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![Peter Zijlstra](/assets/img/avatar_default.png)
Extend lockdep to validate lock wait-type context. The current wait-types are: LD_WAIT_FREE, /* wait free, rcu etc.. */ LD_WAIT_SPIN, /* spin loops, raw_spinlock_t etc.. */ LD_WAIT_CONFIG, /* CONFIG_PREEMPT_LOCK, spinlock_t etc.. */ LD_WAIT_SLEEP, /* sleeping locks, mutex_t etc.. */ Where lockdep validates that the current lock (the one being acquired) fits in the current wait-context (as generated by the held stack). This ensures that there is no attempt to acquire mutexes while holding spinlocks, to acquire spinlocks while holding raw_spinlocks and so on. In other words, its a more fancy might_sleep(). Obviously RCU made the entire ordeal more complex than a simple single value test because RCU can be acquired in (pretty much) any context and while it presents a context to nested locks it is not the same as it got acquired in. Therefore its necessary to split the wait_type into two values, one representing the acquire (outer) and one representing the nested context (inner). For most 'normal' locks these two are the same. [ To make static initialization easier we have the rule that: .outer == INV means .outer == .inner; because INV == 0. ] It further means that its required to find the minimal .inner of the held stack to compare against the outer of the new lock; because while 'normal' RCU presents a CONFIG type to nested locks, if it is taken while already holding a SPIN type it obviously doesn't relax the rules. Below is an example output generated by the trivial test code: raw_spin_lock(&foo); spin_lock(&bar); spin_unlock(&bar); raw_spin_unlock(&foo); [ BUG: Invalid wait context ] ----------------------------- swapper/0/1 is trying to lock: ffffc90000013f20 (&bar){....}-{3:3}, at: kernel_init+0xdb/0x187 other info that might help us debug this: 1 lock held by swapper/0/1: #0: ffffc90000013ee0 (&foo){+.+.}-{2:2}, at: kernel_init+0xd1/0x187 The way to read it is to look at the new -{n,m} part in the lock description; -{3:3} for the attempted lock, and try and match that up to the held locks, which in this case is the one: -{2,2}. This tells that the acquiring lock requires a more relaxed environment than presented by the lock stack. Currently only the normal locks and RCU are converted, the rest of the lockdep users defaults to .inner = INV which is ignored. More conversions can be done when desired. The check for spinlock_t nesting is not enabled by default. It's a separate config option for now as there are known problems which are currently addressed. The config option allows to identify these problems and to verify that the solutions found are indeed solving them. The config switch will be removed and the checks will permanently enabled once the vast majority of issues has been addressed. [ bigeasy: Move LD_WAIT_FREE,… out of CONFIG_LOCKDEP to avoid compile failure with CONFIG_DEBUG_SPINLOCK + !CONFIG_LOCKDEP] [ tglx: Add the config option ] Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200321113242.427089655@linutronix.de
495 lines
14 KiB
C
495 lines
14 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_SPINLOCK_H
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#define __LINUX_SPINLOCK_H
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/*
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* include/linux/spinlock.h - generic spinlock/rwlock declarations
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*
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* here's the role of the various spinlock/rwlock related include files:
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*
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* on SMP builds:
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*
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* asm/spinlock_types.h: contains the arch_spinlock_t/arch_rwlock_t and the
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* initializers
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*
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* linux/spinlock_types.h:
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* defines the generic type and initializers
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*
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* asm/spinlock.h: contains the arch_spin_*()/etc. lowlevel
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* implementations, mostly inline assembly code
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*
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* (also included on UP-debug builds:)
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*
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* linux/spinlock_api_smp.h:
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* contains the prototypes for the _spin_*() APIs.
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*
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* linux/spinlock.h: builds the final spin_*() APIs.
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*
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* on UP builds:
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*
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* linux/spinlock_type_up.h:
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* contains the generic, simplified UP spinlock type.
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* (which is an empty structure on non-debug builds)
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*
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* linux/spinlock_types.h:
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* defines the generic type and initializers
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*
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* linux/spinlock_up.h:
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* contains the arch_spin_*()/etc. version of UP
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* builds. (which are NOPs on non-debug, non-preempt
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* builds)
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*
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* (included on UP-non-debug builds:)
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*
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* linux/spinlock_api_up.h:
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* builds the _spin_*() APIs.
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*
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* linux/spinlock.h: builds the final spin_*() APIs.
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*/
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#include <linux/typecheck.h>
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#include <linux/preempt.h>
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#include <linux/linkage.h>
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#include <linux/compiler.h>
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#include <linux/irqflags.h>
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#include <linux/thread_info.h>
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#include <linux/kernel.h>
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#include <linux/stringify.h>
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#include <linux/bottom_half.h>
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#include <asm/barrier.h>
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#include <asm/mmiowb.h>
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/*
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* Must define these before including other files, inline functions need them
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*/
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#define LOCK_SECTION_NAME ".text..lock."KBUILD_BASENAME
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#define LOCK_SECTION_START(extra) \
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".subsection 1\n\t" \
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extra \
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".ifndef " LOCK_SECTION_NAME "\n\t" \
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LOCK_SECTION_NAME ":\n\t" \
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".endif\n"
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#define LOCK_SECTION_END \
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".previous\n\t"
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#define __lockfunc __attribute__((section(".spinlock.text")))
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/*
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* Pull the arch_spinlock_t and arch_rwlock_t definitions:
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*/
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#include <linux/spinlock_types.h>
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/*
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* Pull the arch_spin*() functions/declarations (UP-nondebug doesn't need them):
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*/
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#ifdef CONFIG_SMP
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# include <asm/spinlock.h>
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#else
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# include <linux/spinlock_up.h>
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#endif
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#ifdef CONFIG_DEBUG_SPINLOCK
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extern void __raw_spin_lock_init(raw_spinlock_t *lock, const char *name,
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struct lock_class_key *key, short inner);
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# define raw_spin_lock_init(lock) \
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do { \
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static struct lock_class_key __key; \
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\
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__raw_spin_lock_init((lock), #lock, &__key, LD_WAIT_SPIN); \
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} while (0)
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#else
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# define raw_spin_lock_init(lock) \
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do { *(lock) = __RAW_SPIN_LOCK_UNLOCKED(lock); } while (0)
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#endif
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#define raw_spin_is_locked(lock) arch_spin_is_locked(&(lock)->raw_lock)
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#ifdef arch_spin_is_contended
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#define raw_spin_is_contended(lock) arch_spin_is_contended(&(lock)->raw_lock)
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#else
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#define raw_spin_is_contended(lock) (((void)(lock), 0))
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#endif /*arch_spin_is_contended*/
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/*
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* smp_mb__after_spinlock() provides the equivalent of a full memory barrier
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* between program-order earlier lock acquisitions and program-order later
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* memory accesses.
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*
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* This guarantees that the following two properties hold:
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*
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* 1) Given the snippet:
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*
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* { X = 0; Y = 0; }
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*
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* CPU0 CPU1
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*
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* WRITE_ONCE(X, 1); WRITE_ONCE(Y, 1);
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* spin_lock(S); smp_mb();
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* smp_mb__after_spinlock(); r1 = READ_ONCE(X);
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* r0 = READ_ONCE(Y);
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* spin_unlock(S);
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*
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* it is forbidden that CPU0 does not observe CPU1's store to Y (r0 = 0)
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* and CPU1 does not observe CPU0's store to X (r1 = 0); see the comments
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* preceding the call to smp_mb__after_spinlock() in __schedule() and in
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* try_to_wake_up().
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*
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* 2) Given the snippet:
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*
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* { X = 0; Y = 0; }
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*
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* CPU0 CPU1 CPU2
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*
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* spin_lock(S); spin_lock(S); r1 = READ_ONCE(Y);
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* WRITE_ONCE(X, 1); smp_mb__after_spinlock(); smp_rmb();
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* spin_unlock(S); r0 = READ_ONCE(X); r2 = READ_ONCE(X);
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* WRITE_ONCE(Y, 1);
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* spin_unlock(S);
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*
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* it is forbidden that CPU0's critical section executes before CPU1's
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* critical section (r0 = 1), CPU2 observes CPU1's store to Y (r1 = 1)
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* and CPU2 does not observe CPU0's store to X (r2 = 0); see the comments
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* preceding the calls to smp_rmb() in try_to_wake_up() for similar
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* snippets but "projected" onto two CPUs.
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*
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* Property (2) upgrades the lock to an RCsc lock.
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*
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* Since most load-store architectures implement ACQUIRE with an smp_mb() after
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* the LL/SC loop, they need no further barriers. Similarly all our TSO
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* architectures imply an smp_mb() for each atomic instruction and equally don't
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* need more.
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*
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* Architectures that can implement ACQUIRE better need to take care.
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*/
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#ifndef smp_mb__after_spinlock
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#define smp_mb__after_spinlock() do { } while (0)
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#endif
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#ifdef CONFIG_DEBUG_SPINLOCK
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extern void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock);
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#define do_raw_spin_lock_flags(lock, flags) do_raw_spin_lock(lock)
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extern int do_raw_spin_trylock(raw_spinlock_t *lock);
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extern void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock);
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#else
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static inline void do_raw_spin_lock(raw_spinlock_t *lock) __acquires(lock)
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{
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__acquire(lock);
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arch_spin_lock(&lock->raw_lock);
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mmiowb_spin_lock();
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}
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#ifndef arch_spin_lock_flags
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#define arch_spin_lock_flags(lock, flags) arch_spin_lock(lock)
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#endif
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static inline void
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do_raw_spin_lock_flags(raw_spinlock_t *lock, unsigned long *flags) __acquires(lock)
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{
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__acquire(lock);
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arch_spin_lock_flags(&lock->raw_lock, *flags);
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mmiowb_spin_lock();
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}
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static inline int do_raw_spin_trylock(raw_spinlock_t *lock)
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{
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int ret = arch_spin_trylock(&(lock)->raw_lock);
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if (ret)
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mmiowb_spin_lock();
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return ret;
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}
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static inline void do_raw_spin_unlock(raw_spinlock_t *lock) __releases(lock)
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{
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mmiowb_spin_unlock();
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arch_spin_unlock(&lock->raw_lock);
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__release(lock);
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}
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#endif
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/*
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* Define the various spin_lock methods. Note we define these
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* regardless of whether CONFIG_SMP or CONFIG_PREEMPTION are set. The
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* various methods are defined as nops in the case they are not
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* required.
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*/
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#define raw_spin_trylock(lock) __cond_lock(lock, _raw_spin_trylock(lock))
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#define raw_spin_lock(lock) _raw_spin_lock(lock)
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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# define raw_spin_lock_nested(lock, subclass) \
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_raw_spin_lock_nested(lock, subclass)
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# define raw_spin_lock_nest_lock(lock, nest_lock) \
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do { \
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typecheck(struct lockdep_map *, &(nest_lock)->dep_map);\
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_raw_spin_lock_nest_lock(lock, &(nest_lock)->dep_map); \
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} while (0)
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#else
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/*
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* Always evaluate the 'subclass' argument to avoid that the compiler
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* warns about set-but-not-used variables when building with
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* CONFIG_DEBUG_LOCK_ALLOC=n and with W=1.
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*/
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# define raw_spin_lock_nested(lock, subclass) \
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_raw_spin_lock(((void)(subclass), (lock)))
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# define raw_spin_lock_nest_lock(lock, nest_lock) _raw_spin_lock(lock)
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#endif
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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#define raw_spin_lock_irqsave(lock, flags) \
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do { \
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typecheck(unsigned long, flags); \
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flags = _raw_spin_lock_irqsave(lock); \
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} while (0)
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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#define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
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do { \
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typecheck(unsigned long, flags); \
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flags = _raw_spin_lock_irqsave_nested(lock, subclass); \
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} while (0)
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#else
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#define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
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do { \
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typecheck(unsigned long, flags); \
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flags = _raw_spin_lock_irqsave(lock); \
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} while (0)
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#endif
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#else
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#define raw_spin_lock_irqsave(lock, flags) \
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do { \
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typecheck(unsigned long, flags); \
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_raw_spin_lock_irqsave(lock, flags); \
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} while (0)
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#define raw_spin_lock_irqsave_nested(lock, flags, subclass) \
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raw_spin_lock_irqsave(lock, flags)
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#endif
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#define raw_spin_lock_irq(lock) _raw_spin_lock_irq(lock)
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#define raw_spin_lock_bh(lock) _raw_spin_lock_bh(lock)
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#define raw_spin_unlock(lock) _raw_spin_unlock(lock)
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#define raw_spin_unlock_irq(lock) _raw_spin_unlock_irq(lock)
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#define raw_spin_unlock_irqrestore(lock, flags) \
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do { \
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typecheck(unsigned long, flags); \
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_raw_spin_unlock_irqrestore(lock, flags); \
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} while (0)
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#define raw_spin_unlock_bh(lock) _raw_spin_unlock_bh(lock)
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#define raw_spin_trylock_bh(lock) \
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__cond_lock(lock, _raw_spin_trylock_bh(lock))
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#define raw_spin_trylock_irq(lock) \
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({ \
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local_irq_disable(); \
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raw_spin_trylock(lock) ? \
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1 : ({ local_irq_enable(); 0; }); \
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})
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#define raw_spin_trylock_irqsave(lock, flags) \
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({ \
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local_irq_save(flags); \
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raw_spin_trylock(lock) ? \
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1 : ({ local_irq_restore(flags); 0; }); \
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})
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/* Include rwlock functions */
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#include <linux/rwlock.h>
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/*
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* Pull the _spin_*()/_read_*()/_write_*() functions/declarations:
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*/
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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# include <linux/spinlock_api_smp.h>
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#else
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# include <linux/spinlock_api_up.h>
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#endif
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/*
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* Map the spin_lock functions to the raw variants for PREEMPT_RT=n
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*/
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static __always_inline raw_spinlock_t *spinlock_check(spinlock_t *lock)
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{
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return &lock->rlock;
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}
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#ifdef CONFIG_DEBUG_SPINLOCK
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# define spin_lock_init(lock) \
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do { \
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static struct lock_class_key __key; \
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\
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__raw_spin_lock_init(spinlock_check(lock), \
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#lock, &__key, LD_WAIT_CONFIG); \
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} while (0)
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#else
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# define spin_lock_init(_lock) \
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do { \
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spinlock_check(_lock); \
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*(_lock) = __SPIN_LOCK_UNLOCKED(_lock); \
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} while (0)
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#endif
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static __always_inline void spin_lock(spinlock_t *lock)
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{
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raw_spin_lock(&lock->rlock);
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}
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static __always_inline void spin_lock_bh(spinlock_t *lock)
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{
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raw_spin_lock_bh(&lock->rlock);
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}
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static __always_inline int spin_trylock(spinlock_t *lock)
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{
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return raw_spin_trylock(&lock->rlock);
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}
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#define spin_lock_nested(lock, subclass) \
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do { \
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raw_spin_lock_nested(spinlock_check(lock), subclass); \
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} while (0)
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#define spin_lock_nest_lock(lock, nest_lock) \
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do { \
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raw_spin_lock_nest_lock(spinlock_check(lock), nest_lock); \
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} while (0)
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static __always_inline void spin_lock_irq(spinlock_t *lock)
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{
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raw_spin_lock_irq(&lock->rlock);
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}
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#define spin_lock_irqsave(lock, flags) \
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do { \
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raw_spin_lock_irqsave(spinlock_check(lock), flags); \
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} while (0)
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#define spin_lock_irqsave_nested(lock, flags, subclass) \
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do { \
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raw_spin_lock_irqsave_nested(spinlock_check(lock), flags, subclass); \
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} while (0)
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static __always_inline void spin_unlock(spinlock_t *lock)
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{
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raw_spin_unlock(&lock->rlock);
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}
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static __always_inline void spin_unlock_bh(spinlock_t *lock)
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{
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raw_spin_unlock_bh(&lock->rlock);
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}
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static __always_inline void spin_unlock_irq(spinlock_t *lock)
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{
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raw_spin_unlock_irq(&lock->rlock);
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}
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static __always_inline void spin_unlock_irqrestore(spinlock_t *lock, unsigned long flags)
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{
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raw_spin_unlock_irqrestore(&lock->rlock, flags);
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}
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static __always_inline int spin_trylock_bh(spinlock_t *lock)
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{
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return raw_spin_trylock_bh(&lock->rlock);
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}
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static __always_inline int spin_trylock_irq(spinlock_t *lock)
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{
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return raw_spin_trylock_irq(&lock->rlock);
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}
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#define spin_trylock_irqsave(lock, flags) \
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({ \
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raw_spin_trylock_irqsave(spinlock_check(lock), flags); \
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})
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/**
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* spin_is_locked() - Check whether a spinlock is locked.
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* @lock: Pointer to the spinlock.
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*
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* This function is NOT required to provide any memory ordering
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* guarantees; it could be used for debugging purposes or, when
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* additional synchronization is needed, accompanied with other
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* constructs (memory barriers) enforcing the synchronization.
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*
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* Returns: 1 if @lock is locked, 0 otherwise.
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*
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* Note that the function only tells you that the spinlock is
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* seen to be locked, not that it is locked on your CPU.
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*
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* Further, on CONFIG_SMP=n builds with CONFIG_DEBUG_SPINLOCK=n,
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* the return value is always 0 (see include/linux/spinlock_up.h).
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* Therefore you should not rely heavily on the return value.
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*/
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static __always_inline int spin_is_locked(spinlock_t *lock)
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{
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return raw_spin_is_locked(&lock->rlock);
|
|
}
|
|
|
|
static __always_inline int spin_is_contended(spinlock_t *lock)
|
|
{
|
|
return raw_spin_is_contended(&lock->rlock);
|
|
}
|
|
|
|
#define assert_spin_locked(lock) assert_raw_spin_locked(&(lock)->rlock)
|
|
|
|
/*
|
|
* Pull the atomic_t declaration:
|
|
* (asm-mips/atomic.h needs above definitions)
|
|
*/
|
|
#include <linux/atomic.h>
|
|
/**
|
|
* atomic_dec_and_lock - lock on reaching reference count zero
|
|
* @atomic: the atomic counter
|
|
* @lock: the spinlock in question
|
|
*
|
|
* Decrements @atomic by 1. If the result is 0, returns true and locks
|
|
* @lock. Returns false for all other cases.
|
|
*/
|
|
extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
|
|
#define atomic_dec_and_lock(atomic, lock) \
|
|
__cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
|
|
|
|
extern int _atomic_dec_and_lock_irqsave(atomic_t *atomic, spinlock_t *lock,
|
|
unsigned long *flags);
|
|
#define atomic_dec_and_lock_irqsave(atomic, lock, flags) \
|
|
__cond_lock(lock, _atomic_dec_and_lock_irqsave(atomic, lock, &(flags)))
|
|
|
|
int __alloc_bucket_spinlocks(spinlock_t **locks, unsigned int *lock_mask,
|
|
size_t max_size, unsigned int cpu_mult,
|
|
gfp_t gfp, const char *name,
|
|
struct lock_class_key *key);
|
|
|
|
#define alloc_bucket_spinlocks(locks, lock_mask, max_size, cpu_mult, gfp) \
|
|
({ \
|
|
static struct lock_class_key key; \
|
|
int ret; \
|
|
\
|
|
ret = __alloc_bucket_spinlocks(locks, lock_mask, max_size, \
|
|
cpu_mult, gfp, #locks, &key); \
|
|
ret; \
|
|
})
|
|
|
|
void free_bucket_spinlocks(spinlock_t *locks);
|
|
|
|
#endif /* __LINUX_SPINLOCK_H */
|