lkml.org 
[lkml]   [2011]   [Nov]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] net: Add back alignment for size for __alloc_skb
On 02/11/2011 23:43, Tony Lindgren wrote:

> Commit 87fb4b7b533073eeeaed0b6bf7c2328995f6c075 (net: more
> accurate skb truesize) changed the alignment of size. This
> can cause problems at least on some machines with NFS root:
>
> Unhandled fault: alignment exception (0x801) at 0xc183a43a
> Internal error: : 801 [#1] PREEMPT
> Modules linked in:
> CPU: 0 Not tainted (3.1.0-08784-g5eeee4a #733)
> pc : [<c02fbba0>] lr : [<c02fbb9c>] psr: 60000013
> sp : c180fef8 ip : 00000000 fp : c181f580
> r10: 00000000 r9 : c044b28c r8 : 00000001
> r7 : c183a3a0 r6 : c1835be0 r5 : c183a412 r4 : 000001f2
> r3 : 00000000 r2 : 00000000 r1 : ffffffe6 r0 : c183a43a
> Flags: nZCv IRQs on FIQs on Mode SVC_32 ISA ARM Segment kernel
> Control: 0005317f Table: 10004000 DAC: 00000017
> Process swapper (pid: 1, stack limit = 0xc180e270)
> Stack: (0xc180fef8 to 0xc1810000)
> fee0: 00000024 00000000
> ff00: 00000000 c183b9c0 c183b8e0 c044b28c c0507ccc c019dfc4 c180ff2c c0503cf8
> ff20: c180ff4c c180ff4c 00000000 c1835420 c182c740 c18349c0 c05233c0 00000000
> ff40: 00000000 c00e6bb8 c180e000 00000000 c04dd82c c0507e7c c050cc18 c183b9c0
> ff60: c05233c0 00000000 00000000 c01f34f4 c0430d70 c019d364 c04dd898 c04dd898
> ff80: c04dd82c c0507e7c c180e000 00000000 c04c584c c01f4918 c04dd898 c04dd82c
> ffa0: c04ddd28 c180e000 00000000 c0008758 c181fa60 3231d82c 00000037 00000000
> ffc0: 00000000 c04dd898 c04dd82c c04ddd28 00000013 00000000 00000000 00000000
> ffe0: 00000000 c04b2224 00000000 c04b21a0 c001056c c001056c 00000000 00000000
> Function entered at [<c02fbba0>] from [<c019dfc4>]
> Function entered at [<c019dfc4>] from [<c01f34f4>]
> Function entered at [<c01f34f4>] from [<c01f4918>]
> Function entered at [<c01f4918>] from [<c0008758>]
> Function entered at [<c0008758>] from [<c04b2224>]
> Function entered at [<c04b2224>] from [<c001056c>]
> Code: e1a00005 e3a01028 ebfa7cb0 e35a0000 (e5858028)
>
> Here PC is at __alloc_skb and &shinfo->dataref is unaligned because
> skb->end can be unaligned without this patch.
>
> Cc: Eric Dumazet <eric.dumazet@gmail.com>
> Signed-off-by: Tony Lindgren <tony@atomide.com>
>
> --- a/net/core/skbuff.c
> +++ b/net/core/skbuff.c
> @@ -189,6 +189,7 @@ struct sk_buff *__alloc_skb(unsigned int size, gfp_t gfp_mask,
> * aligned memory blocks, unless SLUB/SLAB debug is enabled.
> * Both skb->head and skb_shared_info are cache line aligned.
> */
> + size = SKB_DATA_ALIGN(size);
> size += SKB_DATA_ALIGN(sizeof(struct skb_shared_info));
> data = kmalloc_node_track_caller(size, gfp_mask, node);
> if (!data)



Hmm, I dont think this is the right way to fix the bug.

There is a problem with your kmalloc() or alignments on your architecture.

What is the SMP_CACHE_BYTES value ?



\
 
 \ /
  Last update: 2011-11-02 23:57    [W:0.034 / U:65.248 seconds]
©2003-2018 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site