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

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Message-Id: <20190408023015.GH14111@linux.ibm.com>
Date:   Sun, 7 Apr 2019 19:30:15 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     "Joel Fernandes (Google)" <joel@...lfernandes.org>
Cc:     linux-kernel@...r.kernel.org,
        Josh Triplett <josh@...htriplett.org>,
        Steven Rostedt <rostedt@...dmis.org>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
        Lai Jiangshan <jiangshanlai@...il.com>,
        kernel-team@...roid.com, Arnd Bergmann <arnd@...db.de>,
        linux-arch@...r.kernel.org
Subject: Re: [PATCH v2] srcu: Remove unused vmlinux srcu linker entries

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@...htriplett.org>
> Cc: Steven Rostedt <rostedt@...dmis.org>
> Cc: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
> Cc: Lai Jiangshan <jiangshanlai@...il.com>
> Cc: kernel-team@...roid.com
> Cc: paulmck@...ux.vnet.ibm.com
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.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
>