+#ifndef _LTTNG_TRACE_CLOCK_H
+#define _LTTNG_TRACE_CLOCK_H
+
/*
- * Copyright (C) 2011 Mathieu Desnoyers (mathieu.desnoyers@efficios.com)
+ * 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.
*
- * Dual LGPL v2.1/GPL v2 license.
+ * 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/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 "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
+
+#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".
+ */
+static inline u64 trace_clock_fixup(u64 src_now, u32 last)
+{
+ u64 now;
+
+ 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.
+ */
+static inline u64 trace_clock_fixup(u64 src_now, u64 last)
+{
+ return last;
+}
+#endif /* #else #if (BITS_PER_LONG == 32) */
+
+/*
+ * 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;
+
+ /* 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);
+ /*
+ * 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 (((long) now - (long) last) < 0)
+ now = trace_clock_fixup(now, last);
+ result = local_cmpxchg(last_tsc, last, (unsigned long) 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 trace_clock_fixup(now, result);
+ }
+}
+
+#else /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */
static inline u64 trace_clock_monotonic_wrapper(void)
{
ktime_t ktime;
return (u64) -EIO;
ktime = ktime_get();
- return (u64) ktime.tv64;
-}
-
-static inline u32 trace_clock_read32(void)
-{
- return (u32) trace_clock_monotonic_wrapper();
+ return ktime_to_ns(ktime);
}
+#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */
static inline u64 trace_clock_read64(void)
{
return (u64) NSEC_PER_SEC;
}
-static inline const char *trace_clock_uuid(void)
+static inline int trace_clock_uuid(char *uuid)
{
- return "CLOCK_MONOTONIC";
+ return wrapper_get_bootid(uuid);
}
+#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0))
static inline int get_trace_clock(void)
{
- /*
- * LTTng: Using mainline kernel monotonic clock. NMIs will not be
- * traced, and expect significant performance degradation compared to
- * the LTTng trace clocks. Integration of the LTTng 0.x trace clocks
- * into LTTng 2.0 is planned in a near future.
- */
- printk(KERN_WARNING "LTTng: Using mainline kernel monotonic clock.\n");
- printk(KERN_WARNING " * NMIs will not be traced,\n");
- printk(KERN_WARNING " * expect significant performance degradation compared to the\n");
- printk(KERN_WARNING " LTTng trace clocks.\n");
- printk(KERN_WARNING "Integration of the LTTng 0.x trace clocks into LTTng 2.0 is planned\n");
- printk(KERN_WARNING "in a near future.\n");
-
+ printk(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)) */
+static inline int get_trace_clock(void)
+{
+ printk(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)) */
static inline void put_trace_clock(void)
{
projects / lttng-modules.git / blobdiff