kernel/sched/core_sched.c

   1 // SPDX-License-Identifier: GPL-2.0-only
   2
   3 /*
   4  * A simple wrapper around refcount. An allocated sched_core_cookie's
   5  * address is used to compute the cookie of the task.
   6  */
   7 struct sched_core_cookie {
   8         refcount_t refcnt;
   9 };
  10
  11 static unsigned long sched_core_alloc_cookie(void)
  12 {
  13         struct sched_core_cookie *ck = kmalloc(sizeof(*ck), GFP_KERNEL);
  14         if (!ck)
  15                 return 0;
  16
  17         refcount_set(&ck->refcnt, 1);
  18         sched_core_get();
  19
  20         return (unsigned long)ck;
  21 }
  22
  23 static void sched_core_put_cookie(unsigned long cookie)
  24 {
  25         struct sched_core_cookie *ptr = (void *)cookie;
  26
  27         if (ptr && refcount_dec_and_test(&ptr->refcnt)) {
  28                 kfree(ptr);
  29                 sched_core_put();
  30         }
  31 }
  32
  33 static unsigned long sched_core_get_cookie(unsigned long cookie)
  34 {
  35         struct sched_core_cookie *ptr = (void *)cookie;
  36
  37         if (ptr)
  38                 refcount_inc(&ptr->refcnt);
  39
  40         return cookie;
  41 }
  42
  43 /*
  44  * sched_core_update_cookie - replace the cookie on a task
  45  * @p: the task to update
  46  * @cookie: the new cookie
  47  *
  48  * Effectively exchange the task cookie; caller is responsible for lifetimes on
  49  * both ends.
  50  *
  51  * Returns: the old cookie
  52  */
  53 static unsigned long sched_core_update_cookie(struct task_struct *p,
  54                                               unsigned long cookie)
  55 {
  56         unsigned long old_cookie;
  57         struct rq_flags rf;
  58         struct rq *rq;
  59         bool enqueued;
  60
  61         rq = task_rq_lock(p, &rf);
  62
  63         /*
  64          * Since creating a cookie implies sched_core_get(), and we cannot set
  65          * a cookie until after we've created it, similarly, we cannot destroy
  66          * a cookie until after we've removed it, we must have core scheduling
  67          * enabled here.
  68          */
  69         SCHED_WARN_ON((p->core_cookie || cookie) && !sched_core_enabled(rq));
  70
  71         enqueued = sched_core_enqueued(p);
  72         if (enqueued)
  73                 sched_core_dequeue(rq, p, DEQUEUE_SAVE);
  74
  75         old_cookie = p->core_cookie;
  76         p->core_cookie = cookie;
  77
  78         if (enqueued)
  79                 sched_core_enqueue(rq, p);
  80
  81         /*
  82          * If task is currently running, it may not be compatible anymore after
  83          * the cookie change, so enter the scheduler on its CPU to schedule it
  84          * away.
  85          *
  86          * Note that it is possible that as a result of this cookie change, the
  87          * core has now entered/left forced idle state. Defer accounting to the
  88          * next scheduling edge, rather than always forcing a reschedule here.
  89          */
  90         if (task_running(rq, p))
  91                 resched_curr(rq);
  92
  93         task_rq_unlock(rq, p, &rf);
  94
  95         return old_cookie;
  96 }
  97
  98 static unsigned long sched_core_clone_cookie(struct task_struct *p)
  99 {
 100         unsigned long cookie, flags;
 101
 102         raw_spin_lock_irqsave(&p->pi_lock, flags);
 103         cookie = sched_core_get_cookie(p->core_cookie);
 104         raw_spin_unlock_irqrestore(&p->pi_lock, flags);
 105
 106         return cookie;
 107 }
 108
 109 void sched_core_fork(struct task_struct *p)
 110 {
 111         RB_CLEAR_NODE(&p->core_node);
 112         p->core_cookie = sched_core_clone_cookie(current);
 113 }
 114
 115 void sched_core_free(struct task_struct *p)
 116 {
 117         sched_core_put_cookie(p->core_cookie);
 118 }
 119
 120 static void __sched_core_set(struct task_struct *p, unsigned long cookie)
 121 {
 122         cookie = sched_core_get_cookie(cookie);
 123         cookie = sched_core_update_cookie(p, cookie);
 124         sched_core_put_cookie(cookie);
 125 }
 126
 127 /* Called from prctl interface: PR_SCHED_CORE */
 128 int sched_core_share_pid(unsigned int cmd, pid_t pid, enum pid_type type,
 129                          unsigned long uaddr)
 130 {
 131         unsigned long cookie = 0, id = 0;
 132         struct task_struct *task, *p;
 133         struct pid *grp;
 134         int err = 0;
 135
 136         if (!static_branch_likely(&sched_smt_present))
 137                 return -ENODEV;
 138
 139         BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_THREAD != PIDTYPE_PID);
 140         BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_THREAD_GROUP != PIDTYPE_TGID);
 141         BUILD_BUG_ON(PR_SCHED_CORE_SCOPE_PROCESS_GROUP != PIDTYPE_PGID);
 142
 143         if (type > PIDTYPE_PGID || cmd >= PR_SCHED_CORE_MAX || pid < 0 ||
 144             (cmd != PR_SCHED_CORE_GET && uaddr))
 145                 return -EINVAL;
 146
 147         rcu_read_lock();
 148         if (pid == 0) {
 149                 task = current;
 150         } else {
 151                 task = find_task_by_vpid(pid);
 152                 if (!task) {
 153                         rcu_read_unlock();
 154                         return -ESRCH;
 155                 }
 156         }
 157         get_task_struct(task);
 158         rcu_read_unlock();
 159
 160         /*
 161          * Check if this process has the right to modify the specified
 162          * process. Use the regular "ptrace_may_access()" checks.
 163          */
 164         if (!ptrace_may_access(task, PTRACE_MODE_READ_REALCREDS)) {
 165                 err = -EPERM;
 166                 goto out;
 167         }
 168
 169         switch (cmd) {
 170         case PR_SCHED_CORE_GET:
 171                 if (type != PIDTYPE_PID || uaddr & 7) {
 172                         err = -EINVAL;
 173                         goto out;
 174                 }
 175                 cookie = sched_core_clone_cookie(task);
 176                 if (cookie) {
 177                         /* XXX improve ? */
 178                         ptr_to_hashval((void *)cookie, &id);
 179                 }
 180                 err = put_user(id, (u64 __user *)uaddr);
 181                 goto out;
 182
 183         case PR_SCHED_CORE_CREATE:
 184                 cookie = sched_core_alloc_cookie();
 185                 if (!cookie) {
 186                         err = -ENOMEM;
 187                         goto out;
 188                 }
 189                 break;
 190
 191         case PR_SCHED_CORE_SHARE_TO:
 192                 cookie = sched_core_clone_cookie(current);
 193                 break;
 194
 195         case PR_SCHED_CORE_SHARE_FROM:
 196                 if (type != PIDTYPE_PID) {
 197                         err = -EINVAL;
 198                         goto out;
 199                 }
 200                 cookie = sched_core_clone_cookie(task);
 201                 __sched_core_set(current, cookie);
 202                 goto out;
 203
 204         default:
 205                 err = -EINVAL;
 206                 goto out;
 207         };
 208
 209         if (type == PIDTYPE_PID) {
 210                 __sched_core_set(task, cookie);
 211                 goto out;
 212         }
 213
 214         read_lock(&tasklist_lock);
 215         grp = task_pid_type(task, type);
 216
 217         do_each_pid_thread(grp, type, p) {
 218                 if (!ptrace_may_access(p, PTRACE_MODE_READ_REALCREDS)) {
 219                         err = -EPERM;
 220                         goto out_tasklist;
 221                 }
 222         } while_each_pid_thread(grp, type, p);
 223
 224         do_each_pid_thread(grp, type, p) {
 225                 __sched_core_set(p, cookie);
 226         } while_each_pid_thread(grp, type, p);
 227 out_tasklist:
 228         read_unlock(&tasklist_lock);
 229
 230 out:
 231         sched_core_put_cookie(cookie);
 232         put_task_struct(task);
 233         return err;
 234 }
 235
 236 #ifdef CONFIG_SCHEDSTATS
 237
 238 /* REQUIRES: rq->core's clock recently updated. */
 239 void __sched_core_account_forceidle(struct rq *rq)
 240 {
 241         const struct cpumask *smt_mask = cpu_smt_mask(cpu_of(rq));
 242         u64 delta, now = rq_clock(rq->core);
 243         struct rq *rq_i;
 244         struct task_struct *p;
 245         int i;
 246
 247         lockdep_assert_rq_held(rq);
 248
 249         WARN_ON_ONCE(!rq->core->core_forceidle_count);
 250
 251         if (rq->core->core_forceidle_start == 0)
 252                 return;
 253
 254         delta = now - rq->core->core_forceidle_start;
 255         if (unlikely((s64)delta <= 0))
 256                 return;
 257
 258         rq->core->core_forceidle_start = now;
 259
 260         if (WARN_ON_ONCE(!rq->core->core_forceidle_occupation)) {
 261                 /* can't be forced idle without a running task */
 262         } else if (rq->core->core_forceidle_count > 1 ||
 263                    rq->core->core_forceidle_occupation > 1) {
 264                 /*
 265                  * For larger SMT configurations, we need to scale the charged
 266                  * forced idle amount since there can be more than one forced
 267                  * idle sibling and more than one running cookied task.
 268                  */
 269                 delta *= rq->core->core_forceidle_count;
 270                 delta = div_u64(delta, rq->core->core_forceidle_occupation);
 271         }
 272
 273         for_each_cpu(i, smt_mask) {
 274                 rq_i = cpu_rq(i);
 275                 p = rq_i->core_pick ?: rq_i->curr;
 276
 277                 if (p == rq_i->idle)
 278                         continue;
 279
 280                 __schedstat_add(p->stats.core_forceidle_sum, delta);
 281         }
 282 }
 283
 284 void __sched_core_tick(struct rq *rq)
 285 {
 286         if (!rq->core->core_forceidle_count)
 287                 return;
 288
 289         if (rq != rq->core)
 290                 update_rq_clock(rq->core);
 291
 292         __sched_core_account_forceidle(rq);
 293 }
 294
 295 #endif /* CONFIG_SCHEDSTATS */