X-Git-Url: http://git.lttng.org/?a=blobdiff_plain;f=wrapper%2Ftrace-clock.h;h=496fec4360c7f654c18f454acae564ba43adabe7;hb=a5de5832931b85e6ccb921a8956eba75ce1e51a6;hp=801e640eda894346554cb6fa2fa9e9324de6b256;hpb=a82c63f10514ca43282498ea4fdee3908576528a;p=lttng-modules.git diff --git a/wrapper/trace-clock.h b/wrapper/trace-clock.h index 801e640e..496fec43 100644 --- a/wrapper/trace-clock.h +++ b/wrapper/trace-clock.h @@ -1,15 +1,29 @@ +#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 + * + * 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 */ @@ -18,8 +32,118 @@ #include #include #include -#include "random.h" +#include +#include +#include +#include +#include +#include +#include + +#if ((LTTNG_KERNEL_RANGE(3,10,0, 3,10,14) && !LTTNG_RHEL_KERNEL_RANGE(3,10,0,123,0,0, 3,10,14,0,0,0)) \ + || 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 + +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 + +#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0) \ + && !defined(LTTNG_CLOCK_NMI_SAFE_BROKEN)) + +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; @@ -32,49 +156,112 @@ 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 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */ -static inline u32 trace_clock_read32(void) +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"; +} + +#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) +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 /* #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */ +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 #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) */ + +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 = ACCESS_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 = ACCESS_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 = ACCESS_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 = ACCESS_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 = ACCESS_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 */