[Crash-utility] Re: [PATCH] crash: add pcpu_info support

[Dave Anderson]

Kirill Shileev wrote:
> Dear all,
> 
> We are a team developing the virtualization solution for the Linux
> kernel called OpenVZ. Since many people are running kernels patched by
> OpenVZ, they can definitely benefit from using the crash utility.
> 
> Unfortunately, it's not possible to run crash on top of OpenVZ kernel
> without some slight modification of it's code. The reason is the
> introduction of some additional data structure to the OpenVZ kernel code
> which virtualize runqueues among other things. So the way crash needs to
> read struct rq is a bit different from vanilla kernel.
> 
> Attached patch adds the needed functionality in a backward-compatible
> way. Can you please add it to crash devel tree?

Hi Kirill,

The patch appears completely segregated such that it cannot cause
any problems with non-OpenVZ kernels.  I'll tinker with the patch to
make it apply to the most recent crash version (4.0-4.13):

$ patch -p1 --dry-run < pcpu_info.support.patch
patching file defs.h
Hunk #1 FAILED at 1429.
Hunk #2 succeeded at 1543 (offset 8 lines).
1 out of 2 hunks FAILED -- saving rejects to file defs.h.rej
patching file kernel.c
patching file task.c
Hunk #1 succeeded at 5831 (offset 135 lines).
Hunk #3 succeeded at 5941 (offset 135 lines).
$

Unless I find any unsurmountable problems, consider it queued for
the next release.

Thanks,
   Dave



> 
> 
> 
> ------------------------------------------------------------------------
> 
> --- crash-4.0-4.12/defs.h.kirshil	2008-01-15 18:52:34.000000000 +0300
> +++ crash-4.0-4.12/defs.h	2008-01-15 18:52:42.000000000 +0300
> @@ -1429,6 +1429,9 @@ struct offset_table {                   
>          long kmem_cache_cpu_freelist;
>          long kmem_cache_cpu_page;
>          long kmem_cache_cpu_node;
> +	long pcpu_info_vcpu;
> +	long pcpu_info_idle;
> +	long vcpu_struct_rq;
>  };
>  
>  struct size_table {         /* stash of commonly-used sizes */
> @@ -1532,6 +1535,8 @@ struct size_table {         /* stash of 
>  	long upid;
>  	long kmem_cache_cpu;
>  	long cfs_rq;
> +	long pcpu_info;
> +	long vcpu_struct;
>  };
>  
>  struct array_table {
> --- crash-4.0-4.12/kernel.c.kirshil	2008-01-15 18:52:38.000000000 +0300
> +++ crash-4.0-4.12/kernel.c	2008-01-15 18:52:42.000000000 +0300
> @@ -475,6 +475,14 @@ kernel_init()
>  	if (!(kt->flags & DWARF_UNWIND))
>  		kt->flags |= NO_DWARF_UNWIND; 
>  
> +	if(STRUCT_EXISTS("pcpu_info")) {
> +		MEMBER_OFFSET_INIT(pcpu_info_vcpu, "pcpu_info", "vcpu");
> +		MEMBER_OFFSET_INIT(pcpu_info_idle, "pcpu_info", "idle");
> +		MEMBER_OFFSET_INIT(vcpu_struct_rq, "vcpu_struct", "rq");
> +		STRUCT_SIZE_INIT(pcpu_info, "pcpu_info");
> +		STRUCT_SIZE_INIT(vcpu_struct, "vcpu_struct");
> +	}
> +
>  	BUG_bytes_init();
>  }
>  
> --- crash-4.0-4.12/task.c.kirshil	2008-01-15 18:52:39.000000000 +0300
> +++ crash-4.0-4.12/task.c	2008-01-15 18:53:56.000000000 +0300
> @@ -5696,6 +5696,14 @@ get_idle_threads(ulong *tasklist, int nr
>  			cnt++;
>  		else
>                  	BZERO(tasklist, sizeof(ulong) * NR_CPUS);
> +	} else if (symbol_exists("pcpu_info") ){
> +		runq=symbol_value("pcpu_info");		/* vzk */
> +		runqbuf=GETBUF(SIZE(pcpu_info));
> +		for (i = 0; i < nr_cpus; i++, runq += SIZE(pcpu_info)) {
> +			readmem(runq,KVADDR,runqbuf,SIZE(pcpu_info),"pcpu info",FAULT_ON_ERROR);
> +			tasklist[i] = ULONG(runqbuf + OFFSET(pcpu_info_idle));
> +			if (IS_KVADDR(tasklist[i]))  cnt++;
> +		}
>  	}
>  
>  	if (runqbuf)
> @@ -5777,13 +5785,15 @@ int
>  get_active_set(void)
>  {
>          int i, cnt, per_cpu;
> -        ulong runq, runqaddr;
> +        ulong runq, runqaddr, pcpu_info = 0;
>          char *runqbuf;
>  
>          if (tt->flags & ACTIVE_SET)
>                  return TRUE;
>  
> -	if (symbol_exists("runqueues")) {
> +	if (symbol_exists("pcpu_info") && VALID_MEMBER(pcpu_info_vcpu)) {
> +		pcpu_info = symbol_value("pcpu_info");
> +	} else if (symbol_exists("runqueues")) {
>  		runq = symbol_value("runqueues");
>  		per_cpu = FALSE;
>  	} else if (symbol_exists("per_cpu__runqueues")) {
> @@ -5796,7 +5806,23 @@ get_active_set(void)
>          runqbuf = GETBUF(SIZE(runqueue));
>  	cnt = 0;
>  
> -	if (VALID_MEMBER(runqueue_curr) && per_cpu) {
> +	if (pcpu_info != 0) {
> +		ulong vcpu_struct; 
> +		char *pcpu_info_buf, *vcpu_struct_buf;
> +
> +		pcpu_info_buf   = GETBUF(SIZE(pcpu_info));
> +		vcpu_struct_buf = GETBUF(SIZE(vcpu_struct));
> +		for (i = 0; i < kt->cpus; i++, pcpu_info += SIZE(pcpu_info)) {
> +			readmem(pcpu_info,KVADDR,pcpu_info_buf,SIZE(pcpu_info), "pcpu_info",FAULT_ON_ERROR);
> +			vcpu_struct= ULONG(pcpu_info_buf +OFFSET(pcpu_info_vcpu));
> +			readmem(vcpu_struct,KVADDR,vcpu_struct_buf,SIZE(vcpu_struct),"pcpu_info->vcpu",FAULT_ON_ERROR);
> +			tt->active_set[i] = ULONG(vcpu_struct_buf+OFFSET(vcpu_struct_rq)+OFFSET(runqueue_curr));
> +			if (IS_KVADDR(tt->active_set[i]))
> +				cnt++;
> +		}
> +		FREEBUF(pcpu_info_buf);
> +		FREEBUF(vcpu_struct_buf);
> +	} else if (VALID_MEMBER(runqueue_curr) && per_cpu) {
>                 	for (i = 0; i < kt->cpus; i++) {
>                          if ((kt->flags & SMP) && (kt->flags & PER_CPU_OFF)) {
>                                  runq = symbol_value("per_cpu__runqueues") +