lkml.org 
[lkml]   [2012]   [Apr]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    Date
    From
    Subject[PATCH 1/3] vmevent: Should not grab mutex in the atomic context
    vmevent grabs a mutex in the atomic context, and so this pops up:

    BUG: sleeping function called from invalid context at kernel/mutex.c:271
    in_atomic(): 1, irqs_disabled(): 0, pid: 0, name: swapper/0
    1 lock held by swapper/0/0:
    #0: (&watch->timer){+.-...}, at: [<ffffffff8103eb80>] call_timer_fn+0x0/0xf0
    Pid: 0, comm: swapper/0 Not tainted 3.2.0+ #6
    Call Trace:
    <IRQ> [<ffffffff8102f5da>] __might_sleep+0x12a/0x1e0
    [<ffffffff810bd990>] ? vmevent_match+0xe0/0xe0
    [<ffffffff81321f2c>] mutex_lock_nested+0x3c/0x340
    [<ffffffff81064b33>] ? lock_acquire+0xa3/0xc0
    [<ffffffff8103eb80>] ? internal_add_timer+0x110/0x110
    [<ffffffff810bd990>] ? vmevent_match+0xe0/0xe0
    [<ffffffff810bda21>] vmevent_timer_fn+0x91/0xf0
    [<ffffffff810bd990>] ? vmevent_match+0xe0/0xe0
    [<ffffffff8103ebf5>] call_timer_fn+0x75/0xf0
    [<ffffffff8103eb80>] ? internal_add_timer+0x110/0x110
    [<ffffffff81062fdd>] ? trace_hardirqs_on_caller+0x7d/0x120
    [<ffffffff8103ee9f>] run_timer_softirq+0x10f/0x1e0
    [<ffffffff810bd990>] ? vmevent_match+0xe0/0xe0
    [<ffffffff81038d90>] __do_softirq+0xb0/0x160
    [<ffffffff8105eb0f>] ? tick_program_event+0x1f/0x30
    [<ffffffff8132642c>] call_softirq+0x1c/0x26
    [<ffffffff810036d5>] do_softirq+0x85/0xc0

    This patch fixes the issue by removing the mutex and making the logic
    lock-free.

    Signed-off-by: Anton Vorontsov <anton.vorontsov@linaro.org>
    ---
    mm/vmevent.c | 35 ++++++++++++-----------------------
    1 files changed, 12 insertions(+), 23 deletions(-)

    diff --git a/mm/vmevent.c b/mm/vmevent.c
    index 1847b56..a56174f 100644
    --- a/mm/vmevent.c
    +++ b/mm/vmevent.c
    @@ -1,4 +1,5 @@
    #include <linux/anon_inodes.h>
    +#include <linux/atomic.h>
    #include <linux/vmevent.h>
    #include <linux/syscalls.h>
    #include <linux/timer.h>
    @@ -23,7 +24,7 @@ struct vmevent_watch {
    struct vmevent_config config;

    struct mutex mutex;
    - bool pending;
    + atomic_t pending;

    /*
    * Attributes that are exported as part of delivered VM events.
    @@ -103,20 +104,18 @@ static void vmevent_sample(struct vmevent_watch *watch)
    {
    int i;

    + if (atomic_read(&watch->pending))
    + return;
    if (!vmevent_match(watch))
    return;

    - mutex_lock(&watch->mutex);
    -
    - watch->pending = true;
    -
    for (i = 0; i < watch->nr_attrs; i++) {
    struct vmevent_attr *attr = &watch->sample_attrs[i];

    attr->value = vmevent_sample_attr(watch, attr);
    }

    - mutex_unlock(&watch->mutex);
    + atomic_set(&watch->pending, 1);
    }

    static void vmevent_timer_fn(unsigned long data)
    @@ -125,7 +124,7 @@ static void vmevent_timer_fn(unsigned long data)

    vmevent_sample(watch);

    - if (watch->pending)
    + if (atomic_read(&watch->pending))
    wake_up(&watch->waitq);
    mod_timer(&watch->timer, jiffies +
    nsecs_to_jiffies64(watch->config.sample_period_ns));
    @@ -148,13 +147,9 @@ static unsigned int vmevent_poll(struct file *file, poll_table *wait)

    poll_wait(file, &watch->waitq, wait);

    - mutex_lock(&watch->mutex);
    -
    - if (watch->pending)
    + if (atomic_read(&watch->pending))
    events |= POLLIN;

    - mutex_unlock(&watch->mutex);
    -
    return events;
    }

    @@ -171,15 +166,13 @@ static ssize_t vmevent_read(struct file *file, char __user *buf, size_t count, l
    if (count < size)
    return -EINVAL;

    - mutex_lock(&watch->mutex);
    -
    - if (!watch->pending)
    - goto out_unlock;
    + if (!atomic_read(&watch->pending))
    + goto out;

    event = kmalloc(size, GFP_KERNEL);
    if (!event) {
    ret = -ENOMEM;
    - goto out_unlock;
    + goto out;
    }

    for (i = 0; i < watch->nr_attrs; i++) {
    @@ -195,14 +188,10 @@ static ssize_t vmevent_read(struct file *file, char __user *buf, size_t count, l

    ret = count;

    - watch->pending = false;
    -
    + atomic_set(&watch->pending, 0);
    out_free:
    kfree(event);
    -
    -out_unlock:
    - mutex_unlock(&watch->mutex);
    -
    +out:
    return ret;
    }

    --
    1.7.7.6


    \
     
     \ /
      Last update: 2012-04-09 01:41    [W:0.025 / U:31.200 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site