X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=wrapper%2Ftrace-clock.h;h=28ee90ebf0434aa0fb3015c4f8c42d833a4a0b98;hb=369708f464bedc0682151df9308cebfa14dbdb2b;hp=6ea9e81cb6e44cbb0e172a595cbe33d2f9ae95de;hpb=886d51a3d7ed5fa6b41d7f19b3e14ae6c535a44c;p=lttng-modules.git diff --git a/wrapper/trace-clock.h b/wrapper/trace-clock.h index 6ea9e81c..28ee90eb 100644 --- a/wrapper/trace-clock.h +++ b/wrapper/trace-clock.h @@ -1,29 +1,16 @@ -#ifndef _LTTNG_TRACE_CLOCK_H -#define _LTTNG_TRACE_CLOCK_H - -/* +/* 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 - * - * 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 #else /* CONFIG_HAVE_TRACE_CLOCK */ @@ -32,8 +19,70 @@ #include #include #include -#include "random.h" +#include +#include +#include +#include +#include +#include +#include + +extern struct lttng_trace_clock *lttng_trace_clock; + +/* + * 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 BITS_PER_LONG == 64 +#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 = 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; @@ -46,49 +95,116 @@ static inline u64 trace_clock_monotonic_wrapper(void) return (u64) -EIO; ktime = ktime_get(); - return (u64) ktime.tv64; + 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 u32 trace_clock_read32(void) +static inline u64 trace_clock_freq_monotonic(void) +{ + return (u64) NSEC_PER_SEC; +} + +static inline int trace_clock_uuid_monotonic(char *uuid) +{ + unsigned char *boot_id; + + boot_id = get_kernel_boot_id(); + sprintf(uuid, "%pU", boot_id); + return 0; +} + +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) { - return (u32) trace_clock_monotonic_wrapper(); } static inline u64 trace_clock_read64(void) { - return (u64) trace_clock_monotonic_wrapper(); + 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) { - return (u64) NSEC_PER_SEC; + 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) { - return wrapper_get_bootid(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 int get_trace_clock(void) +static inline const char *trace_clock_name(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"); + struct lttng_trace_clock *ltc = READ_ONCE(lttng_trace_clock); - return 0; + if (!ltc) { + return trace_clock_name_monotonic(); + } else { + read_barrier_depends(); /* load ltc before content */ + return ltc->name(); + } } -static inline void put_trace_clock(void) +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 */