linux-kernel - [PATCH v2 3/4] hotplug, x86: Disable ARCH_CPU_PROBE

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Date:	Thu, 29 Aug 2013 18:22:08 -0600
From:	Toshi Kani <toshi.kani@...com>
To:	rjw@...k.pl
Cc:	mingo@...hat.com, hpa@...ux.intel.com, tglx@...utronix.de,
	gregkh@...uxfoundation.org, benh@...nel.crashing.org,
	linux-acpi@...r.kernel.org, x86@...nel.org,
	linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org,
	nfont@...ux.vnet.ibm.com, fenghua.yu@...el.com, bp@...e.de,
	srivatsa.bhat@...ux.vnet.ibm.com, isimatu.yasuaki@...fujitsu.com,
	Toshi Kani <toshi.kani@...com>
Subject: [PATCH v2 3/4] hotplug, x86: Disable ARCH_CPU_PROBE_RELEASE on x86

Commit d7c53c9e enabled ARCH_CPU_PROBE_RELEASE on x86 in order to
serialize CPU online/offline operations.  Although it is the config
option to enable CPU hotplug test interfaces, probe & release, it is
also the option to enable cpu_hotplug_driver_lock() as well.  Therefore,
this option had to be enabled on x86 with dummy arch_cpu_probe() and
arch_cpu_release().

Since then, lock_device_hotplug() was introduced to serialize CPU
online/offline & hotplug operations.  Therefore, this config option
is no longer required for the serialization.  This patch disables
this config option on x86 and revert the changes made by commit
d7c53c9e.

Signed-off-by: Toshi Kani <toshi.kani@...com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
---
 arch/x86/Kconfig          |    4 ----
 arch/x86/kernel/smpboot.c |   21 ---------------------
 2 files changed, 25 deletions(-)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b32ebf9..c87e49a 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -255,10 +255,6 @@ config ARCH_HWEIGHT_CFLAGS
 	default "-fcall-saved-ecx -fcall-saved-edx" if X86_32
 	default "-fcall-saved-rdi -fcall-saved-rsi -fcall-saved-rdx -fcall-saved-rcx -fcall-saved-r8 -fcall-saved-r9 -fcall-saved-r10 -fcall-saved-r11" if X86_64
 
-config ARCH_CPU_PROBE_RELEASE
-	def_bool y
-	depends on HOTPLUG_CPU
-
 config ARCH_SUPPORTS_UPROBES
 	def_bool y
 
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index aecc98a..5b24a9d 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -82,27 +82,6 @@
 /* State of each CPU */
 DEFINE_PER_CPU(int, cpu_state) = { 0 };
 
-#ifdef CONFIG_HOTPLUG_CPU
-/*
- * We need this for trampoline_base protection from concurrent accesses when
- * off- and onlining cores wildly.
- */
-static DEFINE_MUTEX(x86_cpu_hotplug_driver_mutex);
-
-void cpu_hotplug_driver_lock(void)
-{
-	mutex_lock(&x86_cpu_hotplug_driver_mutex);
-}
-
-void cpu_hotplug_driver_unlock(void)
-{
-	mutex_unlock(&x86_cpu_hotplug_driver_mutex);
-}
-
-ssize_t arch_cpu_probe(const char *buf, size_t count) { return -1; }
-ssize_t arch_cpu_release(const char *buf, size_t count) { return -1; }
-#endif
-
 /* Number of siblings per CPU package */
 int smp_num_siblings = 1;
 EXPORT_SYMBOL(smp_num_siblings);
--
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