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Date: Mon, 26 Oct 2020 09:05:52 +0800
From: "Li, Aubrey" <aubrey.li@...ux.intel.com>
To: "Joel Fernandes (Google)" <joel@...lfernandes.org>,
Nishanth Aravamudan <naravamudan@...italocean.com>,
Julien Desfossez <jdesfossez@...italocean.com>,
Peter Zijlstra <peterz@...radead.org>,
Tim Chen <tim.c.chen@...ux.intel.com>,
Vineeth Pillai <viremana@...ux.microsoft.com>,
Aaron Lu <aaron.lwe@...il.com>,
Aubrey Li <aubrey.intel@...il.com>, tglx@...utronix.de,
linux-kernel@...r.kernel.org
Cc: mingo@...nel.org, torvalds@...ux-foundation.org,
fweisbec@...il.com, keescook@...omium.org, kerrnel@...gle.com,
Phil Auld <pauld@...hat.com>,
Valentin Schneider <valentin.schneider@....com>,
Mel Gorman <mgorman@...hsingularity.net>,
Pawan Gupta <pawan.kumar.gupta@...ux.intel.com>,
Paolo Bonzini <pbonzini@...hat.com>, vineeth@...byteword.org,
Chen Yu <yu.c.chen@...el.com>,
Christian Brauner <christian.brauner@...ntu.com>,
Agata Gruza <agata.gruza@...el.com>,
Antonio Gomez Iglesias <antonio.gomez.iglesias@...el.com>,
graf@...zon.com, konrad.wilk@...cle.com, dfaggioli@...e.com,
pjt@...gle.com, rostedt@...dmis.org, derkling@...gle.com,
benbjiang@...cent.com,
Alexandre Chartre <alexandre.chartre@...cle.com>,
James.Bottomley@...senpartnership.com, OWeisse@...ch.edu,
Dhaval Giani <dhaval.giani@...cle.com>,
Junaid Shahid <junaids@...gle.com>, jsbarnes@...gle.com,
chris.hyser@...cle.com, "Paul E. McKenney" <paulmck@...nel.org>,
Tim Chen <tim.c.chen@...el.com>
Subject: Re: [PATCH v8 -tip 24/26] sched: Move core-scheduler interfacing code
to a new file
On 2020/10/20 9:43, Joel Fernandes (Google) wrote:
> core.c is already huge. The core-tagging interface code is largely
> independent of it. Move it to its own file to make both files easier to
> maintain.
>
> Tested-by: Julien Desfossez <jdesfossez@...italocean.com>
> Signed-off-by: Joel Fernandes (Google) <joel@...lfernandes.org>
> ---
> kernel/sched/Makefile | 1 +
> kernel/sched/core.c | 481 +----------------------------------------
> kernel/sched/coretag.c | 468 +++++++++++++++++++++++++++++++++++++++
> kernel/sched/sched.h | 56 ++++-
> 4 files changed, 523 insertions(+), 483 deletions(-)
> create mode 100644 kernel/sched/coretag.c
>
> diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
> index 5fc9c9b70862..c526c20adf9d 100644
> --- a/kernel/sched/Makefile
> +++ b/kernel/sched/Makefile
> @@ -36,3 +36,4 @@ obj-$(CONFIG_CPU_FREQ_GOV_SCHEDUTIL) += cpufreq_schedutil.o
> obj-$(CONFIG_MEMBARRIER) += membarrier.o
> obj-$(CONFIG_CPU_ISOLATION) += isolation.o
> obj-$(CONFIG_PSI) += psi.o
> +obj-$(CONFIG_SCHED_CORE) += coretag.o
> diff --git a/kernel/sched/core.c b/kernel/sched/core.c
> index b3afbba5abe1..211e0784675f 100644
> --- a/kernel/sched/core.c
> +++ b/kernel/sched/core.c
> @@ -162,11 +162,6 @@ static bool sched_core_empty(struct rq *rq)
> return RB_EMPTY_ROOT(&rq->core_tree);
> }
>
> -static bool sched_core_enqueued(struct task_struct *task)
> -{
> - return !RB_EMPTY_NODE(&task->core_node);
> -}
> -
> static struct task_struct *sched_core_first(struct rq *rq)
> {
> struct task_struct *task;
> @@ -188,7 +183,7 @@ static void sched_core_flush(int cpu)
> rq->core->core_task_seq++;
> }
>
> -static void sched_core_enqueue(struct rq *rq, struct task_struct *p)
> +void sched_core_enqueue(struct rq *rq, struct task_struct *p)
> {
> struct rb_node *parent, **node;
> struct task_struct *node_task;
> @@ -215,7 +210,7 @@ static void sched_core_enqueue(struct rq *rq, struct task_struct *p)
> rb_insert_color(&p->core_node, &rq->core_tree);
> }
>
> -static void sched_core_dequeue(struct rq *rq, struct task_struct *p)
> +void sched_core_dequeue(struct rq *rq, struct task_struct *p)
> {
> rq->core->core_task_seq++;
>
> @@ -310,7 +305,6 @@ static int __sched_core_stopper(void *data)
> }
>
> static DEFINE_MUTEX(sched_core_mutex);
> -static DEFINE_MUTEX(sched_core_tasks_mutex);
> static int sched_core_count;
>
> static void __sched_core_enable(void)
> @@ -346,16 +340,6 @@ void sched_core_put(void)
> __sched_core_disable();
> mutex_unlock(&sched_core_mutex);
> }
> -
> -static int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2);
> -
> -#else /* !CONFIG_SCHED_CORE */
> -
> -static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { }
> -static inline void sched_core_dequeue(struct rq *rq, struct task_struct *p) { }
> -static bool sched_core_enqueued(struct task_struct *task) { return false; }
> -static int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2) { }
> -
> #endif /* CONFIG_SCHED_CORE */
>
> /*
> @@ -8505,9 +8489,6 @@ void sched_offline_group(struct task_group *tg)
> spin_unlock_irqrestore(&task_group_lock, flags);
> }
>
> -#define SCHED_CORE_GROUP_COOKIE_MASK ((1UL << (sizeof(unsigned long) * 4)) - 1)
> -static unsigned long cpu_core_get_group_cookie(struct task_group *tg);
> -
> static void sched_change_group(struct task_struct *tsk, int type)
> {
> struct task_group *tg;
> @@ -8583,11 +8564,6 @@ void sched_move_task(struct task_struct *tsk)
> task_rq_unlock(rq, tsk, &rf);
> }
>
> -static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
> -{
> - return css ? container_of(css, struct task_group, css) : NULL;
> -}
> -
> static struct cgroup_subsys_state *
> cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css)
> {
> @@ -9200,459 +9176,6 @@ static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css,
> }
> #endif /* CONFIG_RT_GROUP_SCHED */
>
> -#ifdef CONFIG_SCHED_CORE
> -/*
> - * A simple wrapper around refcount. An allocated sched_core_cookie's
> - * address is used to compute the cookie of the task.
> - */
> -struct sched_core_cookie {
> - refcount_t refcnt;
> -};
> -
> -/*
> - * sched_core_tag_requeue - Common helper for all interfaces to set a cookie.
> - * @p: The task to assign a cookie to.
> - * @cookie: The cookie to assign.
> - * @group: is it a group interface or a per-task interface.
> - *
> - * This function is typically called from a stop-machine handler.
> - */
> -void sched_core_tag_requeue(struct task_struct *p, unsigned long cookie, bool group)
> -{
> - if (!p)
> - return;
> -
> - if (group)
> - p->core_group_cookie = cookie;
> - else
> - p->core_task_cookie = cookie;
> -
> - /* Use up half of the cookie's bits for task cookie and remaining for group cookie. */
> - p->core_cookie = (p->core_task_cookie <<
> - (sizeof(unsigned long) * 4)) + p->core_group_cookie;
> -
> - if (sched_core_enqueued(p)) {
> - sched_core_dequeue(task_rq(p), p);
> - if (!p->core_cookie)
> - return;
> - }
> -
> - if (sched_core_enabled(task_rq(p)) &&
> - p->core_cookie && task_on_rq_queued(p))
> - sched_core_enqueue(task_rq(p), p);
> -}
> -
> -/* Per-task interface */
> -static unsigned long sched_core_alloc_task_cookie(void)
> -{
> - struct sched_core_cookie *ptr =
> - kmalloc(sizeof(struct sched_core_cookie), GFP_KERNEL);
> -
> - if (!ptr)
> - return 0;
> - refcount_set(&ptr->refcnt, 1);
> -
> - /*
> - * NOTE: sched_core_put() is not done by put_task_cookie(). Instead, it
> - * is done after the stopper runs.
> - */
> - sched_core_get();
> - return (unsigned long)ptr;
> -}
> -
> -static bool sched_core_get_task_cookie(unsigned long cookie)
> -{
> - struct sched_core_cookie *ptr = (struct sched_core_cookie *)cookie;
> -
> - /*
> - * NOTE: sched_core_put() is not done by put_task_cookie(). Instead, it
> - * is done after the stopper runs.
> - */
> - sched_core_get();
> - return refcount_inc_not_zero(&ptr->refcnt);
> -}
> -
> -static void sched_core_put_task_cookie(unsigned long cookie)
> -{
> - struct sched_core_cookie *ptr = (struct sched_core_cookie *)cookie;
> -
> - if (refcount_dec_and_test(&ptr->refcnt))
> - kfree(ptr);
> -}
> -
> -struct sched_core_task_write_tag {
> - struct task_struct *tasks[2];
> - unsigned long cookies[2];
> -};
> -
> -/*
> - * Ensure that the task has been requeued. The stopper ensures that the task cannot
> - * be migrated to a different CPU while its core scheduler queue state is being updated.
> - * It also makes sure to requeue a task if it was running actively on another CPU.
> - */
> -static int sched_core_task_join_stopper(void *data)
> -{
> - struct sched_core_task_write_tag *tag = (struct sched_core_task_write_tag *)data;
> - int i;
> -
> - for (i = 0; i < 2; i++)
> - sched_core_tag_requeue(tag->tasks[i], tag->cookies[i], false /* !group */);
> -
> - return 0;
> -}
> -
> -static int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2)
> -{
> - struct sched_core_task_write_tag wr = {}; /* for stop machine. */
> - bool sched_core_put_after_stopper = false;
> - unsigned long cookie;
> - int ret = -ENOMEM;
> -
> - mutex_lock(&sched_core_tasks_mutex);
> -
> - /*
> - * NOTE: sched_core_get() is done by sched_core_alloc_task_cookie() or
> - * sched_core_put_task_cookie(). However, sched_core_put() is done
> - * by this function *after* the stopper removes the tasks from the
> - * core queue, and not before. This is just to play it safe.
> - */
> - if (t2 == NULL) {
> - if (t1->core_task_cookie) {
> - sched_core_put_task_cookie(t1->core_task_cookie);
> - sched_core_put_after_stopper = true;
> - wr.tasks[0] = t1; /* Keep wr.cookies[0] reset for t1. */
> - }
> - } else if (t1 == t2) {
> - /* Assign a unique per-task cookie solely for t1. */
> -
> - cookie = sched_core_alloc_task_cookie();
> - if (!cookie)
> - goto out_unlock;
> -
> - if (t1->core_task_cookie) {
> - sched_core_put_task_cookie(t1->core_task_cookie);
> - sched_core_put_after_stopper = true;
> - }
> - wr.tasks[0] = t1;
> - wr.cookies[0] = cookie;
> - } else
> - /*
> - * t1 joining t2
> - * CASE 1:
> - * before 0 0
> - * after new cookie new cookie
> - *
> - * CASE 2:
> - * before X (non-zero) 0
> - * after 0 0
> - *
> - * CASE 3:
> - * before 0 X (non-zero)
> - * after X X
> - *
> - * CASE 4:
> - * before Y (non-zero) X (non-zero)
> - * after X X
> - */
> - if (!t1->core_task_cookie && !t2->core_task_cookie) {
> - /* CASE 1. */
> - cookie = sched_core_alloc_task_cookie();
> - if (!cookie)
> - goto out_unlock;
> -
> - /* Add another reference for the other task. */
> - if (!sched_core_get_task_cookie(cookie)) {
> - return -EINVAL;
> - goto out_unlock;
> - }
> -
> - wr.tasks[0] = t1;
> - wr.tasks[1] = t2;
> - wr.cookies[0] = wr.cookies[1] = cookie;
> -
> - } else if (t1->core_task_cookie && !t2->core_task_cookie) {
> - /* CASE 2. */
> - sched_core_put_task_cookie(t1->core_task_cookie);
> - sched_core_put_after_stopper = true;
> -
> - wr.tasks[0] = t1; /* Reset cookie for t1. */
> -
> - } else if (!t1->core_task_cookie && t2->core_task_cookie) {
> - /* CASE 3. */
> - if (!sched_core_get_task_cookie(t2->core_task_cookie)) {
> - ret = -EINVAL;
> - goto out_unlock;
> - }
> -
> - wr.tasks[0] = t1;
> - wr.cookies[0] = t2->core_task_cookie;
> -
> - } else {
> - /* CASE 4. */
> - if (!sched_core_get_task_cookie(t2->core_task_cookie)) {
> - ret = -EINVAL;
> - goto out_unlock;
> - }
> - sched_core_put_task_cookie(t1->core_task_cookie);
> - sched_core_put_after_stopper = true;
> -
> - wr.tasks[0] = t1;
> - wr.cookies[0] = t2->core_task_cookie;
> - }
> -
> - stop_machine(sched_core_task_join_stopper, (void *)&wr, NULL);
> -
> - if (sched_core_put_after_stopper)
> - sched_core_put();
> -
> - ret = 0;
> -out_unlock:
> - mutex_unlock(&sched_core_tasks_mutex);
> - return ret;
> -}
> -
> -/* Called from prctl interface: PR_SCHED_CORE_SHARE */
> -int sched_core_share_pid(pid_t pid)
> -{
> - struct task_struct *task;
> - int err;
> -
> - if (pid == 0) { /* Recent current task's cookie. */
> - /* Resetting a cookie requires privileges. */
> - if (current->core_task_cookie)
> - if (!capable(CAP_SYS_ADMIN))
> - return -EPERM;
> - task = NULL;
> - } else {
> - rcu_read_lock();
> - task = pid ? find_task_by_vpid(pid) : current;
> - if (!task) {
> - rcu_read_unlock();
> - return -ESRCH;
> - }
> -
> - get_task_struct(task);
> -
> - /*
> - * Check if this process has the right to modify the specified
> - * process. Use the regular "ptrace_may_access()" checks.
> - */
> - if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
> - rcu_read_unlock();
> - err = -EPERM;
> - goto out_put;
> - }
> - rcu_read_unlock();
> - }
> -
> - err = sched_core_share_tasks(current, task);
> -out_put:
> - if (task)
> - put_task_struct(task);
> - return err;
> -}
> -
> -/* CGroup interface */
> -
> -/*
> - * Helper to get the cookie in a hierarchy.
> - * The cookie is a combination of a tag and color. Any ancestor
> - * can have a tag/color. tag is the first-level cookie setting
> - * with color being the second. Atmost one color and one tag is
> - * allowed.
> - */
> -static unsigned long cpu_core_get_group_cookie(struct task_group *tg)
> -{
> - unsigned long color = 0;
> -
> - if (!tg)
> - return 0;
> -
> - for (; tg; tg = tg->parent) {
> - if (tg->core_tag_color) {
> - WARN_ON_ONCE(color);
> - color = tg->core_tag_color;
> - }
> -
> - if (tg->core_tagged) {
> - unsigned long cookie = ((unsigned long)tg << 8) | color;
> - cookie &= SCHED_CORE_GROUP_COOKIE_MASK;
> - return cookie;
> - }
> - }
> -
> - return 0;
> -}
> -
> -/* Determine if any group in @tg's children are tagged or colored. */
> -static bool cpu_core_check_descendants(struct task_group *tg, bool check_tag,
> - bool check_color)
> -{
> - struct task_group *child;
> -
> - rcu_read_lock();
> - list_for_each_entry_rcu(child, &tg->children, siblings) {
> - if ((child->core_tagged && check_tag) ||
> - (child->core_tag_color && check_color)) {
> - rcu_read_unlock();
> - return true;
> - }
> -
> - rcu_read_unlock();
> - return cpu_core_check_descendants(child, check_tag, check_color);
> - }
> -
> - rcu_read_unlock();
> - return false;
> -}
> -
> -static u64 cpu_core_tag_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
> -{
> - struct task_group *tg = css_tg(css);
> -
> - return !!tg->core_tagged;
> -}
> -
> -static u64 cpu_core_tag_color_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
> -{
> - struct task_group *tg = css_tg(css);
> -
> - return tg->core_tag_color;
> -}
> -
> -#ifdef CONFIG_SCHED_DEBUG
> -static u64 cpu_core_group_cookie_read_u64(struct cgroup_subsys_state *css, struct cftype *cft)
> -{
> - return cpu_core_get_group_cookie(css_tg(css));
> -}
> -#endif
> -
> -struct write_core_tag {
> - struct cgroup_subsys_state *css;
> - unsigned long cookie;
> -};
> -
> -static int __sched_write_tag(void *data)
> -{
> - struct write_core_tag *tag = (struct write_core_tag *) data;
> - struct task_struct *p;
> - struct cgroup_subsys_state *css;
> -
> - rcu_read_lock();
> - css_for_each_descendant_pre(css, tag->css) {
> - struct css_task_iter it;
> -
> - css_task_iter_start(css, 0, &it);
> - /*
> - * Note: css_task_iter_next will skip dying tasks.
> - * There could still be dying tasks left in the core queue
> - * when we set cgroup tag to 0 when the loop is done below.
> - */
> - while ((p = css_task_iter_next(&it)))
> - sched_core_tag_requeue(p, tag->cookie, true /* group */);
> -
> - css_task_iter_end(&it);
> - }
> - rcu_read_unlock();
> -
> - return 0;
> -}
> -
> -static int cpu_core_tag_write_u64(struct cgroup_subsys_state *css, struct cftype *cft, u64 val)
> -{
> - struct task_group *tg = css_tg(css);
> - struct write_core_tag wtag;
> -
> - if (val > 1)
> - return -ERANGE;
> -
> - if (!static_branch_likely(&sched_smt_present))
> - return -EINVAL;
> -
> - if (!tg->core_tagged && val) {
> - /* Tag is being set. Check ancestors and descendants. */
> - if (cpu_core_get_group_cookie(tg) ||
> - cpu_core_check_descendants(tg, true /* tag */, true /* color */))
> - return -EBUSY;
> - } else if (tg->core_tagged && !val) {
> - /* Tag is being reset. Check descendants. */
> - if (cpu_core_check_descendants(tg, true /* tag */, true /* color */))
> - return -EBUSY;
> - } else {
> - return 0;
> - }
> -
> - if (!!val)
> - sched_core_get();
> -
> - wtag.css = css;
> - wtag.cookie = (unsigned long)tg << 8; /* Reserve lower 8 bits for color. */
> -
> - /* Truncate the upper 32-bits - those are used by the per-task cookie. */
> - wtag.cookie &= (1UL << (sizeof(unsigned long) * 4)) - 1;
> -
> - tg->core_tagged = val;
> -
> - stop_machine(__sched_write_tag, (void *) &wtag, NULL);
> - if (!val)
> - sched_core_put();
> -
> - return 0;
> -}
> -
> -static int cpu_core_tag_color_write_u64(struct cgroup_subsys_state *css,
> - struct cftype *cft, u64 val)
> -{
> - struct task_group *tg = css_tg(css);
> - struct write_core_tag wtag;
> - u64 cookie;
> -
> - if (val > 255)
> - return -ERANGE;
> -
> - if (!static_branch_likely(&sched_smt_present))
> - return -EINVAL;
> -
> - cookie = cpu_core_get_group_cookie(tg);
> - /* Can't set color if nothing in the ancestors were tagged. */
> - if (!cookie)
> - return -EINVAL;
> -
> - /*
> - * Something in the ancestors already colors us. Can't change the color
> - * at this level.
> - */
> - if (!tg->core_tag_color && (cookie & 255))
> - return -EINVAL;
> -
> - /*
> - * Check if any descendants are colored. If so, we can't recolor them.
> - * Don't need to check if descendants are tagged, since we don't allow
> - * tagging when already tagged.
> - */
> - if (cpu_core_check_descendants(tg, false /* tag */, true /* color */))
> - return -EINVAL;
> -
> - cookie &= ~255;
> - cookie |= val;
> - wtag.css = css;
> - wtag.cookie = cookie;
> - tg->core_tag_color = val;
> -
> - stop_machine(__sched_write_tag, (void *) &wtag, NULL);
> -
> - return 0;
> -}
> -
> -void sched_tsk_free(struct task_struct *tsk)
> -{
> - if (!tsk->core_task_cookie)
> - return;
> - sched_core_put_task_cookie(tsk->core_task_cookie);
> - sched_core_put();
> -}
> -#endif
> -
> static struct cftype cpu_legacy_files[] = {
> #ifdef CONFIG_FAIR_GROUP_SCHED
> {
> diff --git a/kernel/sched/coretag.c b/kernel/sched/coretag.c
> new file mode 100644
> index 000000000000..3333c9b0afc5
> --- /dev/null
> +++ b/kernel/sched/coretag.c
> @@ -0,0 +1,468 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +/*
> + * kernel/sched/core-tag.c
> + *
> + * Core-scheduling tagging interface support.
> + *
> + * Copyright(C) 2020, Joel Fernandes.
> + * Initial interfacing code by Peter Ziljstra.
> + */
> +
> +#include "sched.h"
> +
> +/*
> + * A simple wrapper around refcount. An allocated sched_core_cookie's
> + * address is used to compute the cookie of the task.
> + */
> +struct sched_core_cookie {
> + refcount_t refcnt;
> +};
> +
> +static DEFINE_MUTEX(sched_core_tasks_mutex);
> +
> +/*
> + * sched_core_tag_requeue - Common helper for all interfaces to set a cookie.
> + * @p: The task to assign a cookie to.
> + * @cookie: The cookie to assign.
> + * @group: is it a group interface or a per-task interface.
> + *
> + * This function is typically called from a stop-machine handler.
> + */
> +void sched_core_tag_requeue(struct task_struct *p, unsigned long cookie, bool group)
> +{
> + if (!p)
> + return;
> +
> + if (group)
> + p->core_group_cookie = cookie;
> + else
> + p->core_task_cookie = cookie;
> +
> + /* Use up half of the cookie's bits for task cookie and remaining for group cookie. */
> + p->core_cookie = (p->core_task_cookie <<
> + (sizeof(unsigned long) * 4)) + p->core_group_cookie;
> +
> + if (sched_core_enqueued(p)) {
> + sched_core_dequeue(task_rq(p), p);
> + if (!p->core_cookie)
> + return;
> + }
> +
> + if (sched_core_enabled(task_rq(p)) &&
> + p->core_cookie && task_on_rq_queued(p))
> + sched_core_enqueue(task_rq(p), p);
> +}
> +
> +/* Per-task interface: Used by fork(2) and prctl(2). */
> +static unsigned long sched_core_alloc_task_cookie(void)
> +{
> + struct sched_core_cookie *ptr =
> + kmalloc(sizeof(struct sched_core_cookie), GFP_KERNEL);
> +
> + if (!ptr)
> + return 0;
> + refcount_set(&ptr->refcnt, 1);
> +
> + /*
> + * NOTE: sched_core_put() is not done by put_task_cookie(). Instead, it
> + * is done after the stopper runs.
> + */
> + sched_core_get();
> + return (unsigned long)ptr;
> +}
> +
> +static bool sched_core_get_task_cookie(unsigned long cookie)
> +{
> + struct sched_core_cookie *ptr = (struct sched_core_cookie *)cookie;
> +
> + /*
> + * NOTE: sched_core_put() is not done by put_task_cookie(). Instead, it
> + * is done after the stopper runs.
> + */
> + sched_core_get();
> + return refcount_inc_not_zero(&ptr->refcnt);
> +}
> +
> +static void sched_core_put_task_cookie(unsigned long cookie)
> +{
> + struct sched_core_cookie *ptr = (struct sched_core_cookie *)cookie;
> +
> + if (refcount_dec_and_test(&ptr->refcnt))
> + kfree(ptr);
> +}
> +
> +struct sched_core_task_write_tag {
> + struct task_struct *tasks[2];
> + unsigned long cookies[2];
> +};
> +
> +/*
> + * Ensure that the task has been requeued. The stopper ensures that the task cannot
> + * be migrated to a different CPU while its core scheduler queue state is being updated.
> + * It also makes sure to requeue a task if it was running actively on another CPU.
> + */
> +static int sched_core_task_join_stopper(void *data)
> +{
> + struct sched_core_task_write_tag *tag = (struct sched_core_task_write_tag *)data;
> + int i;
> +
> + for (i = 0; i < 2; i++)
> + sched_core_tag_requeue(tag->tasks[i], tag->cookies[i], false /* !group */);
> +
> + return 0;
> +}
> +
> +int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2)
> +{
> + struct sched_core_task_write_tag wr = {}; /* for stop machine. */
> + bool sched_core_put_after_stopper = false;
> + unsigned long cookie;
> + int ret = -ENOMEM;
> +
> + mutex_lock(&sched_core_tasks_mutex);
> +
> + /*
> + * NOTE: sched_core_get() is done by sched_core_alloc_task_cookie() or
> + * sched_core_put_task_cookie(). However, sched_core_put() is done
> + * by this function *after* the stopper removes the tasks from the
> + * core queue, and not before. This is just to play it safe.
> + */
> + if (t2 == NULL) {
> + if (t1->core_task_cookie) {
> + sched_core_put_task_cookie(t1->core_task_cookie);
> + sched_core_put_after_stopper = true;
> + wr.tasks[0] = t1; /* Keep wr.cookies[0] reset for t1. */
> + }
> + } else if (t1 == t2) {
> + /* Assign a unique per-task cookie solely for t1. */
> +
> + cookie = sched_core_alloc_task_cookie();
> + if (!cookie)
> + goto out_unlock;
> +
> + if (t1->core_task_cookie) {
> + sched_core_put_task_cookie(t1->core_task_cookie);
> + sched_core_put_after_stopper = true;
> + }
> + wr.tasks[0] = t1;
> + wr.cookies[0] = cookie;
> + } else
> + /*
> + * t1 joining t2
> + * CASE 1:
> + * before 0 0
> + * after new cookie new cookie
> + *
> + * CASE 2:
> + * before X (non-zero) 0
> + * after 0 0
> + *
> + * CASE 3:
> + * before 0 X (non-zero)
> + * after X X
> + *
> + * CASE 4:
> + * before Y (non-zero) X (non-zero)
> + * after X X
> + */
> + if (!t1->core_task_cookie && !t2->core_task_cookie) {
> + /* CASE 1. */
> + cookie = sched_core_alloc_task_cookie();
> + if (!cookie)
> + goto out_unlock;
> +
> + /* Add another reference for the other task. */
> + if (!sched_core_get_task_cookie(cookie)) {
> + return -EINVAL;
ret = -EINVAL; mutex is not released otherwise...
> + goto out_unlock;
> + }
> +
> + wr.tasks[0] = t1;
> + wr.tasks[1] = t2;
> + wr.cookies[0] = wr.cookies[1] = cookie;
> +
> + } else if (t1->core_task_cookie && !t2->core_task_cookie) {
> + /* CASE 2. */
> + sched_core_put_task_cookie(t1->core_task_cookie);
> + sched_core_put_after_stopper = true;
> +
> + wr.tasks[0] = t1; /* Reset cookie for t1. */
> +
> + } else if (!t1->core_task_cookie && t2->core_task_cookie) {
> + /* CASE 3. */
> + if (!sched_core_get_task_cookie(t2->core_task_cookie)) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> +
> + wr.tasks[0] = t1;
> + wr.cookies[0] = t2->core_task_cookie;
> +
> + } else {
> + /* CASE 4. */
> + if (!sched_core_get_task_cookie(t2->core_task_cookie)) {
> + ret = -EINVAL;
> + goto out_unlock;
> + }
> + sched_core_put_task_cookie(t1->core_task_cookie);
> + sched_core_put_after_stopper = true;
> +
> + wr.tasks[0] = t1;
> + wr.cookies[0] = t2->core_task_cookie;
> + }
> +
> + stop_machine(sched_core_task_join_stopper, (void *)&wr, NULL);
> +
> + if (sched_core_put_after_stopper)
> + sched_core_put();
> +
> + ret = 0;
> +out_unlock:
> + mutex_unlock(&sched_core_tasks_mutex);
> + return ret;
> +}
> +
> +/* Called from prctl interface: PR_SCHED_CORE_SHARE */
> +int sched_core_share_pid(pid_t pid)
> +{
> + struct task_struct *task;
> + int err;
> +
> + if (pid == 0) { /* Recent current task's cookie. */
> + /* Resetting a cookie requires privileges. */
> + if (current->core_task_cookie)
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> + task = NULL;
> + } else {
> + rcu_read_lock();
> + task = pid ? find_task_by_vpid(pid) : current;
> + if (!task) {
> + rcu_read_unlock();
> + return -ESRCH;
> + }
> +
> + get_task_struct(task);
> +
> + /*
> + * Check if this process has the right to modify the specified
> + * process. Use the regular "ptrace_may_access()" checks.
> + */
> + if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
> + rcu_read_unlock();
> + err = -EPERM;
> + goto out_put;
> + }
> + rcu_read_unlock();
> + }
> +
> + err = sched_core_share_tasks(current, task);
> +out_put:
> + if (task)
> + put_task_struct(task);
> + return err;
> +}
> +
> +/* CGroup core-scheduling interface support. */
> +
> +/*
> + * Helper to get the cookie in a hierarchy.
> + * The cookie is a combination of a tag and color. Any ancestor
> + * can have a tag/color. tag is the first-level cookie setting
> + * with color being the second. Atmost one color and one tag is
> + * allowed.
> + */
> +unsigned long cpu_core_get_group_cookie(struct task_group *tg)
> +{
> + unsigned long color = 0;
> +
> + if (!tg)
> + return 0;
> +
> + for (; tg; tg = tg->parent) {
> + if (tg->core_tag_color) {
> + WARN_ON_ONCE(color);
> + color = tg->core_tag_color;
> + }
> +
> + if (tg->core_tagged) {
> + unsigned long cookie = ((unsigned long)tg << 8) | color;
> + cookie &= SCHED_CORE_GROUP_COOKIE_MASK;
> + return cookie;
> + }
> + }
> +
> + return 0;
> +}
> +
> +/* Determine if any group in @tg's children are tagged or colored. */
> +static bool cpu_core_check_descendants(struct task_group *tg, bool check_tag,
> + bool check_color)
> +{
> + struct task_group *child;
> +
> + rcu_read_lock();
> + list_for_each_entry_rcu(child, &tg->children, siblings) {
> + if ((child->core_tagged && check_tag) ||
> + (child->core_tag_color && check_color)) {
> + rcu_read_unlock();
> + return true;
> + }
> +
> + rcu_read_unlock();
> + return cpu_core_check_descendants(child, check_tag, check_color);
> + }
> +
> + rcu_read_unlock();
> + return false;
> +}
> +
> +u64 cpu_core_tag_read_u64(struct cgroup_subsys_state *css,
> + struct cftype *cft)
> +{
> + struct task_group *tg = css_tg(css);
> +
> + return !!tg->core_tagged;
> +}
> +
> +u64 cpu_core_tag_color_read_u64(struct cgroup_subsys_state *css,
> + struct cftype *cft)
> +{
> + struct task_group *tg = css_tg(css);
> +
> + return tg->core_tag_color;
> +}
> +
> +#ifdef CONFIG_SCHED_DEBUG
> +u64 cpu_core_group_cookie_read_u64(struct cgroup_subsys_state *css,
> + struct cftype *cft)
> +{
> + return cpu_core_get_group_cookie(css_tg(css));
> +}
> +#endif
> +
> +struct write_core_tag {
> + struct cgroup_subsys_state *css;
> + unsigned long cookie;
> +};
> +
> +static int __sched_write_tag(void *data)
> +{
> + struct write_core_tag *tag = (struct write_core_tag *) data;
> + struct task_struct *p;
> + struct cgroup_subsys_state *css;
> +
> + rcu_read_lock();
> + css_for_each_descendant_pre(css, tag->css) {
> + struct css_task_iter it;
> +
> + css_task_iter_start(css, 0, &it);
> + /*
> + * Note: css_task_iter_next will skip dying tasks.
> + * There could still be dying tasks left in the core queue
> + * when we set cgroup tag to 0 when the loop is done below.
> + */
> + while ((p = css_task_iter_next(&it)))
> + sched_core_tag_requeue(p, tag->cookie, true /* group */);
> +
> + css_task_iter_end(&it);
> + }
> + rcu_read_unlock();
> +
> + return 0;
> +}
> +
> +int cpu_core_tag_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
> + u64 val)
> +{
> + struct task_group *tg = css_tg(css);
> + struct write_core_tag wtag;
> +
> + if (val > 1)
> + return -ERANGE;
> +
> + if (!static_branch_likely(&sched_smt_present))
> + return -EINVAL;
> +
> + if (!tg->core_tagged && val) {
> + /* Tag is being set. Check ancestors and descendants. */
> + if (cpu_core_get_group_cookie(tg) ||
> + cpu_core_check_descendants(tg, true /* tag */, true /* color */))
> + return -EBUSY;
> + } else if (tg->core_tagged && !val) {
> + /* Tag is being reset. Check descendants. */
> + if (cpu_core_check_descendants(tg, true /* tag */, true /* color */))
> + return -EBUSY;
> + } else {
> + return 0;
> + }
> +
> + if (!!val)
> + sched_core_get();
> +
> + wtag.css = css;
> + wtag.cookie = (unsigned long)tg << 8; /* Reserve lower 8 bits for color. */
> +
> + /* Truncate the upper 32-bits - those are used by the per-task cookie. */
> + wtag.cookie &= (1UL << (sizeof(unsigned long) * 4)) - 1;
> +
> + tg->core_tagged = val;
> +
> + stop_machine(__sched_write_tag, (void *) &wtag, NULL);
> + if (!val)
> + sched_core_put();
> +
> + return 0;
> +}
> +
> +int cpu_core_tag_color_write_u64(struct cgroup_subsys_state *css,
> + struct cftype *cft, u64 val)
> +{
> + struct task_group *tg = css_tg(css);
> + struct write_core_tag wtag;
> + u64 cookie;
> +
> + if (val > 255)
> + return -ERANGE;
> +
> + if (!static_branch_likely(&sched_smt_present))
> + return -EINVAL;
> +
> + cookie = cpu_core_get_group_cookie(tg);
> + /* Can't set color if nothing in the ancestors were tagged. */
> + if (!cookie)
> + return -EINVAL;
> +
> + /*
> + * Something in the ancestors already colors us. Can't change the color
> + * at this level.
> + */
> + if (!tg->core_tag_color && (cookie & 255))
> + return -EINVAL;
> +
> + /*
> + * Check if any descendants are colored. If so, we can't recolor them.
> + * Don't need to check if descendants are tagged, since we don't allow
> + * tagging when already tagged.
> + */
> + if (cpu_core_check_descendants(tg, false /* tag */, true /* color */))
> + return -EINVAL;
> +
> + cookie &= ~255;
> + cookie |= val;
> + wtag.css = css;
> + wtag.cookie = cookie;
> + tg->core_tag_color = val;
> +
> + stop_machine(__sched_write_tag, (void *) &wtag, NULL);
> +
> + return 0;
> +}
> +
> +void sched_tsk_free(struct task_struct *tsk)
> +{
> + if (!tsk->core_task_cookie)
> + return;
> + sched_core_put_task_cookie(tsk->core_task_cookie);
> + sched_core_put();
> +}
> diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h
> index aebeb91c4a0f..290a3b8be3d3 100644
> --- a/kernel/sched/sched.h
> +++ b/kernel/sched/sched.h
> @@ -437,6 +437,11 @@ struct task_group {
>
> };
>
> +static inline struct task_group *css_tg(struct cgroup_subsys_state *css)
> +{
> + return css ? container_of(css, struct task_group, css) : NULL;
> +}
> +
> #ifdef CONFIG_FAIR_GROUP_SCHED
> #define ROOT_TASK_GROUP_LOAD NICE_0_LOAD
>
> @@ -1104,6 +1109,8 @@ static inline int cpu_of(struct rq *rq)
> #ifdef CONFIG_SCHED_CORE
> DECLARE_STATIC_KEY_FALSE(__sched_core_enabled);
>
> +#define SCHED_CORE_GROUP_COOKIE_MASK ((1UL << (sizeof(unsigned long) * 4)) - 1)
> +
> static inline bool sched_core_enabled(struct rq *rq)
> {
> return static_branch_unlikely(&__sched_core_enabled) && rq->core_enabled;
> @@ -1148,10 +1155,54 @@ static inline bool sched_core_cookie_match(struct rq *rq, struct task_struct *p)
> return idle_core || rq->core->core_cookie == p->core_cookie;
> }
>
> -extern void queue_core_balance(struct rq *rq);
> +static inline bool sched_core_enqueued(struct task_struct *task)
> +{
> + return !RB_EMPTY_NODE(&task->core_node);
> +}
> +
> +void queue_core_balance(struct rq *rq);
> +
> +void sched_core_enqueue(struct rq *rq, struct task_struct *p);
> +void sched_core_dequeue(struct rq *rq, struct task_struct *p);
> +void sched_core_get(void);
> +void sched_core_put(void);
> +
> +void sched_core_tag_requeue(struct task_struct *p, unsigned long cookie,
> + bool group);
> +
> +int sched_core_share_pid(pid_t pid);
> +int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2);
> +
> +unsigned long cpu_core_get_group_cookie(struct task_group *tg);
> +
> +u64 cpu_core_tag_read_u64(struct cgroup_subsys_state *css,
> + struct cftype *cft);
> +
> +u64 cpu_core_tag_color_read_u64(struct cgroup_subsys_state *css,
> + struct cftype *cft);
> +
> +#ifdef CONFIG_SCHED_DEBUG
> +u64 cpu_core_group_cookie_read_u64(struct cgroup_subsys_state *css,
> + struct cftype *cft);
> +#endif
> +
> +int cpu_core_tag_write_u64(struct cgroup_subsys_state *css, struct cftype *cft,
> + u64 val);
> +
> +int cpu_core_tag_color_write_u64(struct cgroup_subsys_state *css,
> + struct cftype *cft, u64 val);
> +
> +#ifndef TIF_UNSAFE_RET
> +#define TIF_UNSAFE_RET (0)
> +#endif
>
> #else /* !CONFIG_SCHED_CORE */
>
> +static inline bool sched_core_enqueued(struct task_struct *task) { return false; }
> +static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { }
> +static inline void sched_core_dequeue(struct rq *rq, struct task_struct *p) { }
> +static inline int sched_core_share_tasks(struct task_struct *t1, struct task_struct *t2) { }
> +
> static inline bool sched_core_enabled(struct rq *rq)
> {
> return false;
> @@ -2779,7 +2830,4 @@ void swake_up_all_locked(struct swait_queue_head *q);
> void __prepare_to_swait(struct swait_queue_head *q, struct swait_queue *wait);
>
> #ifdef CONFIG_SCHED_CORE
> -#ifndef TIF_UNSAFE_RET
> -#define TIF_UNSAFE_RET (0)
> -#endif
> #endif
>
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