diff --git a/include/linux/sched.h b/include/linux/sched.h index f2e752377eadd..3ce3e07fbf6f5 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -2011,15 +2011,12 @@ static __always_inline void scheduler_ipi(void) */ preempt_fold_need_resched(); } -extern unsigned long wait_task_inactive(struct task_struct *, unsigned int match_state); #else static inline void scheduler_ipi(void) { } -static inline unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state) -{ - return 1; -} #endif +extern unsigned long wait_task_inactive(struct task_struct *, unsigned int match_state); + /* * Set thread flags in other task's structures. * See asm/thread_info.h for TIF_xxxx flags available: diff --git a/include/linux/sched/signal.h b/include/linux/sched/signal.h index b38ce53576000..669e8cff40c74 100644 --- a/include/linux/sched/signal.h +++ b/include/linux/sched/signal.h @@ -22,7 +22,6 @@ struct sighand_struct { refcount_t count; wait_queue_head_t signalfd_wqh; struct k_sigaction action[_NSIG]; - struct sigqueue *sigqueue_cache; }; /* @@ -350,7 +349,6 @@ extern int send_sig(int, struct task_struct *, int); extern int zap_other_threads(struct task_struct *p); extern struct sigqueue *sigqueue_alloc(void); extern void sigqueue_free(struct sigqueue *); -extern void sigqueue_free_cached_entry(struct sigqueue *q); extern int send_sigqueue(struct sigqueue *, struct pid *, enum pid_type); extern int do_sigaction(int, struct k_sigaction *, struct k_sigaction *); diff --git a/kernel/fork.c b/kernel/fork.c index 4ba3b5c98ca09..81cba91f30bbe 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -1814,7 +1814,6 @@ static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) RCU_INIT_POINTER(tsk->sighand, sig); if (!sig) return -ENOMEM; - sig->sigqueue_cache = NULL; refcount_set(&sig->count, 1); spin_lock_irq(¤t->sighand->siglock); @@ -1831,17 +1830,7 @@ static int copy_sighand(unsigned long clone_flags, struct task_struct *tsk) void __cleanup_sighand(struct sighand_struct *sighand) { if (refcount_dec_and_test(&sighand->count)) { - struct sigqueue *sigqueue = NULL; - signalfd_cleanup(sighand); - spin_lock_irq(&sighand->siglock); - if (sighand->sigqueue_cache) { - sigqueue = sighand->sigqueue_cache; - sighand->sigqueue_cache = NULL; - } - spin_unlock_irq(&sighand->siglock); - - sigqueue_free_cached_entry(sigqueue); /* * sighand_cachep is SLAB_TYPESAFE_BY_RCU so we can free it * without an RCU grace period, see __lock_task_sighand(). diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 77cde41aeccab..c7c09f1db4572 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -2253,6 +2253,154 @@ void check_preempt_curr(struct rq *rq, struct task_struct *p, int flags) rq_clock_skip_update(rq); } +static __always_inline +int __task_state_match(struct task_struct *p, unsigned int state) +{ + if (READ_ONCE(p->__state) & state) + return 1; + +#ifdef CONFIG_PREEMPT_RT + if (READ_ONCE(p->saved_state) & state) + return -1; +#endif + return 0; +} + +static __always_inline +int task_state_match(struct task_struct *p, unsigned int state) +{ +#ifdef CONFIG_PREEMPT_RT + int match; + + /* + * Serialize against current_save_and_set_rtlock_wait_state() and + * current_restore_rtlock_saved_state(). + */ + raw_spin_lock_irq(&p->pi_lock); + match = __task_state_match(p, state); + raw_spin_unlock_irq(&p->pi_lock); + + return match; +#else + return __task_state_match(p, state); +#endif +} + +/* + * wait_task_inactive - wait for a thread to unschedule. + * + * Wait for the thread to block in any of the states set in @match_state. + * If it changes, i.e. @p might have woken up, then return zero. When we + * succeed in waiting for @p to be off its CPU, we return a positive number + * (its total switch count). If a second call a short while later returns the + * same number, the caller can be sure that @p has remained unscheduled the + * whole time. + * + * The caller must ensure that the task *will* unschedule sometime soon, + * else this function might spin for a *long* time. This function can't + * be called with interrupts off, or it may introduce deadlock with + * smp_call_function() if an IPI is sent by the same process we are + * waiting to become inactive. + */ +unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state) +{ + int running, queued, match; + struct rq_flags rf; + unsigned long ncsw; + struct rq *rq; + + for (;;) { + /* + * We do the initial early heuristics without holding + * any task-queue locks at all. We'll only try to get + * the runqueue lock when things look like they will + * work out! + */ + rq = task_rq(p); + + /* + * If the task is actively running on another CPU + * still, just relax and busy-wait without holding + * any locks. + * + * NOTE! Since we don't hold any locks, it's not + * even sure that "rq" stays as the right runqueue! + * But we don't care, since "task_on_cpu()" will + * return false if the runqueue has changed and p + * is actually now running somewhere else! + */ + while (task_on_cpu(rq, p)) { + if (!task_state_match(p, match_state)) + return 0; + cpu_relax(); + } + + /* + * Ok, time to look more closely! We need the rq + * lock now, to be *sure*. If we're wrong, we'll + * just go back and repeat. + */ + rq = task_rq_lock(p, &rf); + trace_sched_wait_task(p); + running = task_on_cpu(rq, p); + queued = task_on_rq_queued(p); + ncsw = 0; + if ((match = __task_state_match(p, match_state))) { + /* + * When matching on p->saved_state, consider this task + * still queued so it will wait. + */ + if (match < 0) + queued = 1; + ncsw = p->nvcsw | LONG_MIN; /* sets MSB */ + } + task_rq_unlock(rq, p, &rf); + + /* + * If it changed from the expected state, bail out now. + */ + if (unlikely(!ncsw)) + break; + + /* + * Was it really running after all now that we + * checked with the proper locks actually held? + * + * Oops. Go back and try again.. + */ + if (unlikely(running)) { + cpu_relax(); + continue; + } + + /* + * It's not enough that it's not actively running, + * it must be off the runqueue _entirely_, and not + * preempted! + * + * So if it was still runnable (but just not actively + * running right now), it's preempted, and we should + * yield - it could be a while. + */ + if (unlikely(queued)) { + ktime_t to = NSEC_PER_SEC / HZ; + + set_current_state(TASK_UNINTERRUPTIBLE); + schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD); + continue; + } + + /* + * Ahh, all good. It wasn't running, and it wasn't + * runnable, which means that it will never become + * running in the future either. We're all done! + */ + break; + } + + return ncsw; +} + #ifdef CONFIG_SMP static void @@ -3383,185 +3531,6 @@ int migrate_swap(struct task_struct *cur, struct task_struct *p, } #endif /* CONFIG_NUMA_BALANCING */ -#ifdef CONFIG_PREEMPT_RT - -/* - * Consider: - * - * set_special_state(X); - * - * do_things() - * // Somewhere in there is an rtlock that can be contended: - * current_save_and_set_rtlock_wait_state(); - * [...] - * schedule_rtlock(); (A) - * [...] - * current_restore_rtlock_saved_state(); - * - * schedule(); (B) - * - * If p->saved_state is anything else than TASK_RUNNING, then p blocked on an - * rtlock (A) *before* voluntarily calling into schedule() (B) after setting its - * state to X. For things like ptrace (X=TASK_TRACED), the task could have more - * work to do upon acquiring the lock in do_things() before whoever called - * wait_task_inactive() should return. IOW, we have to wait for: - * - * p.saved_state = TASK_RUNNING - * p.__state = X - * - * which implies the task isn't blocked on an RT lock and got to schedule() (B). - * - * Also see comments in ttwu_state_match(). - */ - -static __always_inline bool state_mismatch(struct task_struct *p, unsigned int match_state) -{ - unsigned long flags; - bool mismatch; - - raw_spin_lock_irqsave(&p->pi_lock, flags); - if (READ_ONCE(p->__state) & match_state) - mismatch = false; - else if (READ_ONCE(p->saved_state) & match_state) - mismatch = false; - else - mismatch = true; - - raw_spin_unlock_irqrestore(&p->pi_lock, flags); - return mismatch; -} -static __always_inline bool state_match(struct task_struct *p, unsigned int match_state, - bool *wait) -{ - if (READ_ONCE(p->__state) & match_state) - return true; - if (READ_ONCE(p->saved_state) & match_state) { - *wait = true; - return true; - } - return false; -} -#else -static __always_inline bool state_mismatch(struct task_struct *p, unsigned int match_state) -{ - return !(READ_ONCE(p->__state) & match_state); -} -static __always_inline bool state_match(struct task_struct *p, unsigned int match_state, - bool *wait) -{ - return (READ_ONCE(p->__state) & match_state); -} -#endif - -/* - * wait_task_inactive - wait for a thread to unschedule. - * - * Wait for the thread to block in any of the states set in @match_state. - * If it changes, i.e. @p might have woken up, then return zero. When we - * succeed in waiting for @p to be off its CPU, we return a positive number - * (its total switch count). If a second call a short while later returns the - * same number, the caller can be sure that @p has remained unscheduled the - * whole time. - * - * The caller must ensure that the task *will* unschedule sometime soon, - * else this function might spin for a *long* time. This function can't - * be called with interrupts off, or it may introduce deadlock with - * smp_call_function() if an IPI is sent by the same process we are - * waiting to become inactive. - */ -unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state) -{ - bool running, wait; - struct rq_flags rf; - unsigned long ncsw; - struct rq *rq; - - for (;;) { - /* - * We do the initial early heuristics without holding - * any task-queue locks at all. We'll only try to get - * the runqueue lock when things look like they will - * work out! - */ - rq = task_rq(p); - - /* - * If the task is actively running on another CPU - * still, just relax and busy-wait without holding - * any locks. - * - * NOTE! Since we don't hold any locks, it's not - * even sure that "rq" stays as the right runqueue! - * But we don't care, since "task_on_cpu()" will - * return false if the runqueue has changed and p - * is actually now running somewhere else! - */ - while (task_on_cpu(rq, p)) { - if (state_mismatch(p, match_state)) - return 0; - cpu_relax(); - } - - /* - * Ok, time to look more closely! We need the rq - * lock now, to be *sure*. If we're wrong, we'll - * just go back and repeat. - */ - rq = task_rq_lock(p, &rf); - trace_sched_wait_task(p); - running = task_on_cpu(rq, p); - wait = task_on_rq_queued(p); - ncsw = 0; - - if (state_match(p, match_state, &wait)) - ncsw = p->nvcsw | LONG_MIN; /* sets MSB */ - task_rq_unlock(rq, p, &rf); - - /* - * If it changed from the expected state, bail out now. - */ - if (unlikely(!ncsw)) - break; - - /* - * Was it really running after all now that we - * checked with the proper locks actually held? - * - * Oops. Go back and try again.. - */ - if (unlikely(running)) { - cpu_relax(); - continue; - } - - /* - * It's not enough that it's not actively running, - * it must be off the runqueue _entirely_, and not - * preempted! - * - * So if it was still runnable (but just not actively - * running right now), it's preempted, and we should - * yield - it could be a while. - */ - if (unlikely(wait)) { - ktime_t to = NSEC_PER_SEC / HZ; - - set_current_state(TASK_UNINTERRUPTIBLE); - schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD); - continue; - } - - /* - * Ahh, all good. It wasn't running, and it wasn't - * runnable, which means that it will never become - * running in the future either. We're all done! - */ - break; - } - - return ncsw; -} - /*** * kick_process - kick a running thread to enter/exit the kernel * @p: the to-be-kicked thread @@ -4116,15 +4085,14 @@ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) static __always_inline bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success) { + int match; + if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) { WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) && state != TASK_RTLOCK_WAIT); } - if (READ_ONCE(p->__state) & state) { - *success = 1; - return true; - } + *success = !!(match = __task_state_match(p, state)); #ifdef CONFIG_PREEMPT_RT /* @@ -4140,12 +4108,10 @@ bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success) * p::saved_state to TASK_RUNNING so any further tests will * not result in false positives vs. @success */ - if (p->saved_state & state) { + if (match < 0) p->saved_state = TASK_RUNNING; - *success = 1; - } #endif - return false; + return match > 0; } /* diff --git a/kernel/signal.c b/kernel/signal.c index 5ba6cb05ff4f5..9e07b3075c72e 100644 --- a/kernel/signal.c +++ b/kernel/signal.c @@ -432,18 +432,7 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t gfp_flags, return NULL; if (override_rlimit || likely(sigpending <= task_rlimit(t, RLIMIT_SIGPENDING))) { - - if (!sigqueue_flags) { - struct sighand_struct *sighand = t->sighand; - - lockdep_assert_held(&sighand->siglock); - if (sighand->sigqueue_cache) { - q = sighand->sigqueue_cache; - sighand->sigqueue_cache = NULL; - } - } - if (!q) - q = kmem_cache_alloc(sigqueue_cachep, gfp_flags); + q = kmem_cache_alloc(sigqueue_cachep, gfp_flags); } else { print_dropped_signal(sig); } @@ -458,43 +447,14 @@ __sigqueue_alloc(int sig, struct task_struct *t, gfp_t gfp_flags, return q; } -static bool sigqueue_cleanup_accounting(struct sigqueue *q) +static void __sigqueue_free(struct sigqueue *q) { if (q->flags & SIGQUEUE_PREALLOC) - return false; + return; if (q->ucounts) { dec_rlimit_put_ucounts(q->ucounts, UCOUNT_RLIMIT_SIGPENDING); q->ucounts = NULL; } - return true; -} - -static void __sigqueue_free(struct sigqueue *q) -{ - if (!sigqueue_cleanup_accounting(q)) - return; - kmem_cache_free(sigqueue_cachep, q); -} - -void sigqueue_free_cached_entry(struct sigqueue *q) -{ - if (!q) - return; - kmem_cache_free(sigqueue_cachep, q); -} - -static void sigqueue_cache_or_free(struct sigqueue *q) -{ - struct sighand_struct *sighand = current->sighand; - - if (!sigqueue_cleanup_accounting(q)) - return; - - lockdep_assert_held(&sighand->siglock); - if (!sighand->sigqueue_cache) { - sighand->sigqueue_cache = q; - return; - } kmem_cache_free(sigqueue_cachep, q); } @@ -634,7 +594,7 @@ static void collect_signal(int sig, struct sigpending *list, kernel_siginfo_t *i (info->si_code == SI_TIMER) && (info->si_sys_private); - sigqueue_cache_or_free(first); + __sigqueue_free(first); } else { /* * Ok, it wasn't in the queue. This must be diff --git a/localversion-rt b/localversion-rt index 1445cd65885cd..ad3da1bcab7e8 100644 --- a/localversion-rt +++ b/localversion-rt @@ -1 +1 @@ --rt3 +-rt4