[Report] crash tool cannot resolve struct dm_table properly

[Report] crash tool cannot resolve struct dm_table properly

[Eric Ren]

Hi Mikulas,

When inspecting on coredump with crash tool, I find that 'dm_table' cannot be resolved 
properly as follows:

===
crash> struct dm_table
struct dm_table {
     int undefined__;
}
SIZE: 4
===

Looks this issue is introduced by 83d5e5b (dm: optimize use SRCU and RCU) with this code:
===
+/*
+ * A dummy definition to make RCU happy.
+ * struct dm_table should never be dereferenced in this file.
  + */ +struct dm_table {
+ int undefined__;
+};
+
===

It stops me from looking into dm_table when analyzing coredump. Is there any workaround?
or can be fixed somehow?

Regards,
Eric

Re: [Report] crash tool cannot resolve struct dm_table properly

[Steffen Maier]

On 04/13/2017 04:01 AM, Eric Ren wrote:
> Hi Mikulas,
>
> When inspecting on coredump with crash tool, I find that 'dm_table'
> cannot be resolved properly as follows:
>
> ===
> crash> struct dm_table
> struct dm_table {
>     int undefined__;
> }
> SIZE: 4
> ===
>
> Looks this issue is introduced by 83d5e5b (dm: optimize use SRCU and
> RCU) with this code:
> ===
> +/*
> + * A dummy definition to make RCU happy.
> + * struct dm_table should never be dereferenced in this file.
>  + */ +struct dm_table {
> + int undefined__;
> +};
> +
> ===
>
> It stops me from looking into dm_table when analyzing coredump. Is there
> any workaround?
> or can be fixed somehow?

Does this help somewhat?:

https://www.redhat.com/archives/dm-devel/2015-December/msg00042.html

As workaround for eppic scripts in crash, we currently re-define struct 
dm_table in eppic scripts, because "set scope dm_table_create" has not 
always worked as we liked. Sometimes "whatis dm_table_create" and again 
"set scope dm_table_create" worked and we put this in .crashrc, but 
eventually gave up and kept our struct re-define.

-- 
Mit freundlichen Grüßen / Kind regards
Steffen Maier

Linux on z Systems Development

IBM Deutschland Research & Development GmbH
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschaeftsfuehrung: Dirk Wittkopp
Sitz der Gesellschaft: Boeblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294

Re: [Report] crash tool cannot resolve struct dm_table properly

[Steffen Maier]

On 04/13/2017 12:22 PM, Steffen Maier wrote:
> On 04/13/2017 04:01 AM, Eric Ren wrote:
>> Hi Mikulas,
>>
>> When inspecting on coredump with crash tool, I find that 'dm_table'
>> cannot be resolved properly as follows:
>>
>> ===
>> crash> struct dm_table
>> struct dm_table {
>>     int undefined__;
>> }
>> SIZE: 4
>> ===
>>
>> Looks this issue is introduced by 83d5e5b (dm: optimize use SRCU and
>> RCU) with this code:
>> ===
>> +/*
>> + * A dummy definition to make RCU happy.
>> + * struct dm_table should never be dereferenced in this file.
>>  + */ +struct dm_table {
>> + int undefined__;
>> +};
>> +
>> ===
>>
>> It stops me from looking into dm_table when analyzing coredump. Is there
>> any workaround?
>> or can be fixed somehow?
>
> Does this help somewhat?:
>
> https://www.redhat.com/archives/dm-devel/2015-December/msg00042.html
>
> As workaround for eppic scripts in crash, we currently re-define struct
> dm_table in eppic scripts, because "set scope dm_table_create" has not
> always worked as we liked. Sometimes "whatis dm_table_create" and again
> "set scope dm_table_create" worked and we put this in .crashrc, but
> eventually gave up and kept our struct re-define.

Before we wrote above posting, we tried this; maybe it helps in your case:

crash> set gdb on
gdb: on
gdb> ptype struct dm_table
type = struct dm_table {
     int undefined__;
}
gdb> ptype 'drivers/md/dm-table.c'::dm_table
No symbol "dm_table" in specified context.
gdb: gdb request failed: ptype 'drivers/md/dm-table.c'::dm_table
gdb> ptype struct dm_table
type = struct dm_table {
     uint64_t features;
     struct mapped_device *md;
     unsigned int type;
...

-- 
Mit freundlichen Grüßen / Kind regards
Steffen Maier

Linux on z Systems Development

IBM Deutschland Research & Development GmbH
Vorsitzende des Aufsichtsrats: Martina Koederitz
Geschaeftsfuehrung: Dirk Wittkopp
Sitz der Gesellschaft: Boeblingen
Registergericht: Amtsgericht Stuttgart, HRB 243294

Re: [Report] crash tool cannot resolve struct dm_table properly

[Mikulas Patocka]

On Thu, 13 Apr 2017, Eric Ren wrote:

> Hi Mikulas,
> 
> When inspecting on coredump with crash tool, I find that 'dm_table' cannot be
> resolved properly as follows:
> 
> ===
> crash> struct dm_table
> struct dm_table {
>     int undefined__;
> }
> SIZE: 4
> ===
> 
> Looks this issue is introduced by 83d5e5b (dm: optimize use SRCU and RCU) with
> this code:
> ===
> +/*
> + * A dummy definition to make RCU happy.
> + * struct dm_table should never be dereferenced in this file.
>  + */ +struct dm_table {
> + int undefined__;
> +};
> +
> ===
> 
> It stops me from looking into dm_table when analyzing coredump. Is there any
> workaround?
> or can be fixed somehow?
> 
> Regards,
> Eric

So, move dm_table definition to drivers/md/dm.h

Mikulas

Re: [Report] crash tool cannot resolve struct dm_table properly

[Eric Ren]

Hi,


On 04/13/2017 07:28 PM, Mikulas Patocka wrote:
>
> On Thu, 13 Apr 2017, Eric Ren wrote:
>
>> Hi Mikulas,
>>
>> When inspecting on coredump with crash tool, I find that 'dm_table' cannot be
>> resolved properly as follows:
>>
>> ===
>> crash> struct dm_table
>> struct dm_table {
>>      int undefined__;
>> }
>> SIZE: 4
>> ===
>>
>> Looks this issue is introduced by 83d5e5b (dm: optimize use SRCU and RCU) with
>> this code:
>> ===
>> +/*
>> + * A dummy definition to make RCU happy.
>> + * struct dm_table should never be dereferenced in this file.
>>   + */ +struct dm_table {
>> + int undefined__;
>> +};
>> +
>> ===
>>
>> It stops me from looking into dm_table when analyzing coredump. Is there any
>> workaround?
>> or can be fixed somehow?
>>
>> Regards,
>> Eric
> So, move dm_table definition to drivers/md/dm.h
Thanks. So, are your going to fix this? Or should I test on your suggestion
and send a patch if it works?

Regards,
Eric
>
> Mikulas
>

Re: [Report] crash tool cannot resolve struct dm_table properly

[Eric Ren]

Hey!


On 04/13/2017 06:29 PM, Steffen Maier wrote:
> On 04/13/2017 12:22 PM, Steffen Maier wrote:
>> [...snip...]
>>
>> Does this help somewhat?:
>>
>> https://www.redhat.com/archives/dm-devel/2015-December/msg00042.html
Thanks, I didn't notice that thread. Yes, it will help!
>>
>> As workaround for eppic scripts in crash, we currently re-define struct
>> dm_table in eppic scripts, because "set scope dm_table_create" has not
>> always worked as we liked. Sometimes "whatis dm_table_create" and again
>> "set scope dm_table_create" worked and we put this in .crashrc, but
>> eventually gave up and kept our struct re-define.
>
> Before we wrote above posting, we tried this; maybe it helps in your 
> case:
>
> crash> set gdb on
> gdb: on
> gdb> ptype struct dm_table
> type = struct dm_table {
>     int undefined__;
> }
> gdb> ptype 'drivers/md/dm-table.c'::dm_table
> No symbol "dm_table" in specified context.
> gdb: gdb request failed: ptype 'drivers/md/dm-table.c'::dm_table
> gdb> ptype struct dm_table
> type = struct dm_table {
>     uint64_t features;
>     struct mapped_device *md;
>     unsigned int type;
> ...
>
Great! thanks for your sharing:-)

Regards,
Eric

[PATCH] Re: [Report] crash tool cannot resolve struct dm_table properly

[Mikulas Patocka]

On Thu, 13 Apr 2017, Eric Ren wrote:

> Hi,
> 
> 
> On 04/13/2017 07:28 PM, Mikulas Patocka wrote:
> > 
> > On Thu, 13 Apr 2017, Eric Ren wrote:
> > 
> > > Hi Mikulas,
> > > 
> > > When inspecting on coredump with crash tool, I find that 'dm_table' cannot
> > > be
> > > resolved properly as follows:
> > > 
> > > ===
> > > crash> struct dm_table
> > > struct dm_table {
> > >      int undefined__;
> > > }
> > > SIZE: 4
> > > ===
> > > 
> > > Looks this issue is introduced by 83d5e5b (dm: optimize use SRCU and RCU)
> > > with
> > > this code:
> > > ===
> > > +/*
> > > + * A dummy definition to make RCU happy.
> > > + * struct dm_table should never be dereferenced in this file.
> > >   + */ +struct dm_table {
> > > + int undefined__;
> > > +};
> > > +
> > > ===
> > > 
> > > It stops me from looking into dm_table when analyzing coredump. Is there
> > > any
> > > workaround?
> > > or can be fixed somehow?
> > > 
> > > Regards,
> > > Eric
> > So, move dm_table definition to drivers/md/dm.h
> Thanks. So, are your going to fix this? Or should I test on your suggestion
> and send a patch if it works?
> 
> Regards,
> Eric
> > 
> > Mikulas
> > 
> 

Hi

It turned out that the RCU macros changed and the dummy definition is no 
longer needed. So, we can remove it.



From: Mikulas Patocka <mpatocka@redhat.com>

dm: remove dummy dm_table definition

This dummy structure definition was required for RCU macros, but it
doesn't seem to be required anymore, so delete it.

The dummy definition confuses the crash tool, see
https://www.redhat.com/archives/dm-devel/2017-April/msg00197.html

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>

---
 drivers/md/dm-ioctl.c |    8 --------
 1 file changed, 8 deletions(-)

Index: linux-2.6/drivers/md/dm-ioctl.c
===================================================================
--- linux-2.6.orig/drivers/md/dm-ioctl.c
+++ linux-2.6/drivers/md/dm-ioctl.c
@@ -37,14 +37,6 @@ struct hash_cell {
 	struct dm_table *new_map;
 };
 
-/*
- * A dummy definition to make RCU happy.
- * struct dm_table should never be dereferenced in this file.
- */
-struct dm_table {
-	int undefined__;
-};
-
 struct vers_iter {
     size_t param_size;
     struct dm_target_versions *vers, *old_vers;

Re: [PATCH] Re: [Report] crash tool cannot resolve struct dm_table properly

[Eric Ren]

On 04/14/2017 05:53 AM, Mikulas Patocka wrote:
>
> On Thu, 13 Apr 2017, Eric Ren wrote:
>
>> Hi,
>>
>>
>> On 04/13/2017 07:28 PM, Mikulas Patocka wrote:
>>> On Thu, 13 Apr 2017, Eric Ren wrote:
>>>
>>>> Hi Mikulas,
>>>>
>>>> When inspecting on coredump with crash tool, I find that 'dm_table' cannot
>>>> be
>>>> resolved properly as follows:
>>>>
>>>> ===
>>>> crash> struct dm_table
>>>> struct dm_table {
>>>>       int undefined__;
>>>> }
>>>> SIZE: 4
>>>> ===
>>>>
>>>> Looks this issue is introduced by 83d5e5b (dm: optimize use SRCU and RCU)
>>>> with
>>>> this code:
>>>> ===
>>>> +/*
>>>> + * A dummy definition to make RCU happy.
>>>> + * struct dm_table should never be dereferenced in this file.
>>>>    + */ +struct dm_table {
>>>> + int undefined__;
>>>> +};
>>>> +
>>>> ===
>>>>
>>>> It stops me from looking into dm_table when analyzing coredump. Is there
>>>> any
>>>> workaround?
>>>> or can be fixed somehow?
>>>>
>>>> Regards,
>>>> Eric
>>> So, move dm_table definition to drivers/md/dm.h
>> Thanks. So, are your going to fix this? Or should I test on your suggestion
>> and send a patch if it works?
>>
>> Regards,
>> Eric
>>> Mikulas
>>>
> Hi
>
> It turned out that the RCU macros changed and the dummy definition is no
> longer needed. So, we can remove it.
Hi!

That's great, thanks!

Regards,
Eric
>
>
>
> From: Mikulas Patocka <mpatocka@redhat.com>
>
> dm: remove dummy dm_table definition
>
> This dummy structure definition was required for RCU macros, but it
> doesn't seem to be required anymore, so delete it.
>
> The dummy definition confuses the crash tool, see
> https://www.redhat.com/archives/dm-devel/2017-April/msg00197.html
>
> Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
>
> ---
>   drivers/md/dm-ioctl.c |    8 --------
>   1 file changed, 8 deletions(-)
>
> Index: linux-2.6/drivers/md/dm-ioctl.c
> ===================================================================
> --- linux-2.6.orig/drivers/md/dm-ioctl.c
> +++ linux-2.6/drivers/md/dm-ioctl.c
> @@ -37,14 +37,6 @@ struct hash_cell {
>   	struct dm_table *new_map;
>   };
>   
> -/*
> - * A dummy definition to make RCU happy.
> - * struct dm_table should never be dereferenced in this file.
> - */
> -struct dm_table {
> -	int undefined__;
> -};
> -
>   struct vers_iter {
>       size_t param_size;
>       struct dm_target_versions *vers, *old_vers;
>

Re: [Report] crash tool cannot resolve struct dm_table properly

[Eric Ren]

Hi Steffen,

On 04/13/17 18:22, Steffen Maier wrote:
> On 04/13/2017 04:01 AM, Eric Ren wrote:
>> Hi Mikulas,
>>
>> When inspecting on coredump with crash tool, I find that 'dm_table'
>> cannot be resolved properly as follows:
>>
>> ===
>> crash> struct dm_table
>> struct dm_table {
>>     int undefined__;
>> }
>> SIZE: 4
>> ===
>>
>> Looks this issue is introduced by 83d5e5b (dm: optimize use SRCU and
>> RCU) with this code:
>> ===
>> +/*
>> + * A dummy definition to make RCU happy.
>> + * struct dm_table should never be dereferenced in this file.
>>  + */ +struct dm_table {
>> + int undefined__;
>> +};
>> +
>> ===
>>
>> It stops me from looking into dm_table when analyzing coredump. Is there
>> any workaround?
>> or can be fixed somehow?
>
> Does this help somewhat?:
>
> https://www.redhat.com/archives/dm-devel/2015-December/msg00042.html
>
> As workaround for eppic scripts in crash, we currently re-define struct dm_table in eppic 
> scripts, because "set scope dm_table_create" has not always worked as we liked. Sometimes 
> "whatis dm_table_create" and again "set scope dm_table_create" worked and we put this in 
> .crashrc, but eventually gave up and kept our struct re-define.

Yes, playing with "set" or "gdb ptype" commands doesn't always work. Could you please share 
your eppic scripts and steps how to use it?

Thanks in advance,
Eric