Re: [Xen-devel] Re: xenpm fail

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Fri, 2010-10-29 at 10:26 +0100, Ian Campbell wrote:
> 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?
> 
> > 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?

Please could you also try this debug patch

diff -r a1b39d2b9001 tools/misc/xenpm.c
--- a/tools/misc/xenpm.c        Fri Oct 22 15:14:51 2010 +0100
+++ b/tools/misc/xenpm.c        Fri Oct 29 10:41:37 2010 +0100
@@ -121,6 +121,7 @@ static int get_cxstat_by_cpuid(xc_interf
     cxstat->residencies = malloc(max_cx_num * sizeof(uint64_t));
     if ( !cxstat->residencies )
     {
+        fprintf(stderr, "failed to allocate residencies, freeing triggers\n");
         free(cxstat->triggers);
         return -ENOMEM;
     }
@@ -129,6 +130,7 @@ static int get_cxstat_by_cpuid(xc_interf
     if( ret )
     {
         int temp = errno;
+        fprintf(stderr, "xc_pm_get_cx_stat failed %d %d, freeing buffers\n", 
ret, errno);
         free(cxstat->triggers);
         free(cxstat->residencies);
         cxstat->triggers = NULL;



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