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    Subject[tip:perf/core] perf: Sysfs enumeration
    Commit-ID:  abe43400579d5de0078c2d3a760e6598e183f871
    Gitweb: http://git.kernel.org/tip/abe43400579d5de0078c2d3a760e6598e183f871
    Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
    AuthorDate: Wed, 17 Nov 2010 23:17:37 +0100
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Thu, 16 Dec 2010 11:36:43 +0100

    perf: Sysfs enumeration

    Simple sysfs emumeration of the PMUs.

    Use a "event_source" bus, and add PMU devices using their name.

    Each PMU device has a type attribute which contrains the value needed
    for perf_event_attr::type to identify this PMU.

    This is the minimal stub needed to start using this interface,
    we'll consider extending the sysfs usage later.

    Cc: Kay Sievers <kay.sievers@vrfy.org>
    Cc: Greg KH <gregkh@suse.de>
    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    LKML-Reference: <20101117222056.316982569@chello.nl>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    include/linux/perf_event.h | 1 +
    kernel/perf_event.c | 95 +++++++++++++++++++++++++++++++++++++++++++-
    2 files changed, 95 insertions(+), 1 deletions(-)

    diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
    index 21206d2..dda5b0a 100644
    --- a/include/linux/perf_event.h
    +++ b/include/linux/perf_event.h
    @@ -588,6 +588,7 @@ struct perf_event;
    struct pmu {
    struct list_head entry;

    + struct device *dev;
    char *name;
    int type;

    diff --git a/kernel/perf_event.c b/kernel/perf_event.c
    index 8f09bc8..11847bf 100644
    --- a/kernel/perf_event.c
    +++ b/kernel/perf_event.c
    @@ -24,6 +24,7 @@
    #include <linux/ptrace.h>
    #include <linux/reboot.h>
    #include <linux/vmstat.h>
    +#include <linux/device.h>
    #include <linux/vmalloc.h>
    #include <linux/hardirq.h>
    #include <linux/rculist.h>
    @@ -5308,6 +5309,58 @@ out:
    }
    static struct idr pmu_idr;

    +static ssize_t
    +type_show(struct device *dev, struct device_attribute *attr, char *page)
    +{
    + struct pmu *pmu = dev_get_drvdata(dev);
    +
    + return snprintf(page, PAGE_SIZE-1, "%d\n", pmu->type);
    +}
    +
    +static struct device_attribute pmu_dev_attrs[] = {
    + __ATTR_RO(type),
    + __ATTR_NULL,
    +};
    +
    +static int pmu_bus_running;
    +static struct bus_type pmu_bus = {
    + .name = "event_source",
    + .dev_attrs = pmu_dev_attrs,
    +};
    +
    +static void pmu_dev_release(struct device *dev)
    +{
    + kfree(dev);
    +}
    +
    +static int pmu_dev_alloc(struct pmu *pmu)
    +{
    + int ret = -ENOMEM;
    +
    + pmu->dev = kzalloc(sizeof(struct device), GFP_KERNEL);
    + if (!pmu->dev)
    + goto out;
    +
    + device_initialize(pmu->dev);
    + ret = dev_set_name(pmu->dev, "%s", pmu->name);
    + if (ret)
    + goto free_dev;
    +
    + dev_set_drvdata(pmu->dev, pmu);
    + pmu->dev->bus = &pmu_bus;
    + pmu->dev->release = pmu_dev_release;
    + ret = device_add(pmu->dev);
    + if (ret)
    + goto free_dev;
    +
    +out:
    + return ret;
    +
    +free_dev:
    + put_device(pmu->dev);
    + goto out;
    +}
    +
    int perf_pmu_register(struct pmu *pmu, char *name, int type)
    {
    int cpu, ret;
    @@ -5336,6 +5389,12 @@ int perf_pmu_register(struct pmu *pmu, char *name, int type)
    }
    pmu->type = type;

    + if (pmu_bus_running) {
    + ret = pmu_dev_alloc(pmu);
    + if (ret)
    + goto free_idr;
    + }
    +
    skip_type:
    pmu->pmu_cpu_context = find_pmu_context(pmu->task_ctx_nr);
    if (pmu->pmu_cpu_context)
    @@ -5343,7 +5402,7 @@ skip_type:

    pmu->pmu_cpu_context = alloc_percpu(struct perf_cpu_context);
    if (!pmu->pmu_cpu_context)
    - goto free_ird;
    + goto free_dev;

    for_each_possible_cpu(cpu) {
    struct perf_cpu_context *cpuctx;
    @@ -5387,6 +5446,10 @@ unlock:

    return ret;

    +free_dev:
    + device_del(pmu->dev);
    + put_device(pmu->dev);
    +
    free_idr:
    if (pmu->type >= PERF_TYPE_MAX)
    idr_remove(&pmu_idr, pmu->type);
    @@ -5412,6 +5475,8 @@ void perf_pmu_unregister(struct pmu *pmu)
    free_percpu(pmu->pmu_disable_count);
    if (pmu->type >= PERF_TYPE_MAX)
    idr_remove(&pmu_idr, pmu->type);
    + device_del(pmu->dev);
    + put_device(pmu->dev);
    free_pmu_context(pmu);
    }

    @@ -6603,3 +6668,31 @@ void __init perf_event_init(void)
    ret = init_hw_breakpoint();
    WARN(ret, "hw_breakpoint initialization failed with: %d", ret);
    }
    +
    +static int __init perf_event_sysfs_init(void)
    +{
    + struct pmu *pmu;
    + int ret;
    +
    + mutex_lock(&pmus_lock);
    +
    + ret = bus_register(&pmu_bus);
    + if (ret)
    + goto unlock;
    +
    + list_for_each_entry(pmu, &pmus, entry) {
    + if (!pmu->name || pmu->type < 0)
    + continue;
    +
    + ret = pmu_dev_alloc(pmu);
    + WARN(ret, "Failed to register pmu: %s, reason %d\n", pmu->name, ret);
    + }
    + pmu_bus_running = 1;
    + ret = 0;
    +
    +unlock:
    + mutex_unlock(&pmus_lock);
    +
    + return ret;
    +}
    +device_initcall(perf_event_sysfs_init);

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