[PATCH v3 0/2] Ajust lockdep static allocations for sparc

[PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Babu Moger]

These patches limit the static allocations for lockdep data structures
used for debugging locking correctness. For sparc, all the kernel's code,
data, and bss, must have locked translations in the TLB so that we don't
get TLB misses on kernel code and data. Current sparc chips have 8 TLB
entries available that may be locked down, and with a 4mb page size,
this gives a maximum of 32MB. With PROVE_LOCKING we could go over this
limit and cause system boot-up problems. These patches limit the static
allocations so that everything fits in current required size limit.

patch 1 : Adds new config parameter CONFIG_PROVE_LOCKING_SMALL
Patch 2 : Adjusts the sizes based on the new config parameter

v2-> v3:
   Some more comments from Sam Ravnborg and Peter Zijlstra.
   Defined PROVE_LOCKING_SMALL as invisible and moved the selection to
   arch/sparc/Kconfig. 

v1-> v2:
   As suggested by Peter Zijlstra, keeping the default as is.
   Introduced new config variable CONFIG_PROVE_LOCKING_SMALL
   to handle sparc specific case.

v0:
   Initial revision.

Babu Moger (2):
  config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL
    for sparc
  lockdep: Limit static allocations if PROVE_LOCKING_SMALL is defined

 arch/sparc/Kconfig                 |    1 +
 kernel/locking/lockdep_internals.h |   20 +++++++++++++++++---
 lib/Kconfig.debug                  |    3 +++
 3 files changed, 21 insertions(+), 3 deletions(-)

[PATCH v3 1/2] config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL for sparc

[Babu Moger]

This new config parameter limits the space used for "Lock debugging:
prove locking correctness" by about 4MB. The current sparc systems have
the limitation of 32MB size for kernel size including .text, .data and
.bss sections. With PROVE_LOCKING feature, the kernel size could grow
beyond this limit and causing system boot-up issues. With this option,
kernel limits the size of the entries of lock_chains, stack_trace etc.,
so that kernel fits in required size limit. This is not visible to user
and only used for sparc.

Signed-off-by: Babu Moger <babu.moger@oracle.com>
---
 arch/sparc/Kconfig |    1 +
 lib/Kconfig.debug  |    3 +++
 2 files changed, 4 insertions(+), 0 deletions(-)

diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
index 59b0960..8da321c 100644
--- a/arch/sparc/Kconfig
+++ b/arch/sparc/Kconfig
@@ -44,6 +44,7 @@ config SPARC
 	select ARCH_HAS_SG_CHAIN
 	select CPU_NO_EFFICIENT_FFS
 	select HAVE_ARCH_HARDENED_USERCOPY
+	select PROVE_LOCKING_SMALL if PROVE_LOCKING
 
 config SPARC32
 	def_bool !64BIT
diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index cab7405..597e589 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1084,6 +1084,9 @@ config PROVE_LOCKING
 
 	 For more details, see Documentation/locking/lockdep-design.txt.
 
+config PROVE_LOCKING_SMALL
+	bool
+
 config LOCKDEP
 	bool
 	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
-- 
1.7.1

[PATCH v3 2/2] lockdep: Limit static allocations if PROVE_LOCKING_SMALL is defined

[Babu Moger]

Reduce the size of data structure for lockdep entries by half if
PROVE_LOCKING_SMALL if defined. This is used only for sparc.

Signed-off-by: Babu Moger <babu.moger@oracle.com>
---
 kernel/locking/lockdep_internals.h |   20 +++++++++++++++++---
 1 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
index 51c4b24..c2b8849 100644
--- a/kernel/locking/lockdep_internals.h
+++ b/kernel/locking/lockdep_internals.h
@@ -46,6 +46,14 @@ enum {
 		(LOCKF_USED_IN_HARDIRQ_READ | LOCKF_USED_IN_SOFTIRQ_READ)
 
 /*
+ * CONFIG_PROVE_LOCKING_SMALL is defined for sparc. Sparc requires .text,
+ * .data and .bss to fit in required 32MB limit for the kernel. With
+ * PROVE_LOCKING we could go over this limit and cause system boot-up problems.
+ * So, reduce the static allocations for lockdeps related structures so that
+ * everything fits in current required size limit.
+ */
+#ifdef CONFIG_PROVE_LOCKING_SMALL
+/*
  * MAX_LOCKDEP_ENTRIES is the maximum number of lock dependencies
  * we track.
  *
@@ -54,18 +62,24 @@ enum {
  * table (if it's not there yet), and we check it for lock order
  * conflicts and deadlocks.
  */
+#define MAX_LOCKDEP_ENTRIES	16384UL
+#define MAX_LOCKDEP_CHAINS_BITS	15
+#define MAX_STACK_TRACE_ENTRIES	262144UL
+#else
 #define MAX_LOCKDEP_ENTRIES	32768UL
 
 #define MAX_LOCKDEP_CHAINS_BITS	16
-#define MAX_LOCKDEP_CHAINS	(1UL << MAX_LOCKDEP_CHAINS_BITS)
-
-#define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)
 
 /*
  * Stack-trace: tightly packed array of stack backtrace
  * addresses. Protected by the hash_lock.
  */
 #define MAX_STACK_TRACE_ENTRIES	524288UL
+#endif
+
+#define MAX_LOCKDEP_CHAINS	(1UL << MAX_LOCKDEP_CHAINS_BITS)
+
+#define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)
 
 extern struct list_head all_lock_classes;
 extern struct lock_chain lock_chains[];
-- 
1.7.1

Re: [PATCH v3 1/2] config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL for sparc

[Peter Zijlstra]

On Tue, Sep 27, 2016 at 12:33:27PM -0700, Babu Moger wrote:
> This new config parameter limits the space used for "Lock debugging:
> prove locking correctness" by about 4MB. The current sparc systems have
> the limitation of 32MB size for kernel size including .text, .data and
> .bss sections. With PROVE_LOCKING feature, the kernel size could grow
> beyond this limit and causing system boot-up issues. With this option,
> kernel limits the size of the entries of lock_chains, stack_trace etc.,
> so that kernel fits in required size limit. This is not visible to user
> and only used for sparc.
> 
> Signed-off-by: Babu Moger <babu.moger@oracle.com>

You forgot to Cc Dave, and since you're touching sparc I need an Ack
from him before I can queue this.

Dave?

> ---
>  arch/sparc/Kconfig |    1 +
>  lib/Kconfig.debug  |    3 +++
>  2 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
> index 59b0960..8da321c 100644
> --- a/arch/sparc/Kconfig
> +++ b/arch/sparc/Kconfig
> @@ -44,6 +44,7 @@ config SPARC
>  	select ARCH_HAS_SG_CHAIN
>  	select CPU_NO_EFFICIENT_FFS
>  	select HAVE_ARCH_HARDENED_USERCOPY
> +	select PROVE_LOCKING_SMALL if PROVE_LOCKING
>  
>  config SPARC32
>  	def_bool !64BIT
> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
> index cab7405..597e589 100644
> --- a/lib/Kconfig.debug
> +++ b/lib/Kconfig.debug
> @@ -1084,6 +1084,9 @@ config PROVE_LOCKING
>  
>  	 For more details, see Documentation/locking/lockdep-design.txt.
>  
> +config PROVE_LOCKING_SMALL
> +	bool
> +
>  config LOCKDEP
>  	bool
>  	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
> -- 
> 1.7.1
> 

Re: [PATCH v3 1/2] config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL for sparc

[Sam Ravnborg]

On Tue, Sep 27, 2016 at 12:33:27PM -0700, Babu Moger wrote:
> This new config parameter limits the space used for "Lock debugging:
> prove locking correctness" by about 4MB. The current sparc systems have
> the limitation of 32MB size for kernel size including .text, .data and
> .bss sections. With PROVE_LOCKING feature, the kernel size could grow
> beyond this limit and causing system boot-up issues. With this option,
> kernel limits the size of the entries of lock_chains, stack_trace etc.,
> so that kernel fits in required size limit. This is not visible to user
> and only used for sparc.
> 
> Signed-off-by: Babu Moger <babu.moger@oracle.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>

Re: [PATCH v3 2/2] lockdep: Limit static allocations if PROVE_LOCKING_SMALL is defined

[Sam Ravnborg]

On Tue, Sep 27, 2016 at 12:33:28PM -0700, Babu Moger wrote:
> Reduce the size of data structure for lockdep entries by half if
> PROVE_LOCKING_SMALL if defined. This is used only for sparc.
> 
> Signed-off-by: Babu Moger <babu.moger@oracle.com>
Acked-by: Sam Ravnborg <sam@ravnborg.org>

Re: [PATCH v3 1/2] config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL for sparc

[Babu Moger]

On 9/28/2016 3:39 AM, Peter Zijlstra wrote:
> On Tue, Sep 27, 2016 at 12:33:27PM -0700, Babu Moger wrote:
>> This new config parameter limits the space used for "Lock debugging:
>> prove locking correctness" by about 4MB. The current sparc systems have
>> the limitation of 32MB size for kernel size including .text, .data and
>> .bss sections. With PROVE_LOCKING feature, the kernel size could grow
>> beyond this limit and causing system boot-up issues. With this option,
>> kernel limits the size of the entries of lock_chains, stack_trace etc.,
>> so that kernel fits in required size limit. This is not visible to user
>> and only used for sparc.
>>
>> Signed-off-by: Babu Moger <babu.moger@oracle.com>
> You forgot to Cc Dave, and since you're touching sparc I need an Ack
> from him before I can queue this.
Dave, Can you please take a look at the patch. Please ack it if it looks 
good.
Thanks
>
> Dave?
>
>> ---
>>   arch/sparc/Kconfig |    1 +
>>   lib/Kconfig.debug  |    3 +++
>>   2 files changed, 4 insertions(+), 0 deletions(-)
>>
>> diff --git a/arch/sparc/Kconfig b/arch/sparc/Kconfig
>> index 59b0960..8da321c 100644
>> --- a/arch/sparc/Kconfig
>> +++ b/arch/sparc/Kconfig
>> @@ -44,6 +44,7 @@ config SPARC
>>   	select ARCH_HAS_SG_CHAIN
>>   	select CPU_NO_EFFICIENT_FFS
>>   	select HAVE_ARCH_HARDENED_USERCOPY
>> +	select PROVE_LOCKING_SMALL if PROVE_LOCKING
>>   
>>   config SPARC32
>>   	def_bool !64BIT
>> diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
>> index cab7405..597e589 100644
>> --- a/lib/Kconfig.debug
>> +++ b/lib/Kconfig.debug
>> @@ -1084,6 +1084,9 @@ config PROVE_LOCKING
>>   
>>   	 For more details, see Documentation/locking/lockdep-design.txt.
>>   
>> +config PROVE_LOCKING_SMALL
>> +	bool
>> +
>>   config LOCKDEP
>>   	bool
>>   	depends on DEBUG_KERNEL && TRACE_IRQFLAGS_SUPPORT && STACKTRACE_SUPPORT && LOCKDEP_SUPPORT
>> -- 
>> 1.7.1
>>

Re: [PATCH v3 2/2] lockdep: Limit static allocations if PROVE_LOCKING_SMALL is defined

[Babu Moger]

CCing Dave.

Dave, Please ack it if it looks good. Thanks.


On 9/27/2016 2:33 PM, Babu Moger wrote:
> Reduce the size of data structure for lockdep entries by half if
> PROVE_LOCKING_SMALL if defined. This is used only for sparc.
>
> Signed-off-by: Babu Moger <babu.moger@oracle.com>
> ---
>   kernel/locking/lockdep_internals.h |   20 +++++++++++++++++---
>   1 files changed, 17 insertions(+), 3 deletions(-)
>
> diff --git a/kernel/locking/lockdep_internals.h b/kernel/locking/lockdep_internals.h
> index 51c4b24..c2b8849 100644
> --- a/kernel/locking/lockdep_internals.h
> +++ b/kernel/locking/lockdep_internals.h
> @@ -46,6 +46,14 @@ enum {
>   		(LOCKF_USED_IN_HARDIRQ_READ | LOCKF_USED_IN_SOFTIRQ_READ)
>   
>   /*
> + * CONFIG_PROVE_LOCKING_SMALL is defined for sparc. Sparc requires .text,
> + * .data and .bss to fit in required 32MB limit for the kernel. With
> + * PROVE_LOCKING we could go over this limit and cause system boot-up problems.
> + * So, reduce the static allocations for lockdeps related structures so that
> + * everything fits in current required size limit.
> + */
> +#ifdef CONFIG_PROVE_LOCKING_SMALL
> +/*
>    * MAX_LOCKDEP_ENTRIES is the maximum number of lock dependencies
>    * we track.
>    *
> @@ -54,18 +62,24 @@ enum {
>    * table (if it's not there yet), and we check it for lock order
>    * conflicts and deadlocks.
>    */
> +#define MAX_LOCKDEP_ENTRIES	16384UL
> +#define MAX_LOCKDEP_CHAINS_BITS	15
> +#define MAX_STACK_TRACE_ENTRIES	262144UL
> +#else
>   #define MAX_LOCKDEP_ENTRIES	32768UL
>   
>   #define MAX_LOCKDEP_CHAINS_BITS	16
> -#define MAX_LOCKDEP_CHAINS	(1UL << MAX_LOCKDEP_CHAINS_BITS)
> -
> -#define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)
>   
>   /*
>    * Stack-trace: tightly packed array of stack backtrace
>    * addresses. Protected by the hash_lock.
>    */
>   #define MAX_STACK_TRACE_ENTRIES	524288UL
> +#endif
> +
> +#define MAX_LOCKDEP_CHAINS	(1UL << MAX_LOCKDEP_CHAINS_BITS)
> +
> +#define MAX_LOCKDEP_CHAIN_HLOCKS (MAX_LOCKDEP_CHAINS*5)
>   
>   extern struct list_head all_lock_classes;
>   extern struct lock_chain lock_chains[];

Re: [PATCH v3 1/2] config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL for sparc

[David Miller]

From: Babu Moger <babu.moger@oracle.com>
Date: Thu, 29 Sep 2016 08:53:24 -0500

> 
> On 9/28/2016 3:39 AM, Peter Zijlstra wrote:
>> On Tue, Sep 27, 2016 at 12:33:27PM -0700, Babu Moger wrote:
>>> This new config parameter limits the space used for "Lock debugging:
>>> prove locking correctness" by about 4MB. The current sparc systems
>>> have
>>> the limitation of 32MB size for kernel size including .text, .data and
>>> .bss sections. With PROVE_LOCKING feature, the kernel size could grow
>>> beyond this limit and causing system boot-up issues. With this option,
>>> kernel limits the size of the entries of lock_chains, stack_trace
>>> etc.,
>>> so that kernel fits in required size limit. This is not visible to
>>> user
>>> and only used for sparc.
>>>
>>> Signed-off-by: Babu Moger <babu.moger@oracle.com>
>> You forgot to Cc Dave, and since you're touching sparc I need an Ack
>> from him before I can queue this.
> Dave, Can you please take a look at the patch. Please ack it if it
> looks good.

I am travelling and will look at it when I get a chance.

Re: [PATCH v3 1/2] config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL for sparc

[Babu Moger]

Dave, Gentle reminder to review this patch. Thanks

On 9/30/2016 12:19 AM, David Miller wrote:
> From: Babu Moger <babu.moger@oracle.com>
> Date: Thu, 29 Sep 2016 08:53:24 -0500
>
>> On 9/28/2016 3:39 AM, Peter Zijlstra wrote:
>>> On Tue, Sep 27, 2016 at 12:33:27PM -0700, Babu Moger wrote:
>>>> This new config parameter limits the space used for "Lock debugging:
>>>> prove locking correctness" by about 4MB. The current sparc systems
>>>> have
>>>> the limitation of 32MB size for kernel size including .text, .data and
>>>> .bss sections. With PROVE_LOCKING feature, the kernel size could grow
>>>> beyond this limit and causing system boot-up issues. With this option,
>>>> kernel limits the size of the entries of lock_chains, stack_trace
>>>> etc.,
>>>> so that kernel fits in required size limit. This is not visible to
>>>> user
>>>> and only used for sparc.
>>>>
>>>> Signed-off-by: Babu Moger <babu.moger@oracle.com>
>>> You forgot to Cc Dave, and since you're touching sparc I need an Ack
>>> from him before I can queue this.
>> Dave, Can you please take a look at the patch. Please ack it if it
>> looks good.
> I am travelling and will look at it when I get a chance.

Re: [PATCH v3 1/2] config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL for sparc

[Sam Ravnborg]

On Wed, Oct 05, 2016 at 05:56:16PM -0500, Babu Moger wrote:
> Dave, Gentle reminder to review this patch. Thanks

No need to ping Dave.
It is in patchwork and he will review the patch eventually.

	Sam

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[David Miller]

From: Babu Moger <babu.moger@oracle.com>
Date: Tue, 27 Sep 2016 12:33:26 -0700

> These patches limit the static allocations for lockdep data structures
> used for debugging locking correctness. For sparc, all the kernel's code,
> data, and bss, must have locked translations in the TLB so that we don't
> get TLB misses on kernel code and data. Current sparc chips have 8 TLB
> entries available that may be locked down, and with a 4mb page size,
> this gives a maximum of 32MB. With PROVE_LOCKING we could go over this
> limit and cause system boot-up problems. These patches limit the static
> allocations so that everything fits in current required size limit.
> 
> patch 1 : Adds new config parameter CONFIG_PROVE_LOCKING_SMALL
> Patch 2 : Adjusts the sizes based on the new config parameter
> 
> v2-> v3:
>    Some more comments from Sam Ravnborg and Peter Zijlstra.
>    Defined PROVE_LOCKING_SMALL as invisible and moved the selection to
>    arch/sparc/Kconfig. 
> 
> v1-> v2:
>    As suggested by Peter Zijlstra, keeping the default as is.
>    Introduced new config variable CONFIG_PROVE_LOCKING_SMALL
>    to handle sparc specific case.
> 
> v0:
>    Initial revision.

Series applied, thanks.

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Peter Zijlstra]

On Fri, Nov 18, 2016 at 02:34:07PM -0500, David Miller wrote:
> From: Babu Moger <babu.moger@oracle.com>
> Date: Tue, 27 Sep 2016 12:33:26 -0700
> 
> > These patches limit the static allocations for lockdep data structures
> > used for debugging locking correctness. For sparc, all the kernel's code,
> > data, and bss, must have locked translations in the TLB so that we don't
> > get TLB misses on kernel code and data. Current sparc chips have 8 TLB
> > entries available that may be locked down, and with a 4mb page size,
> > this gives a maximum of 32MB. With PROVE_LOCKING we could go over this
> > limit and cause system boot-up problems. These patches limit the static
> > allocations so that everything fits in current required size limit.
> > 
> > patch 1 : Adds new config parameter CONFIG_PROVE_LOCKING_SMALL
> > Patch 2 : Adjusts the sizes based on the new config parameter
> > 
> > v2-> v3:
> >    Some more comments from Sam Ravnborg and Peter Zijlstra.
> >    Defined PROVE_LOCKING_SMALL as invisible and moved the selection to
> >    arch/sparc/Kconfig. 
> > 
> > v1-> v2:
> >    As suggested by Peter Zijlstra, keeping the default as is.
> >    Introduced new config variable CONFIG_PROVE_LOCKING_SMALL
> >    to handle sparc specific case.
> > 
> > v0:
> >    Initial revision.
> 
> Series applied, thanks.

Heh, I was only waiting for an ACK from you, but this works too :-)

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Ingo Molnar]

* Peter Zijlstra <peterz@infradead.org> wrote:

> On Fri, Nov 18, 2016 at 02:34:07PM -0500, David Miller wrote:
> > From: Babu Moger <babu.moger@oracle.com>
> > Date: Tue, 27 Sep 2016 12:33:26 -0700
> > 
> > > These patches limit the static allocations for lockdep data structures
> > > used for debugging locking correctness. For sparc, all the kernel's code,
> > > data, and bss, must have locked translations in the TLB so that we don't
> > > get TLB misses on kernel code and data. Current sparc chips have 8 TLB
> > > entries available that may be locked down, and with a 4mb page size,
> > > this gives a maximum of 32MB. With PROVE_LOCKING we could go over this
> > > limit and cause system boot-up problems. These patches limit the static
> > > allocations so that everything fits in current required size limit.
> > > 
> > > patch 1 : Adds new config parameter CONFIG_PROVE_LOCKING_SMALL
> > > Patch 2 : Adjusts the sizes based on the new config parameter
> > > 
> > > v2-> v3:
> > >    Some more comments from Sam Ravnborg and Peter Zijlstra.
> > >    Defined PROVE_LOCKING_SMALL as invisible and moved the selection to
> > >    arch/sparc/Kconfig. 
> > > 
> > > v1-> v2:
> > >    As suggested by Peter Zijlstra, keeping the default as is.
> > >    Introduced new config variable CONFIG_PROVE_LOCKING_SMALL
> > >    to handle sparc specific case.
> > > 
> > > v0:
> > >    Initial revision.
> > 
> > Series applied, thanks.
> 
> Heh, I was only waiting for an ACK from you, but this works too :-)

Works for me too - as usual davem is fantastic in terms of efficient patch flow :)

Thanks,

	Ingo

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Geert Uytterhoeven]

CC linux-renesas-soc

On Tue, Sep 27, 2016 at 9:33 PM, Babu Moger <babu.moger@oracle.com> wrote:
> These patches limit the static allocations for lockdep data structures
> used for debugging locking correctness. For sparc, all the kernel's code,
> data, and bss, must have locked translations in the TLB so that we don't
> get TLB misses on kernel code and data. Current sparc chips have 8 TLB
> entries available that may be locked down, and with a 4mb page size,
> this gives a maximum of 32MB. With PROVE_LOCKING we could go over this
> limit and cause system boot-up problems. These patches limit the static
> allocations so that everything fits in current required size limit.
>
> patch 1 : Adds new config parameter CONFIG_PROVE_LOCKING_SMALL
> Patch 2 : Adjusts the sizes based on the new config parameter

Cool, this is also useful on other platforms!
E.g. on r8a7791/koelsch, I cannot boot an shmobile_defconfig plus
CONFIG_PROVE_LOCKING kernel.
Forcing CONFIG_PROVE_LOCKING_SMALL=y in Kconfig fixes that.

Should it become a user-selectable symbol?

> v2-> v3:
>    Some more comments from Sam Ravnborg and Peter Zijlstra.
>    Defined PROVE_LOCKING_SMALL as invisible and moved the selection to
>    arch/sparc/Kconfig.
>
> v1-> v2:
>    As suggested by Peter Zijlstra, keeping the default as is.
>    Introduced new config variable CONFIG_PROVE_LOCKING_SMALL
>    to handle sparc specific case.
>
> v0:
>    Initial revision.
>
> Babu Moger (2):
>   config: Adding the new config parameter CONFIG_PROVE_LOCKING_SMALL
>     for sparc
>   lockdep: Limit static allocations if PROVE_LOCKING_SMALL is defined
>
>  arch/sparc/Kconfig                 |    1 +
>  kernel/locking/lockdep_internals.h |   20 +++++++++++++++++---
>  lib/Kconfig.debug                  |    3 +++
>  3 files changed, 21 insertions(+), 3 deletions(-)

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Peter Zijlstra]

On Tue, Nov 29, 2016 at 12:14:48PM +0100, Geert Uytterhoeven wrote:
> CC linux-renesas-soc
> 
> On Tue, Sep 27, 2016 at 9:33 PM, Babu Moger <babu.moger@oracle.com> wrote:
> > These patches limit the static allocations for lockdep data structures
> > used for debugging locking correctness. For sparc, all the kernel's code,
> > data, and bss, must have locked translations in the TLB so that we don't
> > get TLB misses on kernel code and data. Current sparc chips have 8 TLB
> > entries available that may be locked down, and with a 4mb page size,
> > this gives a maximum of 32MB. With PROVE_LOCKING we could go over this
> > limit and cause system boot-up problems. These patches limit the static
> > allocations so that everything fits in current required size limit.
> >
> > patch 1 : Adds new config parameter CONFIG_PROVE_LOCKING_SMALL
> > Patch 2 : Adjusts the sizes based on the new config parameter
> 
> Cool, this is also useful on other platforms!
> E.g. on r8a7791/koelsch, I cannot boot an shmobile_defconfig plus
> CONFIG_PROVE_LOCKING kernel.
> Forcing CONFIG_PROVE_LOCKING_SMALL=y in Kconfig fixes that.
> 
> Should it become a user-selectable symbol?

Nah, users don't need more senseless options. This is really only useful
for dinky platforms or platforms with limited static image size (like
sparc64).

If you make this user selectable, someone will do, and then an endless
stream of table not big enough warnings will be posted.

Also, its only 4MB (IIRC), so who cares.

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Geert Uytterhoeven]

Hi Peter,

On Tue, Nov 29, 2016 at 12:41 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, Nov 29, 2016 at 12:14:48PM +0100, Geert Uytterhoeven wrote:
>> CC linux-renesas-soc
>>
>> On Tue, Sep 27, 2016 at 9:33 PM, Babu Moger <babu.moger@oracle.com> wrote:
>> > These patches limit the static allocations for lockdep data structures
>> > used for debugging locking correctness. For sparc, all the kernel's code,
>> > data, and bss, must have locked translations in the TLB so that we don't
>> > get TLB misses on kernel code and data. Current sparc chips have 8 TLB
>> > entries available that may be locked down, and with a 4mb page size,
>> > this gives a maximum of 32MB. With PROVE_LOCKING we could go over this
>> > limit and cause system boot-up problems. These patches limit the static
>> > allocations so that everything fits in current required size limit.
>> >
>> > patch 1 : Adds new config parameter CONFIG_PROVE_LOCKING_SMALL
>> > Patch 2 : Adjusts the sizes based on the new config parameter
>>
>> Cool, this is also useful on other platforms!
>> E.g. on r8a7791/koelsch, I cannot boot an shmobile_defconfig plus
>> CONFIG_PROVE_LOCKING kernel.
>> Forcing CONFIG_PROVE_LOCKING_SMALL=y in Kconfig fixes that.
>>
>> Should it become a user-selectable symbol?
>
> Nah, users don't need more senseless options. This is really only useful
> for dinky platforms or platforms with limited static image size (like
> sparc64).
>
> If you make this user selectable, someone will do, and then an endless
> stream of table not big enough warnings will be posted.
>
> Also, its only 4MB (IIRC), so who cares.

I care :-)

Not because of platforms with not limited memory, but because of platforms
with boot loaders that have silly kernel size limitations, and start
scribbling over the DTB or even theirselves when copying a large kernel image.

BTW, is there any particular reason these huge arrays are in BSS, and not
allocated dynamically? That would solve my problems as well...

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Peter Zijlstra]

On Tue, Nov 29, 2016 at 12:52:04PM +0100, Geert Uytterhoeven wrote:
> > Nah, users don't need more senseless options. This is really only useful
> > for dinky platforms or platforms with limited static image size (like
> > sparc64).
> >
> > If you make this user selectable, someone will do, and then an endless
> > stream of table not big enough warnings will be posted.
> >
> > Also, its only 4MB (IIRC), so who cares.
> 
> I care :-)
> 
> Not because of platforms with not limited memory, but because of platforms
> with boot loaders that have silly kernel size limitations, and start
> scribbling over the DTB or even theirselves when copying a large kernel image.

Right, that's the weird platforms clause above, and those can select the
option.

> BTW, is there any particular reason these huge arrays are in BSS, and not
> allocated dynamically? That would solve my problems as well...

Is there a memory allocator available before _any_ locks are used, and
that itself also doesn't use locks?

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Peter Zijlstra]

On Tue, Nov 29, 2016 at 01:29:07PM +0100, Peter Zijlstra wrote:
> > BTW, is there any particular reason these huge arrays are in BSS, and not
> > allocated dynamically? That would solve my problems as well...
> 
> Is there a memory allocator available before _any_ locks are used, and
> that itself also doesn't use locks?

And if that is, the platform could use that to allocate .bss, no?

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Geert Uytterhoeven]

On Tue, Nov 29, 2016 at 1:29 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, Nov 29, 2016 at 12:52:04PM +0100, Geert Uytterhoeven wrote:
>> > Nah, users don't need more senseless options. This is really only useful
>> > for dinky platforms or platforms with limited static image size (like
>> > sparc64).
>> >
>> > If you make this user selectable, someone will do, and then an endless
>> > stream of table not big enough warnings will be posted.
>> >
>> > Also, its only 4MB (IIRC), so who cares.
>>
>> I care :-)
>>
>> Not because of platforms with not limited memory, but because of platforms
>> with boot loaders that have silly kernel size limitations, and start
>> scribbling over the DTB or even theirselves when copying a large kernel image.
>
> Right, that's the weird platforms clause above, and those can select the
> option.

Their Kconfig files can select it. The users can't.
What about making it visible depending on EXPERT?

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Peter Zijlstra]

On Tue, Nov 29, 2016 at 02:26:47PM +0100, Geert Uytterhoeven wrote:
> On Tue, Nov 29, 2016 at 1:29 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> > On Tue, Nov 29, 2016 at 12:52:04PM +0100, Geert Uytterhoeven wrote:

> >> Not because of platforms with not limited memory, but because of platforms
> >> with boot loaders that have silly kernel size limitations, and start
> >> scribbling over the DTB or even theirselves when copying a large kernel image.
> >
> > Right, that's the weird platforms clause above, and those can select the
> > option.
> 
> Their Kconfig files can select it. The users can't.
> What about making it visible depending on EXPERT?

Not understanding, why would a user ever need it? The platform knows if
its has funny boot image size limits, no?

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Geert Uytterhoeven]

Hi Peter,

On Tue, Nov 29, 2016 at 2:31 PM, Peter Zijlstra <peterz@infradead.org> wrote:
> On Tue, Nov 29, 2016 at 02:26:47PM +0100, Geert Uytterhoeven wrote:
>> On Tue, Nov 29, 2016 at 1:29 PM, Peter Zijlstra <peterz@infradead.org> wrote:
>> > On Tue, Nov 29, 2016 at 12:52:04PM +0100, Geert Uytterhoeven wrote:
>
>> >> Not because of platforms with not limited memory, but because of platforms
>> >> with boot loaders that have silly kernel size limitations, and start
>> >> scribbling over the DTB or even theirselves when copying a large kernel image.
>> >
>> > Right, that's the weird platforms clause above, and those can select the
>> > option.
>>
>> Their Kconfig files can select it. The users can't.
>> What about making it visible depending on EXPERT?
>
> Not understanding, why would a user ever need it? The platform knows if
> its has funny boot image size limits, no?

The boot loader does not come with the kernel, so the platform cannot
know for sure.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds

Re: [PATCH v3 0/2] Ajust lockdep static allocations for sparc

[Peter Zijlstra]

On Tue, Nov 29, 2016 at 02:39:20PM +0100, Geert Uytterhoeven wrote:

> > Not understanding, why would a user ever need it? The platform knows if
> > its has funny boot image size limits, no?
> 
> The boot loader does not come with the kernel, so the platform cannot
> know for sure.

Why would anybody use a bootloader that imposes weird restrictions on
their platform? That is, isn't that simply a broken bootloader?