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Message-Id: <20080213011310.e27dd9cf.akpm@linux-foundation.org>
Date: Wed, 13 Feb 2008 01:13:10 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, a.p.zijlstra@...llo.nl
Subject: Re: [RFC v2 PATCH] RTTIME watchdog timer proc interface
On Tue, 12 Feb 2008 14:41:42 -0800 Hiroshi Shimamoto <h-shimamoto@...jp.nec.com> wrote:
> From: Hiroshi Shimamoto <h-shimamoto@...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.
How does one set it to `unlimited'?
> And /proc/<pid>/task/<tid>/rttime is also accessible.
Please describe the format in the changelog.
> Signed-off-by: Hiroshi Shimamoto <h-shimamoto@...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;
> +}
get_proc_task() can return NULL, in which case it appears that the kernel
will later oops?
> +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;
`n' should be size_t. And a better name would be nice.
> + 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;
min()
> + 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;
min()
> + if (copy_from_user(buffer, buf, n))
> + return -EFAULT;
> + new_rlim.rlim_max = simple_strtoul(buffer, &end, 0);
strict_strtoul()?
> + }
> + 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);
hm. Why do we lock on ->group_leader rather than the task itself?
> + 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),
--
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