> > @@ -159,6 +165,44 @@ static void refresh_zone_stat_thresholds(void)
> > }
> > }
> >
> > +void reduce_pgdat_percpu_threshold(pg_data_t *pgdat)
> > +{
> > + struct zone *zone;
> > + int cpu;
> > + int threshold;
> > + int i;
> > +
>
> get_online_cpus();
This caused following runtime warnings. but I don't think here is
real lock inversion.
=================================
[ INFO: inconsistent lock state ]
2.6.37-rc1-mm1+ #150
---------------------------------
inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
kswapd0/419 [HC0[0]:SC0[0]:HE1:SE1] takes:
(cpu_hotplug.lock){+.+.?.}, at: [<ffffffff810520d1>] get_online_cpus+0x41/0x60
{RECLAIM_FS-ON-W} state was registered at:
[<ffffffff8108a1a3>] mark_held_locks+0x73/0xa0
[<ffffffff8108a296>] lockdep_trace_alloc+0xc6/0x100
[<ffffffff8113fba9>] kmem_cache_alloc+0x39/0x2b0
[<ffffffff812eea10>] idr_pre_get+0x60/0x90
[<ffffffff812ef5b7>] ida_pre_get+0x27/0xf0
[<ffffffff8106ebf5>] create_worker+0x55/0x190
[<ffffffff814fb4f4>] workqueue_cpu_callback+0xbc/0x235
[<ffffffff8151934c>] notifier_call_chain+0x8c/0xe0
[<ffffffff8107a34e>] __raw_notifier_call_chain+0xe/0x10
[<ffffffff81051f30>] __cpu_notify+0x20/0x40
[<ffffffff8150bff7>] _cpu_up+0x73/0x113
[<ffffffff8150c175>] cpu_up+0xde/0xf1
[<ffffffff81dcc81d>] kernel_init+0x21b/0x342
[<ffffffff81003724>] kernel_thread_helper+0x4/0x10
irq event stamp: 27
hardirqs last enabled at (27): [<ffffffff815152c0>] _raw_spin_unlock_irqrestore+0x40/0x80
hardirqs last disabled at (26): [<ffffffff81514982>] _raw_spin_lock_irqsave+0x32/0xa0
softirqs last enabled at (20): [<ffffffff810614c4>] del_timer_sync+0x54/0xa0
softirqs last disabled at (18): [<ffffffff8106148c>] del_timer_sync+0x1c/0xa0
other info that might help us debug this:
no locks held by kswapd0/419.
stack backtrace:
Pid: 419, comm: kswapd0 Not tainted 2.6.37-rc1-mm1+ #150
Call Trace:
[<ffffffff810890b1>] print_usage_bug+0x171/0x180
[<ffffffff8108a057>] mark_lock+0x377/0x450
[<ffffffff8108ab67>] __lock_acquire+0x267/0x15e0
[<ffffffff8107af0f>] ? local_clock+0x6f/0x80
[<ffffffff81086789>] ? trace_hardirqs_off_caller+0x29/0x150
[<ffffffff8108bf94>] lock_acquire+0xb4/0x150
[<ffffffff810520d1>] ? get_online_cpus+0x41/0x60
[<ffffffff81512cf4>] __mutex_lock_common+0x44/0x3f0
[<ffffffff810520d1>] ? get_online_cpus+0x41/0x60
[<ffffffff810744f0>] ? prepare_to_wait+0x60/0x90
[<ffffffff81086789>] ? trace_hardirqs_off_caller+0x29/0x150
[<ffffffff810520d1>] ? get_online_cpus+0x41/0x60
[<ffffffff810868bd>] ? trace_hardirqs_off+0xd/0x10
[<ffffffff8107af0f>] ? local_clock+0x6f/0x80
[<ffffffff815131a8>] mutex_lock_nested+0x48/0x60
[<ffffffff810520d1>] get_online_cpus+0x41/0x60
[<ffffffff811138b2>] set_pgdat_percpu_threshold+0x22/0xe0
[<ffffffff81113970>] ? calculate_normal_threshold+0x0/0x60
[<ffffffff8110b552>] kswapd+0x1f2/0x360
[<ffffffff81074180>] ? autoremove_wake_function+0x0/0x40
[<ffffffff8110b360>] ? kswapd+0x0/0x360
[<ffffffff81073ae6>] kthread+0xa6/0xb0
[<ffffffff81003724>] kernel_thread_helper+0x4/0x10
[<ffffffff81515710>] ? restore_args+0x0/0x30
[<ffffffff81073a40>] ? kthread+0x0/0xb0
[<ffffffff81003720>] ? kernel_thread_helper+0x0/0x10
I think we have two option 1) call lockdep_clear_current_reclaim_state()
every time 2) use for_each_possible_cpu instead for_each_online_cpu.
Following patch use (2) beucase removing get_online_cpus() makes good
side effect. It reduce potentially cpu-hotplug vs memory-shortage deadlock
risk.
-------------------------------------------------------------------------
>From 74b809353c42a440d0bac6b83ac84281299bb09e Mon Sep 17 00:00:00 2001
From: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
Date: Fri, 3 Dec 2010 20:21:40 +0900
Subject: [PATCH] set_pgdat_percpu_threshold() don't use for_each_online_cpu
This patch fixes following lockdep warning.
=================================
[ INFO: inconsistent lock state ]
2.6.37-rc1-mm1+ #150
---------------------------------
inconsistent {RECLAIM_FS-ON-W} -> {IN-RECLAIM_FS-W} usage.
kswapd0/419 [HC0[0]:SC0[0]:HE1:SE1] takes:
(cpu_hotplug.lock){+.+.?.}, at: [<ffffffff810520d1>]
get_online_cpus+0x41/0x60
{RECLAIM_FS-ON-W} state was registered at:
[<ffffffff8108a1a3>] mark_held_locks+0x73/0xa0
[<ffffffff8108a296>] lockdep_trace_alloc+0xc6/0x100
[<ffffffff8113fba9>] kmem_cache_alloc+0x39/0x2b0
[<ffffffff812eea10>] idr_pre_get+0x60/0x90
[<ffffffff812ef5b7>] ida_pre_get+0x27/0xf0
[<ffffffff8106ebf5>] create_worker+0x55/0x190
[<ffffffff814fb4f4>] workqueue_cpu_callback+0xbc/0x235
[<ffffffff8151934c>] notifier_call_chain+0x8c/0xe0
[<ffffffff8107a34e>] __raw_notifier_call_chain+0xe/0x10
[<ffffffff81051f30>] __cpu_notify+0x20/0x40
[<ffffffff8150bff7>] _cpu_up+0x73/0x113
[<ffffffff8150c175>] cpu_up+0xde/0xf1
[<ffffffff81dcc81d>] kernel_init+0x21b/0x342
[<ffffffff81003724>] kernel_thread_helper+0x4/0x10
irq event stamp: 27
hardirqs last enabled at (27): [<ffffffff815152c0>] _raw_spin_unlock_irqrestore+0x40/0x80
hardirqs last disabled at (26): [<ffffffff81514982>] _raw_spin_lock_irqsave+0x32/0xa0
softirqs last enabled at (20): [<ffffffff810614c4>] del_timer_sync+0x54/0xa0
softirqs last disabled at (18): [<ffffffff8106148c>] del_timer_sync+0x1c/0xa0
other info that might help us debug this:
no locks held by kswapd0/419.
stack backtrace:
Pid: 419, comm: kswapd0 Not tainted 2.6.37-rc1-mm1+ #150
Call Trace:
[<ffffffff810890b1>] print_usage_bug+0x171/0x180
[<ffffffff8108a057>] mark_lock+0x377/0x450
[<ffffffff8108ab67>] __lock_acquire+0x267/0x15e0
[<ffffffff8107af0f>] ? local_clock+0x6f/0x80
[<ffffffff81086789>] ? trace_hardirqs_off_caller+0x29/0x150
[<ffffffff8108bf94>] lock_acquire+0xb4/0x150
[<ffffffff810520d1>] ? get_online_cpus+0x41/0x60
[<ffffffff81512cf4>] __mutex_lock_common+0x44/0x3f0
[<ffffffff810520d1>] ? get_online_cpus+0x41/0x60
[<ffffffff810744f0>] ? prepare_to_wait+0x60/0x90
[<ffffffff81086789>] ? trace_hardirqs_off_caller+0x29/0x150
[<ffffffff810520d1>] ? get_online_cpus+0x41/0x60
[<ffffffff810868bd>] ? trace_hardirqs_off+0xd/0x10
[<ffffffff8107af0f>] ? local_clock+0x6f/0x80
[<ffffffff815131a8>] mutex_lock_nested+0x48/0x60
[<ffffffff810520d1>] get_online_cpus+0x41/0x60
[<ffffffff811138b2>] set_pgdat_percpu_threshold+0x22/0xe0
[<ffffffff81113970>] ? calculate_normal_threshold+0x0/0x60
[<ffffffff8110b552>] kswapd+0x1f2/0x360
[<ffffffff81074180>] ? autoremove_wake_function+0x0/0x40
[<ffffffff8110b360>] ? kswapd+0x0/0x360
[<ffffffff81073ae6>] kthread+0xa6/0xb0
[<ffffffff81003724>] kernel_thread_helper+0x4/0x10
[<ffffffff81515710>] ? restore_args+0x0/0x30
[<ffffffff81073a40>] ? kthread+0x0/0xb0
[<ffffffff81003720>] ? kernel_thread_helper+0x0/0x10
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@xxxxxxxxxxxxxx>
---
mm/vmstat.c | 4 +---
1 files changed, 1 insertions(+), 3 deletions(-)
diff --git a/mm/vmstat.c b/mm/vmstat.c
index 2ab01f2..ca2d3be 100644
--- a/mm/vmstat.c
+++ b/mm/vmstat.c
@@ -193,18 +193,16 @@ void set_pgdat_percpu_threshold(pg_data_t *pgdat,
int threshold;
int i;
- get_online_cpus();
for (i = 0; i < pgdat->nr_zones; i++) {
zone = &pgdat->node_zones[i];
if (!zone->percpu_drift_mark)
continue;
threshold = (*calculate_pressure)(zone);
- for_each_online_cpu(cpu)
+ for_each_possible_cpu(cpu)
per_cpu_ptr(zone->pageset, cpu)->stat_threshold
= threshold;
}
- put_online_cpus();
}
/*
--
1.6.5.2
--
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