linux-kernel - [PATCH tip/core/rcu 2/4] srcu: Remove unused vmlinux srcu linker entries

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Date:   Thu, 30 May 2019 08:04:47 -0700
From:   "Paul E. McKenney" <paulmck@...ux.ibm.com>
To:     rcu@...r.kernel.org
Cc:     linux-kernel@...r.kernel.org, mingo@...nel.org,
        jiangshanlai@...il.com, dipankar@...ibm.com,
        akpm@...ux-foundation.org, mathieu.desnoyers@...icios.com,
        josh@...htriplett.org, tglx@...utronix.de, peterz@...radead.org,
        rostedt@...dmis.org, dhowells@...hat.com, edumazet@...gle.com,
        fweisbec@...il.com, oleg@...hat.com, joel@...lfernandes.org,
        kernel-team@...roid.com, paulmck@...ux.vnet.ibm.com,
        "Paul E . McKenney" <paulmck@...ux.ibm.com>
Subject: [PATCH tip/core/rcu 2/4] srcu: Remove unused vmlinux srcu linker entries

From: "Joel Fernandes (Google)" <joel@...lfernandes.org>

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>
Signed-off-by: Paul E. McKenney <paulmck@...ux.ibm.com>
---
 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 ba1ad39468fc..088987e9a3ea 100644
--- a/include/asm-generic/vmlinux.lds.h
+++ b/include/asm-generic/vmlinux.lds.h
@@ -337,10 +337,6 @@
 		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) {		\
-- 
2.17.1