Update Linux to v5.4.2
Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/kernel/sched/membarrier.c b/kernel/sched/membarrier.c
index 76e0eaf..168479a 100644
--- a/kernel/sched/membarrier.c
+++ b/kernel/sched/membarrier.c
@@ -1,17 +1,8 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
/*
* Copyright (C) 2010-2017 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
*
* membarrier system call
- *
- * This program is free software; you can redistribute it and/or modify
- * it under the terms of the GNU General Public License as published by
- * the Free Software Foundation; either version 2 of the License, or
- * (at your option) any later version.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
*/
#include "sched.h"
@@ -39,10 +30,42 @@
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)
@@ -54,17 +77,11 @@
*/
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;
@@ -79,23 +96,28 @@
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 (!(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);
}
- if (!fallback) {
- preempt_disable();
- smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
- preempt_enable();
- free_cpumask_var(tmpmask);
- }
+ rcu_read_unlock();
+
+ preempt_disable();
+ smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
+ preempt_enable();
+
+ free_cpumask_var(tmpmask);
cpus_read_unlock();
/*
@@ -110,22 +132,22 @@
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;
/*
@@ -134,17 +156,11 @@
*/
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;
@@ -158,22 +174,17 @@
*/
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();
+ p = rcu_dereference(cpu_rq(cpu)->curr);
+ if (p && p->mm == mm)
+ __cpumask_set_cpu(cpu, tmpmask);
}
- if (!fallback) {
- preempt_disable();
- smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
- preempt_enable();
- free_cpumask_var(tmpmask);
- }
+ rcu_read_unlock();
+
+ preempt_disable();
+ smp_call_function_many(tmpmask, ipi_mb, NULL, 1);
+ preempt_enable();
+
+ free_cpumask_var(tmpmask);
cpus_read_unlock();
/*
@@ -186,32 +197,78 @@
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_sched();
- }
+ ret = sync_runqueues_membarrier_state(mm);
+ if (ret)
+ return ret;
atomic_or(MEMBARRIER_STATE_GLOBAL_EXPEDITED_READY,
&mm->membarrier_state);
@@ -222,12 +279,15 @@
{
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;
}
/*
@@ -235,20 +295,15 @@
* 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_sched();
- }
- 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;
}
@@ -262,8 +317,10 @@
* 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
@@ -298,7 +355,7 @@
if (tick_nohz_full_enabled())
return -EINVAL;
if (num_online_cpus() > 1)
- synchronize_sched();
+ synchronize_rcu();
return 0;
case MEMBARRIER_CMD_GLOBAL_EXPEDITED:
return membarrier_global_expedited();