linux-kernel - Re: [PATCH] debugobjects: Use GFP_ATOMIC to allocate when initializing

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Message-ID: <1333391754.2960.70.camel@laptop>
Date:	Mon, 02 Apr 2012 20:35:54 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	Sasha Levin <levinsasha928@...il.com>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] debugobjects: Use GFP_ATOMIC to allocate when
 initializing

On Mon, 2012-04-02 at 11:12 +0200, Thomas Gleixner wrote:
> On Sun, 1 Apr 2012, Sasha Levin wrote:
> > On Sun, Apr 1, 2012 at 7:36 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> > > On Sat, 31 Mar 2012, Sasha Levin wrote:
> 
> Peter ????
> 
> > >> During the init stage, we have only 1 cpu and run with IRQs disabled,
> > >> we can't allocate with GFP_KERNEL.
> > >>
> > >> This also fixes the related warning on boot.
> > >
> > > Hrmm. This should not be the case. In early boot GFP_KERNEL
> > > allocations should not trigger a warning when interrupts are
> > > disabled. Which kind of warning are you observing ?
> > 
> > There were two, both pointing at the same WARN(). I don't have the
> > first one which was fixed in this patch handy, but the second one is:
> > 
> > [    0.000000] WARNING: at kernel/lockdep.c:2739
> > lockdep_trace_alloc+0x11f/0x130()
> > [    0.000000] Pid: 0, comm: swapper/0 Not tainted
> > 3.3.0-next-20120330-sasha-dirty #40
> > [    0.000000] Call Trace:
> > [    0.000000]  [<ffffffff810b4175>] warn_slowpath_common+0x75/0xb0
> > [    0.000000]  [<ffffffff810b41c5>] warn_slowpath_null+0x15/0x20
> > [    0.000000]  [<ffffffff8111999f>] lockdep_trace_alloc+0x11f/0x130
> > [    0.000000]  [<ffffffff81182e0c>] __alloc_pages_nodemask+0x9c/0x260
> > [    0.000000]  [<ffffffff826bcea7>] ? retint_restore_args+0x6/0x13
> > [    0.000000]  [<ffffffff811cc2cd>] kmemcheck_alloc_shadow+0x4d/0xf0
> > [    0.000000]  [<ffffffff811c5597>] allocate_slab+0x197/0x270
> > [    0.000000]  [<ffffffff811c569b>] new_slab+0x2b/0x190
> > [    0.000000]  [<ffffffff811c7e7a>] ? __slab_alloc+0x5a/0x6b0
> > [    0.000000]  [<ffffffff811c82b3>] __slab_alloc+0x493/0x6b0
> > [    0.000000]  [<ffffffff81114f61>] ? trace_hardirqs_off_caller+0xe1/0x150
> > [    0.000000]  [<ffffffff81886f1d>] ? trace_hardirqs_off_thunk+0x3a/0x3c
> > [    0.000000]  [<ffffffff8395eb55>] ?
> > debug_objects_replace_static_objects+0x2a/0x1f5
> > [    0.000000]  [<ffffffff8395eb55>] ?
> > debug_objects_replace_static_objects+0x2a/0x1f5
> > [    0.000000]  [<ffffffff811c900e>] kmem_cache_alloc+0x17e/0x1a0
> > [    0.000000]  [<ffffffff8395eb55>]
> > debug_objects_replace_static_objects+0x2a/0x1f5
> > [    0.000000]  [<ffffffff8395ed59>] debug_objects_mem_init+0x39/0x68
> > [    0.000000]  [<ffffffff8392af65>] start_kernel+0x33a/0x3f8
> > [    0.000000]  [<ffffffff8392aa13>] ? kernel_init+0x280/0x280
> > [    0.000000]  [<ffffffff8392a2b6>] x86_64_start_reservations+0xa1/0xa6
> > [    0.000000]  [<ffffffff8392a410>] x86_64_start_kernel+0x155/0x164
> > [    0.000000] ---[ end trace a7919e7f17c0a725 ]---
> 
>  

Something like so?

---
 kernel/lockdep.c |    7 +++++++
 1 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/kernel/lockdep.c b/kernel/lockdep.c
index ea9ee45..a028ba9 100644
--- a/kernel/lockdep.c
+++ b/kernel/lockdep.c
@@ -2718,6 +2718,13 @@ static void __lockdep_trace_alloc(gfp_t gfp_mask, unsigned long flags)
 {
 	struct task_struct *curr = current;
 
+	/*
+	 * We do GFP_KERNEL allocations with IRQs disabled during system
+	 * bringup..
+	 */
+	if (unlikely(system_state != SYSTEM_RUNNING))
+		return;
+
 	if (unlikely(!debug_locks))
 		return;
 


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