rcu: Make SRCU optional by using CONFIG_SRCU

SRCU is not necessary to be compiled by default in all cases. For tinification
efforts not compiling SRCU unless necessary is desirable.

The current patch tries to make compiling SRCU optional by introducing a new
Kconfig option CONFIG_SRCU which is selected when any of the components making
use of SRCU are selected.

If we do not select CONFIG_SRCU, srcu.o will not be compiled at all.

   text    data     bss     dec     hex filename
   2007       0       0    2007     7d7 kernel/rcu/srcu.o

Size of arch/powerpc/boot/zImage changes from

   text    data     bss     dec     hex filename
 831552   64180   23944  919676   e087c arch/powerpc/boot/zImage : before
 829504   64180   23952  917636   e0084 arch/powerpc/boot/zImage : after

so the savings are about ~2000 bytes.

Signed-off-by: Pranith Kumar <bobby.prani@gmail.com>
CC: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
CC: Josh Triplett <josh@joshtriplett.org>
CC: Lai Jiangshan <laijs@cn.fujitsu.com>
Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
[ paulmck: resolve conflict due to removal of arch/ia64/kvm/Kconfig. ]

diff --git a/arch/arm/kvm/Kconfig b/arch/arm/kvm/Kconfig
index 466bd29..3afee5f 100644 (file)
--- a/arch/arm/kvm/Kconfig
+++ b/arch/arm/kvm/Kconfig
@@ -23,6 +23,7 @@ config KVM
        select HAVE_KVM_CPU_RELAX_INTERCEPT
        select KVM_MMIO
        select KVM_ARM_HOST
+       select SRCU
        depends on ARM_VIRT_EXT && ARM_LPAE
        ---help---
          Support hosting virtualized guest machines. You will also

diff --git a/arch/arm64/kvm/Kconfig b/arch/arm64/kvm/Kconfig
index 8ba85e9..b334084 100644 (file)
--- a/arch/arm64/kvm/Kconfig
+++ b/arch/arm64/kvm/Kconfig
@@ -26,6 +26,7 @@ config KVM
        select KVM_ARM_HOST
        select KVM_ARM_VGIC
        select KVM_ARM_TIMER
+       select SRCU
        ---help---
          Support hosting virtualized guest machines.
 

diff --git a/arch/mips/kvm/Kconfig b/arch/mips/kvm/Kconfig
index 30e334e..2ae1282 100644 (file)
--- a/arch/mips/kvm/Kconfig
+++ b/arch/mips/kvm/Kconfig
@@ -20,6 +20,7 @@ config KVM
        select PREEMPT_NOTIFIERS
        select ANON_INODES
        select KVM_MMIO
+       select SRCU
        ---help---
          Support for hosting Guest kernels.
          Currently supported on MIPS32 processors.

diff --git a/arch/powerpc/kvm/Kconfig b/arch/powerpc/kvm/Kconfig
index f5769f1..11850f3 100644 (file)
--- a/arch/powerpc/kvm/Kconfig
+++ b/arch/powerpc/kvm/Kconfig
@@ -21,6 +21,7 @@ config KVM
        select PREEMPT_NOTIFIERS
        select ANON_INODES
        select HAVE_KVM_EVENTFD
+       select SRCU
 
 config KVM_BOOK3S_HANDLER
        bool

diff --git a/arch/s390/kvm/Kconfig b/arch/s390/kvm/Kconfig
index 646db9c..5fce52c 100644 (file)
--- a/arch/s390/kvm/Kconfig
+++ b/arch/s390/kvm/Kconfig
@@ -28,6 +28,7 @@ config KVM
        select HAVE_KVM_IRQCHIP
        select HAVE_KVM_IRQFD
        select HAVE_KVM_IRQ_ROUTING
+       select SRCU
        ---help---
          Support hosting paravirtualized guest machines using the SIE
          virtualization capability on the mainframe. This should work

diff --git a/arch/tile/kvm/Kconfig b/arch/tile/kvm/Kconfig
index 2298cb1..1e968f7 100644 (file)
--- a/arch/tile/kvm/Kconfig
+++ b/arch/tile/kvm/Kconfig
@@ -21,6 +21,7 @@ config KVM
        depends on HAVE_KVM && MODULES
        select PREEMPT_NOTIFIERS
        select ANON_INODES
+       select SRCU
        ---help---
          Support hosting paravirtualized guest machines.
 

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ba397bd..6612699 100644 (file)
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -138,6 +138,7 @@ config X86
        select HAVE_ACPI_APEI_NMI if ACPI
        select ACPI_LEGACY_TABLES_LOOKUP if ACPI
        select X86_FEATURE_NAMES if PROC_FS
+       select SRCU
 
 config INSTRUCTION_DECODER
        def_bool y

diff --git a/arch/x86/kvm/Kconfig b/arch/x86/kvm/Kconfig
index f9d16ff..7dc7ba5 100644 (file)
--- a/arch/x86/kvm/Kconfig
+++ b/arch/x86/kvm/Kconfig
@@ -40,6 +40,7 @@ config KVM
        select HAVE_KVM_MSI
        select HAVE_KVM_CPU_RELAX_INTERCEPT
        select KVM_VFIO
+       select SRCU
        ---help---
          Support hosting fully virtualized guest machines using hardware
          virtualization extensions.  You will need a fairly recent

diff --git a/drivers/clk/Kconfig b/drivers/clk/Kconfig
index 3f44f29..91f8613 100644 (file)
--- a/drivers/clk/Kconfig
+++ b/drivers/clk/Kconfig
@@ -13,6 +13,7 @@ config COMMON_CLK
        bool
        select HAVE_CLK_PREPARE
        select CLKDEV_LOOKUP
+       select SRCU
        ---help---
          The common clock framework is a single definition of struct
          clk, useful across many platforms, as well as an

diff --git a/drivers/cpufreq/Kconfig b/drivers/cpufreq/Kconfig
index 29b2ef5..a171fef 100644 (file)
--- a/drivers/cpufreq/Kconfig
+++ b/drivers/cpufreq/Kconfig
@@ -2,6 +2,7 @@ menu "CPU Frequency scaling"
 
 config CPU_FREQ
        bool "CPU Frequency scaling"
+       select SRCU
        help
          CPU Frequency scaling allows you to change the clock speed of 
          CPUs on the fly. This is a nice method to save power, because 

diff --git a/drivers/devfreq/Kconfig b/drivers/devfreq/Kconfig
index faf4e70..3891f67 100644 (file)
--- a/drivers/devfreq/Kconfig
+++ b/drivers/devfreq/Kconfig
@@ -1,5 +1,6 @@
 menuconfig PM_DEVFREQ
        bool "Generic Dynamic Voltage and Frequency Scaling (DVFS) support"
+       select SRCU
        help
          A device may have a list of frequencies and voltages available.
          devfreq, a generic DVFS framework can be registered for a device

diff --git a/drivers/md/Kconfig b/drivers/md/Kconfig
index 5bdedf6..c355a22 100644 (file)
--- a/drivers/md/Kconfig
+++ b/drivers/md/Kconfig
@@ -5,6 +5,7 @@
 menuconfig MD
        bool "Multiple devices driver support (RAID and LVM)"
        depends on BLOCK
+       select SRCU
        help
          Support multiple physical spindles through a single logical device.
          Required for RAID and logical volume management.

diff --git a/drivers/net/Kconfig b/drivers/net/Kconfig
index d6607ee..84673eb 100644 (file)
--- a/drivers/net/Kconfig
+++ b/drivers/net/Kconfig
@@ -197,6 +197,7 @@ config NETCONSOLE_DYNAMIC
 
 config NETPOLL
        def_bool NETCONSOLE
+       select SRCU
 
 config NET_POLL_CONTROLLER
        def_bool NETPOLL

diff --git a/fs/btrfs/Kconfig b/fs/btrfs/Kconfig
index a66768e..80e9c18 100644 (file)
--- a/fs/btrfs/Kconfig
+++ b/fs/btrfs/Kconfig
@@ -8,6 +8,7 @@ config BTRFS_FS
        select LZO_DECOMPRESS
        select RAID6_PQ
        select XOR_BLOCKS
+       select SRCU
 
        help
          Btrfs is a general purpose copy-on-write filesystem with extents,

diff --git a/fs/notify/Kconfig b/fs/notify/Kconfig
index 22c629e..2a24249 100644 (file)
--- a/fs/notify/Kconfig
+++ b/fs/notify/Kconfig
@@ -1,5 +1,6 @@
 config FSNOTIFY
        def_bool n
+       select SRCU
 
 source "fs/notify/dnotify/Kconfig"
 source "fs/notify/inotify/Kconfig"

diff --git a/fs/quota/Kconfig b/fs/quota/Kconfig
index c51df1d..4a09975 100644 (file)
--- a/fs/quota/Kconfig
+++ b/fs/quota/Kconfig
@@ -5,6 +5,7 @@
 config QUOTA
        bool "Quota support"
        select QUOTACTL
+       select SRCU
        help
          If you say Y here, you will be able to set per user limits for disk
          usage (also called disk quotas). Currently, it works for the

diff --git a/init/Kconfig b/init/Kconfig
index 9afb971..f085969 100644 (file)
--- a/init/Kconfig
+++ b/init/Kconfig
@@ -501,9 +501,17 @@ config TINY_RCU
 
 endchoice
 
+config SRCU
+       bool
+       help
+         This option selects the sleepable version of RCU. This version
+         permits arbitrary sleeping or blocking within RCU read-side critical
+         sections.
+
 config TASKS_RCU
        bool "Task_based RCU implementation using voluntary context switch"
        default n
+       select SRCU
        help
          This option enables a task-based RCU implementation that uses
          only voluntary context switch (not preemption!), idle, and
@@ -1595,6 +1603,7 @@ config PERF_EVENTS
        depends on HAVE_PERF_EVENTS
        select ANON_INODES
        select IRQ_WORK
+       select SRCU
        help
          Enable kernel support for various performance events provided
          by software and hardware.

diff --git a/kernel/notifier.c b/kernel/notifier.c
index 4803da6..ae9fc7c 100644 (file)
--- a/kernel/notifier.c
+++ b/kernel/notifier.c
@@ -402,6 +402,7 @@ int raw_notifier_call_chain(struct raw_notifier_head *nh,
 }
 EXPORT_SYMBOL_GPL(raw_notifier_call_chain);
 
+#ifdef CONFIG_SRCU
 /*
  *     SRCU notifier chain routines.    Registration and unregistration
  *     use a mutex, and call_chain is synchronized by SRCU (no locks).
@@ -528,6 +529,8 @@ void srcu_init_notifier_head(struct srcu_notifier_head *nh)
 }
 EXPORT_SYMBOL_GPL(srcu_init_notifier_head);
 
+#endif /* CONFIG_SRCU */
+
 static ATOMIC_NOTIFIER_HEAD(die_chain);
 
 int notrace notify_die(enum die_val val, const char *str,

diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig
index 48b28d3..7e01f78 100644 (file)
--- a/kernel/power/Kconfig
+++ b/kernel/power/Kconfig
@@ -251,6 +251,7 @@ config APM_EMULATION
 
 config PM_OPP
        bool
+       select SRCU
        ---help---
          SOCs have a standard set of tuples consisting of frequency and
          voltage pairs that the device will support per voltage domain. This

diff --git a/kernel/rcu/Makefile b/kernel/rcu/Makefile
index e6fae50..50a8084 100644 (file)
--- a/kernel/rcu/Makefile
+++ b/kernel/rcu/Makefile
@@ -1,4 +1,5 @@
-obj-y += update.o srcu.o
+obj-y += update.o
+obj-$(CONFIG_SRCU) += srcu.o
 obj-$(CONFIG_RCU_TORTURE_TEST) += rcutorture.o
 obj-$(CONFIG_TREE_RCU) += tree.o
 obj-$(CONFIG_PREEMPT_RCU) += tree.o

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 5f2ce61..7a9c93e 100644 (file)
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -1215,6 +1215,7 @@ config RCU_TORTURE_TEST
        tristate "torture tests for RCU"
        depends on DEBUG_KERNEL
        select TORTURE_TEST
+       select SRCU
        default n
        help
          This option provides a kernel module that runs torture tests

diff --git a/mm/Kconfig b/mm/Kconfig
index 1d1ae6b..4395b12 100644 (file)
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -325,6 +325,7 @@ config VIRT_TO_BUS
 
 config MMU_NOTIFIER
        bool
+       select SRCU
 
 config KSM
        bool "Enable KSM for page merging"

diff --git a/security/tomoyo/Kconfig b/security/tomoyo/Kconfig
index 8eb779b..604e718 100644 (file)
--- a/security/tomoyo/Kconfig
+++ b/security/tomoyo/Kconfig
@@ -5,6 +5,7 @@ config SECURITY_TOMOYO
        select SECURITYFS
        select SECURITY_PATH
        select SECURITY_NETWORK
+       select SRCU
        default n
        help
          This selects TOMOYO Linux, pathname-based access control.