__field(void *, rhp)
> > -- 
> > 2.4.0
> >

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