X-Git-Url: http://git.liburcu.org/?a=blobdiff_plain;f=wrapper%2Ftrace-clock.h;h=9f4e366afbcbeecc89302a2cb205b41b3e9012e5;hb=9153ad231edfa178b83bb4c81891b7b812158b08;hp=d7d18429ba1c1f17d22d35c4ce6ec8484aef422e;hpb=f30ae671364af1a69a5c5ad562e10a38c1bbaf2e;p=lttng-modules.git diff --git a/wrapper/trace-clock.h b/wrapper/trace-clock.h index d7d18429..9f4e366a 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 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 - * - * 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 */ @@ -35,72 +22,57 @@ #include #include #include -#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)) +#include +#include +#include +#include +#include +#include -DECLARE_PER_CPU(local_t, lttng_last_tsc); +extern struct lttng_trace_clock *lttng_trace_clock; -#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); /* - * Always called with preemption disabled. Can be interrupted. + * 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. */ - last_tsc = lttng_this_cpu_ptr(<tng_last_tsc); - last = local_read(last_tsc); + 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 @@ -109,9 +81,10 @@ static inline u64 trace_clock_monotonic_wrapper(void) */ 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. */ return now; @@ -121,11 +94,11 @@ static inline u64 trace_clock_monotonic_wrapper(void) * "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; @@ -140,41 +113,112 @@ static inline u64 trace_clock_monotonic_wrapper(void) 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(void) +static inline u64 trace_clock_read64_monotonic(void) { return (u64) trace_clock_monotonic_wrapper(); } -static inline u64 trace_clock_freq(void) +static inline u64 trace_clock_freq_monotonic(void) { return (u64) NSEC_PER_SEC; } -static inline int trace_clock_uuid(char *uuid) +static inline int trace_clock_uuid_monotonic(char *uuid) { return wrapper_get_bootid(uuid); } -#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) +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(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 = 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 */