sched: Use lockdep-based checking on rcu_dereference()

Update the rcu_dereference() usages to take advantage of the new lockdep-based checking. Signed-off-by: Paul E. McKenney <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] LKML-Reference: <[email protected]> [ -v2: fix allmodconfig missing symbol export build failure on x86 ] Signed-off-by: Ingo Molnar <[email protected]>
torvalds · Feb 25, 2010 · d11c563 · d11c563
1 parent a898def
commit d11c563
Show file tree

Hide file tree

Showing 9 changed files with 45 additions and 12 deletions.
diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
@@ -28,6 +28,7 @@ struct css_id;
 extern int cgroup_init_early(void);
 extern int cgroup_init(void);
 extern void cgroup_lock(void);
+extern int cgroup_lock_is_held(void);
 extern bool cgroup_lock_live_group(struct cgroup *cgrp);
 extern void cgroup_unlock(void);
 extern void cgroup_fork(struct task_struct *p);
@@ -486,7 +487,9 @@ static inline struct cgroup_subsys_state *cgroup_subsys_state(
 static inline struct cgroup_subsys_state *task_subsys_state(
  struct task_struct *task, int subsys_id)
 {
- return rcu_dereference(task->cgroups->subsys[subsys_id]);
+ return rcu_dereference_check(task->cgroups->subsys[subsys_id],
+ rcu_read_lock_held() ||
+ cgroup_lock_is_held());
 }
 
 static inline struct cgroup* task_cgroup(struct task_struct *task,

diff --git a/include/linux/cred.h b/include/linux/cred.h
@@ -280,7 +280,7 @@ static inline void put_cred(const struct cred *_cred)
  * task or by holding tasklist_lock to prevent it from being unlinked.
  */
 #define __task_cred(task) \
- ((const struct cred *)(rcu_dereference((task)->real_cred)))
+ ((const struct cred *)(rcu_dereference_check((task)->real_cred, rcu_read_lock_held() || lockdep_is_held(&tasklist_lock))))
 
 /**
  * get_task_cred - Get another task's objective credentials

diff --git a/init/main.c b/init/main.c
@@ -416,7 +416,9 @@ static noinline void __init_refok rest_init(void)
  kernel_thread(kernel_init, NULL, CLONE_FS | CLONE_SIGHAND);
  numa_default_policy();
  pid = kernel_thread(kthreadd, NULL, CLONE_FS | CLONE_FILES);
+ rcu_read_lock();
  kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
+ rcu_read_unlock();
  unlock_kernel();
 
  /*

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
@@ -166,6 +166,20 @@ static DEFINE_SPINLOCK(hierarchy_id_lock);
  */
 static int need_forkexit_callback __read_mostly;
 
+#ifdef CONFIG_PROVE_LOCKING
+int cgroup_lock_is_held(void)
+{
+ return lockdep_is_held(&cgroup_mutex);
+}
+#else /* #ifdef CONFIG_PROVE_LOCKING */
+int cgroup_lock_is_held(void)
+{
+ return mutex_is_locked(&cgroup_mutex);
+}
+#endif /* #else #ifdef CONFIG_PROVE_LOCKING */
+
+EXPORT_SYMBOL_GPL(cgroup_lock_is_held);
+
 /* convenient tests for these bits */
 inline int cgroup_is_removed(const struct cgroup *cgrp)
 {

diff --git a/kernel/exit.c b/kernel/exit.c
@@ -85,7 +85,9 @@ static void __exit_signal(struct task_struct *tsk)
  BUG_ON(!sig);
  BUG_ON(!atomic_read(&sig->count));
 
- sighand = rcu_dereference(tsk->sighand);
+ sighand = rcu_dereference_check(tsk->sighand,
+ rcu_read_lock_held() ||
+ lockdep_is_held(&tasklist_lock));
  spin_lock(&sighand->siglock);
 
  posix_cpu_timers_exit(tsk);
@@ -170,8 +172,10 @@ void release_task(struct task_struct * p)
 repeat:
  tracehook_prepare_release_task(p);
  /* don't need to get the RCU readlock here - the process is dead and
- * can't be modifying its own credentials */
+ * can't be modifying its own credentials. But shut RCU-lockdep up */
+ rcu_read_lock();
  atomic_dec(&__task_cred(p)->user->processes);
+ rcu_read_unlock();
 
  proc_flush_task(p);
 
@@ -473,9 +477,11 @@ static void close_files(struct files_struct * files)
  /*
  * It is safe to dereference the fd table without RCU or
  * ->file_lock because this is the last reference to the
- * files structure.
+ * files structure. But use RCU to shut RCU-lockdep up.
  */
+ rcu_read_lock();
  fdt = files_fdtable(files);
+ rcu_read_unlock();
  for (;;) {
  unsigned long set;
  i = j * __NFDBITS;
@@ -521,10 +527,12 @@ void put_files_struct(struct files_struct *files)
  * at the end of the RCU grace period. Otherwise,
  * you can free files immediately.
  */
+ rcu_read_lock();
  fdt = files_fdtable(files);
  if (fdt != &files->fdtab)
  kmem_cache_free(files_cachep, files);
  free_fdtable(fdt);
+ rcu_read_unlock();
  }
 }
 

diff --git a/kernel/fork.c b/kernel/fork.c
@@ -86,6 +86,7 @@ int max_threads; /* tunable limit on nr_threads */
 DEFINE_PER_CPU(unsigned long, process_counts) = 0;
 
 __cacheline_aligned DEFINE_RWLOCK(tasklist_lock); /* outer */
+EXPORT_SYMBOL_GPL(tasklist_lock);
 
 int nr_processes(void)
 {

diff --git a/kernel/notifier.c b/kernel/notifier.c
@@ -78,10 +78,10 @@ static int __kprobes notifier_call_chain(struct notifier_block **nl,
  int ret = NOTIFY_DONE;
  struct notifier_block *nb, *next_nb;
 
- nb = rcu_dereference(*nl);
+ nb = rcu_dereference_raw(*nl);
 
  while (nb && nr_to_call) {
- next_nb = rcu_dereference(nb->next);
+ next_nb = rcu_dereference_raw(nb->next);
 
 #ifdef CONFIG_DEBUG_NOTIFIERS
  if (unlikely(!func_ptr_is_kernel_text(nb->notifier_call))) {
@@ -309,7 +309,7 @@ int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
  * racy then it does not matter what the result of the test
  * is, we re-check the list after having taken the lock anyway:
  */
- if (rcu_dereference(nh->head)) {
+ if (rcu_dereference_raw(nh->head)) {
  down_read(&nh->rwsem);
  ret = notifier_call_chain(&nh->head, val, v, nr_to_call,
  nr_calls);

diff --git a/kernel/pid.c b/kernel/pid.c
@@ -367,7 +367,7 @@ struct task_struct *pid_task(struct pid *pid, enum pid_type type)
  struct task_struct *result = NULL;
  if (pid) {
  struct hlist_node *first;
- first = rcu_dereference(pid->tasks[type].first);
+ first = rcu_dereference_check(pid->tasks[type].first, rcu_read_lock_held() || lockdep_is_held(&tasklist_lock));
  if (first)
  result = hlist_entry(first, struct task_struct, pids[(type)].node);
  }

diff --git a/kernel/sched.c b/kernel/sched.c
@@ -645,6 +645,11 @@ static inline int cpu_of(struct rq *rq)
 #endif
 }
 
+#define for_each_domain_rd(p) \
+ rcu_dereference_check((p), \
+ rcu_read_lock_sched_held() || \
+ lockdep_is_held(&sched_domains_mutex))
+
 /*
  * The domain tree (rq->sd) is protected by RCU's quiescent state transition.
  * See detach_destroy_domains: synchronize_sched for details.
@@ -653,7 +658,7 @@ static inline int cpu_of(struct rq *rq)
  * preempt-disabled sections.
  */
 #define for_each_domain(cpu, __sd) \
- for (__sd = rcu_dereference(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent)
+ for (__sd = for_each_domain_rd(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent)
 
 #define cpu_rq(cpu) (&per_cpu(runqueues, (cpu)))
 #define this_rq() (&__get_cpu_var(runqueues))
@@ -1531,7 +1536,7 @@ static unsigned long target_load(int cpu, int type)
 
 static struct sched_group *group_of(int cpu)
 {
- struct sched_domain *sd = rcu_dereference(cpu_rq(cpu)->sd);
+ struct sched_domain *sd = rcu_dereference_sched(cpu_rq(cpu)->sd);
 
  if (!sd)
  return NULL;
@@ -4888,7 +4893,7 @@ static void run_rebalance_domains(struct softirq_action *h)
 
 static inline int on_null_domain(int cpu)
 {
- return !rcu_dereference(cpu_rq(cpu)->sd);
+ return !rcu_dereference_sched(cpu_rq(cpu)->sd);
 }
 
 /*