If a program needs monitor lots of process's status, it needs two
syscalls for every process. The first one is telling kernel which
pid/tgid should be monitored by send a command(write socket) to kernel.
The second one is read the statistics by read socket. This patch add
a new interface /dev/taskstats to reduce two syscalls to one ioctl.
The user just set the target pid/tgid to the struct taskstats.ac_pid,
then kernel will collect statistics for that pid/tgid.
Signed-off-by: Weiping Zhang <zhangweip...@didiglobal.com>
---
kernel/taskstats.c | 71 +++++++++++++++++++++++++++++++++++++++++++++-
1 file changed, 70 insertions(+), 1 deletion(-)
diff --git a/kernel/taskstats.c b/kernel/taskstats.c
index a2802b6ff4bb..68188cc9663d 100644
--- a/kernel/taskstats.c
+++ b/kernel/taskstats.c
@@ -21,6 +21,8 @@
#include <net/genetlink.h>
#include <linux/atomic.h>
#include <linux/sched/cputime.h>
+#include <linux/miscdevice.h>
+#include <linux/uio.h>
/*
* Maximum length of a cpumask that can be specified in
@@ -666,6 +668,67 @@ static struct genl_family family __ro_after_init = {
.n_ops = ARRAY_SIZE(taskstats_ops),
};
+static long taskstats_ioctl_pid_tgid(unsigned long arg, bool tgid)
+{
+ struct taskstats kstat;
+ struct taskstats *ustat = (struct taskstats *)arg;
+ u32 id;
+ unsigned long offset = offsetof(struct taskstats, ac_pid);
+ long ret;
+
+ /* userspace set monitored pid/tgid to the field "ac_pid" */
+ if (unlikely(copy_from_user(&id, (void *)(arg + offset), sizeof(u32))))
+ return -EFAULT;
+
+ if (tgid)
+ ret = fill_stats_for_tgid(id, &kstat);
+ else
+ ret = fill_stats_for_pid(id, &kstat);
+ if (ret < 0)
+ return ret;
+
+ if (unlikely(copy_to_user(ustat, &kstat, sizeof(struct taskstats))))
+ return -EFAULT;
+
+ return 0;
+}
+
+static long taskstats_ioctl(struct file *file, unsigned int cmd, unsigned long
arg)
+{
+ long ret;
+
+ switch (cmd) {
+ case TASKSTATS_CMD_ATTR_PID:
+ ret = taskstats_ioctl_pid_tgid(arg, false);
+ break;
+ case TASKSTATS_CMD_ATTR_TGID:
+ ret = taskstats_ioctl_pid_tgid(arg, true);
+ break;
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ return ret;
+}
+
+static const struct file_operations taskstats_ctl_fops = {
+ .open = nonseekable_open,
+ .unlocked_ioctl = taskstats_ioctl,
+#ifdef CONFIG_COMPAT
+ .compat_ioctl = taskstats_ioctl,
+#endif
+ .owner = THIS_MODULE,
+ .llseek = noop_llseek,
+};
+
+static struct miscdevice taskstats_misc = {
+ .minor = MISC_DYNAMIC_MINOR,
+ .name = "taskstats",
+ .fops = &taskstats_ctl_fops,
+};
+
+
/* Needed early in initialization */
void __init taskstats_init_early(void)
{
@@ -682,9 +745,15 @@ static int __init taskstats_init(void)
{
int rc;
+ rc = misc_register(&taskstats_misc);
+ if (rc < 0)
+ return rc;
+
rc = genl_register_family(&family);
- if (rc)
+ if (rc) {
+ misc_deregister(&taskstats_misc);
return rc;
+ }
family_registered = 1;
pr_info("registered taskstats version %d\n", TASKSTATS_GENL_VERSION);
--
2.17.2
