Re: [PATCH 1/1] PATCH: KGDB/KDB Fix no KDB config problem.

[Mike Travis]

On 10/3/2013 10:15 AM, Ingo Molnar wrote:
> 
> * Mike Travis <travis@xxxxxxx> wrote:
> 
>>
>>
>> On 10/3/2013 9:51 AM, Ingo Molnar wrote:
>>>
>>> * Mike Travis <travis@xxxxxxx> wrote:
>>>
>>>> Some code added to the debug_core module had KDB dependencies
>>>> that it shouldn't have.
>>>>
>>>> Signed-off-by: Mike Travis <travis@xxxxxxx>
>>>> ---
>>>>  kernel/debug/debug_core.c |    8 ++++----
>>>>  kernel/debug/debug_core.h |    2 ++
>>>>  2 files changed, 6 insertions(+), 4 deletions(-)
>>>>
>>>> --- linux.orig/kernel/debug/debug_core.c
>>>> +++ linux/kernel/debug/debug_core.c
>>>> @@ -575,8 +575,8 @@ return_normal:
>>>>  		raw_spin_lock(&dbg_slave_lock);
>>>>  
>>>>  #ifdef CONFIG_SMP
>>>> -	/* If SYSTEM_NMI, slaves are already waiting */
>>>> -	if (ks->err_code == KDB_REASON_SYSTEM_NMI)
>>>> +	/* If send_ready set, slaves are already waiting */
>>>> +	if (ks->send_ready)
>>>>  		atomic_set(ks->send_ready, 1);
>>>>  
>>>>  	/* Signal the other CPUs to enter kgdb_wait() */
>>>> @@ -682,11 +682,11 @@ kgdb_handle_exception(int evector, int s
>>>>  	if (arch_kgdb_ops.enable_nmi)
>>>>  		arch_kgdb_ops.enable_nmi(0);
>>>>  
>>>> +	memset(ks, 0, sizeof(struct kgdb_state));
>>>>  	ks->cpu			= raw_smp_processor_id();
>>>>  	ks->ex_vector		= evector;
>>>>  	ks->signo		= signo;
>>>>  	ks->err_code		= ecode;
>>>> -	ks->kgdb_usethreadid	= 0;
>>>>  	ks->linux_regs		= regs;
>>>>  
>>>>  	if (kgdb_reenter_check(ks))
>>>> @@ -750,7 +750,7 @@ int kgdb_nmicallin(int cpu, int trapnr,
>>>>  		ks->cpu			= cpu;
>>>>  		ks->ex_vector		= trapnr;
>>>>  		ks->signo		= SIGTRAP;
>>>> -		ks->err_code		= KDB_REASON_SYSTEM_NMI;
>>>> +		ks->err_code		= KGDB_KDB_REASON_SYSTEM_NMI;
>>>>  		ks->linux_regs		= regs;
>>>>  		ks->send_ready		= send_ready;
>>>>  		kgdb_cpu_enter(ks, regs, DCPU_WANT_MASTER);
>>>> --- linux.orig/kernel/debug/debug_core.h
>>>> +++ linux/kernel/debug/debug_core.h
>>>> @@ -75,11 +75,13 @@ extern int kdb_stub(struct kgdb_state *k
>>>>  extern int kdb_parse(const char *cmdstr);
>>>>  extern int kdb_common_init_state(struct kgdb_state *ks);
>>>>  extern int kdb_common_deinit_state(void);
>>>> +#define KGDB_KDB_REASON_SYSTEM_NMI KDB_REASON_SYSTEM_NMI
>>>>  #else /* ! CONFIG_KGDB_KDB */
>>>>  static inline int kdb_stub(struct kgdb_state *ks)
>>>>  {
>>>>  	return DBG_PASS_EVENT;
>>>>  }
>>>> +#define KGDB_KDB_REASON_SYSTEM_NMI 0
>>>>  #endif /* CONFIG_KGDB_KDB */
>>>>  
>>>>  #endif /* _DEBUG_CORE_H_ */
>>>
>>> Hm, the KGDB_KDB_REASON_SYSTEM_NMI definition is a bit ugly. I still think 
>>> there are layering violations here and just kludging it around doesn't 
>>> solve it - a helper function that keeps kgdb details to the kgdb code 
>>> would.
>>>
>>> Anyway, if Jason is fine with this solution and upholds his Acked-by then 
>>> I'll merge this into the first patch and apply the two patches.
>>>
>>> Thanks,
>>>
>>> 	Ingo
>>>
>>
>> Would you prefer a simple #ifdef CONFIG_KGDB_KDB around the assignment?
> 
> An #ifdef doesn't solve the layering violation!
> 
> kernel/debug/debug_core.c didn't have any serious use of #ifdef 
> CONFIG_KGDB_KDB before (it used it to flavor a few printks) and I'm not 
> convinced it needs one for this feature either.
> 
> So if that whole chunk is kdb dependent, why not shuffle that into a 
> nicely named function and host it somewhere appropriate in 
> kernel/debug/kdb/? That function would turn into an empty inline function 
> in the !CONFIG_KGDB_KDB case.
> 
> But ... it's up to Jason really whether he wants to abstract that piece of 
> code out, I'm just kibitzing here really.
> 
> Thanks,
> 
> 	Ingo
> 

If I moved it to KDB then we would lose the capability to enter KGDB
mode and the gdb_stub functionality.  The #ifdef could have a comment
to this effect?
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