Re: [Xen-devel] [PATCH v2] xmalloc: add support for checking the pool integrity

[Mihai DonÈu <mdontu@xxxxxxxxxxxxxxx>]

On Monday 08 December 2014 16:04:55 Ian Campbell wrote:
> On Mon, 2014-12-08 at 18:00 +0200, Mihai DonÈu wrote:
> > On Monday 08 December 2014 10:18:01 Jan Beulich wrote:
> > > >>> On 08.12.14 at 03:30, <mdontu@xxxxxxxxxxxxxxx> wrote:
> > > > +#ifndef NDEBUG
> > > > +static bool_t xmem_pool_check_size(const struct bhdr *b, int fl, int 
> > > > sl)
> > > > +{
> > > > +    while ( b )
> > > > +    {
> > > > +        int __fl;
> > > > +        int __sl;
> > > > +
> > > > +        MAPPING_INSERT(b->size, &__fl, &__sl);
> > > > +        if ( __fl != fl || __sl != sl )
> > > > +        {
> > > > +            printk(XENLOG_ERR "xmem_pool: for block %p size = %u, { fl 
> > > > = %d, sl = %d } should be { fl = %d, sl = %d }\n",
> > > 
> > > Quoting my reply to v1: "Long line. Only the format message alone
> > > is allowed to exceed 80 characters."
> > > 
> > 
> > Just so I don't send another faulty patch, you would see that printk()
> > being:
> > 
> >   printk(XENLOG_ERR
> >          "xmem_pool: for block %p size = %u, { fl = %d, sl = %d } should be 
> > { fl = %d, sl = %d }\n",
> >          b, b->size, fl, sl, __fl, __sl);
> > 
> > ?
> 
> The log message here is going to be substantially more than 80
> characters (the format string by itself already is). Could you find a
> more compact representation of the useful info?
> 

Ah! I see. I apologize for being so slow. :-) How about:

printk(XENLOG_ERR "xmem_pool: %s: misplaced block %p:%u ({%d,%d} -> {%d,%d})\n",
       pool->name, b, b->size, fl, sl, __fl, __sl); 

Looks a bit cryptic, but the TLSF itself is pretty complex and for
brave souls wishing to debug it, the message format will be the last
thing on their minds. :-)

Preview:

[2014-12-04 15:41:23] (XEN) [ 1374.507125] xmem_pool: xmalloc: misplaced block 
ffff8304004fb9b0:0 ({3,9} -> {0,0})
[2014-12-04 15:41:23] (XEN) [ 1374.507127] xmem_pool: xmalloc: the TLSF chunk 
matrix is corrupted

Thanks,

-- 
Mihai DONÈU

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