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    Subject[RFC v2 PATCH] RTTIME watchdog timer proc interface
    From: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>

    Introduce new proc interface for RTTIME watchdog.
    It makes administrator able to set RTTIME watchdog to existing
    real-time applications without impact.

    $ echo 10000000 > /proc/<pid>/rttime
    set RTTIME current value to 10000000, it means 10sec.

    $ echo "10000000 20000000" > /proc/<pid>/rttime
    set RTTIME current value to 10000000 and max value to 20000000.

    And /proc/<pid>/task/<tid>/rttime is also accessible.

    Signed-off-by: Hiroshi Shimamoto <h-shimamoto@ct.jp.nec.com>
    ---
    fs/proc/base.c | 89 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
    1 files changed, 89 insertions(+), 0 deletions(-)

    diff --git a/fs/proc/base.c b/fs/proc/base.c
    index 7c6b4ec..3212b44 100644
    --- a/fs/proc/base.c
    +++ b/fs/proc/base.c
    @@ -381,6 +381,93 @@ static const struct file_operations proc_lstats_operations = {

    #endif

    +static int rttime_show_proc(struct seq_file *m, void *v)
    +{
    + struct task_struct *task = m->private;
    + struct signal_struct *signal = task->signal;
    + struct rlimit *rt = &signal->rlim[RLIMIT_RTTIME];
    +
    + if (rt->rlim_cur == RLIM_INFINITY)
    + seq_printf(m, "unlimited ");
    + else
    + seq_printf(m, "%lu ", rt->rlim_cur);
    +
    + if (rt->rlim_max == RLIM_INFINITY)
    + seq_printf(m, "unlimited\n");
    + else
    + seq_printf(m, "%lu\n", rt->rlim_max);
    +
    + return 0;
    +}
    +
    +static int rttime_open(struct inode *inode, struct file *file)
    +{
    + int ret;
    + struct seq_file *m;
    + struct task_struct *task = get_proc_task(inode);
    +
    + ret = single_open(file, rttime_show_proc, NULL);
    + if (!ret) {
    + m = file->private_data;
    + m->private = task;
    + }
    + return ret;
    +}
    +
    +static ssize_t rttime_write(struct file *file,
    + const char __user *buf,
    + size_t count,
    + loff_t *ppos)
    +{
    + struct seq_file *m = file->private_data;
    + struct task_struct *task = m->private;
    + char buffer[PROC_NUMBUF], *end;
    + struct rlimit new_rlim, *old_rlim;
    + int n, ret;
    +
    + old_rlim = task->signal->rlim + RLIMIT_RTTIME;
    + new_rlim = *old_rlim;
    + memset(buffer, 0, sizeof(buffer));
    + n = count;
    + if (n > sizeof(buffer) - 1)
    + n = sizeof(buffer) - 1;
    + if (copy_from_user(buffer, buf, n))
    + return -EFAULT;
    + new_rlim.rlim_cur = simple_strtoul(buffer, &end, 0);
    + if (*end == ' ') {
    + ++end;
    + buf += end - buffer;
    + memset(buffer, 0, sizeof(buffer));
    + n = count - (end - buffer);
    + if (n > sizeof(buffer) - 1)
    + n = sizeof(buffer) - 1;
    + if (copy_from_user(buffer, buf, n))
    + return -EFAULT;
    + new_rlim.rlim_max = simple_strtoul(buffer, &end, 0);
    + }
    + if (new_rlim.rlim_cur > new_rlim.rlim_max)
    + return -EINVAL;
    + if ((new_rlim.rlim_max > old_rlim->rlim_max) &&
    + !capable(CAP_SYS_RESOURCE))
    + return -EPERM;
    + ret = security_task_setrlimit(RLIMIT_RTTIME, &new_rlim);
    + if (ret)
    + return ret;
    + task_lock(task->group_leader);
    + *old_rlim = new_rlim;
    + task_unlock(task->group_leader);
    +
    + return count;
    +}
    +
    +static const struct file_operations proc_rttime_operations = {
    + .open = rttime_open,
    + .read = seq_read,
    + .write = rttime_write,
    + .llseek = seq_lseek,
    + .release = single_release,
    +};
    +
    /* The badness from the OOM killer */
    unsigned long badness(struct task_struct *p, unsigned long uptime);
    static int proc_oom_score(struct task_struct *task, char *buffer)
    @@ -2300,6 +2387,7 @@ static const struct pid_entry tgid_base_stuff[] = {
    LNK("exe", exe),
    REG("mounts", S_IRUGO, mounts),
    REG("mountstats", S_IRUSR, mountstats),
    + REG("rttime", S_IRUSR|S_IWUSR, rttime),
    #ifdef CONFIG_PROC_PAGE_MONITOR
    REG("clear_refs", S_IWUSR, clear_refs),
    REG("smaps", S_IRUGO, smaps),
    @@ -2630,6 +2718,7 @@ static const struct pid_entry tid_base_stuff[] = {
    LNK("root", root),
    LNK("exe", exe),
    REG("mounts", S_IRUGO, mounts),
    + REG("rttime", S_IRUSR|S_IWUSR, rttime),
    #ifdef CONFIG_PROC_PAGE_MONITOR
    REG("clear_refs", S_IWUSR, clear_refs),
    REG("smaps", S_IRUGO, smaps),
    --
    1.5.3.8


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