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9ea4c38006
Currently all _bh_ lock functions do two preempt_count operations:
local_bh_disable();
preempt_disable();
and for the unlock:
preempt_enable_no_resched();
local_bh_enable();
Since its a waste of perfectly good cycles to modify the same variable
twice when you can do it in one go; use the new
__local_bh_{dis,en}able_ip() functions that allow us to provide a
preempt_count value to add/sub.
So define SOFTIRQ_LOCK_OFFSET as the offset a _bh_ lock needs to
add/sub to be done in one go.
As a bonus it gets rid of the preempt_enable_no_resched() usage.
This reduces a 1000 loops of:
spin_lock_bh(&bh_lock);
spin_unlock_bh(&bh_lock);
from 53596 cycles to 51995 cycles. I didn't do enough measurements to
say for absolute sure that the result is significant but the the few
runs I did for each suggest it is so.
Reviewed-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra <peterz@infradead.org>
Cc: jacob.jun.pan@linux.intel.com
Cc: Mike Galbraith <bitbucket@online.de>
Cc: hpa@zytor.com
Cc: Arjan van de Ven <arjan@linux.intel.com>
Cc: lenb@kernel.org
Cc: rjw@rjwysocki.net
Cc: rui.zhang@intel.com
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20131119151338.GF3694@twins.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
92 lines
3.3 KiB
C
92 lines
3.3 KiB
C
#ifndef __LINUX_SPINLOCK_API_UP_H
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#define __LINUX_SPINLOCK_API_UP_H
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#ifndef __LINUX_SPINLOCK_H
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# error "please don't include this file directly"
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#endif
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/*
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* include/linux/spinlock_api_up.h
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*
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* spinlock API implementation on UP-nondebug (inlined implementation)
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*
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* portions Copyright 2005, Red Hat, Inc., Ingo Molnar
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* Released under the General Public License (GPL).
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*/
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#define in_lock_functions(ADDR) 0
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#define assert_raw_spin_locked(lock) do { (void)(lock); } while (0)
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/*
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* In the UP-nondebug case there's no real locking going on, so the
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* only thing we have to do is to keep the preempt counts and irq
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* flags straight, to suppress compiler warnings of unused lock
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* variables, and to add the proper checker annotations:
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*/
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#define ___LOCK(lock) \
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do { __acquire(lock); (void)(lock); } while (0)
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#define __LOCK(lock) \
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do { preempt_disable(); ___LOCK(lock); } while (0)
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#define __LOCK_BH(lock) \
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do { __local_bh_disable_ip(_THIS_IP_, SOFTIRQ_LOCK_OFFSET); ___LOCK(lock); } while (0)
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#define __LOCK_IRQ(lock) \
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do { local_irq_disable(); __LOCK(lock); } while (0)
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#define __LOCK_IRQSAVE(lock, flags) \
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do { local_irq_save(flags); __LOCK(lock); } while (0)
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#define ___UNLOCK(lock) \
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do { __release(lock); (void)(lock); } while (0)
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#define __UNLOCK(lock) \
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do { preempt_enable(); ___UNLOCK(lock); } while (0)
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#define __UNLOCK_BH(lock) \
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do { __local_bh_enable_ip(_THIS_IP_, SOFTIRQ_LOCK_OFFSET); \
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___UNLOCK(lock); } while (0)
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#define __UNLOCK_IRQ(lock) \
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do { local_irq_enable(); __UNLOCK(lock); } while (0)
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#define __UNLOCK_IRQRESTORE(lock, flags) \
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do { local_irq_restore(flags); __UNLOCK(lock); } while (0)
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#define _raw_spin_lock(lock) __LOCK(lock)
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#define _raw_spin_lock_nested(lock, subclass) __LOCK(lock)
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#define _raw_read_lock(lock) __LOCK(lock)
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#define _raw_write_lock(lock) __LOCK(lock)
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#define _raw_spin_lock_bh(lock) __LOCK_BH(lock)
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#define _raw_read_lock_bh(lock) __LOCK_BH(lock)
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#define _raw_write_lock_bh(lock) __LOCK_BH(lock)
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#define _raw_spin_lock_irq(lock) __LOCK_IRQ(lock)
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#define _raw_read_lock_irq(lock) __LOCK_IRQ(lock)
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#define _raw_write_lock_irq(lock) __LOCK_IRQ(lock)
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#define _raw_spin_lock_irqsave(lock, flags) __LOCK_IRQSAVE(lock, flags)
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#define _raw_read_lock_irqsave(lock, flags) __LOCK_IRQSAVE(lock, flags)
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#define _raw_write_lock_irqsave(lock, flags) __LOCK_IRQSAVE(lock, flags)
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#define _raw_spin_trylock(lock) ({ __LOCK(lock); 1; })
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#define _raw_read_trylock(lock) ({ __LOCK(lock); 1; })
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#define _raw_write_trylock(lock) ({ __LOCK(lock); 1; })
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#define _raw_spin_trylock_bh(lock) ({ __LOCK_BH(lock); 1; })
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#define _raw_spin_unlock(lock) __UNLOCK(lock)
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#define _raw_read_unlock(lock) __UNLOCK(lock)
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#define _raw_write_unlock(lock) __UNLOCK(lock)
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#define _raw_spin_unlock_bh(lock) __UNLOCK_BH(lock)
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#define _raw_write_unlock_bh(lock) __UNLOCK_BH(lock)
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#define _raw_read_unlock_bh(lock) __UNLOCK_BH(lock)
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#define _raw_spin_unlock_irq(lock) __UNLOCK_IRQ(lock)
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#define _raw_read_unlock_irq(lock) __UNLOCK_IRQ(lock)
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#define _raw_write_unlock_irq(lock) __UNLOCK_IRQ(lock)
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#define _raw_spin_unlock_irqrestore(lock, flags) \
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__UNLOCK_IRQRESTORE(lock, flags)
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#define _raw_read_unlock_irqrestore(lock, flags) \
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__UNLOCK_IRQRESTORE(lock, flags)
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#define _raw_write_unlock_irqrestore(lock, flags) \
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__UNLOCK_IRQRESTORE(lock, flags)
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#endif /* __LINUX_SPINLOCK_API_UP_H */
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