linux-kernel - Re: [PATCH] slab: cache

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Date:	Sun, 28 Jan 2007 13:14:57 +0200
From:	"Pekka Enberg" <penberg@...helsinki.fi>
To:	"Andrew Morton" <akpm@...l.org>
Cc:	linux-kernel@...r.kernel.org, hugh@...itas.com, clameter@....com
Subject: Re: [PATCH] slab: cache_grow cleanup

Hi Andrew,

On 1/28/07, Andrew Morton <akpm@...l.org> wrote:
> This gets its local interrupt state mucked up.
>
> BUG: sleeping function called from invalid context at mm/slab.c:3038
> in_atomic():0, irqs_disabled():1
> no locks held by init/1.
> irq event stamp: 656902
> hardirqs last  enabled at (656901): [<c015f48b>] mod_zone_page_state+0x4b/0x50
> hardirqs last disabled at (656902): [<c0171f54>] cache_alloc_refill+0x384/0x6a0
> softirqs last  enabled at (650628): [<c03a6317>] unix_release_sock+0x67/0x220
> softirqs last disabled at (650626): [<c03cfe8e>] _write_lock_bh+0xe/0x40
>  [<c0103f7a>] show_trace_log_lvl+0x1a/0x30
>  [<c0104682>] show_trace+0x12/0x20
>  [<c0104736>] dump_stack+0x16/0x20
>  [<c01175ea>] __might_sleep+0xba/0xd0
>  [<c017262f>] kmem_cache_alloc+0xaf/0xd0
>  [<c0172131>] cache_alloc_refill+0x561/0x6a0
>  [<c0172574>] kmem_cache_zalloc+0xe4/0xf0
>  [<c011cb49>] copy_process+0x89/0x1280
>  [<c011dfcb>] do_fork+0x6b/0x1c0
>  [<c0100e13>] sys_clone+0x33/0x40
>  [<c0102edc>] sysenter_past_esp+0x5d/0x99

Hmm, alloc_slabmgmt calls kmem_cache_alloc with interrupts disabled
which triggers the warning. We won't deadlock though as we enable
interrupts in kmem_getpages in case we need to refill
cachep->slabp_cache. So the debug check is bogus when calling
kmem_cache_alloc within the slab allocator, I think.

I'll whack it some more and resend. Thanks Andrew!

                               Pekka
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