mirror of https://gitee.com/openkylin/linux.git
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: Paul 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: Ingo Molnar <mingo@elte.hu>
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@ -97,6 +97,11 @@ extern struct lockdep_map rcu_sched_lock_map;
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# define rcu_read_release_sched() \
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lock_release(&rcu_sched_lock_map, 1, _THIS_IP_)
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static inline int debug_lockdep_rcu_enabled(void)
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{
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return likely(rcu_scheduler_active && debug_locks);
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}
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/**
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* rcu_read_lock_held - might we be in RCU read-side critical section?
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*
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@ -104,12 +109,14 @@ extern struct lockdep_map rcu_sched_lock_map;
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* an RCU read-side critical section. In absence of CONFIG_PROVE_LOCKING,
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* this assumes we are in an RCU read-side critical section unless it can
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* prove otherwise.
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*
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* Check rcu_scheduler_active to prevent false positives during boot.
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*/
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static inline int rcu_read_lock_held(void)
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{
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if (debug_locks)
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return lock_is_held(&rcu_lock_map);
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return 1;
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if (!debug_lockdep_rcu_enabled())
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return 1;
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return lock_is_held(&rcu_lock_map);
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}
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/**
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@ -119,12 +126,14 @@ static inline int rcu_read_lock_held(void)
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* an RCU-bh read-side critical section. In absence of CONFIG_PROVE_LOCKING,
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* this assumes we are in an RCU-bh read-side critical section unless it can
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* prove otherwise.
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*
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* Check rcu_scheduler_active to prevent false positives during boot.
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*/
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static inline int rcu_read_lock_bh_held(void)
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{
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if (debug_locks)
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return lock_is_held(&rcu_bh_lock_map);
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return 1;
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if (!debug_lockdep_rcu_enabled())
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return 1;
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return lock_is_held(&rcu_bh_lock_map);
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}
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/**
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@ -135,15 +144,19 @@ static inline int rcu_read_lock_bh_held(void)
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* this assumes we are in an RCU-sched read-side critical section unless it
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* can prove otherwise. Note that disabling of preemption (including
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* disabling irqs) counts as an RCU-sched read-side critical section.
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*
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* Check rcu_scheduler_active to prevent false positives during boot.
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*/
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#ifdef CONFIG_PREEMPT
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static inline int rcu_read_lock_sched_held(void)
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{
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int lockdep_opinion = 0;
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if (!debug_lockdep_rcu_enabled())
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return 1;
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if (debug_locks)
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lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
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return lockdep_opinion || preempt_count() != 0 || !rcu_scheduler_active;
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return lockdep_opinion || preempt_count() != 0;
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}
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#else /* #ifdef CONFIG_PREEMPT */
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static inline int rcu_read_lock_sched_held(void)
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@ -174,7 +187,7 @@ static inline int rcu_read_lock_bh_held(void)
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#ifdef CONFIG_PREEMPT
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static inline int rcu_read_lock_sched_held(void)
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{
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return preempt_count() != 0 || !rcu_scheduler_active;
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return !rcu_scheduler_active || preempt_count() != 0;
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}
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#else /* #ifdef CONFIG_PREEMPT */
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static inline int rcu_read_lock_sched_held(void)
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@ -198,7 +211,7 @@ static inline int rcu_read_lock_sched_held(void)
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*/
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#define rcu_dereference_check(p, c) \
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({ \
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if (debug_locks && !(c)) \
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if (debug_lockdep_rcu_enabled() && !(c)) \
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lockdep_rcu_dereference(__FILE__, __LINE__); \
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rcu_dereference_raw(p); \
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})
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