linux-kernel - Re: bootmem code - reboots after 'uncompressing linux' on old computers

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Message-ID: <501C0877.7010303@computer.org>
Date:	Fri, 03 Aug 2012 19:20:55 +0200
From:	Jan Ceuleers <jan.ceuleers@...puter.org>
To:	Piotr Gluszenia Slawinski <curious@...190.internetdsl.tpnet.pl>
CC:	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	David Miller <davem@...emloft.net>
Subject: Re: bootmem code - reboots after 'uncompressing linux' on old computers

On 08/03/2012 03:37 AM, Piotr Gluszenia Slawinski wrote:
> Hello.
> while bisecting old pcmcia bug i've noticed kernels ~2.6.36
> and up do not boot on 586 machines with small amounts of ram (16M)

Copying David Miller.

Not trimming the rest of the message for David's benefit; no further comments from me.

> suprisingly 3.5 kernel booted fine.
> 
> i've bisected the problem and found fix :
> 
> solidstate linux # git bisect good
> 4e1c2b284461fd8aa8d7b295a1e911fc4390755b is the first bad commit
> commit 4e1c2b284461fd8aa8d7b295a1e911fc4390755b
> Author: David Miller <davem@...emloft.net>
> Date:   Wed Apr 25 16:10:50 2012 -0400
> 
>     mm: nobootmem: Correct alloc_bootmem semantics.
> 
>     The comments above __alloc_bootmem_node() claim that the code will
>     first try the allocation using 'goal' and if that fails it will
>     try again but with the 'goal' requirement dropped.
> 
>     Unfortunately, this is not what the code does, so fix it to do so.
> 
>     This is important for nobootmem conversions to architectures such
>     as sparc where MAX_DMA_ADDRESS is infinity.
> 
>     On such architectures all of the allocations done by generic spots,
>     such as the sparse-vmemmap implementation, will pass in:
> 
>         __pa(MAX_DMA_ADDRESS)
> 
>     as the goal, and with the limit given as "-1" this will always fail
>     unless we add the appropriate fallback logic here.
> 
>     Signed-off-by: David S. Miller <davem@...emloft.net>
>     Acked-by: Yinghai Lu <yinghai@...nel.org>
>     Signed-off-by: Linus Torvalds <torvalds@...ux-foundation.org>
> 
> :040000 040000 5c42bbd13a81426248901205b051968bab14e6ff 3e7fad8afb42036c6bbb1fcf5fcf12c87bbba9e2 M      mm
> 
> 
> kernels before 3.6.39 do not have nobootmem.c , but they still have same bug!
> 
> this patch fixes the problem for them (useful for bisecting, etc, imho should be merged into 2.6.35-stable branch) :
> 
> 
> diff --git a/mm/bootmem.c b/mm/bootmem.c
> index 13b0caa..b0ccada 100644
> --- a/mm/bootmem.c
> +++ b/mm/bootmem.c
> @@ -848,6 +848,7 @@ void * __init __alloc_bootmem_node(pg_data_t *pgdat, unsigned long size,
>                 return kzalloc_node(size, GFP_NOWAIT, pgdat->node_id);
> 
>  #ifdef CONFIG_NO_BOOTMEM
> +again:
>         ptr = __alloc_memory_core_early(pgdat->node_id, size, align,
>                                          goal, -1ULL);
>         if (ptr)
> @@ -859,6 +860,10 @@ void * __init __alloc_bootmem_node(pg_data_t *pgdat, unsigned long size,
>         ptr = ___alloc_bootmem_node(pgdat->bdata, size, align, goal, 0);
>  #endif
> 
> +       if (!ptr && goal) {
> +               goal = 0;
> +               goto again;
> +       }
>         return ptr;
>  }
> 
> 

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