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Date: Wed, 13 Feb 2008 09:45:54 -0800
From: Hiroshi Shimamoto <h-shimamoto@...jp.nec.com>
To: Andrew Morton <akpm@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org, mingo@...e.hu, a.p.zijlstra@...llo.nl
Subject: Re: [RFC v2 PATCH] RTTIME watchdog timer proc interface
Andrew Morton wrote:
> 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'?
There is no way now. Will add.
>
>> And /proc/<pid>/task/<tid>/rttime is also accessible.
>
> Please describe the format in the changelog.
I'm sorry I cannot catch your meaning.
>
>> 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?
Yes, it could cause oops. Will fix.
>
>> +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.
Agree.
>
>> + 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()
Thanks, I hadn't noticed 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()?
OK, I should look at it.
>
>> + }
>> + 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?
It's same as setrlimit.
>
>> + 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),
Thanks for reviewing.
Hiroshi Shimamoto
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