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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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