Commit 54dbf96c authored by Paul E. McKenney's avatar Paul E. McKenney Committed by Ingo Molnar
Browse files

rcu: Suppress RCU lockdep warnings during early boot 



RCU is used during very early boot, before RCU and lockdep have
been initialized.  So make the underlying primitives
(rcu_read_lock_held(), rcu_read_lock_bh_held(),
rcu_read_lock_sched_held(), and rcu_dereference_check()) check
for early boot via the rcu_scheduler_active flag.  This will
suppress false positives.

Also introduce a debug_lockdep_rcu_enabled() static inline
helper function, which tags the CONTINUE_PROVE_RCU case as
likely(), as suggested by Ingo Molnar.

Signed-off-by: default avatarPaul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: laijs@cn.fujitsu.com
Cc: dipankar@in.ibm.com
Cc: mathieu.desnoyers@polymtl.ca
Cc: josh@joshtriplett.org
Cc: dvhltc@us.ibm.com
Cc: niv@us.ibm.com
Cc: peterz@infradead.org
Cc: rostedt@goodmis.org
Cc: Valdis.Kletnieks@vt.edu
Cc: dhowells@redhat.com
LKML-Reference: <1267631219-8713-2-git-send-email-paulmck@linux.vnet.ibm.com>
[ v2: removed incomplete debug_lockdep_rcu_update() bits ]
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8d53dd54

include/linux/rcupdate.h

+22 −9
Original line number Diff line number Diff line
@@ -97,6 +97,11 @@ extern struct lockdep_map rcu_sched_lock_map; 
# define rcu_read_release_sched() \

		lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)



static inline int debug_lockdep_rcu_enabled(void)

{

	return likely(rcu_scheduler_active && debug_locks);

}



/**

 * rcu_read_lock_held - might we be in RCU read-side critical section?

 *
@@ -104,12 +109,14 @@ extern struct lockdep_map rcu_sched_lock_map; 
 * an RCU read-side critical section.  In absence of CONFIG_PROVE_LOCKING,

 * this assumes we are in an RCU read-side critical section unless it can

 * prove otherwise.

 *

 * Check rcu_scheduler_active to prevent false positives during boot.

 */

static inline int rcu_read_lock_held(void)

{

	if (debug_locks)

		return lock_is_held(&rcu_lock_map);

	if (!debug_lockdep_rcu_enabled())

		return 1;

	return lock_is_held(&rcu_lock_map);

}



/**
@@ -119,12 +126,14 @@ static inline int rcu_read_lock_held(void) 
 * an RCU-bh read-side critical section.  In absence of CONFIG_PROVE_LOCKING,

 * this assumes we are in an RCU-bh read-side critical section unless it can

 * prove otherwise.

 *

 * Check rcu_scheduler_active to prevent false positives during boot.

 */

static inline int rcu_read_lock_bh_held(void)

{

	if (debug_locks)

		return lock_is_held(&rcu_bh_lock_map);

	if (!debug_lockdep_rcu_enabled())

		return 1;

	return lock_is_held(&rcu_bh_lock_map);

}



/**
@@ -135,15 +144,19 @@ static inline int rcu_read_lock_bh_held(void) 
 * this assumes we are in an RCU-sched read-side critical section unless it

 * can prove otherwise.  Note that disabling of preemption (including

 * disabling irqs) counts as an RCU-sched read-side critical section.

 *

 * Check rcu_scheduler_active to prevent false positives during boot.

 */

#ifdef CONFIG_PREEMPT

static inline int rcu_read_lock_sched_held(void)

{

	int lockdep_opinion = 0;



	if (!debug_lockdep_rcu_enabled())

		return 1;

	if (debug_locks)

		lockdep_opinion = lock_is_held(&rcu_sched_lock_map);

	return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active;

	return lockdep_opinion || preempt_count() != 0;

}

#else /* #ifdef CONFIG_PREEMPT */

static inline int rcu_read_lock_sched_held(void)
@@ -174,7 +187,7 @@ static inline int rcu_read_lock_bh_held(void) 
#ifdef CONFIG_PREEMPT

static inline int rcu_read_lock_sched_held(void)

{

	return preempt_count() != 0 || !rcu_scheduler_active;

	return !rcu_scheduler_active || preempt_count() != 0;

}

#else /* #ifdef CONFIG_PREEMPT */

static inline int rcu_read_lock_sched_held(void)
@@ -198,7 +211,7 @@ static inline int rcu_read_lock_sched_held(void) 
 */

#define rcu_dereference_check(p, c) \

	({ \

		if (debug_locks && !(c)) \

		if (debug_lockdep_rcu_enabled() && !(c)) \

			lockdep_rcu_dereference(__FILE__, __LINE__); \

		rcu_dereference_raw(p); \

	})

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