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Message-ID: <3579218.MGhjC2kLWm@vostro.rjw.lan>
Date: Sun, 18 Aug 2013 03:01:42 +0200
From: "Rafael J. Wysocki" <rjw@...k.pl>
To: Toshi Kani <toshi.kani@...com>
Cc: mingo@...hat.com, hpa@...ux.intel.com, tglx@...utronix.de,
gregkh@...uxfoundation.org, benh@...nel.crashing.org,
x86@...nel.org, linuxppc-dev@...ts.ozlabs.org,
linux-kernel@...r.kernel.org, fenghua.yu@...el.com, bp@...e.de,
srivatsa.bhat@...ux.vnet.ibm.com, isimatu.yasuaki@...fujitsu.com
Subject: Re: [PATCH 4/4] hotplug, powerpc, x86: Remove cpu_hotplug_driver_lock()
On Saturday, August 17, 2013 01:46:59 PM Toshi Kani wrote:
> cpu_hotplug_driver_lock() serializes CPU online/offline operations
> when ARCH_CPU_PROBE_RELEASE is set. This lock interface is no longer
> necessary with the following reason:
>
> - lock_device_hotplug() now protects CPU online/offline operations,
> including the probe & release interfaces enabled by
> ARCH_CPU_PROBE_RELEASE. The use of cpu_hotplug_driver_lock() is
> redundant.
> - cpu_hotplug_driver_lock() is only valid when ARCH_CPU_PROBE_RELEASE
> is defined, which is misleading and is only enabled on powerpc.
>
> This patch removes the cpu_hotplug_driver_lock() interface. As
> a result, ARCH_CPU_PROBE_RELEASE only enables / disables the cpu
> probe & release interface as intended. There is no functional change
> in this patch.
>
> Signed-off-by: Toshi Kani <toshi.kani@...com>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@...el.com>
> ---
> Performed build test only on powerpc.
> ---
> arch/powerpc/kernel/smp.c | 12 ----------
> arch/powerpc/platforms/pseries/dlpar.c | 40 ++++++++++++--------------------
> arch/x86/kernel/topology.c | 2 --
> drivers/base/cpu.c | 10 +-------
> include/linux/cpu.h | 13 ----------
> 5 files changed, 16 insertions(+), 61 deletions(-)
>
> diff --git a/arch/powerpc/kernel/smp.c b/arch/powerpc/kernel/smp.c
> index 38b0ba6..1667269 100644
> --- a/arch/powerpc/kernel/smp.c
> +++ b/arch/powerpc/kernel/smp.c
> @@ -763,18 +763,6 @@ void __cpu_die(unsigned int cpu)
> smp_ops->cpu_die(cpu);
> }
>
> -static DEFINE_MUTEX(powerpc_cpu_hotplug_driver_mutex);
> -
> -void cpu_hotplug_driver_lock()
> -{
> - mutex_lock(&powerpc_cpu_hotplug_driver_mutex);
> -}
> -
> -void cpu_hotplug_driver_unlock()
> -{
> - mutex_unlock(&powerpc_cpu_hotplug_driver_mutex);
> -}
> -
> void cpu_die(void)
> {
> if (ppc_md.cpu_die)
> diff --git a/arch/powerpc/platforms/pseries/dlpar.c b/arch/powerpc/platforms/pseries/dlpar.c
> index a1a7b9a..e39325d 100644
> --- a/arch/powerpc/platforms/pseries/dlpar.c
> +++ b/arch/powerpc/platforms/pseries/dlpar.c
> @@ -387,18 +387,13 @@ static ssize_t dlpar_cpu_probe(const char *buf, size_t count)
> char *cpu_name;
> int rc;
>
> - cpu_hotplug_driver_lock();
> rc = strict_strtoul(buf, 0, &drc_index);
> - if (rc) {
> - rc = -EINVAL;
> - goto out;
> - }
> + if (rc)
> + return -EINVAL;
>
> dn = dlpar_configure_connector(drc_index);
> - if (!dn) {
> - rc = -EINVAL;
> - goto out;
> - }
> + if (!dn)
> + return -EINVAL;
>
> /* configure-connector reports cpus as living in the base
> * directory of the device tree. CPUs actually live in the
> @@ -407,8 +402,7 @@ static ssize_t dlpar_cpu_probe(const char *buf, size_t count)
> cpu_name = kasprintf(GFP_KERNEL, "/cpus%s", dn->full_name);
> if (!cpu_name) {
> dlpar_free_cc_nodes(dn);
> - rc = -ENOMEM;
> - goto out;
> + return -ENOMEM;
> }
>
> kfree(dn->full_name);
> @@ -417,22 +411,21 @@ static ssize_t dlpar_cpu_probe(const char *buf, size_t count)
> rc = dlpar_acquire_drc(drc_index);
> if (rc) {
> dlpar_free_cc_nodes(dn);
> - rc = -EINVAL;
> - goto out;
> + return -EINVAL;
> }
>
> rc = dlpar_attach_node(dn);
> if (rc) {
> dlpar_release_drc(drc_index);
> dlpar_free_cc_nodes(dn);
> - goto out;
> + return rc;
> }
>
> rc = dlpar_online_cpu(dn);
> -out:
> - cpu_hotplug_driver_unlock();
> + if (rc)
> + return rc;
>
> - return rc ? rc : count;
> + return count;
> }
>
> static int dlpar_offline_cpu(struct device_node *dn)
> @@ -505,30 +498,27 @@ static ssize_t dlpar_cpu_release(const char *buf, size_t count)
> return -EINVAL;
> }
>
> - cpu_hotplug_driver_lock();
> rc = dlpar_offline_cpu(dn);
> if (rc) {
> of_node_put(dn);
> - rc = -EINVAL;
> - goto out;
> + return -EINVAL;
> }
>
> rc = dlpar_release_drc(*drc_index);
> if (rc) {
> of_node_put(dn);
> - goto out;
> + return rc;
> }
>
> rc = dlpar_detach_node(dn);
> if (rc) {
> dlpar_acquire_drc(*drc_index);
> - goto out;
> + return rc;
> }
>
> of_node_put(dn);
> -out:
> - cpu_hotplug_driver_unlock();
> - return rc ? rc : count;
> +
> + return count;
> }
>
> static int __init pseries_dlpar_init(void)
> diff --git a/arch/x86/kernel/topology.c b/arch/x86/kernel/topology.c
> index a3f35eb..649b010 100644
> --- a/arch/x86/kernel/topology.c
> +++ b/arch/x86/kernel/topology.c
> @@ -66,7 +66,6 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
> return -EINVAL;
>
> lock_device_hotplug();
> - cpu_hotplug_driver_lock();
>
> switch (action) {
> case 0:
> @@ -91,7 +90,6 @@ int __ref _debug_hotplug_cpu(int cpu, int action)
> ret = -EINVAL;
> }
>
> - cpu_hotplug_driver_unlock();
> unlock_device_hotplug();
>
> return ret;
> diff --git a/drivers/base/cpu.c b/drivers/base/cpu.c
> index 4cc6928..b4ebd7b 100644
> --- a/drivers/base/cpu.c
> +++ b/drivers/base/cpu.c
> @@ -45,8 +45,6 @@ static int __ref cpu_subsys_online(struct device *dev)
> int from_nid, to_nid;
> int ret;
>
> - cpu_hotplug_driver_lock();
> -
> from_nid = cpu_to_node(cpuid);
> ret = cpu_up(cpuid);
> /*
> @@ -57,18 +55,12 @@ static int __ref cpu_subsys_online(struct device *dev)
> if (from_nid != to_nid)
> change_cpu_under_node(cpu, from_nid, to_nid);
>
> - cpu_hotplug_driver_unlock();
> return ret;
> }
>
> static int cpu_subsys_offline(struct device *dev)
> {
> - int ret;
> -
> - cpu_hotplug_driver_lock();
> - ret = cpu_down(dev->id);
> - cpu_hotplug_driver_unlock();
> - return ret;
> + return cpu_down(dev->id);
> }
>
> void unregister_cpu(struct cpu *cpu)
> diff --git a/include/linux/cpu.h b/include/linux/cpu.h
> index ab0eade..e847ef8 100644
> --- a/include/linux/cpu.h
> +++ b/include/linux/cpu.h
> @@ -182,19 +182,6 @@ extern void cpu_hotplug_enable(void);
> void clear_tasks_mm_cpumask(int cpu);
> int cpu_down(unsigned int cpu);
>
> -#ifdef CONFIG_ARCH_CPU_PROBE_RELEASE
> -extern void cpu_hotplug_driver_lock(void);
> -extern void cpu_hotplug_driver_unlock(void);
> -#else
> -static inline void cpu_hotplug_driver_lock(void)
> -{
> -}
> -
> -static inline void cpu_hotplug_driver_unlock(void)
> -{
> -}
> -#endif
> -
> #else /* CONFIG_HOTPLUG_CPU */
>
> #define get_online_cpus() do { } while (0)
> --
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--
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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