diff --git a/fs/exec.c b/fs/exec.c
index f7f6a140856a8315c9403eeaac0c2376071e95ec..555e93c7dec82ae6b81db2c5402d838824e50c3c 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 5183e0d77dfa6cf6fdcfb1c928bf315a61aec900..2222fa795284183344d603c5286fcfd8c40dffa3 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 563290fc194f247d92ab2cd430fcf99d8706f725..75c97e4bbc574794e9320e4a01085537dc16c698 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 70db597d6fd4f2ceb53b1a71c0db243e681d7070..2c2e56bd8913250e88982ee8e47e36b23081fe23 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 4a7944078cc35dddcea4963f1099e81d147c6936..e6770012db1819e3c8d2975ffbd1a9e84fdac372 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 3d90ed8f75f0992e98d9169f087c74b8fd5a4d74..4b1c3b664f517e5e35e6f581282e432649f734d7 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 22ab6a4bdc513ce04c059b81bad920dd0308b2c9..a46a50d67002d9877b00c8052ba922e02e9740af 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 @@ void release_task(struct task_struct *p)
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 60763c043aa3c7d71da8c3a1eaa78b4b0b634c68..f9572f416126283dd2e8ac6ce3bfd66899e58016 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 f9a1346a5fa9502be6ca45ecb1bd822bf706725e..7880f4f64d0eea19dab03a0408625a505b4454ed 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 d4bbf68c31611fcd6fa3da456ef435021cefae53..83ab35e2374f632e0211029d7e1baa70150c388a 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 aa8d7580410887d319623353c88b37dfe54d7645..a39bed2c784f42be244082e5d80320f72e9d8daf 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 b3cb895d14a2088eef7a8853f00e7fc9b5823dd6..0db2c1b3361e03077d3971876f9dc06cf9bbb027 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 020c44f49a9e675e2419b9d50dc689206887de14..f2f7ec0a99b4d2aa6761112ee1a31489197aaa3c 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 97e3bdf3d1e96f27f10bcef4e10a4dd373b6f602..34d1c81a2324a692193e5b16f9ec09f86a1a0c46 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
similarity index 95%
rename from tools/testing/selftests/membarrier/membarrier_test.c
rename to tools/testing/selftests/membarrier/membarrier_test_impl.h
index 70b4ddbf126b059e3336d0e25f74409b59fe52fb..186be69f0a59b1855e6e8d48ba60d96e3602036a 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 0000000000000000000000000000000000000000..ac5613e5b0ebf9fbbdcd71e68431080f2a198ace
--- /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 0000000000000000000000000000000000000000..c1c963902854c5e0ab543a546f58ed0a6b21f345
--- /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();
+}