[PATCH v2] srcu: Remove unused vmlinux srcu linker entries

[PATCH v2] srcu: Remove unused vmlinux srcu linker entries

[Joel Fernandes (Google)]

The SRCU for modules optimization (commit title "srcu: Allocate per-CPU
data for DEFINE_SRCU() in modules") introduced vmlinux linker entries
which is unused since it applies only to the built-in vmlinux. So remove
it to prevent any space usage due to the 8 byte alignment it added.
vmlinux.lds.h has no effect on module loading and is not used for
building the module object, so the changes were not needed in the first
place since the optimization is specific to modules.

Tested with SRCU torture_type and rcutorture. Put prints in module
loader to confirm it is able to find and initialize the srcu structures.

Cc: Josh Triplett <josh@joshtriplett.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Cc: Lai Jiangshan <jiangshanlai@gmail.com>
Cc: kernel-team@android.com
Cc: paulmck@linux.vnet.ibm.com
Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>
---
v1->v2: Added more context to change log.

 include/asm-generic/vmlinux.lds.h | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
index c2d919a1566e..f8f6f04c4453 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -338,10 +338,6 @@
 		KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \
 		__stop___tracepoints_ptrs = .;				\
 		*(__tracepoints_strings)/* Tracepoints: strings */	\
-		. = ALIGN(8);						\
-		__start___srcu_struct = .;				\
-		*(___srcu_struct_ptrs)					\
-		__end___srcu_struct = .;				\
 	}								\
 									\
 	.rodata1          : AT(ADDR(.rodata1) - LOAD_OFFSET) {		\
-- 
2.21.0.392.gf8f6787159e-goog

Re: [PATCH v2] srcu: Remove unused vmlinux srcu linker entries

[Paul E. McKenney]

On Sun, Apr 07, 2019 at 08:47:19PM -0400, Joel Fernandes (Google) wrote:
> The SRCU for modules optimization (commit title "srcu: Allocate per-CPU
> data for DEFINE_SRCU() in modules") introduced vmlinux linker entries
> which is unused since it applies only to the built-in vmlinux. So remove
> it to prevent any space usage due to the 8 byte alignment it added.
> vmlinux.lds.h has no effect on module loading and is not used for
> building the module object, so the changes were not needed in the first
> place since the optimization is specific to modules.
> 
> Tested with SRCU torture_type and rcutorture. Put prints in module
> loader to confirm it is able to find and initialize the srcu structures.
> 
> Cc: Josh Triplett <josh@joshtriplett.org>
> Cc: Steven Rostedt <rostedt@goodmis.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
> Cc: Lai Jiangshan <jiangshanlai@gmail.com>
> Cc: kernel-team@android.com
> Cc: paulmck@linux.vnet.ibm.com
> Signed-off-by: Joel Fernandes (Google) <joel@joelfernandes.org>

Queued, thank you, Joel!

							Thanx, Paul

> ---
> v1->v2: Added more context to change log.
> 
>  include/asm-generic/vmlinux.lds.h | 4 ----
>  1 file changed, 4 deletions(-)
> 
> diff --git a/include/asm-generic/vmlinux.lds.h b/include/asm-generic/vmlinux.lds.h
> index c2d919a1566e..f8f6f04c4453 100644
> --- a/include/asm-generic/vmlinux.lds.h
> +++ b/include/asm-generic/vmlinux.lds.h
> @@ -338,10 +338,6 @@
>  		KEEP(*(__tracepoints_ptrs)) /* Tracepoints: pointer array */ \
>  		__stop___tracepoints_ptrs = .;				\
>  		*(__tracepoints_strings)/* Tracepoints: strings */	\
> -		. = ALIGN(8);						\
> -		__start___srcu_struct = .;				\
> -		*(___srcu_struct_ptrs)					\
> -		__end___srcu_struct = .;				\
>  	}								\
>  									\
>  	.rodata1          : AT(ADDR(.rodata1) - LOAD_OFFSET) {		\
> -- 
> 2.21.0.392.gf8f6787159e-goog
>