[patch] rt: res_counter fix

Ingo Molnar
2009-02-12T10:17:13Z

* Frederic Weisbecker <fweisbec@gmail.com> wrote:

> > I get some sleep while atomic warnings.
> > I've put the log and my config in attachment.
>
> Note, it's a wicked bug: I can't reproduce it anymore.
> I would have been glad to give you an irqsoff trace but I can't :-)

i tried your config and after a few bootups the warning did trigger.

It's the new resource counter code. The IRQ flags disabling it does
seems a bit dubious to me. Peter, what do you think?

Frederic, could you try the patch below?

Ingo

----------->
Subject: rt: res_counter fix
From: Ingo Molnar <mingo@elte.hu>
Date: Thu Feb 12 11:11:47 CET 2009

Frederic Weisbecker reported this warning:

[ 45.228562] BUG: sleeping function called from invalid context at kernel/rtmutex.c:683
[ 45.228571] in_atomic(): 0, irqs_disabled(): 1, pid: 4290, name: ntpdate
[ 45.228576] INFO: lockdep is turned off.
[ 45.228580] irq event stamp: 0
[ 45.228583] hardirqs last enabled at (0): [<(null)>] (null)
[ 45.228589] hardirqs last disabled at (0): [<ffffffff8025449d>] copy_process+0x68d/0x1500
[ 45.228602] softirqs last enabled at (0): [<ffffffff8025449d>] copy_process+0x68d/0x1500
[ 45.228609] softirqs last disabled at (0): [<(null)>] (null)
[ 45.228617] Pid: 4290, comm: ntpdate Tainted: G W 2.6.29-rc4-rt1-tip #1
[ 45.228622] Call Trace:
[ 45.228632] [<ffffffff8027dfb0>] ? print_irqtrace_events+0xd0/0xe0
[ 45.228639] [<ffffffff8024cd73>] __might_sleep+0x113/0x130
[ 45.228646] [<ffffffff8077c811>] rt_spin_lock+0xa1/0xb0
[ 45.228653] [<ffffffff80296a3d>] res_counter_charge+0x5d/0x130
[ 45.228660] [<ffffffff802fb67f>] __mem_cgroup_try_charge+0x7f/0x180
[ 45.228667] [<ffffffff802fc407>] mem_cgroup_charge_common+0x57/0x90
[ 45.228674] [<ffffffff80212096>] ? ftrace_call+0x5/0x2b
[ 45.228680] [<ffffffff802fc49d>] mem_cgroup_newpage_charge+0x5d/0x60
[ 45.228688] [<ffffffff802d94ce>] __do_fault+0x29e/0x4c0
[ 45.228694] [<ffffffff8077c843>] ? rt_spin_unlock+0x23/0x80
[ 45.228700] [<ffffffff802db8b5>] handle_mm_fault+0x205/0x890
[ 45.228707] [<ffffffff80212096>] ? ftrace_call+0x5/0x2b
[ 45.228714] [<ffffffff8023495e>] do_page_fault+0x11e/0x2a0
[ 45.228720] [<ffffffff8077e5a5>] page_fault+0x25/0x30
[ 45.228727] [<ffffffff8043e1ed>] ? __clear_user+0x3d/0x70
[ 45.228733] [<ffffffff8043e1d1>] ? __clear_user+0x21/0x70

The reason is the raw IRQ flag use of kernel/res_counter.c.

The irq flags tricks there seem a bit pointless: it cannot
protect the c->parent linkage because local_irq_save() is
only per CPU.

So replace it with _nort(). This code needs a second look.

Reported-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
---
kernel/res_counter.c | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)

Index: tip/kernel/res_counter.c
===================================================================
--- tip.orig/kernel/res_counter.c
+++ tip/kernel/res_counter.c
@@ -43,7 +43,7 @@ int res_counter_charge(struct res_counte
struct res_counter *c, *u;

*limit_fail_at = NULL;
- local_irq_save(flags);
+ local_irq_save_nort(flags);
for (c = counter; c != NULL; c = c->parent) {
spin_lock(&c->lock);
ret = res_counter_charge_locked(c, val);
@@ -62,7 +62,7 @@ undo:
spin_unlock(&u->lock);
}
done:
- local_irq_restore(flags);
+ local_irq_restore_nort(flags);
return ret;
}

@@ -79,13 +79,13 @@ void res_counter_uncharge(struct res_cou
unsigned long flags;
struct res_counter *c;

- local_irq_save(flags);
+ local_irq_save_nort(flags);
for (c = counter; c != NULL; c = c->parent) {
spin_lock(&c->lock);
res_counter_uncharge_locked(c, val);
spin_unlock(&c->lock);
}
- local_irq_restore(flags);
+ local_irq_restore_nort(flags);
}