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eb7d96a13b
The annotations for bit_spinlock.h have simply been using "bitlock" as the token. For Sparse, that was likely sufficient in most cases. But Clang's context analysis is more precise, and we need to ensure we can distinguish different bitlocks. To do so, add a token context, and a macro __bitlock(bitnum, addr) that is used to construct unique per-bitlock tokens. Add the appropriate test. <linux/list_bl.h> is implicitly included through other includes, and requires 2 annotations to indicate that acquisition (without release) and release (without prior acquisition) of its bitlock is intended. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://patch.msgid.link/20251219154418.3592607-14-elver@google.com
118 lines
3.1 KiB
C
118 lines
3.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef __LINUX_BIT_SPINLOCK_H
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#define __LINUX_BIT_SPINLOCK_H
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#include <linux/kernel.h>
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#include <linux/preempt.h>
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#include <linux/atomic.h>
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#include <linux/bug.h>
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#include <asm/processor.h> /* for cpu_relax() */
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/*
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* For static context analysis, we need a unique token for each possible bit
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* that can be used as a bit_spinlock. The easiest way to do that is to create a
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* fake context that we can cast to with the __bitlock(bitnum, addr) macro
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* below, which will give us unique instances for each (bit, addr) pair that the
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* static analysis can use.
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*/
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context_lock_struct(__context_bitlock) { };
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#define __bitlock(bitnum, addr) (struct __context_bitlock *)(bitnum + (addr))
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/*
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* bit-based spin_lock()
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*
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* Don't use this unless you really need to: spin_lock() and spin_unlock()
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* are significantly faster.
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*/
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static __always_inline void bit_spin_lock(int bitnum, unsigned long *addr)
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__acquires(__bitlock(bitnum, addr))
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{
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/*
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* Assuming the lock is uncontended, this never enters
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* the body of the outer loop. If it is contended, then
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* within the inner loop a non-atomic test is used to
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* busywait with less bus contention for a good time to
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* attempt to acquire the lock bit.
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*/
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preempt_disable();
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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while (unlikely(test_and_set_bit_lock(bitnum, addr))) {
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preempt_enable();
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do {
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cpu_relax();
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} while (test_bit(bitnum, addr));
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preempt_disable();
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}
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#endif
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__acquire(__bitlock(bitnum, addr));
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}
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/*
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* Return true if it was acquired
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*/
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static __always_inline int bit_spin_trylock(int bitnum, unsigned long *addr)
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__cond_acquires(true, __bitlock(bitnum, addr))
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{
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preempt_disable();
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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if (unlikely(test_and_set_bit_lock(bitnum, addr))) {
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preempt_enable();
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return 0;
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}
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#endif
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__acquire(__bitlock(bitnum, addr));
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return 1;
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}
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/*
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* bit-based spin_unlock()
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*/
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static __always_inline void bit_spin_unlock(int bitnum, unsigned long *addr)
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__releases(__bitlock(bitnum, addr))
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{
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#ifdef CONFIG_DEBUG_SPINLOCK
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BUG_ON(!test_bit(bitnum, addr));
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#endif
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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clear_bit_unlock(bitnum, addr);
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#endif
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preempt_enable();
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__release(__bitlock(bitnum, addr));
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}
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/*
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* bit-based spin_unlock()
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* non-atomic version, which can be used eg. if the bit lock itself is
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* protecting the rest of the flags in the word.
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*/
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static __always_inline void __bit_spin_unlock(int bitnum, unsigned long *addr)
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__releases(__bitlock(bitnum, addr))
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{
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#ifdef CONFIG_DEBUG_SPINLOCK
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BUG_ON(!test_bit(bitnum, addr));
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#endif
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#if defined(CONFIG_SMP) || defined(CONFIG_DEBUG_SPINLOCK)
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__clear_bit_unlock(bitnum, addr);
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#endif
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preempt_enable();
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__release(__bitlock(bitnum, addr));
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}
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/*
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* Return true if the lock is held.
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*/
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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_COUNT
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return preempt_count();
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#else
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return 1;
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#endif
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}
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#endif /* __LINUX_BIT_SPINLOCK_H */
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