Re: [patch 1/4] add basic task isolation prctl interface

Marcelo Tosatti
2021-08-02T14:17:52Z

On Mon, Aug 02, 2021 at 10:02:03AM -0400, Nitesh Lal wrote:
> On Fri, Jul 30, 2021 at 4:21 PM Marcelo Tosatti <mtosatti@redhat.com> wrote:
>
> > Add basic prctl task isolation interface, which allows
> > informing the kernel that application is executing
> > latency sensitive code (where interruptions are undesired).
> >
> > Interface is described by task_isolation.rst (added by this patch).
> >
> > Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
> >
> >
> [...]
>
> +extern void __tsk_isol_exit(struct task_struct *tsk);
> > +
> > +static inline void tsk_isol_exit(struct task_struct *tsk)
> > +{
> > + if (tsk->isol_info)
> > + __tsk_isol_exit(tsk);
> > +}
> > +
> > +
> >
>
> nit: we can get rid of this extra line.
>
>
> > +int prctl_task_isolation_feat(unsigned long arg2, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5);
> > +int prctl_task_isolation_get(unsigned long arg2, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5);
> > +int prctl_task_isolation_set(unsigned long arg2, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5);
> > +int prctl_task_isolation_ctrl_get(unsigned long arg2, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5);
> > +int prctl_task_isolation_ctrl_set(unsigned long arg2, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5);
> > +
> > +#else
> > +
> > +static inline void tsk_isol_exit(struct task_struct *tsk)
> > +{
> > +}
> > +
> > +static inline int prctl_task_isolation_feat(unsigned long arg2,
> > + unsigned long arg3,
> > + unsigned long arg4,
> > + unsigned long arg5)
> > +{
> > + return -EOPNOTSUPP;
> > +}
> > +
> > +static inline int prctl_task_isolation_get(unsigned long arg2,
> > + unsigned long arg3,
> > + unsigned long arg4,
> > + unsigned long arg5)
> > +{
> > + return -EOPNOTSUPP;
> > +}
> > +
> > +static inline int prctl_task_isolation_set(unsigned long arg2,
> > + unsigned long arg3,
> > + unsigned long arg4,
> > + unsigned long arg5)
> > +{
> > + return -EOPNOTSUPP;
> > +}
> > +
> > +static inline int prctl_task_isolation_ctrl_get(unsigned long arg2,
> > + unsigned long arg3,
> > + unsigned long arg4,
> > + unsigned long arg5)
> > +{
> > + return -EOPNOTSUPP;
> > +}
> > +
> > +static inline int prctl_task_isolation_ctrl_set(unsigned long arg2,
> > + unsigned long arg3,
> > + unsigned long arg4,
> > + unsigned long arg5)
> > +{
> > + return -EOPNOTSUPP;
> > +}
> > +
> > +#endif /* CONFIG_CPU_ISOLATION */
> > +
> > +#endif /* __LINUX_TASK_ISOL_H */
> > Index: linux-2.6/kernel/task_isolation.c
> > ===================================================================
> > --- /dev/null
> > +++ linux-2.6/kernel/task_isolation.c
> > @@ -0,0 +1,274 @@
> > +// SPDX-License-Identifier: GPL-2.0-only
> > +/*
> > + * Implementation of task isolation.
> > + *
> > + * Authors:
> > + * Chris Metcalf <cmetcalf@mellanox.com>
> > + * Alex Belits <abelits@belits.com>
> > + * Yuri Norov <ynorov@marvell.com>
> > + * Marcelo Tosatti <mtosatti@redhat.com>
> > + */
> > +
> > +#include <linux/sched.h>
> > +#include <linux/task_isolation.h>
> > +#include <linux/prctl.h>
> > +#include <linux/slab.h>
> > +#include <linux/kobject.h>
> > +#include <linux/string.h>
> > +#include <linux/sysfs.h>
> > +#include <linux/init.h>
> > +
> > +static unsigned long default_quiesce_mask;
> > +
> > +static int tsk_isol_alloc_context(struct task_struct *task)
> > +{
> > + struct isol_info *info;
> > +
> > + info = kzalloc(sizeof(*info), GFP_KERNEL);
> > + if (unlikely(!info))
> > + return -ENOMEM;
> > +
> > + task->isol_info = info;
> > + return 0;
> > +}
> > +
> > +void __tsk_isol_exit(struct task_struct *tsk)
> > +{
> > + kfree(tsk->isol_info);
> > + tsk->isol_info = NULL;
> > +}
> > +
> > +static int prctl_task_isolation_feat_quiesce(unsigned long type)
> > +{
> > + switch (type) {
> > + case 0:
> > + return ISOL_F_QUIESCE_VMSTATS;
> > + case ISOL_F_QUIESCE_DEFMASK:
> > + return default_quiesce_mask;
> > + default:
> > + break;
> > + }
> > +
> > + return -EINVAL;
> > +}
> > +
> > +static int task_isolation_get_quiesce(void)
> > +{
> > + if (current->isol_info != NULL)
> >
>
> Should replace the above with just 'if (current->isol_info)'.
>
> + return current->isol_info->quiesce_mask;
> > +
> > + return 0;
> > +}
> > +
> > +static int task_isolation_set_quiesce(unsigned long quiesce_mask)
> > +{
> > + if (quiesce_mask != ISOL_F_QUIESCE_VMSTATS && quiesce_mask != 0)
> > + return -EINVAL;
> > +
> > + current->isol_info->quiesce_mask = quiesce_mask;
> > + return 0;
> > +}
> > +
> > +int prctl_task_isolation_feat(unsigned long feat, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5)
> > +{
> > + switch (feat) {
> > + case 0:
> > + return ISOL_F_QUIESCE;
> > + case ISOL_F_QUIESCE:
> > + return prctl_task_isolation_feat_quiesce(arg3);
> > + default:
> > + break;
> > + }
> > + return -EINVAL;
> > +}
> > +
> > +int prctl_task_isolation_get(unsigned long feat, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5)
> > +{
> > + switch (feat) {
> > + case ISOL_F_QUIESCE:
> > + return task_isolation_get_quiesce();
> > + default:
> > + break;
> > + }
> > + return -EINVAL;
> > +}
> > +
> > +int prctl_task_isolation_set(unsigned long feat, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5)
> > +{
> > + int ret;
> > + bool err_free_ctx = false;
> > +
> > + if (current->isol_info == NULL)
> >
>
> Can replace this with 'if (!current->isol_info).
> There are other places below where similar improvement can be done.
>
>
> > + err_free_ctx = true;
> > +
> > + ret = tsk_isol_alloc_context(current);
> > + if (ret)
> > + return ret;
> > +
> > + switch (feat) {
> > + case ISOL_F_QUIESCE:
> > + ret = task_isolation_set_quiesce(arg3);
> > + if (ret)
> > + break;
> > + return 0;
> > + default:
> > + break;
> > + }
> > +
> > + if (err_free_ctx)
> > + __tsk_isol_exit(current);
> > + return -EINVAL;
> > +}
> > +
> > +int prctl_task_isolation_ctrl_set(unsigned long feat, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5)
> > +{
> > + if (current->isol_info == NULL)
> > + return -EINVAL;
> > +
> > + if (feat != ISOL_F_QUIESCE && feat != 0)
> > + return -EINVAL;
> > +
> > + current->isol_info->active_mask = feat;
> > + return 0;
> > +}
> > +
> > +int prctl_task_isolation_ctrl_get(unsigned long arg2, unsigned long arg3,
> > + unsigned long arg4, unsigned long arg5)
> > +{
> > + if (current->isol_info == NULL)
> > + return 0;
> > +
> > + return current->isol_info->active_mask;
> > +}
> > +
> > +struct qoptions {
> > + unsigned long mask;
> > + char *name;
> > +};
> > +
> > +static struct qoptions qopts[] = {
> > + {ISOL_F_QUIESCE_VMSTATS, "vmstat"},
> > +};
> > +
> > +#define QLEN (sizeof(qopts) / sizeof(struct qoptions))
> > +
> > +static ssize_t default_quiesce_store(struct kobject *kobj,
> > + struct kobj_attribute *attr,
> > + const char *buf, size_t count)
> > +{
> > + char *p, *s;
> > + unsigned long defmask = 0;
> > +
> > + s = (char *)buf;
> > + if (count == 1 && strlen(strim(s)) == 0) {
> > + default_quiesce_mask = 0;
> > + return count;
> > + }
> > +
> > + while ((p = strsep(&s, ",")) != NULL) {
> > + int i;
> > + bool found = false;
> > +
> > + if (!*p)
> > + continue;
> > +
> > + for (i = 0; i < QLEN; i++) {
> > + struct qoptions *opt = &qopts[i];
> > +
> > + if (strncmp(strim(p), opt->name,
> > strlen(opt->name)) == 0) {
> > + defmask |= opt->mask;
> > + found = true;
> > + break;
> > + }
> > + }
> > + if (found == true)
> > + continue;
> > + return -EINVAL;
> > + }
> > + default_quiesce_mask = defmask;
> > +
> > + return count;
> > +}
> > +
> > +#define MAXARRLEN 100
> > +
> > +static ssize_t default_quiesce_show(struct kobject *kobj,
> > + struct kobj_attribute *attr, char *buf)
> > +{
> > + int i;
> > + char tbuf[MAXARRLEN] = "";
> > +
> > + for (i = 0; i < QLEN; i++) {
> > + struct qoptions *opt = &qopts[i];
> > +
> > + if (default_quiesce_mask & opt->mask) {
> > + strlcat(tbuf, opt->name, MAXARRLEN);
> > + strlcat(tbuf, "\n", MAXARRLEN);
> > + }
> > + }
> > +
> > + return sprintf(buf, "%s", tbuf);
> > +}
> > +
> > +static struct kobj_attribute default_quiesce_attr =
> > + __ATTR_RW(default_quiesce);
> > +
> > +static ssize_t available_quiesce_show(struct kobject *kobj,
> > + struct kobj_attribute *attr, char
> > *buf)
> > +{
> > + int i;
> > + char tbuf[MAXARRLEN] = "";
> > +
> > + for (i = 0; i < QLEN; i++) {
> > + struct qoptions *opt = &qopts[i];
> > +
> > + strlcat(tbuf, opt->name, MAXARRLEN);
> > + strlcat(tbuf, "\n", MAXARRLEN);
> > + }
> > +
> > + return sprintf(buf, "%s", tbuf);
> > +}
> > +
> > +static struct kobj_attribute available_quiesce_attr =
> > + __ATTR_RO(available_quiesce);
> > +
> > +static struct attribute *task_isol_attrs[] = {
> > + &available_quiesce_attr.attr,
> > + &default_quiesce_attr.attr,
> > + NULL,
> > +};
> > +
> > +static const struct attribute_group task_isol_attr_group = {
> > + .attrs = task_isol_attrs,
> > + .bin_attrs = NULL,
> > +};
> > +
> > +static int __init task_isol_ksysfs_init(void)
> > +{
> > + int ret;
> > + struct kobject *task_isol_kobj;
> > +
> > + task_isol_kobj = kobject_create_and_add("task_isolation",
> > + kernel_kobj);
> > + if (!task_isol_kobj) {
> > + ret = -ENOMEM;
> > + goto out;
> > + }
> > +
> > + ret = sysfs_create_group(task_isol_kobj, &task_isol_attr_group);
> > + if (ret)
> > + goto out_task_isol_kobj;
> > +
> > + return 0;
> > +
> > +out_task_isol_kobj:
> > + kobject_put(task_isol_kobj);
> > +out:
> > + return ret;
> > +}
> > +
> > +arch_initcall(task_isol_ksysfs_init);
> > Index: linux-2.6/samples/Kconfig
> > ===================================================================
> > --- linux-2.6.orig/samples/Kconfig
> > +++ linux-2.6/samples/Kconfig
> > @@ -223,4 +223,11 @@ config SAMPLE_WATCH_QUEUE
> > Build example userspace program to use the new mount_notify(),
> > sb_notify() syscalls and the KEYCTL_WATCH_KEY keyctl() function.
> >
> > +config SAMPLE_TASK_ISOLATION
> > + bool "task isolation sample"
> > + depends on CC_CAN_LINK && HEADERS_INSTALL
> > + help
> > + Build example userspace program to use prctl task isolation
> > + interface.
> > +
> > endif # SAMPLES
> > Index: linux-2.6/samples/Makefile
> > ===================================================================
> > --- linux-2.6.orig/samples/Makefile
> > +++ linux-2.6/samples/Makefile
> > @@ -30,3 +30,4 @@ obj-$(CONFIG_SAMPLE_INTEL_MEI) += mei/
> > subdir-$(CONFIG_SAMPLE_WATCHDOG) += watchdog
> > subdir-$(CONFIG_SAMPLE_WATCH_QUEUE) += watch_queue
> > obj-$(CONFIG_DEBUG_KMEMLEAK_TEST) += kmemleak/
> > +subdir-$(CONFIG_SAMPLE_TASK_ISOLATION) += task_isolation
> > Index: linux-2.6/samples/task_isolation/Makefile
> > ===================================================================
> > --- /dev/null
> > +++ linux-2.6/samples/task_isolation/Makefile
> > @@ -0,0 +1,4 @@
> > +# SPDX-License-Identifier: GPL-2.0
> > +userprogs-always-y += task_isolation
> > +
> > +userccflags += -I usr/include
> >
> >
> >
> I am wondering if it is possible to further split this patch into smaller
> ones?

OK, will try to split in smaller patches and fix the
style issues.

Thanks.