sched: Isolate preempt counting in its own config option
Create a new CONFIG_PREEMPT_COUNT that handles the inc/dec of preempt count offset independently. So that the offset can be updated by preempt_disable() and preempt_enable() even without the need for CONFIG_PREEMPT beeing set. This prepares to make CONFIG_DEBUG_SPINLOCK_SLEEP working with !CONFIG_PREEMPT where it currently doesn't detect code that sleeps inside explicit preemption disabled sections. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Acked-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Ingo Molnar <mingo@elte.hu> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
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bdd4e85dc3
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@ -88,7 +88,7 @@ static inline int bit_spin_is_locked(int bitnum, unsigned long *addr)
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{
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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return test_bit(bitnum, addr);
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#elif defined CONFIG_PREEMPT
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#elif defined CONFIG_PREEMPT_COUNT
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return preempt_count();
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#else
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return 1;
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@ -93,7 +93,7 @@
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*/
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#define in_nmi() (preempt_count() & NMI_MASK)
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#if defined(CONFIG_PREEMPT)
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#if defined(CONFIG_PREEMPT_COUNT)
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# define PREEMPT_CHECK_OFFSET 1
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#else
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# define PREEMPT_CHECK_OFFSET 0
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@ -115,7 +115,7 @@
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#define in_atomic_preempt_off() \
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((preempt_count() & ~PREEMPT_ACTIVE) != PREEMPT_CHECK_OFFSET)
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#ifdef CONFIG_PREEMPT
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#ifdef CONFIG_PREEMPT_COUNT
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# define preemptible() (preempt_count() == 0 && !irqs_disabled())
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# define IRQ_EXIT_OFFSET (HARDIRQ_OFFSET-1)
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#else
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@ -134,7 +134,7 @@ static inline int page_cache_get_speculative(struct page *page)
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VM_BUG_ON(in_interrupt());
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#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
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# ifdef CONFIG_PREEMPT
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# ifdef CONFIG_PREEMPT_COUNT
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VM_BUG_ON(!in_atomic());
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# endif
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/*
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@ -172,7 +172,7 @@ static inline int page_cache_add_speculative(struct page *page, int count)
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VM_BUG_ON(in_interrupt());
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#if !defined(CONFIG_SMP) && defined(CONFIG_TREE_RCU)
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# ifdef CONFIG_PREEMPT
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# ifdef CONFIG_PREEMPT_COUNT
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VM_BUG_ON(!in_atomic());
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# endif
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VM_BUG_ON(page_count(page) == 0);
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@ -27,6 +27,21 @@
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asmlinkage void preempt_schedule(void);
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#define preempt_check_resched() \
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do { \
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if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
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preempt_schedule(); \
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} while (0)
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#else /* !CONFIG_PREEMPT */
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#define preempt_check_resched() do { } while (0)
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#endif /* CONFIG_PREEMPT */
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#ifdef CONFIG_PREEMPT_COUNT
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#define preempt_disable() \
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do { \
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inc_preempt_count(); \
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@ -39,12 +54,6 @@ do { \
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dec_preempt_count(); \
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} while (0)
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#define preempt_check_resched() \
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do { \
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if (unlikely(test_thread_flag(TIF_NEED_RESCHED))) \
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preempt_schedule(); \
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} while (0)
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#define preempt_enable() \
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do { \
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preempt_enable_no_resched(); \
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@ -80,18 +89,17 @@ do { \
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preempt_check_resched(); \
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} while (0)
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#else
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#else /* !CONFIG_PREEMPT_COUNT */
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#define preempt_disable() do { } while (0)
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#define preempt_enable_no_resched() do { } while (0)
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#define preempt_enable() do { } while (0)
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#define preempt_check_resched() do { } while (0)
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#define preempt_disable_notrace() do { } while (0)
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#define preempt_enable_no_resched_notrace() do { } while (0)
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#define preempt_enable_notrace() do { } while (0)
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#endif
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#endif /* CONFIG_PREEMPT_COUNT */
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#ifdef CONFIG_PREEMPT_NOTIFIERS
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@ -239,7 +239,7 @@ extern int rcu_read_lock_bh_held(void);
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* Check debug_lockdep_rcu_enabled() to prevent false positives during boot
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* and while lockdep is disabled.
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*/
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#ifdef CONFIG_PREEMPT
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#ifdef CONFIG_PREEMPT_COUNT
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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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@ -250,12 +250,12 @@ static inline int rcu_read_lock_sched_held(void)
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lockdep_opinion = lock_is_held(&rcu_sched_lock_map);
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return lockdep_opinion || preempt_count() != 0 || irqs_disabled();
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}
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#else /* #ifdef CONFIG_PREEMPT */
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#else /* #ifdef CONFIG_PREEMPT_COUNT */
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static inline int rcu_read_lock_sched_held(void)
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{
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return 1;
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}
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#endif /* #else #ifdef CONFIG_PREEMPT */
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#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */
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#else /* #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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@ -276,17 +276,17 @@ static inline int rcu_read_lock_bh_held(void)
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return 1;
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}
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#ifdef CONFIG_PREEMPT
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#ifdef CONFIG_PREEMPT_COUNT
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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 || irqs_disabled();
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}
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#else /* #ifdef CONFIG_PREEMPT */
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#else /* #ifdef CONFIG_PREEMPT_COUNT */
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static inline int rcu_read_lock_sched_held(void)
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{
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return 1;
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}
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#endif /* #else #ifdef CONFIG_PREEMPT */
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#endif /* #else #ifdef CONFIG_PREEMPT_COUNT */
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#endif /* #else #ifdef CONFIG_DEBUG_LOCK_ALLOC */
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@ -2502,7 +2502,7 @@ extern int _cond_resched(void);
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extern int __cond_resched_lock(spinlock_t *lock);
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#ifdef CONFIG_PREEMPT
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#ifdef CONFIG_PREEMPT_COUNT
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#define PREEMPT_LOCK_OFFSET PREEMPT_OFFSET
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#else
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#define PREEMPT_LOCK_OFFSET 0
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@ -35,6 +35,7 @@ config PREEMPT_VOLUNTARY
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config PREEMPT
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bool "Preemptible Kernel (Low-Latency Desktop)"
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select PREEMPT_COUNT
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help
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This option reduces the latency of the kernel by making
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all kernel code (that is not executing in a critical section)
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@ -52,3 +53,5 @@ config PREEMPT
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endchoice
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config PREEMPT_COUNT
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bool
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@ -2843,7 +2843,7 @@ void sched_fork(struct task_struct *p)
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#if defined(CONFIG_SMP)
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p->on_cpu = 0;
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#endif
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#ifdef CONFIG_PREEMPT
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#ifdef CONFIG_PREEMPT_COUNT
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/* Want to start with kernel preemption disabled. */
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task_thread_info(p)->preempt_count = 1;
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#endif
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