From 4a23fd34e0457fdb0582dd916494815419a59479 Mon Sep 17 00:00:00 2001 From: Richard Braun Date: Fri, 13 Sep 2019 12:04:22 +0200 Subject: Fix the documentation according to the memory model Also, change the ordering requirements of some operations. --- arch/x86/machine/cpu.h | 41 +++++++++++++++++++++-------------------- kern/atomic.h | 3 --- kern/rcu.h | 8 ++++---- kern/thread.h | 22 +++++++++++----------- 4 files changed, 36 insertions(+), 38 deletions(-) diff --git a/arch/x86/machine/cpu.h b/arch/x86/machine/cpu.h index dcb18012..67111d2a 100644 --- a/arch/x86/machine/cpu.h +++ b/arch/x86/machine/cpu.h @@ -266,7 +266,7 @@ cpu_get_ ## name(void) \ { \ unsigned long name; \ \ - asm volatile("mov %%" __QUOTE(name) ", %0" : "=r" (name) : : "memory"); \ + asm volatile("mov %%" __QUOTE(name) ", %0" : "=r" (name)); \ return name; \ } \ \ @@ -285,7 +285,7 @@ cpu_set_ ## name(unsigned long value) \ * * Setting a control register executes a serializing instruction. * - * These are intra-thread release-acquire operations. + * There is a strong sequence point when setting a control register. */ CPU_DECL_GETSET_CR(cr0) CPU_DECL_GETSET_CR(cr2) @@ -295,7 +295,7 @@ CPU_DECL_GETSET_CR(cr4) /* * Enable local interrupts. * - * This is an intra-thread release operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_intr_enable(void) @@ -306,7 +306,7 @@ cpu_intr_enable(void) /* * Disable local interrupts. * - * This is an intra-thread acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_intr_disable(void) @@ -317,7 +317,7 @@ cpu_intr_disable(void) /* * Restore the content of the EFLAGS register, possibly enabling interrupts. * - * This is an intra-thread release operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_intr_restore(unsigned long flags) @@ -332,7 +332,7 @@ cpu_intr_restore(unsigned long flags) * Disable local interrupts, returning the previous content of the EFLAGS * register. * - * This is an intra-thread acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_intr_save(unsigned long *flags) @@ -356,7 +356,7 @@ cpu_intr_enabled(void) /* * Spin-wait loop hint. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_pause(void) @@ -371,7 +371,7 @@ cpu_pause(void) * allow the processor handling them before entering the idle state if they * were disabled before calling this function. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_idle(void) @@ -382,7 +382,7 @@ cpu_idle(void) /* * Halt the CPU. * - * This is an intra-thread release operation. + * There is a strong sequence point during this operation. */ noreturn static __always_inline void cpu_halt(void) @@ -472,7 +472,7 @@ cpu_has_feature(const struct cpu *cpu, enum cpu_feature feature) * * This function executes a serializing instruction. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_enable_pse(void) @@ -485,7 +485,7 @@ cpu_enable_pse(void) * * This function executes a serializing instruction. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_enable_pae(void) @@ -507,7 +507,7 @@ cpu_has_global_pages(void) * * This function executes a serializing instruction. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_enable_global_pages(void) @@ -520,7 +520,7 @@ cpu_enable_global_pages(void) * * This function executes a serializing instruction. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_cpuid(unsigned int *eax, unsigned int *ebx, unsigned int *ecx, @@ -550,7 +550,7 @@ cpu_get_msr64(uint32_t msr) * * This function executes a serializing instruction. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static inline void cpu_set_msr(uint32_t msr, uint32_t high, uint32_t low) @@ -563,7 +563,7 @@ cpu_set_msr(uint32_t msr, uint32_t high, uint32_t low) * * This function executes a serializing instruction. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static inline void cpu_set_msr64(uint32_t msr, uint64_t value) @@ -580,7 +580,7 @@ cpu_set_msr64(uint32_t msr, uint64_t value) * * This function executes a serializing instruction. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_tlb_flush(void) @@ -593,7 +593,7 @@ cpu_tlb_flush(void) * * This function executes a serializing instruction. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_tlb_flush_all(void) @@ -621,7 +621,7 @@ cpu_tlb_flush_all(void) * * This function executes a serializing instruction. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static __always_inline void cpu_tlb_flush_va(unsigned long va) @@ -661,8 +661,9 @@ uint64_t cpu_get_freq(void); /* * Busy-wait for a given amount of time, in microseconds. * - * If the function produces a delay, i.e. the duration argument is strictly - * greater than zero, this is an intra-thread release-acquire operation. + * If calling this function produces a delay, i.e. the duration argument + * is strictly greater than zero, there is a strong sequence point during + * this operation. */ void cpu_delay(unsigned long usecs); diff --git a/kern/atomic.h b/kern/atomic.h index 2ecb28f7..04a08f3f 100644 --- a/kern/atomic.h +++ b/kern/atomic.h @@ -24,9 +24,6 @@ * Some configurations may not support 64-bit operations. Check if the * ATOMIC_HAVE_64B_OPS macro is defined to find out. * - * TODO Replace mentions of "memory barriers" throughout the code with - * C11 memory model terminology. - * * TODO Decide if architecture-specific atomic operations should be * provided, and if so, how. */ diff --git a/kern/rcu.h b/kern/rcu.h index eb82a6af..55663311 100644 --- a/kern/rcu.h +++ b/kern/rcu.h @@ -80,24 +80,24 @@ struct rcu_reader; /* * Enter a read-side critical section. * - * This is an intra-thread acquire operation. + * There is a strong sequence point during this operation. */ static inline void rcu_read_enter(void) { rcu_reader_inc(thread_rcu_reader(thread_self())); - latomic_fence(LATOMIC_ACQ_REL); + latomic_fence(LATOMIC_SEQ_CST); } /* * Leave a read-side critical section. * - * This is an intra-thread release operation. + * There is a strong sequence point during this operation. */ static inline void rcu_read_leave(void) { - latomic_fence(LATOMIC_ACQ_REL); + latomic_fence(LATOMIC_SEQ_CST); rcu_reader_dec(thread_rcu_reader(thread_self())); } diff --git a/kern/thread.h b/kern/thread.h index 75ff4b24..9afad463 100644 --- a/kern/thread.h +++ b/kern/thread.h @@ -229,7 +229,7 @@ void thread_join(struct thread *thread); * the thread is awoken. * * If this function causes the current thread to yield the processor, - * this is an intra-thread release-acquire operation. + * there is a strong sequence point during this operation. */ void thread_sleep(struct spinlock *interlock, const void *wchan_addr, const char *wchan_desc); @@ -272,7 +272,7 @@ int thread_resume(struct thread *thread); * Suspend execution of the calling thread. * * If this function causes the calling thread to yield the processor, - * this is an intra-thread release-acquire operation. + * there is a strong sequence point during this operation. */ void thread_delay(uint64_t ticks, bool absolute); @@ -545,7 +545,7 @@ thread_pinned(void) /* * Pin the current thread to the current processor. * - * This is an intra-thread release-acquire operation. + * There is a strong sequence point during this operation. */ static inline void thread_pin(void) @@ -561,7 +561,7 @@ thread_pin(void) /* * Unpin the current thread from the current processor. * - * This is an intra-thread release operation. + * There is a strong sequence point during this operation. */ static inline void thread_unpin(void) @@ -592,7 +592,7 @@ thread_preempt_enabled(void) /* * Disable preemption. * - * This is an intra-thread acquire operation. + * There is a strong sequence point during this operation. */ static inline void thread_preempt_disable(void) @@ -613,7 +613,7 @@ thread_preempt_disable(void) * never performs voluntary preemption. This may break real-time behavior * and should never be used in application code. * - * This is an intra-thread release operation. + * There is a strong sequence point during this operation. */ static inline void thread_preempt_enable_no_resched(void) @@ -635,7 +635,7 @@ thread_preempt_enable_no_resched(void) /* * Enable preemption. * - * This is an intra-thread release operation. + * There is a strong sequence point during this operation. */ static inline void thread_preempt_enable(void) @@ -653,7 +653,7 @@ thread_preempt_enable(void) /* * Disable preemption and interrupts. * - * This is an intra-thread acquire operation. + * There is a strong sequence point during this operation. */ static inline void thread_preempt_disable_intr_save(unsigned long *flags) @@ -665,7 +665,7 @@ thread_preempt_disable_intr_save(unsigned long *flags) /* * Enable preemption and restore interrupts. * - * This is an intra-thread release operation. + * There is a strong sequence point during this operation. */ static inline void thread_preempt_enable_intr_restore(unsigned long flags) @@ -705,7 +705,7 @@ thread_check_intr_context(void) /* * Enter interrupt context. * - * This is an intra-thread acquire operation. + * There is a strong sequence point during this operation. */ static inline void thread_intr_enter(void) @@ -726,7 +726,7 @@ thread_intr_enter(void) /* * Leave interrupt context. * - * This is an intra-thread release operation. + * There is a strong sequence point during this operation. */ static inline void thread_intr_leave(void) -- cgit v1.2.3