From: Mathieu Desnoyers Date: Sun, 13 Jul 2014 17:20:57 +0000 (-0400) Subject: Use 3.17 ktime_get_mono_fast_ns() new API X-Git-Tag: v2.6.0-rc1~10 X-Git-Url: https://git.lttng.org./?a=commitdiff_plain;h=b07252070edd244987bf160c1ee488d4796bb3a3;p=lttng-modules.git Use 3.17 ktime_get_mono_fast_ns() new API The new ktime_get_mono_fast_ns() API introduced in kernel 3.17 allows tracing NMI handlers. Signed-off-by: Mathieu Desnoyers Cc: Thomas Gleixner --- diff --git a/Makefile b/Makefile index aa4835d3..eeffdfe9 100644 --- a/Makefile +++ b/Makefile @@ -35,7 +35,7 @@ lttng-tracer-objs := lttng-events.o lttng-abi.o \ lttng-context-vtid.o lttng-context-ppid.o \ lttng-context-vppid.o lttng-calibrate.o \ lttng-context-hostname.o wrapper/random.o \ - probes/lttng.o + probes/lttng.o wrapper/trace-clock.o obj-m += lttng-statedump.o lttng-statedump-objs := lttng-statedump-impl.o wrapper/irqdesc.o \ diff --git a/wrapper/trace-clock.c b/wrapper/trace-clock.c new file mode 100644 index 00000000..1b7a2176 --- /dev/null +++ b/wrapper/trace-clock.c @@ -0,0 +1,29 @@ +/* + * wrapper/trace-clock.c + * + * 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 + */ + +#include "trace-clock.h" + +#if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,17,0)) +DEFINE_PER_CPU(local_t, lttng_last_tsc); +EXPORT_PER_CPU_SYMBOL(lttng_last_tsc); +#endif /* #else #if (LINUX_VERSION_CODE >= KERNEL_VERSION(3,16,0)) */ diff --git a/wrapper/trace-clock.h b/wrapper/trace-clock.h index 9c0c8067..b145b826 100644 --- a/wrapper/trace-clock.h +++ b/wrapper/trace-clock.h @@ -32,7 +32,9 @@ #include #include #include +#include #include +#include #include "../lttng-kernel-version.h" #include "random.h" @@ -40,6 +42,88 @@ #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) */ + +/* + * Always called with preemption disabled. 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. */ + last_tsc = &__get_cpu_var(lttng_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); + 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; @@ -54,6 +138,7 @@ 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)) */ static inline u32 trace_clock_read32(void) { @@ -75,23 +160,19 @@ static inline int trace_clock_uuid(char *uuid) 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) {