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 /proc/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 <[email protected]> --- Changes since v1: * use /proc/taskstats instead of /dev/taskstats include/uapi/linux/taskstats.h | 5 +++ kernel/taskstats.c | 73 +++++++++++++++++++++++++++++++++- 2 files changed, 77 insertions(+), 1 deletion(-) diff --git a/include/uapi/linux/taskstats.h b/include/uapi/linux/taskstats.h index ccbd08709321..077eab84c77e 100644 --- a/include/uapi/linux/taskstats.h +++ b/include/uapi/linux/taskstats.h @@ -214,6 +214,11 @@ enum { #define TASKSTATS_CMD_ATTR_MAX (__TASKSTATS_CMD_ATTR_MAX - 1) +/* ioctl command */ +#define TASKSTATS_IOC_ATTR_PID _IO('T', TASKSTATS_CMD_ATTR_PID) +#define TASKSTATS_IOC_ATTR_TGID _IO('T', TASKSTATS_CMD_ATTR_TGID) + + /* NETLINK_GENERIC related info */ #define TASKSTATS_GENL_NAME "TASKSTATS" diff --git a/kernel/taskstats.c b/kernel/taskstats.c index a2802b6ff4bb..c0f9e2f2308b 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/proc_fs.h> +#include <linux/uio.h> /* * Maximum length of a cpumask that can be specified in @@ -28,6 +30,10 @@ */ #define TASKSTATS_CPUMASK_MAXLEN (100+6*NR_CPUS) +#ifdef CONFIG_PROC_FS +#define PROC_TASKSTATS "taskstats" +#endif + static DEFINE_PER_CPU(__u32, taskstats_seqnum); static int family_registered; struct kmem_cache *taskstats_cache; @@ -666,6 +672,60 @@ static struct genl_family family __ro_after_init = { .n_ops = ARRAY_SIZE(taskstats_ops), }; +#ifdef CONFIG_PROC_FS +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_IOC_ATTR_PID: + ret = taskstats_ioctl_pid_tgid(arg, false); + break; + case TASKSTATS_IOC_ATTR_TGID: + ret = taskstats_ioctl_pid_tgid(arg, true); + break; + default: + ret = -EINVAL; + break; + } + + return ret; +} + +static const struct proc_ops taskstats_proc_ops = { + .proc_ioctl = taskstats_ioctl, +#ifdef CONFIG_COMPAT + .proc_compat_ioctl = taskstats_ioctl, +#endif +}; +#endif + + /* Needed early in initialization */ void __init taskstats_init_early(void) { @@ -682,9 +742,20 @@ static int __init taskstats_init(void) { int rc; +#ifdef CONFIG_PROC_FS + if (!proc_create(PROC_TASKSTATS, 0, NULL, &taskstats_proc_ops)) { + pr_err("failed to create /proc/%s\n", PROC_TASKSTATS); + return -1; + } +#endif + rc = genl_register_family(&family); - if (rc) + if (rc) { +#ifdef CONFIG_PROC_FS + remove_proc_entry(PROC_TASKSTATS, NULL); +#endif return rc; + } family_registered = 1; pr_info("registered taskstats version %d\n", TASKSTATS_GENL_VERSION); -- 2.17.2
