+++ /dev/null
-/* SPDX-License-Identifier: (GPL-2.0-only or LGPL-2.1-only)
- *
- * wrapper/trace-clock.h
- *
- * Contains LTTng trace clock mapping to LTTng trace clock or mainline monotonic
- * clock. This wrapper depends on CONFIG_HIGH_RES_TIMERS=y.
- *
- * Copyright (C) 2011-2012 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
- */
-
-#ifndef _LTTNG_TRACE_CLOCK_H
-#define _LTTNG_TRACE_CLOCK_H
-
-#ifdef CONFIG_HAVE_TRACE_CLOCK
-#include <linux/trace-clock.h>
-#else /* CONFIG_HAVE_TRACE_CLOCK */
-
-#include <linux/hardirq.h>
-#include <linux/ktime.h>
-#include <linux/time.h>
-#include <linux/hrtimer.h>
-#include <linux/percpu.h>
-#include <linux/version.h>
-#include <asm/local.h>
-#include <lttng/kernel-version.h>
-#include <lttng/clock.h>
-#include <wrapper/compiler.h>
-#include <wrapper/percpu-defs.h>
-#include <wrapper/random.h>
-#include <blacklist/timekeeping.h>
-
-extern struct lttng_trace_clock *lttng_trace_clock;
-
-/*
- * Upstream Linux commit 27727df240c7 ("Avoid taking lock in NMI path with
- * CONFIG_DEBUG_TIMEKEEPING") introduces a buggy ktime_get_mono_fast_ns().
- * This is fixed by patch "timekeeping: Fix __ktime_get_fast_ns() regression".
- */
-#if (LTTNG_KERNEL_RANGE(4,8,0, 4,8,2) \
- || LTTNG_KERNEL_RANGE(4,7,4, 4,7,8) \
- || LTTNG_KERNEL_RANGE(4,4,20, 4,4,25) \
- || LTTNG_KERNEL_RANGE(4,1,32, 4,1,35))
-#define LTTNG_CLOCK_NMI_SAFE_BROKEN
-#endif
-
-/*
- * We need clock values to be monotonically increasing per-cpu, which is
- * not strictly guaranteed by ktime_get_mono_fast_ns(). It is
- * straightforward to do on architectures with a 64-bit cmpxchg(), but
- * not so on architectures without 64-bit cmpxchg. For now, only enable
- * this feature on 64-bit architectures.
- */
-
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0) \
- && BITS_PER_LONG == 64 \
- && !defined(LTTNG_CLOCK_NMI_SAFE_BROKEN))
-#define LTTNG_USE_NMI_SAFE_CLOCK
-#endif
-
-#ifdef LTTNG_USE_NMI_SAFE_CLOCK
-
-DECLARE_PER_CPU(u64, lttng_last_tsc);
-
-/*
- * Sometimes called with preemption enabled. Can be interrupted.
- */
-static inline u64 trace_clock_monotonic_wrapper(void)
-{
- u64 now, last, result;
- u64 *last_tsc_ptr;
-
- /* Use fast nmi-safe monotonic clock provided by the Linux kernel. */
- preempt_disable();
- last_tsc_ptr = lttng_this_cpu_ptr(<tng_last_tsc);
- last = *last_tsc_ptr;
- /*
- * Read "last" before "now". It is not strictly required, but it ensures
- * that an interrupt coming in won't artificially trigger a case where
- * "now" < "last". This kind of situation should only happen if the
- * mono_fast time source goes slightly backwards.
- */
- barrier();
- now = ktime_get_mono_fast_ns();
- if (U64_MAX / 2 < now - last)
- now = last;
- result = cmpxchg64_local(last_tsc_ptr, last, now);
- preempt_enable();
- if (result == last) {
- /* Update done. */
- return now;
- } else {
- /*
- * Update not done, due to concurrent update. We can use
- * "result", since it has been sampled concurrently with our
- * time read, so it should not be far from "now".
- */
- return result;
- }
-}
-
-#else /* #ifdef LTTNG_USE_NMI_SAFE_CLOCK */
-static inline u64 trace_clock_monotonic_wrapper(void)
-{
- ktime_t ktime;
-
- /*
- * Refuse to trace from NMIs with this wrapper, because an NMI could
- * nest over the xtime write seqlock and deadlock.
- */
- if (in_nmi())
- return (u64) -EIO;
-
- ktime = ktime_get();
- return ktime_to_ns(ktime);
-}
-#endif /* #else #ifdef LTTNG_USE_NMI_SAFE_CLOCK */
-
-static inline u64 trace_clock_read64_monotonic(void)
-{
- return (u64) trace_clock_monotonic_wrapper();
-}
-
-static inline u64 trace_clock_freq_monotonic(void)
-{
- return (u64) NSEC_PER_SEC;
-}
-
-static inline int trace_clock_uuid_monotonic(char *uuid)
-{
- return wrapper_get_bootid(uuid);
-}
-
-static inline const char *trace_clock_name_monotonic(void)
-{
- return "monotonic";
-}
-
-static inline const char *trace_clock_description_monotonic(void)
-{
- return "Monotonic Clock";
-}
-
-#ifdef LTTNG_USE_NMI_SAFE_CLOCK
-static inline int get_trace_clock(void)
-{
- printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic fast clock, which is NMI-safe.\n");
- return 0;
-}
-#else /* #ifdef LTTNG_USE_NMI_SAFE_CLOCK */
-static inline int get_trace_clock(void)
-{
- printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic clock. NMIs will not be traced.\n");
- return 0;
-}
-#endif /* #else #ifdef LTTNG_USE_NMI_SAFE_CLOCK */
-
-static inline void put_trace_clock(void)
-{
-}
-
-static inline u64 trace_clock_read64(void)
-{
- struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
-
- if (likely(!ltc)) {
- return trace_clock_read64_monotonic();
- } else {
- read_barrier_depends(); /* load ltc before content */
- return ltc->read64();
- }
-}
-
-static inline u64 trace_clock_freq(void)
-{
- struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
-
- if (!ltc) {
- return trace_clock_freq_monotonic();
- } else {
- read_barrier_depends(); /* load ltc before content */
- return ltc->freq();
- }
-}
-
-static inline int trace_clock_uuid(char *uuid)
-{
- struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
-
- read_barrier_depends(); /* load ltc before content */
- /* Use default UUID cb when NULL */
- if (!ltc || !ltc->uuid) {
- return trace_clock_uuid_monotonic(uuid);
- } else {
- return ltc->uuid(uuid);
- }
-}
-
-static inline const char *trace_clock_name(void)
-{
- struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
-
- if (!ltc) {
- return trace_clock_name_monotonic();
- } else {
- read_barrier_depends(); /* load ltc before content */
- return ltc->name();
- }
-}
-
-static inline const char *trace_clock_description(void)
-{
- struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
-
- if (!ltc) {
- return trace_clock_description_monotonic();
- } else {
- read_barrier_depends(); /* load ltc before content */
- return ltc->description();
- }
-}
-
-#endif /* CONFIG_HAVE_TRACE_CLOCK */
-
-#endif /* _LTTNG_TRACE_CLOCK_H */
projects / lttng-modules.git / blobdiff