-#ifndef _LTTNG_TRACE_CLOCK_H
-#define _LTTNG_TRACE_CLOCK_H
-
-/*
+/* SPDX-License-Identifier: (GPL-2.0 or LGPL-2.1)
+ *
* 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>
- *
- * This library is free software; you can redistribute it and/or
- * modify it under the terms of the GNU Lesser General Public
- * License as published by the Free Software Foundation; only
- * version 2.1 of the License.
- *
- * This library is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
- * Lesser General Public License for more details.
- *
- * You should have received a copy of the GNU Lesser General Public
- * License along with this library; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
*/
+#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/percpu.h>
#include <linux/version.h>
#include <asm/local.h>
-#include "../lttng-kernel-version.h"
-#include "../lttng-clock.h"
-#include "percpu-defs.h"
-#include "random.h"
-
-#if ((LTTNG_KERNEL_RANGE(3,10,0, 3,10,14) && !LTTNG_RHEL_KERNEL_RANGE(3,10,0,7,0, 3,10,14,0,0)) \
- || LTTNG_KERNEL_RANGE(3,11,0, 3,11,3))
-#error "Linux kernels 3.10 and 3.11 introduce a deadlock in the timekeeping subsystem. Fixed by commit 7bd36014460f793c19e7d6c94dab67b0afcfcb7f \"timekeeping: Fix HRTICK related deadlock from ntp lock changes\" in Linux."
-#endif
+#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;
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0))
-
-DECLARE_PER_CPU(local_t, lttng_last_tsc);
-
-#if (BITS_PER_LONG == 32)
/*
- * Fixup "src_now" using the 32 LSB from "last". We need to handle overflow and
- * underflow of the 32nd bit. "last" can be above, below or equal to the 32 LSB
- * of "src_now".
+ * 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".
*/
-static inline u64 trace_clock_fixup(u64 src_now, u32 last)
-{
- u64 now;
+#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
- now = src_now & 0xFFFFFFFF00000000ULL;
- now |= (u64) last;
- /* Detect overflow or underflow between now and last. */
- if ((src_now & 0x80000000U) && !(last & 0x80000000U)) {
- /*
- * If 32nd bit transitions from 1 to 0, and we move forward in
- * time from "now" to "last", then we have an overflow.
- */
- if (((s32) now - (s32) last) < 0)
- now += 0x0000000100000000ULL;
- } else if (!(src_now & 0x80000000U) && (last & 0x80000000U)) {
- /*
- * If 32nd bit transitions from 0 to 1, and we move backward in
- * time from "now" to "last", then we have an underflow.
- */
- if (((s32) now - (s32) last) > 0)
- now -= 0x0000000100000000ULL;
- }
- return now;
-}
-#else /* #if (BITS_PER_LONG == 32) */
/*
- * The fixup is pretty easy on 64-bit architectures: "last" is a 64-bit
- * value, so we can use last directly as current time.
+ * 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.
*/
-static inline u64 trace_clock_fixup(u64 src_now, u64 last)
-{
- return last;
-}
-#endif /* #else #if (BITS_PER_LONG == 32) */
+
+#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;
- unsigned long last, result;
- local_t *last_tsc;
+ u64 now, last, result;
+ u64 *last_tsc_ptr;
/* Use fast nmi-safe monotonic clock provided by the Linux kernel. */
preempt_disable();
- last_tsc = lttng_this_cpu_ptr(<tng_last_tsc);
- last = local_read(last_tsc);
+ 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
*/
barrier();
now = ktime_get_mono_fast_ns();
- if (((long) now - (long) last) < 0)
- now = trace_clock_fixup(now, last);
- result = local_cmpxchg(last_tsc, last, (unsigned long) now);
+ if (U64_MAX / 2 < now - last)
+ now = last;
+ result = cmpxchg64_local(last_tsc_ptr, last, now);
preempt_enable();
if (result == last) {
/* Update done. */
* "result", since it has been sampled concurrently with our
* time read, so it should not be far from "now".
*/
- return trace_clock_fixup(now, result);
+ return result;
}
}
-#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */
+#else /* #ifdef LTTNG_USE_NMI_SAFE_CLOCK */
static inline u64 trace_clock_monotonic_wrapper(void)
{
ktime_t ktime;
ktime = ktime_get();
return ktime_to_ns(ktime);
}
-#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */
+#endif /* #else #ifdef LTTNG_USE_NMI_SAFE_CLOCK */
static inline u64 trace_clock_read64_monotonic(void)
{
return "Monotonic Clock";
}
-#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0))
+#ifdef LTTNG_USE_NMI_SAFE_CLOCK
static inline int get_trace_clock(void)
{
- printk(KERN_WARNING "LTTng: Using mainline kernel monotonic fast clock, which is NMI-safe.\n");
+ printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic fast clock, which is NMI-safe.\n");
return 0;
}
-#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */
+#else /* #ifdef LTTNG_USE_NMI_SAFE_CLOCK */
static inline int get_trace_clock(void)
{
- printk(KERN_WARNING "LTTng: Using mainline kernel monotonic clock. NMIs will not be traced.\n");
+ printk_once(KERN_WARNING "LTTng: Using mainline kernel monotonic clock. NMIs will not be traced.\n");
return 0;
}
-#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */
+#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 = ACCESS_ONCE(lttng_trace_clock);
+ struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
if (likely(!ltc)) {
return trace_clock_read64_monotonic();
static inline u64 trace_clock_freq(void)
{
- struct lttng_trace_clock *ltc = ACCESS_ONCE(lttng_trace_clock);
+ struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
if (!ltc) {
return trace_clock_freq_monotonic();
static inline int trace_clock_uuid(char *uuid)
{
- struct lttng_trace_clock *ltc = ACCESS_ONCE(lttng_trace_clock);
+ struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
read_barrier_depends(); /* load ltc before content */
/* Use default UUID cb when NULL */
static inline const char *trace_clock_name(void)
{
- struct lttng_trace_clock *ltc = ACCESS_ONCE(lttng_trace_clock);
+ struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
if (!ltc) {
return trace_clock_name_monotonic();
static inline const char *trace_clock_description(void)
{
- struct lttng_trace_clock *ltc = ACCESS_ONCE(lttng_trace_clock);
+ struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock);
if (!ltc) {
return trace_clock_description_monotonic();
projects / lttng-modules.git / blobdiff