[Xen-devel] RE: xenpm fail

["Zhang, Yang Z" <yang.z.zhang@xxxxxxxxx>]

> -----Original Message-----
> From: Ian Campbell [mailto:Ian.Campbell@xxxxxxxxxxxxx]
> Sent: Friday, October 29, 2010 5:26 PM
> To: Zhang, Yang Z
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxx; Ian Jackson
> Subject: Re: xenpm fail
> 
> On Fri, 2010-10-29 at 09:32 +0100, Zhang, Yang Z wrote:
> > Hi ian
> > I find Cs 22292 cause xenpm broken. When run "xenpm start" or "xenpm
> > get-cpuidle-states" and other xenmpm command, it will get segment
> > fault.
> > After do some investigation, I find call xc_pm_get_cxstat() will free
> > the cxstat->tiggers,
> > For example:
> > Here is some code form my test.c.
> >
> > struct xc_cx_stat cxstatinfo, *cxstat = &cxstatinfo;
> >
> > cxstat->triggers = malloc(max_cx_num * sizeof(uint64_t));
> >
> > if ( !cxstat->triggers ) {
> >     printf("get memory fail");
> >     return NOMEM;
> > }
> > ret = xc_pm_get_cxstat(xc_handle, cpu, cxstat);
> 
> what is ret at this point?
> 
ret = 0

> > printf("triggers=%lx \n", cxstat->triggers[0]);
> >
> > Run it, and it will show segment fault at print the cxtat->tiggers[0].
> > It seems that xc_pm_get_cxstat() will free cxstat->triggers which we
> > allocate memory before, and then when try to touch cxstat->tiggers[0],
> > the issue raised.
> 
> I can't see any code which frees cxstat->triggers in xc_pm_get_cxstat,
> there is only code which frees the bounce buffer.
> 
> Perhaps the issue you are seeing is with get_cxstat_by_cpuid from
> xenpm.c rather than xc_pm_get_cxstat directly? I notice that
> get_cxstat_by_cpuid is called on one occasion without checking the
> return code and that it frees the trigger array when xc_pm_get_cxstat
> fails so a new failure introduced by 22292 could cause this?
> 
> What hardware is this on? What is max_cx_num and max_cpu_nr for you?
> 
I used westmere-ep.  max_cx_num equal to 4 and I didn't get the max_cpu_nr in 
my test case.

> > If remove the patch 22292, everything is ok.
> >
> > best regards
> > yang
> >
> >
> 

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