Commit c5bcab75 authored by Sebastian Andrzej Siewior's avatar Sebastian Andrzej Siewior Committed by Jakub Kicinski
Browse files

locking/local_lock: Add local nested BH locking infrastructure. 



Add local_lock_nested_bh() locking. It is based on local_lock_t and the
naming follows the preempt_disable_nested() example.

For !PREEMPT_RT + !LOCKDEP it is a per-CPU annotation for locking
assumptions based on local_bh_disable(). The macro is optimized away
during compilation.
For !PREEMPT_RT + LOCKDEP the local_lock_nested_bh() is reduced to
the usual lock-acquire plus lockdep_assert_in_softirq() - ensuring that
BH is disabled.

For PREEMPT_RT local_lock_nested_bh() acquires the specified per-CPU
lock. It does not disable CPU migration because it relies on
local_bh_disable() disabling CPU migration.
With LOCKDEP it performans the usual lockdep checks as with !PREEMPT_RT.
Due to include hell the softirq check has been moved spinlock.c.

The intention is to use this locking in places where locking of a per-CPU
variable relies on BH being disabled. Instead of treating disabled
bottom halves as a big per-CPU lock, PREEMPT_RT can use this to reduce
the locking scope to what actually needs protecting.
A side effect is that it also documents the protection scope of the
per-CPU variables.

Acked-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: default avatarThomas Gleixner <tglx@linutronix.de>
Signed-off-by: default avatarSebastian Andrzej Siewior <bigeasy@linutronix.de>
Link: https://patch.msgid.link/20240620132727.660738-3-bigeasy@linutronix.de


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 07e4fd4c

include/linux/local_lock.h

+10 −0
Original line number Diff line number Diff line
@@ -62,4 +62,14 @@ DEFINE_LOCK_GUARD_1(local_lock_irqsave, local_lock_t __percpu, 
		    local_unlock_irqrestore(_T->lock, _T->flags),

		    unsigned long flags)



#define local_lock_nested_bh(_lock)				\

	__local_lock_nested_bh(_lock)



#define local_unlock_nested_bh(_lock)				\

	__local_unlock_nested_bh(_lock)



DEFINE_GUARD(local_lock_nested_bh, local_lock_t __percpu*,

	     local_lock_nested_bh(_T),

	     local_unlock_nested_bh(_T))



#endif

include/linux/local_lock_internal.h

+31 −0
Original line number Diff line number Diff line
@@ -62,6 +62,17 @@ do { \ 
	local_lock_debug_init(lock);				\

} while (0)



#define __spinlock_nested_bh_init(lock)				\

do {								\

	static struct lock_class_key __key;			\

								\

	debug_check_no_locks_freed((void *)lock, sizeof(*lock));\

	lockdep_init_map_type(&(lock)->dep_map, #lock, &__key,  \

			      0, LD_WAIT_CONFIG, LD_WAIT_INV,	\

			      LD_LOCK_NORMAL);			\

	local_lock_debug_init(lock);				\

} while (0)



#define __local_lock(lock)					\

	do {							\

		preempt_disable();				\
@@ -98,6 +109,15 @@ do { \ 
		local_irq_restore(flags);			\

	} while (0)



#define __local_lock_nested_bh(lock)				\

	do {							\

		lockdep_assert_in_softirq();			\

		local_lock_acquire(this_cpu_ptr(lock));	\

	} while (0)



#define __local_unlock_nested_bh(lock)				\

	local_lock_release(this_cpu_ptr(lock))



#else /* !CONFIG_PREEMPT_RT */



/*
@@ -138,4 +158,15 @@ typedef spinlock_t local_lock_t; 


#define __local_unlock_irqrestore(lock, flags)	__local_unlock(lock)



#define __local_lock_nested_bh(lock)				\

do {								\

	lockdep_assert_in_softirq_func();			\

	spin_lock(this_cpu_ptr(lock));				\

} while (0)



#define __local_unlock_nested_bh(lock)				\

do {								\

	spin_unlock(this_cpu_ptr((lock)));			\

} while (0)



#endif /* CONFIG_PREEMPT_RT */

include/linux/lockdep.h

+3 −0
Original line number Diff line number Diff line
@@ -600,6 +600,8 @@ do { \ 
		     (!in_softirq() || in_irq() || in_nmi()));		\

} while (0)



extern void lockdep_assert_in_softirq_func(void);



#else

# define might_lock(lock) do { } while (0)

# define might_lock_read(lock) do { } while (0)
@@ -613,6 +615,7 @@ do { \ 
# define lockdep_assert_preemption_enabled() do { } while (0)

# define lockdep_assert_preemption_disabled() do { } while (0)

# define lockdep_assert_in_softirq() do { } while (0)

# define lockdep_assert_in_softirq_func() do { } while (0)

#endif



#ifdef CONFIG_PROVE_RAW_LOCK_NESTING

kernel/locking/spinlock.c

+8 −0
Original line number Diff line number Diff line
@@ -413,3 +413,11 @@ notrace int in_lock_functions(unsigned long addr) 
	&& addr < (unsigned long)__lock_text_end;

}

EXPORT_SYMBOL(in_lock_functions);



#if defined(CONFIG_PROVE_LOCKING) && defined(CONFIG_PREEMPT_RT)

void notrace lockdep_assert_in_softirq_func(void)

{

	lockdep_assert_in_softirq();

}

EXPORT_SYMBOL(lockdep_assert_in_softirq_func);

#endif