Re: [Xen-devel] [PATCH] tools/xenconsoled: Initialise static data before use

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Thu, 2013-03-07 at 18:54 +0000, Andrew Cooper wrote:
> On 07/03/13 18:45, Andrew Cooper wrote:
> > 'fds' and 'current_array_size' are used in a memset() in reset_fds(), and 
> > for
> > the first call to set_fds() before being initialised.
> >
> > Also initialise nr_fds for sanity sake.
> >
> > This is another regression introduced by
> >
> > "Switch from select() to poll() in xenconsoled's IO loop."
> >   hg c/s 26405:7359c3122c5d
> >   git cc5434c933153c4b8812d1df901f8915c22830a8
> >
> > Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > Signed-off-by: Marcus Granado <marcus.granado@xxxxxxxxxx>
> >
> > ---
> >
> > This is still not enough to fix the issue of xenconsoled exiting after 384
> > VMs, but does allow us to reliably reach the 383rd VM.
> 
> On second thoughts, memset(NULL, 0, 0); is still silly.   I shall resin
> tomorrow.
> 

I googled "memset NULL", presumably this is undefined and should be
fix. :-(

You fix here is quite odd, because these static variables should be
initialized to 0 automatically. Is this something related to compiler /
CFLAGS settings that trigger the bug?

I just tested booting up >384 mini-os, with you previous patch applied,
everything worked fine. I'm setting up LVM on my test box to test with
normal Linux guests.

A hint on "128", set_fds expands the array on a multiple of 128.


Wei.

> ~Andrew
> 
> >
> > diff -r 94ece33caae2 -r 803a5869bfb5 tools/console/daemon/io.c
> > --- a/tools/console/daemon/io.c
> > +++ b/tools/console/daemon/io.c
> > @@ -70,9 +70,9 @@ static int log_hv_fd = -1;
> >  
> >  static xc_gnttab *xcg_handle = NULL;
> >  
> > -static struct pollfd  *fds;
> > -static unsigned int current_array_size;
> > -static unsigned int nr_fds;
> > +static struct pollfd  *fds = NULL;
> > +static unsigned int current_array_size = 0;
> > +static unsigned int nr_fds = 0;
> >  
> >  #define ROUNDUP(_x,_w) (((unsigned long)(_x)+(1UL<<(_w))-1) & 
> > ~((1UL<<(_w))-1))
> >  
> >
> > _______________________________________________
> > Xen-devel mailing list
> > Xen-devel@xxxxxxxxxxxxx
> > http://lists.xen.org/xen-devel
> 



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