diff options
| -rw-r--r-- | fs/exec.c | 2 | ||||
| -rw-r--r-- | include/linux/mm_types.h | 14 | ||||
| -rw-r--r-- | include/linux/rcuwait.h | 20 | ||||
| -rw-r--r-- | include/linux/sched.h | 10 | ||||
| -rw-r--r-- | include/linux/sched/mm.h | 10 | ||||
| -rw-r--r-- | include/linux/sched/task.h | 2 | ||||
| -rw-r--r-- | kernel/exit.c | 74 | ||||
| -rw-r--r-- | kernel/fork.c | 8 | ||||
| -rw-r--r-- | kernel/sched/core.c | 28 | ||||
| -rw-r--r-- | kernel/sched/fair.c | 39 | ||||
| -rw-r--r-- | kernel/sched/membarrier.c | 239 | ||||
| -rw-r--r-- | kernel/sched/sched.h | 34 | ||||
| -rw-r--r-- | tools/testing/selftests/membarrier/.gitignore | 3 | ||||
| -rw-r--r-- | tools/testing/selftests/membarrier/Makefile | 5 | ||||
| -rw-r--r-- | tools/testing/selftests/membarrier/membarrier_test_impl.h (renamed from tools/testing/selftests/membarrier/membarrier_test.c) | 40 | ||||
| -rw-r--r-- | tools/testing/selftests/membarrier/membarrier_test_multi_thread.c | 73 | ||||
| -rw-r--r-- | tools/testing/selftests/membarrier/membarrier_test_single_thread.c | 24 |
17 files changed, 375 insertions, 250 deletions
diff --git a/fs/exec.c b/fs/exec.c index f7f6a140856a..555e93c7dec8 100644 --- a/fs/exec.c +++ b/fs/exec.c @@ -1033,6 +1033,7 @@ static int exec_mmap(struct mm_struct *mm) } task_lock(tsk); active_mm = tsk->active_mm; + membarrier_exec_mmap(mm); tsk->mm = mm; tsk->active_mm = mm; activate_mm(active_mm, mm); @@ -1825,7 +1826,6 @@ static int __do_execve_file(int fd, struct filename *filename, /* execve succeeded */ current->fs->in_exec = 0; current->in_execve = 0; - membarrier_execve(current); rseq_execve(current); acct_update_integrals(current); task_numa_free(current, false); diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h index 5183e0d77dfa..2222fa795284 100644 --- a/include/linux/mm_types.h +++ b/include/linux/mm_types.h @@ -383,6 +383,16 @@ struct mm_struct { unsigned long highest_vm_end; /* highest vma end address */ pgd_t * pgd; +#ifdef CONFIG_MEMBARRIER + /** + * @membarrier_state: Flags controlling membarrier behavior. + * + * This field is close to @pgd to hopefully fit in the same + * cache-line, which needs to be touched by switch_mm(). + */ + atomic_t membarrier_state; +#endif + /** * @mm_users: The number of users including userspace. * @@ -452,9 +462,7 @@ struct mm_struct { unsigned long flags; /* Must use atomic bitops to access */ struct core_state *core_state; /* coredumping support */ -#ifdef CONFIG_MEMBARRIER - atomic_t membarrier_state; -#endif + #ifdef CONFIG_AIO spinlock_t ioctx_lock; struct kioctx_table __rcu *ioctx_table; diff --git a/include/linux/rcuwait.h b/include/linux/rcuwait.h index 563290fc194f..75c97e4bbc57 100644 --- a/include/linux/rcuwait.h +++ b/include/linux/rcuwait.h @@ -6,16 +6,11 @@ /* * rcuwait provides a way of blocking and waking up a single - * task in an rcu-safe manner; where it is forbidden to use - * after exit_notify(). task_struct is not properly rcu protected, - * unless dealing with rcu-aware lists, ie: find_task_by_*(). + * task in an rcu-safe manner. * - * Alternatively we have task_rcu_dereference(), but the return - * semantics have different implications which would break the - * wakeup side. The only time @task is non-nil is when a user is - * blocked (or checking if it needs to) on a condition, and reset - * as soon as we know that the condition has succeeded and are - * awoken. + * The only time @task is non-nil is when a user is blocked (or + * checking if it needs to) on a condition, and reset as soon as we + * know that the condition has succeeded and are awoken. */ struct rcuwait { struct task_struct __rcu *task; @@ -37,13 +32,6 @@ extern void rcuwait_wake_up(struct rcuwait *w); */ #define rcuwait_wait_event(w, condition) \ ({ \ - /* \ - * Complain if we are called after do_exit()/exit_notify(), \ - * as we cannot rely on the rcu critical region for the \ - * wakeup side. \ - */ \ - WARN_ON(current->exit_state); \ - \ rcu_assign_pointer((w)->task, current); \ for (;;) { \ /* \ diff --git a/include/linux/sched.h b/include/linux/sched.h index 70db597d6fd4..2c2e56bd8913 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -1130,7 +1130,10 @@ struct task_struct { struct tlbflush_unmap_batch tlb_ubc; - struct rcu_head rcu; + union { + refcount_t rcu_users; + struct rcu_head rcu; + }; /* Cache last used pipe for splice(): */ struct pipe_inode_info *splice_pipe; @@ -1839,7 +1842,10 @@ static inline void set_task_cpu(struct task_struct *p, unsigned int cpu) * running or not. */ #ifndef vcpu_is_preempted -# define vcpu_is_preempted(cpu) false +static inline bool vcpu_is_preempted(int cpu) +{ + return false; +} #endif extern long sched_setaffinity(pid_t pid, const struct cpumask *new_mask); diff --git a/include/linux/sched/mm.h b/include/linux/sched/mm.h index 4a7944078cc3..e6770012db18 100644 --- a/include/linux/sched/mm.h +++ b/include/linux/sched/mm.h @@ -362,16 +362,16 @@ enum { static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm) { + if (current->mm != mm) + return; if (likely(!(atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE))) return; sync_core_before_usermode(); } -static inline void membarrier_execve(struct task_struct *t) -{ - atomic_set(&t->mm->membarrier_state, 0); -} +extern void membarrier_exec_mmap(struct mm_struct *mm); + #else #ifdef CONFIG_ARCH_HAS_MEMBARRIER_CALLBACKS static inline void membarrier_arch_switch_mm(struct mm_struct *prev, @@ -380,7 +380,7 @@ static inline void membarrier_arch_switch_mm(struct mm_struct *prev, { } #endif -static inline void membarrier_execve(struct task_struct *t) +static inline void membarrier_exec_mmap(struct mm_struct *mm) { } static inline void membarrier_mm_sync_core_before_usermode(struct mm_struct *mm) diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h index 3d90ed8f75f0..4b1c3b664f51 100644 --- a/include/linux/sched/task.h +++ b/include/linux/sched/task.h @@ -119,7 +119,7 @@ static inline void put_task_struct(struct task_struct *t) __put_task_struct(t); } -struct task_struct *task_rcu_dereference(struct task_struct **ptask); +void put_task_struct_rcu_user(struct task_struct *task); #ifdef CONFIG_ARCH_WANTS_DYNAMIC_TASK_STRUCT extern int arch_task_struct_size __read_mostly; diff --git a/kernel/exit.c b/kernel/exit.c index 22ab6a4bdc51..a46a50d67002 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -182,6 +182,11 @@ static void delayed_put_task_struct(struct rcu_head *rhp) put_task_struct(tsk); } +void put_task_struct_rcu_user(struct task_struct *task) +{ + if (refcount_dec_and_test(&task->rcu_users)) + call_rcu(&task->rcu, delayed_put_task_struct); +} void release_task(struct task_struct *p) { @@ -222,76 +227,13 @@ repeat: write_unlock_irq(&tasklist_lock); release_thread(p); - call_rcu(&p->rcu, delayed_put_task_struct); + put_task_struct_rcu_user(p); p = leader; if (unlikely(zap_leader)) goto repeat; } -/* - * Note that if this function returns a valid task_struct pointer (!NULL) - * task->usage must remain >0 for the duration of the RCU critical section. - */ -struct task_struct *task_rcu_dereference(struct task_struct **ptask) -{ - struct sighand_struct *sighand; - struct task_struct *task; - - /* - * We need to verify that release_task() was not called and thus - * delayed_put_task_struct() can't run and drop the last reference - * before rcu_read_unlock(). We check task->sighand != NULL, - * but we can read the already freed and reused memory. - */ -retry: - task = rcu_dereference(*ptask); - if (!task) - return NULL; - - probe_kernel_address(&task->sighand, sighand); - - /* - * Pairs with atomic_dec_and_test() in put_task_struct(). If this task - * was already freed we can not miss the preceding update of this - * pointer. - */ - smp_rmb(); - if (unlikely(task != READ_ONCE(*ptask))) - goto retry; - - /* - * We've re-checked that "task == *ptask", now we have two different - * cases: - * - * 1. This is actually the same task/task_struct. In this case - * sighand != NULL tells us it is still alive. - * - * 2. This is another task which got the same memory for task_struct. - * We can't know this of course, and we can not trust - * sighand != NULL. - * - * In this case we actually return a random value, but this is - * correct. - * - * If we return NULL - we can pretend that we actually noticed that - * *ptask was updated when the previous task has exited. Or pretend - * that probe_slab_address(&sighand) reads NULL. - * - * If we return the new task (because sighand is not NULL for any - * reason) - this is fine too. This (new) task can't go away before - * another gp pass. - * - * And note: We could even eliminate the false positive if re-read - * task->sighand once again to avoid the falsely NULL. But this case - * is very unlikely so we don't care. - */ - if (!sighand) - return NULL; - - return task; -} - void rcuwait_wake_up(struct rcuwait *w) { struct task_struct *task; @@ -311,10 +253,6 @@ void rcuwait_wake_up(struct rcuwait *w) */ smp_mb(); /* (B) */ - /* - * Avoid using task_rcu_dereference() magic as long as we are careful, - * see comment in rcuwait_wait_event() regarding ->exit_state. - */ task = rcu_dereference(w->task); if (task) wake_up_process(task); diff --git a/kernel/fork.c b/kernel/fork.c index 60763c043aa3..f9572f416126 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -915,10 +915,12 @@ static struct task_struct *dup_task_struct(struct task_struct *orig, int node) tsk->cpus_ptr = &tsk->cpus_mask; /* - * One for us, one for whoever does the "release_task()" (usually - * parent) + * One for the user space visible state that goes away when reaped. + * One for the scheduler. */ - refcount_set(&tsk->usage, 2); + refcount_set(&tsk->rcu_users, 2); + /* One for the rcu users */ + refcount_set(&tsk->usage, 1); #ifdef CONFIG_BLK_DEV_IO_TRACE tsk->btrace_seq = 0; #endif diff --git a/kernel/sched/core.c b/kernel/sched/core.c index f9a1346a5fa9..7880f4f64d0e 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -1656,7 +1656,8 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, if (cpumask_equal(p->cpus_ptr, new_mask)) goto out; - if (!cpumask_intersects(new_mask, cpu_valid_mask)) { + dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask); + if (dest_cpu >= nr_cpu_ids) { ret = -EINVAL; goto out; } @@ -1677,7 +1678,6 @@ static int __set_cpus_allowed_ptr(struct task_struct *p, if (cpumask_test_cpu(task_cpu(p), new_mask)) goto out; - dest_cpu = cpumask_any_and(cpu_valid_mask, new_mask); if (task_running(rq, p) || p->state == TASK_WAKING) { struct migration_arg arg = { p, dest_cpu }; /* Need help from migration thread: drop lock and wait. */ @@ -3254,7 +3254,7 @@ static struct rq *finish_task_switch(struct task_struct *prev) /* Task is done with its stack. */ put_task_stack(prev); - put_task_struct(prev); + put_task_struct_rcu_user(prev); } tick_nohz_task_switch(); @@ -3358,15 +3358,15 @@ context_switch(struct rq *rq, struct task_struct *prev, else prev->active_mm = NULL; } else { // to user + membarrier_switch_mm(rq, prev->active_mm, next->mm); /* * sys_membarrier() requires an smp_mb() between setting - * rq->curr and returning to userspace. + * rq->curr / membarrier_switch_mm() and returning to userspace. * * The below provides this either through switch_mm(), or in * case 'prev->active_mm == next->mm' through * finish_task_switch()'s mmdrop(). */ - switch_mm_irqs_off(prev->active_mm, next->mm, next); if (!prev->mm) { // from kernel @@ -4042,7 +4042,11 @@ static void __sched notrace __schedule(bool preempt) if (likely(prev != next)) { rq->nr_switches++; - rq->curr = next; + /* + * RCU users of rcu_dereference(rq->curr) may not see + * changes to task_struct made by pick_next_task(). + */ + RCU_INIT_POINTER(rq->curr, next); /* * The membarrier system call requires each architecture * to have a full memory barrier after updating @@ -4223,9 +4227,8 @@ static void __sched notrace preempt_schedule_common(void) #ifdef CONFIG_PREEMPTION /* - * this is the entry point to schedule() from in-kernel preemption - * off of preempt_enable. Kernel preemptions off return from interrupt - * occur there and call schedule directly. + * This is the entry point to schedule() from in-kernel preemption + * off of preempt_enable. */ asmlinkage __visible void __sched notrace preempt_schedule(void) { @@ -4296,7 +4299,7 @@ EXPORT_SYMBOL_GPL(preempt_schedule_notrace); #endif /* CONFIG_PREEMPTION */ /* - * this is the entry point to schedule() from kernel preemption + * This is the entry point to schedule() from kernel preemption * off of irq context. * Note, that this is called and return with irqs disabled. This will * protect us against recursive calling from irq. @@ -6069,7 +6072,8 @@ void init_idle(struct task_struct *idle, int cpu) __set_task_cpu(idle, cpu); rcu_read_unlock(); - rq->curr = rq->idle = idle; + rq->idle = idle; + rcu_assign_pointer(rq->curr, idle); idle->on_rq = TASK_ON_RQ_QUEUED; #ifdef CONFIG_SMP idle->on_cpu = 1; @@ -6430,8 +6434,6 @@ int sched_cpu_activate(unsigned int cpu) } rq_unlock_irqrestore(rq, &rf); - update_max_interval(); - return 0; } diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c index d4bbf68c3161..83ab35e2374f 100644 --- a/kernel/sched/fair.c +++ b/kernel/sched/fair.c @@ -749,7 +749,6 @@ void init_entity_runnable_average(struct sched_entity *se) /* when this task enqueue'ed, it will contribute to its cfs_rq's load_avg */ } -static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq); static void attach_entity_cfs_rq(struct sched_entity *se); /* @@ -1603,7 +1602,7 @@ static void task_numa_compare(struct task_numa_env *env, return; rcu_read_lock(); - cur = task_rcu_dereference(&dst_rq->curr); + cur = rcu_dereference(dst_rq->curr); if (cur && ((cur->flags & PF_EXITING) || is_idle_task(cur))) cur = NULL; @@ -4354,21 +4353,16 @@ static inline u64 sched_cfs_bandwidth_slice(void) } /* - * Replenish runtime according to assigned quota and update expiration time. - * We use sched_clock_cpu directly instead of rq->clock to avoid adding - * additional synchronization around rq->lock. + * Replenish runtime according to assigned quota. We use sched_clock_cpu + * directly instead of rq->clock to avoid adding additional synchronization + * around rq->lock. * * requires cfs_b->lock */ void __refill_cfs_bandwidth_runtime(struct cfs_bandwidth *cfs_b) { - u64 now; - - if (cfs_b->quota == RUNTIME_INF) - return; - - now = sched_clock_cpu(smp_processor_id()); - cfs_b->runtime = cfs_b->quota; + if (cfs_b->quota != RUNTIME_INF) + cfs_b->runtime = cfs_b->quota; } static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) @@ -4376,15 +4370,6 @@ static inline struct cfs_bandwidth *tg_cfs_bandwidth(struct task_group *tg) return &tg->cfs_bandwidth; } -/* rq->task_clock normalized against any time this cfs_rq has spent throttled */ -static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) -{ - if (unlikely(cfs_rq->throttle_count)) - return cfs_rq->throttled_clock_task - cfs_rq->throttled_clock_task_time; - - return rq_clock_task(rq_of(cfs_rq)) - cfs_rq->throttled_clock_task_time; -} - /* returns 0 on failure to allocate runtime */ static int assign_cfs_rq_runtime(struct cfs_rq *cfs_rq) { @@ -4476,7 +4461,6 @@ static int tg_unthrottle_up(struct task_group *tg, void *data) cfs_rq->throttle_count--; if (!cfs_rq->throttle_count) { - /* adjust cfs_rq_clock_task() */ cfs_rq->throttled_clock_task_time += rq_clock_task(rq) - cfs_rq->throttled_clock_task; @@ -4994,15 +4978,13 @@ static void init_cfs_rq_runtime(struct cfs_rq *cfs_rq) void start_cfs_bandwidth(struct cfs_bandwidth *cfs_b) { - u64 overrun; - lockdep_assert_held(&cfs_b->lock); if (cfs_b->period_active) return; cfs_b->period_active = 1; - overrun = hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period); + hrtimer_forward_now(&cfs_b->period_timer, cfs_b->period); hrtimer_start_expires(&cfs_b->period_timer, HRTIMER_MODE_ABS_PINNED); } @@ -5080,11 +5062,6 @@ static inline bool cfs_bandwidth_used(void) return false; } -static inline u64 cfs_rq_clock_task(struct cfs_rq *cfs_rq) -{ - return rq_clock_task(rq_of(cfs_rq)); -} - static void account_cfs_rq_runtime(struct cfs_rq *cfs_rq, u64 delta_exec) {} static bool check_cfs_rq_runtime(struct cfs_rq *cfs_rq) { return false; } static void check_enqueue_throttle(struct cfs_rq *cfs_rq) {} @@ -6412,7 +6389,7 @@ static int find_energy_efficient_cpu(struct task_struct *p, int prev_cpu) } /* Evaluate the energy impact of using this CPU. */ - if (max_spare_cap_cpu >= 0) { + if (max_spare_cap_cpu >= 0 && max_spare_cap_cpu != prev_cpu) { cur_delta = compute_energy(p, max_spare_cap_cpu, pd); cur_delta -= base_energy_pd; if (cur_delta < best_delta) { diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c index aa8d75804108..a39bed2c784f 100644 --- a/kernel/sched/membarrier.c +++ b/kernel/sched/membarrier.c @@ -30,10 +30,42 @@ static void ipi_mb(void *info) smp_mb(); /* IPIs should be serializing but paranoid. */ } +static void ipi_sync_rq_state(void *info) +{ + struct mm_struct *mm = (struct mm_struct *) info; + + if (current->mm != mm) + return; + this_cpu_write(runqueues.membarrier_state, + atomic_read(&mm->membarrier_state)); + /* + * Issue a memory barrier after setting + * MEMBARRIER_STATE_GLOBAL_EXPEDITED in the current runqueue to + * guarantee that no memory access following registration is reordered + * before registration. + */ + smp_mb(); +} + +void membarrier_exec_mmap(struct mm_struct *mm) +{ + /* + * Issue a memory barrier before clearing membarrier_state to + * guarantee that no memory access prior to exec is reordered after + * clearing this state. + */ + smp_mb(); + atomic_set(&mm->membarrier_state, 0); + /* + * Keep the runqueue membarrier_state in sync with this mm + * membarrier_state. + */ + this_cpu_write(runqueues.membarrier_state, 0); +} + static int membarrier_global_expedited(void) { int cpu; - bool fallback = false; cpumask_var_t tmpmask; if (num_online_cpus() == 1) @@ -45,17 +77,11 @@ static int membarrier_global_expedited(void) */ smp_mb(); /* system call entry is not a mb. */ - /* - * Expedited membarrier commands guarantee that they won't - * block, hence the GFP_NOWAIT allocation flag and fallback - * implementation. - */ - if (!zalloc_cpumask_var(&tmpmask, GFP_NOWAIT)) { - /* Fallback for OOM. */ - fallback = true; - } + if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL)) + return -ENOMEM; cpus_read_lock(); + rcu_read_lock(); for_each_online_cpu(cpu) { struct task_struct *p; @@ -70,23 +96,28 @@ static int membarrier_global_expedited(void) if (cpu == raw_smp_processor_id()) continue; - rcu_read_lock(); - p = task_rcu_dereference(&cpu_rq(cpu)->curr); - if (p && p->mm && (atomic_read(&p->mm->membarrier_state) & - MEMBARRIER_STATE_GLOBAL_EXPEDITED)) { - if (!fallback) - __cpumask_set_cpu(cpu, tmpmask); - else - smp_call_function_single(cpu, ipi_mb, NULL, 1); - } - rcu_read_unlock(); - } - if (!fallback) { - preempt_disable(); - smp_call_function_many(tmpmask, ipi_mb, NULL, 1); - preempt_enable(); - free_cpumask_var(tmpmask); + if (!(READ_ONCE(cpu_rq(cpu)->membarrier_state) & + MEMBARRIER_STATE_GLOBAL_EXPEDITED)) + continue; + + /* + * Skip the CPU if it runs a kernel thread. The scheduler + * leaves the prior task mm in place as an optimization when + * scheduling a kthread. + */ + p = rcu_dereference(cpu_rq(cpu)->curr); + if (p->flags & PF_KTHREAD) + continue; + + __cpumask_set_cpu(cpu, tmpmask); } + rcu_read_unlock(); + + preempt_disable(); + smp_call_function_many(tmpmask, ipi_mb, NULL, 1); + preempt_enable(); + + free_cpumask_var(tmpmask); cpus_read_unlock(); /* @@ -101,22 +132,22 @@ static int membarrier_global_expedited(void) static int membarrier_private_expedited(int flags) { int cpu; - bool fallback = false; cpumask_var_t tmpmask; + struct mm_struct *mm = current->mm; if (flags & MEMBARRIER_FLAG_SYNC_CORE) { if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE)) return -EINVAL; - if (!(atomic_read(¤t->mm->membarrier_state) & + if (!(atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY)) return -EPERM; } else { - if (!(atomic_read(¤t->mm->membarrier_state) & + if (!(atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY)) return -EPERM; } - if (num_online_cpus() == 1) + if (atomic_read(&mm->mm_users) == 1 || num_online_cpus() == 1) return 0; /* @@ -125,17 +156,11 @@ static int membarrier_private_expedited(int flags) */ smp_mb(); /* system call entry is not a mb. */ - /* - * Expedited membarrier commands guarantee that they won't - * block, hence the GFP_NOWAIT allocation flag and fallback - * implementation. - */ - if (!zalloc_cpumask_var(&tmpmask, GFP_NOWAIT)) { - /* Fallback for OOM. */ - fallback = true; - } + if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL)) + return -ENOMEM; cpus_read_lock(); + rcu_read_lock(); for_each_online_cpu(cpu) { struct task_struct *p; @@ -150,21 +175,17 @@ static int membarrier_private_expedited(int flags) if (cpu == raw_smp_processor_id()) continue; rcu_read_lock(); - p = task_rcu_dereference(&cpu_rq(cpu)->curr); - if (p && p->mm == current->mm) { - if (!fallback) - __cpumask_set_cpu(cpu, tmpmask); - else - smp_call_function_single(cpu, ipi_mb, NULL, 1); - } - rcu_read_unlock(); - } - if (!fallback) { - preempt_disable(); - smp_call_function_many(tmpmask, ipi_mb, NULL, 1); - preempt_enable(); - free_cpumask_var(tmpmask); + p = rcu_dereference(cpu_rq(cpu)->curr); + if (p && p->mm == mm) + __cpumask_set_cpu(cpu, tmpmask); } + rcu_read_unlock(); + + preempt_disable(); + smp_call_function_many(tmpmask, ipi_mb, NULL, 1); + preempt_enable(); + + free_cpumask_var(tmpmask); cpus_read_unlock(); /* @@ -177,32 +198,78 @@ static int membarrier_private_expedited(int flags) return 0; } +static int sync_runqueues_membarrier_state(struct mm_struct *mm) +{ + int membarrier_state = atomic_read(&mm->membarrier_state); + cpumask_var_t tmpmask; + int cpu; + + if (atomic_read(&mm->mm_users) == 1 || num_online_cpus() == 1) { + this_cpu_write(runqueues.membarrier_state, membarrier_state); + + /* + * For single mm user, we can simply issue a memory barrier + * after setting MEMBARRIER_STATE_GLOBAL_EXPEDITED in the + * mm and in the current runqueue to guarantee that no memory + * access following registration is reordered before + * registration. + */ + smp_mb(); + return 0; + } + + if (!zalloc_cpumask_var(&tmpmask, GFP_KERNEL)) + return -ENOMEM; + + /* + * For mm with multiple users, we need to ensure all future + * scheduler executions will observe @mm's new membarrier + * state. + */ + synchronize_rcu(); + + /* + * For each cpu runqueue, if the task's mm match @mm, ensure that all + * @mm's membarrier state set bits are also set in in the runqueue's + * membarrier state. This ensures that a runqueue scheduling + * between threads which are users of @mm has its membarrier state + * updated. + */ + cpus_read_lock(); + rcu_read_lock(); + for_each_online_cpu(cpu) { + struct rq *rq = cpu_rq(cpu); + struct task_struct *p; + + p = rcu_dereference(rq->curr); + if (p && p->mm == mm) + __cpumask_set_cpu(cpu, tmpmask); + } + rcu_read_unlock(); + + preempt_disable(); + smp_call_function_many(tmpmask, ipi_sync_rq_state, mm, 1); + preempt_enable(); + + free_cpumask_var(tmpmask); + cpus_read_unlock(); + + return 0; +} + static int membarrier_register_global_expedited(void) { struct task_struct *p = current; struct mm_struct *mm = p->mm; + int ret; if (atomic_read(&mm->membarrier_state) & MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY) return 0; atomic_or(MEMBARRIER_STATE_GLOBAL_EXPEDITED, &mm->membarrier_state); - if (atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1) { - /* - * For single mm user, single threaded process, we can - * simply issue a memory barrier after setting - * MEMBARRIER_STATE_GLOBAL_EXPEDITED to guarantee that - * no memory access following registration is reordered - * before registration. - */ - smp_mb(); - } else { - /* - * For multi-mm user threads, we need to ensure all - * future scheduler executions will observe the new - * thread flag state for this mm. - */ - synchronize_rcu(); - } + ret = sync_runqueues_membarrier_state(mm); + if (ret) + return ret; atomic_or(MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY, &mm->membarrier_state); @@ -213,12 +280,15 @@ static int membarrier_register_private_expedited(int flags) { struct task_struct *p = current; struct mm_struct *mm = p->mm; - int state = MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY; + int ready_state = MEMBARRIER_STATE_PRIVATE_EXPEDITED_READY, + set_state = MEMBARRIER_STATE_PRIVATE_EXPEDITED, + ret; if (flags & MEMBARRIER_FLAG_SYNC_CORE) { if (!IS_ENABLED(CONFIG_ARCH_HAS_MEMBARRIER_SYNC_CORE)) return -EINVAL; - state = MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY; + ready_state = + MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE_READY; } /* @@ -226,20 +296,15 @@ static int membarrier_register_private_expedited(int flags) * groups, which use the same mm. (CLONE_VM but not * CLONE_THREAD). */ - if (atomic_read(&mm->membarrier_state) & state) + if ((atomic_read(&mm->membarrier_state) & ready_state) == ready_state) return 0; - atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED, &mm->membarrier_state); if (flags & MEMBARRIER_FLAG_SYNC_CORE) - atomic_or(MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE, - &mm->membarrier_state); - if (!(atomic_read(&mm->mm_users) == 1 && get_nr_threads(p) == 1)) { - /* - * Ensure all future scheduler executions will observe the - * new thread flag state for this process. - */ - synchronize_rcu(); - } - atomic_or(state, &mm->membarrier_state); + set_state |= MEMBARRIER_STATE_PRIVATE_EXPEDITED_SYNC_CORE; + atomic_or(set_state, &mm->membarrier_state); + ret = sync_runqueues_membarrier_state(mm); + if (ret) + return ret; + atomic_or(ready_state, &mm->membarrier_state); return 0; } @@ -253,8 +318,10 @@ static int membarrier_register_private_expedited(int flags) * command specified does not exist, not available on the running * kernel, or if the command argument is invalid, this system call * returns -EINVAL. For a given command, with flags argument set to 0, - * this system call is guaranteed to always return the same value until - * reboot. + * if this system call returns -ENOSYS or -EINVAL, it is guaranteed to + * always return the same value until reboot. In addition, it can return + * -ENOMEM if there is not enough memory available to perform the system + * call. * * All memory accesses performed in program order from each targeted thread * is guaranteed to be ordered with respect to sys_membarrier(). If we use diff --git a/kernel/sched/sched.h b/kernel/sched/sched.h index b3cb895d14a2..0db2c1b3361e 100644 --- a/kernel/sched/sched.h +++ b/kernel/sched/sched.h @@ -911,6 +911,10 @@ struct rq { atomic_t nr_iowait; +#ifdef CONFIG_MEMBARRIER + int membarrier_state; +#endif + #ifdef CONFIG_SMP struct root_domain *rd; struct sched_domain __rcu *sd; @@ -2438,3 +2442,33 @@ static inline bool sched_energy_enabled(void) static inline bool sched_energy_enabled(void) { return false; } #endif /* CONFIG_ENERGY_MODEL && CONFIG_CPU_FREQ_GOV_SCHEDUTIL */ + +#ifdef CONFIG_MEMBARRIER +/* + * The scheduler provides memory barriers required by membarrier between: + * - prior user-space memory accesses and store to rq->membarrier_state, + * - store to rq->membarrier_state and following user-space memory accesses. + * In the same way it provides those guarantees around store to rq->curr. + */ +static inline void membarrier_switch_mm(struct rq *rq, + struct mm_struct *prev_mm, + struct mm_struct *next_mm) +{ + int membarrier_state; + + if (prev_mm == next_mm) + return; + + membarrier_state = atomic_read(&next_mm->membarrier_state); + if (READ_ONCE(rq->membarrier_state) == membarrier_state) + return; + + WRITE_ONCE(rq->membarrier_state, membarrier_state); +} +#else +static inline void membarrier_switch_mm(struct rq *rq, + struct mm_struct *prev_mm, + struct mm_struct *next_mm) +{ +} +#endif diff --git a/tools/testing/selftests/membarrier/.gitignore b/tools/testing/selftests/membarrier/.gitignore index 020c44f49a9e..f2f7ec0a99b4 100644 --- a/tools/testing/selftests/membarrier/.gitignore +++ b/tools/testing/selftests/membarrier/.gitignore @@ -1 +1,2 @@ -membarrier_test +membarrier_test_multi_thread +membarrier_test_single_thread diff --git a/tools/testing/selftests/membarrier/Makefile b/tools/testing/selftests/membarrier/Makefile index 97e3bdf3d1e9..34d1c81a2324 100644 --- a/tools/testing/selftests/membarrier/Makefile +++ b/tools/testing/selftests/membarrier/Makefile @@ -1,7 +1,8 @@ # SPDX-License-Identifier: GPL-2.0-only CFLAGS += -g -I../../../../usr/include/ +LDLIBS += -lpthread -TEST_GEN_PROGS := membarrier_test +TEST_GEN_PROGS := membarrier_test_single_thread \ + membarrier_test_multi_thread include ../lib.mk - diff --git a/tools/testing/selftests/membarrier/membarrier_test.c b/tools/testing/selftests/membarrier/membarrier_test_impl.h index 70b4ddbf126b..186be69f0a59 100644 --- a/tools/testing/selftests/membarrier/membarrier_test.c +++ b/tools/testing/selftests/membarrier/membarrier_test_impl.h @@ -1,10 +1,11 @@ -// SPDX-License-Identifier: GPL-2.0 +/* SPDX-License-Identifier: GPL-2.0 */ #define _GNU_SOURCE #include <linux/membarrier.h> #include <syscall.h> #include <stdio.h> #include <errno.h> #include <string.h> +#include <pthread.h> #include "../kselftest.h" @@ -223,7 +224,7 @@ static int test_membarrier_global_expedited_success(void) return 0; } -static int test_membarrier(void) +static int test_membarrier_fail(void) { int status; @@ -233,10 +234,27 @@ static int test_membarrier(void) status = test_membarrier_flags_fail(); if (status) return status; - status = test_membarrier_global_success(); + status = test_membarrier_private_expedited_fail(); if (status) return status; - status = test_membarrier_private_expedited_fail(); + status = sys_membarrier(MEMBARRIER_CMD_QUERY, 0); + if (status < 0) { + ksft_test_result_fail("sys_membarrier() failed\n"); + return status; + } + if (status & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) { + status = test_membarrier_private_expedited_sync_core_fail(); + if (status) + return status; + } + return 0; +} + +static int test_membarrier_success(void) +{ + int status; + + status = test_membarrier_global_success(); if (status) return status; status = test_membarrier_register_private_expedited_success(); @@ -251,9 +269,6 @@ static int test_membarrier(void) return status; } if (status & MEMBARRIER_CMD_PRIVATE_EXPEDITED_SYNC_CORE) { - status = test_membarrier_private_expedited_sync_core_fail(); - if (status) - return status; status = test_membarrier_register_private_expedited_sync_core_success(); if (status) return status; @@ -300,14 +315,3 @@ static int test_membarrier_query(void) ksft_test_result_pass("sys_membarrier available\n"); return 0; } - -int main(int argc, char **argv) -{ - ksft_print_header(); - ksft_set_plan(13); - - test_membarrier_query(); - test_membarrier(); - - return ksft_exit_pass(); -} diff --git a/tools/testing/selftests/membarrier/membarrier_test_multi_thread.c b/tools/testing/selftests/membarrier/membarrier_test_multi_thread.c new file mode 100644 index 000000000000..ac5613e5b0eb --- /dev/null +++ b/tools/testing/selftests/membarrier/membarrier_test_multi_thread.c @@ -0,0 +1,73 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include <linux/membarrier.h> +#include <syscall.h> +#include <stdio.h> +#include <errno.h> +#include <string.h> +#include <pthread.h> + +#include "membarrier_test_impl.h" + +static int thread_ready, thread_quit; +static pthread_mutex_t test_membarrier_thread_mutex = + PTHREAD_MUTEX_INITIALIZER; +static pthread_cond_t test_membarrier_thread_cond = + PTHREAD_COND_INITIALIZER; + +void *test_membarrier_thread(void *arg) +{ + pthread_mutex_lock(&test_membarrier_thread_mutex); + thread_ready = 1; + pthread_cond_broadcast(&test_membarrier_thread_cond); + pthread_mutex_unlock(&test_membarrier_thread_mutex); + + pthread_mutex_lock(&test_membarrier_thread_mutex); + while (!thread_quit) + pthread_cond_wait(&test_membarrier_thread_cond, + &test_membarrier_thread_mutex); + pthread_mutex_unlock(&test_membarrier_thread_mutex); + + return NULL; +} + +static int test_mt_membarrier(void) +{ + int i; + pthread_t test_thread; + + pthread_create(&test_thread, NULL, + test_membarrier_thread, NULL); + + pthread_mutex_lock(&test_membarrier_thread_mutex); + while (!thread_ready) + pthread_cond_wait(&test_membarrier_thread_cond, + &test_membarrier_thread_mutex); + pthread_mutex_unlock(&test_membarrier_thread_mutex); + + test_membarrier_fail(); + + test_membarrier_success(); + + pthread_mutex_lock(&test_membarrier_thread_mutex); + thread_quit = 1; + pthread_cond_broadcast(&test_membarrier_thread_cond); + pthread_mutex_unlock(&test_membarrier_thread_mutex); + + pthread_join(test_thread, NULL); + + return 0; +} + +int main(int argc, char **argv) +{ + ksft_print_header(); + ksft_set_plan(13); + + test_membarrier_query(); + + /* Multi-threaded */ + test_mt_membarrier(); + + return ksft_exit_pass(); +} diff --git a/tools/testing/selftests/membarrier/membarrier_test_single_thread.c b/tools/testing/selftests/membarrier/membarrier_test_single_thread.c new file mode 100644 index 000000000000..c1c963902854 --- /dev/null +++ b/tools/testing/selftests/membarrier/membarrier_test_single_thread.c @@ -0,0 +1,24 @@ +// SPDX-License-Identifier: GPL-2.0 +#define _GNU_SOURCE +#include <linux/membarrier.h> +#include <syscall.h> +#include <stdio.h> +#include <errno.h> +#include <string.h> +#include <pthread.h> + +#include "membarrier_test_impl.h" + +int main(int argc, char **argv) +{ + ksft_print_header(); + ksft_set_plan(13); + + test_membarrier_query(); + + test_membarrier_fail(); + + test_membarrier_success(); + + return ksft_exit_pass(); +} |