Re: [Qemu-devel] Re: [PATCH v3 2/6] Introduce bit-based phys_ram_dirty for VGA, CODE, MIGRATION and MASTER.

[Avi Kivity <avi@redhat.com>]

On 04/19/2010 02:31 PM, Yoshiaki Tamura wrote:
>
>>>> typedef struct RAMBlock {
>>>> @@ -2825,10 +2825,16 @@ ram_addr_t qemu_ram_alloc(ram_addr_t size)
>>>> new_block->next = ram_blocks;
>>>> ram_blocks = new_block;
>>>>
>>>> - phys_ram_dirty = qemu_realloc(phys_ram_dirty,
>>>> - (last_ram_offset + size)>>  TARGET_PAGE_BITS);
>>>> - memset(phys_ram_dirty + (last_ram_offset>>  TARGET_PAGE_BITS),
>>>> - 0xff, size>>  TARGET_PAGE_BITS);
>>>> + if (BITMAP_SIZE(last_ram_offset + size) !=
>>>> BITMAP_SIZE(last_ram_offset)) {
>>>>          
>>> This check is unneeded - the code will work fine even if the bitmap size
>>> doesn't change.
>>>        
>> OK.  I'll remove it.
>>      
> I have a problem here.
> If I remove this check, glibc reports an error as below.
>
> *** glibc detected *** /usr/local/qemu/bin/qemu-system-x86_64:
> realloc(): invalid pointer: 0x0000000001f0e450 ***
> ======= Backtrace: =========
> /lib64/libc.so.6[0x369fa75a96]
> /lib64/libc.so.6(realloc+0x2a1)[0x369fa7b881]
> /usr/local/qemu/bin/qemu-system-x86_64[0x437d93]
> /usr/local/qemu/bin/qemu-system-x86_64[0x4f03f6]
> /usr/local/qemu/bin/qemu-system-x86_64[0x5b052c]
> /usr/local/qemu/bin/qemu-system-x86_64[0x5b0d8b]
> /usr/local/qemu/bin/qemu-system-x86_64[0x41ec2b]
> /lib64/libc.so.6(__libc_start_main+0xfd)[0x369fa1ea2d]
> /usr/local/qemu/bin/qemu-system-x86_64[0x406479]
> ======= Memory map: ========
>
> I reminded that I put this check to avoid reallocating same size to the bitmap.
> qemu goes this routine at start up, and extends last_ram_offset at
> small numbers.
> The error above is reported at the extension phase.
>
>    

This probably means that an old bitmap pointer leaked somewhere, and we 
realloc() it after free?  Or perhaps a glibc bug.

-- 
error compiling committee.c: too many arguments to function