diff options
Diffstat (limited to 'src/lib/time')
| -rw-r--r-- | src/lib/time/.may_include | 2 | ||||
| -rw-r--r-- | src/lib/time/compat_time.c | 30 | ||||
| -rw-r--r-- | src/lib/time/compat_time.h | 152 | ||||
| -rw-r--r-- | src/lib/time/include.am | 4 | ||||
| -rw-r--r-- | src/lib/time/lib_time.md | 9 | ||||
| -rw-r--r-- | src/lib/time/time_sys.c | 29 | ||||
| -rw-r--r-- | src/lib/time/time_sys.h | 14 | ||||
| -rw-r--r-- | src/lib/time/tvdiff.c | 7 | ||||
| -rw-r--r-- | src/lib/time/tvdiff.h | 4 |
9 files changed, 230 insertions, 21 deletions
diff --git a/src/lib/time/.may_include b/src/lib/time/.may_include index 2c7e37a836..ae01431b60 100644 --- a/src/lib/time/.may_include +++ b/src/lib/time/.may_include @@ -4,8 +4,10 @@ lib/cc/*.h lib/err/*.h lib/intmath/*.h lib/log/*.h +lib/subsys/*.h lib/time/*.h lib/wallclock/*.h +lib/defs/time.h # For load_windows_system_lib. lib/fs/winlib.h
\ No newline at end of file diff --git a/src/lib/time/compat_time.c b/src/lib/time/compat_time.c index 98854bad2c..6bbad4f98a 100644 --- a/src/lib/time/compat_time.c +++ b/src/lib/time/compat_time.c @@ -1,6 +1,6 @@ /* Copyright (c) 2003-2004, Roger Dingledine * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. - * Copyright (c) 2007-2019, The Tor Project, Inc. */ + * Copyright (c) 2007-2020, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** @@ -164,6 +164,8 @@ static int64_t last_tick_count = 0; * to be monotonic; increments them as appropriate so that they actually * _are_ monotonic. * + * The returned time may be the same as the previous returned time. + * * Caller must hold lock. */ STATIC int64_t ratchet_performance_counter(int64_t count_raw) @@ -202,6 +204,8 @@ static struct timeval timeofday_offset = { 0, 0 }; * supposed to be monotonic; increments them as appropriate so that they * actually _are_ monotonic. * + * The returned time may be the same as the previous returned time. + * * Caller must hold lock. */ STATIC void ratchet_timeval(const struct timeval *timeval_raw, struct timeval *out) @@ -270,7 +274,9 @@ monotime_init_internal(void) } /** - * Set "out" to the most recent monotonic time value + * Set "out" to the most recent monotonic time value. + * + * The returned time may be the same as the previous returned time. */ void monotime_get(monotime_t *out) @@ -298,10 +304,12 @@ monotime_coarse_get(monotime_coarse_t *out) #endif /* defined(TOR_UNIT_TESTS) */ out->abstime_ = mach_approximate_time(); } -#endif +#endif /* defined(HAVE_MACH_APPROXIMATE_TIME) */ /** * Return the number of nanoseconds between <b>start</b> and <b>end</b>. + * + * The returned value may be equal to zero. */ int64_t monotime_diff_nsec(const monotime_t *start, @@ -522,7 +530,9 @@ monotime_init_internal(void) GetTickCount64_fn = (GetTickCount64_fn_t) (void(*)(void)) GetProcAddress(h, "GetTickCount64"); } - // FreeLibrary(h) ? + // We can't call FreeLibrary(h) here, because freeing the handle may + // unload the library, and cause future calls to GetTickCount64_fn() + // to fail. See 29642 for details. } void @@ -757,7 +767,7 @@ monotime_coarse_zero(monotime_coarse_t *out) { memset(out, 0, sizeof(*out)); } -#endif +#endif /* defined(MONOTIME_COARSE_TYPE_IS_DIFFERENT) */ int64_t monotime_diff_usec(const monotime_t *start, @@ -787,8 +797,8 @@ monotime_absolute_nsec(void) return monotime_diff_nsec(&initialized_at, &now); } -uint64_t -monotime_absolute_usec(void) +MOCK_IMPL(uint64_t, +monotime_absolute_usec,(void)) { return monotime_absolute_nsec() / 1000; } @@ -823,7 +833,7 @@ monotime_coarse_absolute_msec(void) { return monotime_coarse_absolute_nsec() / ONE_MILLION; } -#else +#else /* !defined(MONOTIME_COARSE_FN_IS_DIFFERENT) */ #define initialized_at_coarse initialized_at #endif /* defined(MONOTIME_COARSE_FN_IS_DIFFERENT) */ @@ -855,7 +865,7 @@ monotime_msec_to_approx_coarse_stamp_units(uint64_t msec) mach_time_info.numer; return abstime_val >> monotime_shift; } -#else +#else /* !defined(__APPLE__) */ uint64_t monotime_coarse_stamp_units_to_approx_msec(uint64_t units) { @@ -866,4 +876,4 @@ monotime_msec_to_approx_coarse_stamp_units(uint64_t msec) { return (msec * STAMP_TICKS_PER_SECOND) / 1000; } -#endif +#endif /* defined(__APPLE__) */ diff --git a/src/lib/time/compat_time.h b/src/lib/time/compat_time.h index 480d426ac7..08fd0f0c25 100644 --- a/src/lib/time/compat_time.h +++ b/src/lib/time/compat_time.h @@ -1,6 +1,6 @@ /* Copyright (c) 2003-2004, Roger Dingledine * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. - * Copyright (c) 2007-2019, The Tor Project, Inc. */ + * Copyright (c) 2007-2020, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** @@ -15,6 +15,120 @@ * of tens of milliseconds. */ +/* Q: When should I use monotonic time? + * + * A: If you need a time that never decreases, use monotonic time. If you need + * to send a time to a user or another process, or store a time, use the + * wall-clock time. + * + * Q: Should you use monotime or monotime_coarse as your source? + * + * A: Generally, you get better precision with monotime, but better + * performance with monotime_coarse. + * + * Q: What is a "monotonic" time, exactly? + * + * A: Monotonic times are strictly non-decreasing. The difference between any + * previous monotonic time, and the current monotonic time, is always greater + * than *or equal to* zero. + * Zero deltas happen more often: + * - on Windows (due to an OS bug), + * - when using monotime_coarse, or on systems with low-resolution timers, + * - on platforms where we emulate monotonic time using wall-clock time, and + * - when using time units that are larger than nanoseconds (due to + * truncation on division). + * + * Q: Should you use monotime_t or monotime_coarse_t directly? Should you use + * usec? msec? "stamp units?" + * + * A: Using monotime_t and monotime_coarse_t directly is most time-efficient, + * since no conversion needs to happen. But they can potentially use more + * memory than you would need for a usec/msec/"stamp unit" count. + * + * Converting to usec or msec on some platforms, and working with them in + * general, creates a risk of doing a 64-bit division. 64-bit division is + * expensive on 32-bit platforms, which still do exist. + * + * The "stamp unit" type is designed to give a type that is cheap to convert + * from monotime_coarse, has resolution of about 1-2ms, and fits nicely in a + * 32-bit integer. Its downside is that it does not correspond directly + * to a natural unit of time. + * + * There is not much point in using "coarse usec" or "coarse nsec", since the + * current coarse monotime implementations give you on the order of + * milliseconds of precision. + * + * Q: So, what backends is monotime_coarse using? + * + * A: Generally speaking, it uses "whatever monotonic-ish time implementation + * does not require a context switch." The various implementations provide + * this by having a view of the current time in a read-only memory page that + * is updated with a frequency corresponding to the kernel's tick count. + * + * On Windows, monotime_coarse uses GetCount64() [or GetTickCount() on + * obsolete systems]. MSDN claims that the resolution is "typically in the + * range of 10-16 msec", but it has said that for years. Storing + * monotime_coarse_t uses 8 bytes. + * + * On OSX/iOS, monotime_coarse uses uses mach_approximate_time() where + * available, and falls back to regular monotime. The precision is not + * documented, but the implementation is open-source: it reads from a page + * that the kernel updates. Storing monotime_coarse_t uses 8 bytes. + * + * On unixy systems, monotime_coarse uses clock_gettime() with + * CLOCK_MONOTONIC_COARSE where available, and falls back to CLOCK_MONOTONIC. + * It typically uses vdso tricks to read from a page that the kernel updates. + * Its precision fixed, but you can get it with clock_getres(): on my Linux + * desktop, it claims to be 1 msec, but it will depend on the system HZ + * setting. Storing monotime_coarse_t uses 16 bytes. + * + * [TODO: Try CLOCK_MONOTONIC_FAST on foobsd.] + * + * Q: What backends is regular monotonic time using? + * + * A: In general, regular monotime uses something that requires a system call. + * On platforms where system calls are cheap, you win! Otherwise, you lose. + * + * On Windows, monotonic time uses QuereyPerformanceCounter. Storing + * monotime_t costs 8 bytes. + * + * On OSX/Apple, monotonic time uses mach_absolute_time. Storing + * monotime_t costs 8 bytes. + * + * On unixy systems, monotonic time uses CLOCK_MONOTONIC. Storing + * monotime_t costs 16 bytes. + * + * Q: Tell me about the costs of converting to a 64-bit nsec, usec, or msec + * count. + * + * A: Windows, coarse: Cheap, since it's all multiplication. + * + * Windows, precise: Expensive on 32-bit: it needs 64-bit division. + * + * Apple, all: Expensive on 32-bit: it needs 64-bit division. + * + * Unixy, all: Fairly cheap, since the only division required is dividing + * tv_nsec 1000, and nanoseconds-per-second fits in a 32-bit value. + * + * All, "timestamp units": Cheap everywhere: it never divides. + * + * Q: This is only somewhat related, but how much precision could I hope for + * from a libevent time? + * + * A: Actually, it's _very_ related if you're timing in order to have a + * timeout happen. + * + * On Windows, it uses select: you could in theory have a microsecond + * resolution, but it usually isn't that accurate. + * + * On OSX, iOS, and BSD, you have kqueue: You could in theory have a nanosecond + * resolution, but it usually isn't that accurate. + * + * On Linux, you have epoll: It has a millisecond resolution. Some recent + * Libevents can also use timerfd for higher resolution if + * EVENT_BASE_FLAG_PRECISE_TIMER is set: Tor doesn't set that flag. + */ + #ifndef TOR_COMPAT_TIME_H #define TOR_COMPAT_TIME_H @@ -86,26 +200,36 @@ void monotime_init(void); void monotime_get(monotime_t *out); /** * Return the number of nanoseconds between <b>start</b> and <b>end</b>. + * The returned value may be equal to zero. */ int64_t monotime_diff_nsec(const monotime_t *start, const monotime_t *end); /** * Return the number of microseconds between <b>start</b> and <b>end</b>. + * The returned value may be equal to zero. + * Fractional units are truncated, not rounded. */ int64_t monotime_diff_usec(const monotime_t *start, const monotime_t *end); /** * Return the number of milliseconds between <b>start</b> and <b>end</b>. + * The returned value may be equal to zero. + * Fractional units are truncated, not rounded. */ int64_t monotime_diff_msec(const monotime_t *start, const monotime_t *end); /** * Return the number of nanoseconds since the timer system was initialized. + * The returned value may be equal to zero. */ uint64_t monotime_absolute_nsec(void); /** * Return the number of microseconds since the timer system was initialized. + * The returned value may be equal to zero. + * Fractional units are truncated, not rounded. */ -uint64_t monotime_absolute_usec(void); +MOCK_DECL(uint64_t, monotime_absolute_usec,(void)); /** * Return the number of milliseconds since the timer system was initialized. + * The returned value may be equal to zero. + * Fractional units are truncated, not rounded. */ uint64_t monotime_absolute_msec(void); @@ -129,10 +253,13 @@ void monotime_add_msec(monotime_t *out, const monotime_t *val, uint32_t msec); * Set <b>out</b> to the current coarse time. */ void monotime_coarse_get(monotime_coarse_t *out); +/** + * Like monotime_absolute_*(), but faster on some platforms. + */ uint64_t monotime_coarse_absolute_nsec(void); uint64_t monotime_coarse_absolute_usec(void); uint64_t monotime_coarse_absolute_msec(void); -#else /* !(defined(MONOTIME_COARSE_FN_IS_DIFFERENT)) */ +#else /* !defined(MONOTIME_COARSE_FN_IS_DIFFERENT) */ #define monotime_coarse_get monotime_get #define monotime_coarse_absolute_nsec monotime_absolute_nsec #define monotime_coarse_absolute_usec monotime_absolute_usec @@ -152,23 +279,32 @@ uint32_t monotime_coarse_to_stamp(const monotime_coarse_t *t); /** * Convert a difference, expressed in the units of monotime_coarse_to_stamp, * into an approximate number of milliseconds. + * + * The returned value may be equal to zero. + * Fractional units are truncated, not rounded. */ uint64_t monotime_coarse_stamp_units_to_approx_msec(uint64_t units); uint64_t monotime_msec_to_approx_coarse_stamp_units(uint64_t msec); uint32_t monotime_coarse_get_stamp(void); #if defined(MONOTIME_COARSE_TYPE_IS_DIFFERENT) +/** + * Like monotime_diff_*(), but faster on some platforms. + */ int64_t monotime_coarse_diff_nsec(const monotime_coarse_t *start, const monotime_coarse_t *end); int64_t monotime_coarse_diff_usec(const monotime_coarse_t *start, const monotime_coarse_t *end); int64_t monotime_coarse_diff_msec(const monotime_coarse_t *start, const monotime_coarse_t *end); +/** + * Like monotime_*(), but faster on some platforms. + */ void monotime_coarse_zero(monotime_coarse_t *out); int monotime_coarse_is_zero(const monotime_coarse_t *val); void monotime_coarse_add_msec(monotime_coarse_t *out, const monotime_coarse_t *val, uint32_t msec); -#else /* !(defined(MONOTIME_COARSE_TYPE_IS_DIFFERENT)) */ +#else /* !defined(MONOTIME_COARSE_TYPE_IS_DIFFERENT) */ #define monotime_coarse_diff_nsec monotime_diff_nsec #define monotime_coarse_diff_usec monotime_diff_usec #define monotime_coarse_diff_msec monotime_diff_msec @@ -182,6 +318,9 @@ void monotime_coarse_add_msec(monotime_coarse_t *out, * * Requires that the difference fit into an int32_t; not for use with * large time differences. + * + * The returned value may be equal to zero. + * Fractional units are truncated, not rounded. */ int32_t monotime_coarse_diff_msec32_(const monotime_coarse_t *start, const monotime_coarse_t *end); @@ -191,6 +330,9 @@ int32_t monotime_coarse_diff_msec32_(const monotime_coarse_t *start, * * Requires that the difference fit into an int32_t; not for use with * large time differences. + * + * The returned value may be equal to zero. + * Fractional units are truncated, not rounded. */ static inline int32_t monotime_coarse_diff_msec32(const monotime_coarse_t *start, @@ -202,7 +344,7 @@ monotime_coarse_diff_msec32(const monotime_coarse_t *start, #else #define USING_32BIT_MSEC_HACK return monotime_coarse_diff_msec32_(start, end); -#endif +#endif /* SIZEOF_VOID_P == 8 */ } #ifdef TOR_UNIT_TESTS diff --git a/src/lib/time/include.am b/src/lib/time/include.am index a3f93a3744..dcb199b142 100644 --- a/src/lib/time/include.am +++ b/src/lib/time/include.am @@ -5,8 +5,10 @@ if UNITTESTS_ENABLED noinst_LIBRARIES += src/lib/libtor-time-testing.a endif +# ADD_C_FILE: INSERT SOURCES HERE. src_lib_libtor_time_a_SOURCES = \ src/lib/time/compat_time.c \ + src/lib/time/time_sys.c \ src/lib/time/tvdiff.c src_lib_libtor_time_testing_a_SOURCES = \ @@ -14,6 +16,8 @@ src_lib_libtor_time_testing_a_SOURCES = \ src_lib_libtor_time_testing_a_CPPFLAGS = $(AM_CPPFLAGS) $(TEST_CPPFLAGS) src_lib_libtor_time_testing_a_CFLAGS = $(AM_CFLAGS) $(TEST_CFLAGS) +# ADD_C_FILE: INSERT HEADERS HERE. noinst_HEADERS += \ src/lib/time/compat_time.h \ + src/lib/time/time_sys.h \ src/lib/time/tvdiff.h diff --git a/src/lib/time/lib_time.md b/src/lib/time/lib_time.md new file mode 100644 index 0000000000..8e58aafcd8 --- /dev/null +++ b/src/lib/time/lib_time.md @@ -0,0 +1,9 @@ +@dir /lib/time +@brief lib/time: Higher-level time functions + +This includes both fine-grained timers and monotonic timers, along with +wrappers for them to try to improve efficiency. + +For "what time is it" in UTC, see \refdir{lib/wallclock}. For parsing and +encoding times and dates, see \refdir{lib/encoding}. + diff --git a/src/lib/time/time_sys.c b/src/lib/time/time_sys.c new file mode 100644 index 0000000000..1c1bc4cd18 --- /dev/null +++ b/src/lib/time/time_sys.c @@ -0,0 +1,29 @@ +/* Copyright (c) 2018-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file time_sys.c + * \brief Subsystem object for monotime setup. + **/ + +#include "orconfig.h" +#include "lib/subsys/subsys.h" +#include "lib/time/time_sys.h" +#include "lib/time/compat_time.h" + +static int +subsys_time_initialize(void) +{ + monotime_init(); + return 0; +} + +const subsys_fns_t sys_time = { + .name = "time", + SUBSYS_DECLARE_LOCATION(), + /* Monotonic time depends on logging, and a lot of other modules depend on + * monotonic time. */ + .level = -80, + .supported = true, + .initialize = subsys_time_initialize, +}; diff --git a/src/lib/time/time_sys.h b/src/lib/time/time_sys.h new file mode 100644 index 0000000000..f2401e1911 --- /dev/null +++ b/src/lib/time/time_sys.h @@ -0,0 +1,14 @@ +/* Copyright (c) 2018-2020, The Tor Project, Inc. */ +/* See LICENSE for licensing information */ + +/** + * \file time_sys.h + * \brief Declare subsystem object for the time module. + **/ + +#ifndef TOR_TIME_SYS_H +#define TOR_TIME_SYS_H + +extern const struct subsys_fns_t sys_time; + +#endif /* !defined(TOR_TIME_SYS_H) */ diff --git a/src/lib/time/tvdiff.c b/src/lib/time/tvdiff.c index a87d0d96dc..14a89bc76e 100644 --- a/src/lib/time/tvdiff.c +++ b/src/lib/time/tvdiff.c @@ -1,6 +1,6 @@ /* Copyright (c) 2003-2004, Roger Dingledine * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. - * Copyright (c) 2007-2019, The Tor Project, Inc. */ + * Copyright (c) 2007-2020, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** @@ -11,6 +11,7 @@ #include "lib/time/tvdiff.h" #include "lib/cc/compat_compiler.h" +#include "lib/defs/time.h" #include "lib/log/log.h" #ifdef _WIN32 @@ -20,8 +21,6 @@ #include <sys/time.h> #endif -#define TOR_USEC_PER_SEC 1000000 - /** Return the difference between start->tv_sec and end->tv_sec. * Returns INT64_MAX on overflow and underflow. */ @@ -31,7 +30,7 @@ tv_secdiff_impl(const struct timeval *start, const struct timeval *end) const int64_t s = (int64_t)start->tv_sec; const int64_t e = (int64_t)end->tv_sec; - /* This may not be the most efficient way of implemeting this check, + /* This may not be the most efficient way of implementing this check, * but it's easy to see that it's correct and doesn't overflow */ if (s > 0 && e < INT64_MIN + s) { diff --git a/src/lib/time/tvdiff.h b/src/lib/time/tvdiff.h index 724af1528a..e779e758f1 100644 --- a/src/lib/time/tvdiff.h +++ b/src/lib/time/tvdiff.h @@ -1,6 +1,6 @@ /* Copyright (c) 2003-2004, Roger Dingledine * Copyright (c) 2004-2006, Roger Dingledine, Nick Mathewson. - * Copyright (c) 2007-2019, The Tor Project, Inc. */ + * Copyright (c) 2007-2020, The Tor Project, Inc. */ /* See LICENSE for licensing information */ /** @@ -20,4 +20,4 @@ int64_t tv_to_msec(const struct timeval *tv); time_t time_diff(const time_t from, const time_t to); -#endif +#endif /* !defined(TOR_TVDIFF_H) */ |