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* [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference()
@ 2010-02-23  1:04 Paul E. McKenney
  2010-02-23  1:04 ` [PATCH tip/core/rcu 01/21] rcu: introduce lockdep-based checking to RCU read-side primitives Paul E. McKenney
                   ` (22 more replies)
  0 siblings, 23 replies; 85+ messages in thread
From: Paul E. McKenney @ 2010-02-23  1:04 UTC (permalink / raw)
  To: linux-kernel
  Cc: mingo, laijs, dipankar, akpm, mathieu.desnoyers, josh, dvhltc,
	niv, tglx, peterz, rostedt, Valdis.Kletnieks, dhowells

Hello!

This patch series adds lockdep-based checking to the rcu_dereference()
primitive in order to flag misuses of RCU.  The first four patches put
the RCU infrastructure in place, the next eight use this infrastructure
in the net, sched, vfs, radix-tree, idr, and security subsystems, and
patch 13 documents how to use the new lockdep-checked rcu_dereference()
primitives.  The remaining eight patches are other changes that also need
to be applied, including some relatively urgent RCU_STALL patches.

The new (and default-disabled) CONFIG_PROVE_RCU makes this safe to
include in tip/core/rcu -- unlike v2 and earlier, your system won't
complain about RCU misuse unless you ask it to.  There are still several
situations that trigger on systems I have access to (and I have email
out on a couple of them), some of the remaining will be triggered only by
hardware I don't have access to and kernel features I am unfamiliar with.
So this is ready for much wider testing.

Changes since v5 (http://lkml.org/lkml/2010/2/17/271)

o	Fix a deadlock located by Thomas Gleixner that affects
	TREE_PREEMPT_RCU in some CPU-stall detection scenarios.

o	Add Dan Carpenter's cleanup to a mod_timer() in rcutorture.

o	Add a RCU_CPU_STALL_VERBOSE to enable dumping more information
	on tasks stalling the current RCU grace period.

o	Applied Acked-by lines that people have sent (thank you all!).

Changes since v4 (http://lkml.org/lkml/2010/2/11/356)

o	Apply review comments from Peter Ziljstra.

o	Another documentation update.

o	Fixes that avoid overflowing signed integers.

o	Rebased Thomas Gleixner's raw-spinlock patch on this series.
	(Thomas's original at http://lkml.org/lkml/2010/2/17/182.)

Changes since v3 (http://lkml.org/lkml/2010/1/14/505)

o	Fix a few more issues identified by the checking.

o	Add a documentation update.

o	Accelerate RCU grace periods when the current CPU is the last
	non-dyntick-idle CPU in the system, which is important for
	some multi-core battery-powered devices.

Changes since v2 (http://lkml.org/lkml/2010/1/4/496):

o	Removed references to the check condition for the non-lockdep
	version of rcu_dereference_check(), thus preventing numerous
	build errors.

o	Create a CONFIG_PROVE_RCU (default disabled) so that developers
	who want to use lockdep only to debug locks aren't bothered 
	by RCU-specific lockdep complaints that will no doubt persist
	for a little bit while some of the more obscure uses of RCU
	are reverse-engineered.

o	Fix a few more issues identified by the checking.

o	Add documentation in Documentation/RCU/lockdep.txt.

Changes since v1 (http://lkml.org/lkml/2009/12/15/553):

o	Made SRCU have per-srcu_struct lockdep maps to prevent lockdep
	from conflating independent uses of SRCU, and updated the
	rcu_dereference() checking in rcutorture to match.

o	Fix a few issues identified by the checking.

o	Disable checking within RCU list macros, RCU radix trees, and
	IDR.

^ permalink raw reply	[flat|nested] 85+ messages in thread
* [PATCH tip/core/rcu 5/8] sched: use lockdep-based checking on rcu_dereference()
@ 2010-01-05  2:04 Paul E. McKenney
  2010-01-13 10:29 ` [tip:core/rcu] sched: Use " tip-bot for Paul E. McKenney
  0 siblings, 1 reply; 85+ messages in thread
From: Paul E. McKenney @ 2010-01-05  2:04 UTC (permalink / raw)
  To: linux-kernel
  Cc: mingo, laijs, dipankar, akpm, mathieu.desnoyers, josh, dvhltc,
	niv, tglx, peterz, rostedt, Valdis.Kletnieks, dhowells,
	Paul E. McKenney

From: Paul E. McKenney <paulmck@linux.vnet.ibm.com>

Update the rcu_dereference() usages to take advantage of the new
lockdep-based checking.

Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
---
 include/linux/cgroup.h |    2 +-
 include/linux/cred.h   |    2 +-
 init/main.c            |    2 ++
 kernel/exit.c          |   14 +++++++++++---
 kernel/fork.c          |    1 +
 kernel/notifier.c      |    6 +++---
 kernel/pid.c           |    2 +-
 kernel/sched.c         |    6 +++---
 8 files changed, 23 insertions(+), 12 deletions(-)

diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
index 0008dee..d4c95c9 100644
--- a/include/linux/cgroup.h
+++ b/include/linux/cgroup.h
@@ -486,7 +486,7 @@ 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_sched(task->cgroups->subsys[subsys_id]);
 }
 
 static inline struct cgroup* task_cgroup(struct task_struct *task,
diff --git a/include/linux/cred.h b/include/linux/cred.h
index 4e3387a..4db09f8 100644
--- 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
index 5988deb..ae2338e 100644
--- a/init/main.c
+++ b/init/main.c
@@ -427,7 +427,9 @@ 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/exit.c b/kernel/exit.c
index e61891f..ddc7cfe 100644
--- a/kernel/exit.c
+++ b/kernel/exit.c
@@ -84,7 +84,9 @@ 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() ||
+					lock_is_held(&tasklist_lock));
 	spin_lock(&sighand->siglock);
 
 	posix_cpu_timers_exit(tsk);
@@ -169,8 +171,10 @@ 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);
 
@@ -474,9 +478,11 @@ 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;
@@ -522,10 +528,12 @@ 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
index 4c20fff..545e024 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -85,6 +85,7 @@ 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
index 61d5aa5..fea84bc 100644
--- 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
index d3f722d..3a39e0a 100644
--- 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
index e69fee4..1fd1c63 100644
--- a/kernel/sched.c
+++ b/kernel/sched.c
@@ -652,7 +652,7 @@ 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 = rcu_dereference_sched(cpu_rq(cpu)->sd); __sd; __sd = __sd->parent)
 
 #define cpu_rq(cpu)		(&per_cpu(runqueues, (cpu)))
 #define this_rq()		(&__get_cpu_var(runqueues))
@@ -1528,7 +1528,7 @@ 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;
@@ -4813,7 +4813,7 @@ 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);
 }
 
 /*
-- 
1.5.2.5


^ permalink raw reply related	[flat|nested] 85+ messages in thread

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2010-02-23  1:04 [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference() Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 01/21] rcu: introduce lockdep-based checking to RCU read-side primitives Paul E. McKenney
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2010-02-23  1:04 ` [PATCH tip/core/rcu 05/21] net: add checking to rcu_dereference() primitives Paul E. McKenney
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2010-02-23  1:04 ` [PATCH tip/core/rcu 06/21] sched: use lockdep-based checking on rcu_dereference() Paul E. McKenney
2010-02-25 10:11   ` [tip:core/rcu] sched: Use " tip-bot for Paul E. McKenney
2010-02-25 11:06   ` [tip:core/rcu] sched, cgroups: Fix module export tip-bot for Ingo Molnar
2010-02-23  1:04 ` [PATCH tip/core/rcu 07/21] sched: better name for for_each_domain_rd Paul E. McKenney
2010-02-25 10:11   ` [tip:core/rcu] sched: Better " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 08/21] vfs: apply lockdep-based checking to rcu_dereference() uses Paul E. McKenney
2010-02-25 10:11   ` [tip:core/rcu] vfs: Apply " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 09/21] vfs: abstract rcu_dereference_check for files-fdtable use Paul E. McKenney
2010-02-25 10:11   ` [tip:core/rcu] vfs: Abstract " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 10/21] radix-tree: disable RCU lockdep checking in radix tree Paul E. McKenney
2010-02-25 10:12   ` [tip:core/rcu] radix-tree: Disable " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 11/21] idr: apply lockdep-based diagnostics to rcu_dereference() uses Paul E. McKenney
2010-02-25 10:12   ` [tip:core/rcu] idr: Apply " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 12/21] security: apply lockdep-based checking " Paul E. McKenney
2010-02-25 10:12   ` [tip:core/rcu] security: Apply " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 13/21] rcu: documentation update for CONFIG_PROVE_RCU Paul E. McKenney
2010-02-25 10:12   ` [tip:core/rcu] rcu: Documentation " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 14/21] rcu: fix citation of Mathieu's dissertation Paul E. McKenney
2010-02-25 10:13   ` [tip:core/rcu] rcu: Fix " tip-bot for Paul E. McKenney
2010-02-23  1:04 ` [PATCH tip/core/rcu 15/21] rcu: accelerate grace period if last non-dynticked CPU Paul E. McKenney
2010-02-25 10:13   ` [tip:core/rcu] rcu: Accelerate " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 16/21] rcu: use canonical URL for Mathieu's dissertation Paul E. McKenney
2010-02-25 10:13   ` [tip:core/rcu] rcu: Use " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 17/21] rcu: stop overflowing signed integers Paul E. McKenney
2010-02-25 10:14   ` [tip:core/rcu] rcu: Stop " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 18/21] rcu: Convert to raw_spinlocks Paul E. McKenney
2010-02-25 10:14   ` [tip:core/rcu] " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 19/21] rcu: fix deadlock in TREE_PREEMPT_RCU CPU stall detection Paul E. McKenney
2010-02-25 10:14   ` [tip:core/rcu] rcu: Fix " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 20/21] rcu: fix rcutorture mod_timer argument to delay one jiffy Paul E. McKenney
2010-02-25 10:14   ` [tip:core/rcu] rcu: Fix " tip-bot for Paul E. McKenney
2010-02-23  1:05 ` [PATCH tip/core/rcu 21/21] rcu: add RCU_CPU_STALL_VERBOSE to dump detailed per-task information Paul E. McKenney
2010-02-25 10:15   ` [tip:core/rcu] rcu: Add " tip-bot for Paul E. McKenney
2010-02-23 12:59 ` [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference() Arnd Bergmann
2010-02-23 13:15   ` Mathieu Desnoyers
2010-02-23 14:35     ` Paul E. McKenney
2010-02-23 15:54     ` Arnd Bergmann
2010-02-23 16:16       ` Paul E. McKenney
2010-02-23 17:15         ` Arnd Bergmann
2010-02-23 18:01           ` Paul E. McKenney
2010-02-24 20:03             ` [PATCH 00/10] __rcu annotations, first draft Arnd Bergmann
2010-02-24 22:18               ` Paul E. McKenney
2010-02-25  8:37               ` Ingo Molnar
2010-02-24 20:03             ` [PATCH 01/10] rcu: define __rcu address space modifier for sparse Arnd Bergmann
2010-02-24 20:12               ` Mathieu Desnoyers
2010-02-24 20:22                 ` Arnd Bergmann
2010-02-24 20:03             ` [PATCH 02/10] rcu: annotated list rcu code Arnd Bergmann
2010-02-24 20:15               ` Mathieu Desnoyers
2010-02-24 20:32                 ` Arnd Bergmann
2010-02-24 20:03             ` [PATCH 03/10] cgroups: __rcu annotations Arnd Bergmann
2010-02-24 20:04             ` [PATCH 04/10] credentials: rcu annotation Arnd Bergmann
2010-02-24 20:04             ` [PATCH 05/10] perf_event: __rcu annotations Arnd Bergmann
2010-02-24 20:04             ` [PATCH 06/10] audit: " Arnd Bergmann
2010-02-24 20:04             ` [PATCH 07/10] module: " Arnd Bergmann
2010-02-24 20:13               ` Alexey Dobriyan
2010-02-24 20:26                 ` Arnd Bergmann
2010-02-24 22:17                   ` Paul E. McKenney
2010-02-24 23:07                     ` Arnd Bergmann
2010-02-24 23:59                       ` Paul E. McKenney
2010-02-25 17:06                         ` Paul E. McKenney
2010-02-25 18:10                           ` Arnd Bergmann
2010-02-25 20:05                             ` Paul E. McKenney
2010-02-26  2:12                               ` Paul E. McKenney
2010-02-24 20:04             ` [PATCH 08/10] pid: " Arnd Bergmann
2010-02-24 20:04             ` [PATCH 09/10] notifiers: " Arnd Bergmann
2010-02-24 20:04             ` [PATCH 10/10] scheduler: " Arnd Bergmann
2010-02-23 13:28   ` [PATCH tip/core/rcu 0/21] v6 add lockdep-based diagnostics to rcu_dereference() Paul E. McKenney
2010-02-25 10:00 ` Ingo Molnar
2010-02-25 10:01   ` Ingo Molnar
2010-02-25 12:04     ` Ingo Molnar
2010-02-25 18:18       ` Paul E. McKenney
2010-02-25 21:36         ` Paul E. McKenney
2010-02-25 21:22       ` Ingo Molnar
  -- strict thread matches above, loose matches on Subject: below --
2010-01-05  2:04 [PATCH tip/core/rcu 5/8] sched: use lockdep-based checking on rcu_dereference() Paul E. McKenney
2010-01-13 10:29 ` [tip:core/rcu] sched: Use " tip-bot for Paul E. McKenney

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