/* SPDX-License-Identifier: GPL-2.0 */ #ifndef _LINUX_JIFFIES_H #define _LINUX_JIFFIES_H #include <linux/cache.h> #include <linux/limits.h> #include <linux/math64.h> #include <linux/minmax.h> #include <linux/types.h> #include <linux/time.h> #include <linux/timex.h> #include <vdso/jiffies.h> #include <asm/param.h> /* for HZ */ #include <generated/timeconst.h> /* * The following defines establish the engineering parameters of the PLL * model. The HZ variable establishes the timer interrupt frequency, 100 Hz * for the SunOS kernel, 256 Hz for the Ultrix kernel and 1024 Hz for the * OSF/1 kernel. The SHIFT_HZ define expresses the same value as the * nearest power of two in order to avoid hardware multiply operations. */ #if HZ >= 12 && HZ < 24 #define SHIFT_HZ … #elif HZ >= 24 && HZ < 48 #define SHIFT_HZ … #elif HZ >= 48 && HZ < 96 #define SHIFT_HZ … #elif HZ >= 96 && HZ < 192 #define SHIFT_HZ … #elif HZ >= 192 && HZ < 384 #define SHIFT_HZ … #elif HZ >= 384 && HZ < 768 #define SHIFT_HZ … #elif HZ >= 768 && HZ < 1536 #define SHIFT_HZ … #elif HZ >= 1536 && HZ < 3072 #define SHIFT_HZ … #elif HZ >= 3072 && HZ < 6144 #define SHIFT_HZ … #elif HZ >= 6144 && HZ < 12288 #define SHIFT_HZ … #else # error Invalid value of HZ. #endif /* Suppose we want to divide two numbers NOM and DEN: NOM/DEN, then we can * improve accuracy by shifting LSH bits, hence calculating: * (NOM << LSH) / DEN * This however means trouble for large NOM, because (NOM << LSH) may no * longer fit in 32 bits. The following way of calculating this gives us * some slack, under the following conditions: * - (NOM / DEN) fits in (32 - LSH) bits. * - (NOM % DEN) fits in (32 - LSH) bits. */ #define SH_DIV(NOM,DEN,LSH) … /* LATCH is used in the interval timer and ftape setup. */ #define LATCH … extern int register_refined_jiffies(long clock_tick_rate); /* TICK_USEC is the time between ticks in usec assuming SHIFTED_HZ */ #define TICK_USEC … /* USER_TICK_USEC is the time between ticks in usec assuming fake USER_HZ */ #define USER_TICK_USEC … #ifndef __jiffy_arch_data #define __jiffy_arch_data #endif /* * The 64-bit value is not atomic on 32-bit systems - you MUST NOT read it * without sampling the sequence number in jiffies_lock. * get_jiffies_64() will do this for you as appropriate. * * jiffies and jiffies_64 are at the same address for little-endian systems * and for 64-bit big-endian systems. * On 32-bit big-endian systems, jiffies is the lower 32 bits of jiffies_64 * (i.e., at address @jiffies_64 + 4). * See arch/ARCH/kernel/vmlinux.lds.S */ extern u64 __cacheline_aligned_in_smp jiffies_64; extern unsigned long volatile __cacheline_aligned_in_smp __jiffy_arch_data jiffies; #if (BITS_PER_LONG < 64) u64 get_jiffies_64(void); #else /** * get_jiffies_64 - read the 64-bit non-atomic jiffies_64 value * * When BITS_PER_LONG < 64, this uses sequence number sampling using * jiffies_lock to protect the 64-bit read. * * Return: current 64-bit jiffies value */ static inline u64 get_jiffies_64(void) { … } #endif /** * DOC: General information about time_* inlines * * These inlines deal with timer wrapping correctly. You are strongly encouraged * to use them: * * #. Because people otherwise forget * #. Because if the timer wrap changes in future you won't have to alter your * driver code. */ /** * time_after - returns true if the time a is after time b. * @a: first comparable as unsigned long * @b: second comparable as unsigned long * * Do this with "<0" and ">=0" to only test the sign of the result. A * good compiler would generate better code (and a really good compiler * wouldn't care). Gcc is currently neither. * * Return: %true is time a is after time b, otherwise %false. */ #define time_after(a,b) … /** * time_before - returns true if the time a is before time b. * @a: first comparable as unsigned long * @b: second comparable as unsigned long * * Return: %true is time a is before time b, otherwise %false. */ #define time_before(a,b) … /** * time_after_eq - returns true if the time a is after or the same as time b. * @a: first comparable as unsigned long * @b: second comparable as unsigned long * * Return: %true is time a is after or the same as time b, otherwise %false. */ #define time_after_eq(a,b) … /** * time_before_eq - returns true if the time a is before or the same as time b. * @a: first comparable as unsigned long * @b: second comparable as unsigned long * * Return: %true is time a is before or the same as time b, otherwise %false. */ #define time_before_eq(a,b) … /** * time_in_range - Calculate whether a is in the range of [b, c]. * @a: time to test * @b: beginning of the range * @c: end of the range * * Return: %true is time a is in the range [b, c], otherwise %false. */ #define time_in_range(a,b,c) … /** * time_in_range_open - Calculate whether a is in the range of [b, c). * @a: time to test * @b: beginning of the range * @c: end of the range * * Return: %true is time a is in the range [b, c), otherwise %false. */ #define time_in_range_open(a,b,c) … /* Same as above, but does so with platform independent 64bit types. * These must be used when utilizing jiffies_64 (i.e. return value of * get_jiffies_64()). */ /** * time_after64 - returns true if the time a is after time b. * @a: first comparable as __u64 * @b: second comparable as __u64 * * This must be used when utilizing jiffies_64 (i.e. return value of * get_jiffies_64()). * * Return: %true is time a is after time b, otherwise %false. */ #define time_after64(a,b) … /** * time_before64 - returns true if the time a is before time b. * @a: first comparable as __u64 * @b: second comparable as __u64 * * This must be used when utilizing jiffies_64 (i.e. return value of * get_jiffies_64()). * * Return: %true is time a is before time b, otherwise %false. */ #define time_before64(a,b) … /** * time_after_eq64 - returns true if the time a is after or the same as time b. * @a: first comparable as __u64 * @b: second comparable as __u64 * * This must be used when utilizing jiffies_64 (i.e. return value of * get_jiffies_64()). * * Return: %true is time a is after or the same as time b, otherwise %false. */ #define time_after_eq64(a,b) … /** * time_before_eq64 - returns true if the time a is before or the same as time b. * @a: first comparable as __u64 * @b: second comparable as __u64 * * This must be used when utilizing jiffies_64 (i.e. return value of * get_jiffies_64()). * * Return: %true is time a is before or the same as time b, otherwise %false. */ #define time_before_eq64(a,b) … /** * time_in_range64 - Calculate whether a is in the range of [b, c]. * @a: time to test * @b: beginning of the range * @c: end of the range * * Return: %true is time a is in the range [b, c], otherwise %false. */ #define time_in_range64(a, b, c) … /* * These eight macros compare jiffies[_64] and 'a' for convenience. */ /** * time_is_before_jiffies - return true if a is before jiffies * @a: time (unsigned long) to compare to jiffies * * Return: %true is time a is before jiffies, otherwise %false. */ #define time_is_before_jiffies(a) … /** * time_is_before_jiffies64 - return true if a is before jiffies_64 * @a: time (__u64) to compare to jiffies_64 * * Return: %true is time a is before jiffies_64, otherwise %false. */ #define time_is_before_jiffies64(a) … /** * time_is_after_jiffies - return true if a is after jiffies * @a: time (unsigned long) to compare to jiffies * * Return: %true is time a is after jiffies, otherwise %false. */ #define time_is_after_jiffies(a) … /** * time_is_after_jiffies64 - return true if a is after jiffies_64 * @a: time (__u64) to compare to jiffies_64 * * Return: %true is time a is after jiffies_64, otherwise %false. */ #define time_is_after_jiffies64(a) … /** * time_is_before_eq_jiffies - return true if a is before or equal to jiffies * @a: time (unsigned long) to compare to jiffies * * Return: %true is time a is before or the same as jiffies, otherwise %false. */ #define time_is_before_eq_jiffies(a) … /** * time_is_before_eq_jiffies64 - return true if a is before or equal to jiffies_64 * @a: time (__u64) to compare to jiffies_64 * * Return: %true is time a is before or the same jiffies_64, otherwise %false. */ #define time_is_before_eq_jiffies64(a) … /** * time_is_after_eq_jiffies - return true if a is after or equal to jiffies * @a: time (unsigned long) to compare to jiffies * * Return: %true is time a is after or the same as jiffies, otherwise %false. */ #define time_is_after_eq_jiffies(a) … /** * time_is_after_eq_jiffies64 - return true if a is after or equal to jiffies_64 * @a: time (__u64) to compare to jiffies_64 * * Return: %true is time a is after or the same as jiffies_64, otherwise %false. */ #define time_is_after_eq_jiffies64(a) … /* * Have the 32-bit jiffies value wrap 5 minutes after boot * so jiffies wrap bugs show up earlier. */ #define INITIAL_JIFFIES … /* * Change timeval to jiffies, trying to avoid the * most obvious overflows.. * * And some not so obvious. * * Note that we don't want to return LONG_MAX, because * for various timeout reasons we often end up having * to wait "jiffies+1" in order to guarantee that we wait * at _least_ "jiffies" - so "jiffies+1" had better still * be positive. */ #define MAX_JIFFY_OFFSET … extern unsigned long preset_lpj; /* * We want to do realistic conversions of time so we need to use the same * values the update wall clock code uses as the jiffies size. This value * is: TICK_NSEC (which is defined in timex.h). This * is a constant and is in nanoseconds. We will use scaled math * with a set of scales defined here as SEC_JIFFIE_SC, USEC_JIFFIE_SC and * NSEC_JIFFIE_SC. Note that these defines contain nothing but * constants and so are computed at compile time. SHIFT_HZ (computed in * timex.h) adjusts the scaling for different HZ values. * Scaled math??? What is that? * * Scaled math is a way to do integer math on values that would, * otherwise, either overflow, underflow, or cause undesired div * instructions to appear in the execution path. In short, we "scale" * up the operands so they take more bits (more precision, less * underflow), do the desired operation and then "scale" the result back * by the same amount. If we do the scaling by shifting we avoid the * costly mpy and the dastardly div instructions. * Suppose, for example, we want to convert from seconds to jiffies * where jiffies is defined in nanoseconds as NSEC_PER_JIFFIE. The * simple math is: jiff = (sec * NSEC_PER_SEC) / NSEC_PER_JIFFIE; We * observe that (NSEC_PER_SEC / NSEC_PER_JIFFIE) is a constant which we * might calculate at compile time, however, the result will only have * about 3-4 bits of precision (less for smaller values of HZ). * * So, we scale as follows: * jiff = (sec) * (NSEC_PER_SEC / NSEC_PER_JIFFIE); * jiff = ((sec) * ((NSEC_PER_SEC * SCALE)/ NSEC_PER_JIFFIE)) / SCALE; * Then we make SCALE a power of two so: * jiff = ((sec) * ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) >> SCALE; * Now we define: * #define SEC_CONV = ((NSEC_PER_SEC << SCALE)/ NSEC_PER_JIFFIE)) * jiff = (sec * SEC_CONV) >> SCALE; * * Often the math we use will expand beyond 32-bits so we tell C how to * do this and pass the 64-bit result of the mpy through the ">> SCALE" * which should take the result back to 32-bits. We want this expansion * to capture as much precision as possible. At the same time we don't * want to overflow so we pick the SCALE to avoid this. In this file, * that means using a different scale for each range of HZ values (as * defined in timex.h). * * For those who want to know, gcc will give a 64-bit result from a "*" * operator if the result is a long long AND at least one of the * operands is cast to long long (usually just prior to the "*" so as * not to confuse it into thinking it really has a 64-bit operand, * which, buy the way, it can do, but it takes more code and at least 2 * mpys). * We also need to be aware that one second in nanoseconds is only a * couple of bits away from overflowing a 32-bit word, so we MUST use * 64-bits to get the full range time in nanoseconds. */ /* * Here are the scales we will use. One for seconds, nanoseconds and * microseconds. * * Within the limits of cpp we do a rough cut at the SEC_JIFFIE_SC and * check if the sign bit is set. If not, we bump the shift count by 1. * (Gets an extra bit of precision where we can use it.) * We know it is set for HZ = 1024 and HZ = 100 not for 1000. * Haven't tested others. * Limits of cpp (for #if expressions) only long (no long long), but * then we only need the most signicant bit. */ #define SEC_JIFFIE_SC … #if !((((NSEC_PER_SEC << 2) / TICK_NSEC) << (SEC_JIFFIE_SC - 2)) & 0x80000000) #undef SEC_JIFFIE_SC #define SEC_JIFFIE_SC … #endif #define NSEC_JIFFIE_SC … #define SEC_CONVERSION … #define NSEC_CONVERSION … /* * The maximum jiffie value is (MAX_INT >> 1). Here we translate that * into seconds. The 64-bit case will overflow if we are not careful, * so use the messy SH_DIV macro to do it. Still all constants. */ #if BITS_PER_LONG < 64 #define MAX_SEC_IN_JIFFIES … #else /* take care of overflow on 64-bit machines */ #define MAX_SEC_IN_JIFFIES … #endif /* * Convert various time units to each other: */ extern unsigned int jiffies_to_msecs(const unsigned long j); extern unsigned int jiffies_to_usecs(const unsigned long j); /** * jiffies_to_nsecs - Convert jiffies to nanoseconds * @j: jiffies value * * Return: nanoseconds value */ static inline u64 jiffies_to_nsecs(const unsigned long j) { … } extern u64 jiffies64_to_nsecs(u64 j); extern u64 jiffies64_to_msecs(u64 j); extern unsigned long __msecs_to_jiffies(const unsigned int m); #if HZ <= MSEC_PER_SEC && !(MSEC_PER_SEC % HZ) /* * HZ is equal to or smaller than 1000, and 1000 is a nice round * multiple of HZ, divide with the factor between them, but round * upwards: */ static inline unsigned long _msecs_to_jiffies(const unsigned int m) { … } #elif HZ > MSEC_PER_SEC && !(HZ % MSEC_PER_SEC) /* * HZ is larger than 1000, and HZ is a nice round multiple of 1000 - * simply multiply with the factor between them. * * But first make sure the multiplication result cannot overflow: */ static inline unsigned long _msecs_to_jiffies(const unsigned int m) { if (m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) return MAX_JIFFY_OFFSET; return m * (HZ / MSEC_PER_SEC); } #else /* * Generic case - multiply, round and divide. But first check that if * we are doing a net multiplication, that we wouldn't overflow: */ static inline unsigned long _msecs_to_jiffies(const unsigned int m) { if (HZ > MSEC_PER_SEC && m > jiffies_to_msecs(MAX_JIFFY_OFFSET)) return MAX_JIFFY_OFFSET; return (MSEC_TO_HZ_MUL32 * m + MSEC_TO_HZ_ADJ32) >> MSEC_TO_HZ_SHR32; } #endif /** * msecs_to_jiffies: - convert milliseconds to jiffies * @m: time in milliseconds * * conversion is done as follows: * * - negative values mean 'infinite timeout' (MAX_JIFFY_OFFSET) * * - 'too large' values [that would result in larger than * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. * * - all other values are converted to jiffies by either multiplying * the input value by a factor or dividing it with a factor and * handling any 32-bit overflows. * for the details see __msecs_to_jiffies() * * msecs_to_jiffies() checks for the passed in value being a constant * via __builtin_constant_p() allowing gcc to eliminate most of the * code. __msecs_to_jiffies() is called if the value passed does not * allow constant folding and the actual conversion must be done at * runtime. * The HZ range specific helpers _msecs_to_jiffies() are called both * directly here and from __msecs_to_jiffies() in the case where * constant folding is not possible. * * Return: jiffies value */ static __always_inline unsigned long msecs_to_jiffies(const unsigned int m) { … } extern unsigned long __usecs_to_jiffies(const unsigned int u); #if !(USEC_PER_SEC % HZ) static inline unsigned long _usecs_to_jiffies(const unsigned int u) { … } #else static inline unsigned long _usecs_to_jiffies(const unsigned int u) { return (USEC_TO_HZ_MUL32 * u + USEC_TO_HZ_ADJ32) >> USEC_TO_HZ_SHR32; } #endif /** * usecs_to_jiffies: - convert microseconds to jiffies * @u: time in microseconds * * conversion is done as follows: * * - 'too large' values [that would result in larger than * MAX_JIFFY_OFFSET values] mean 'infinite timeout' too. * * - all other values are converted to jiffies by either multiplying * the input value by a factor or dividing it with a factor and * handling any 32-bit overflows as for msecs_to_jiffies. * * usecs_to_jiffies() checks for the passed in value being a constant * via __builtin_constant_p() allowing gcc to eliminate most of the * code. __usecs_to_jiffies() is called if the value passed does not * allow constant folding and the actual conversion must be done at * runtime. * The HZ range specific helpers _usecs_to_jiffies() are called both * directly here and from __msecs_to_jiffies() in the case where * constant folding is not possible. * * Return: jiffies value */ static __always_inline unsigned long usecs_to_jiffies(const unsigned int u) { … } extern unsigned long timespec64_to_jiffies(const struct timespec64 *value); extern void jiffies_to_timespec64(const unsigned long jiffies, struct timespec64 *value); extern clock_t jiffies_to_clock_t(unsigned long x); static inline clock_t jiffies_delta_to_clock_t(long delta) { … } static inline unsigned int jiffies_delta_to_msecs(long delta) { … } extern unsigned long clock_t_to_jiffies(unsigned long x); extern u64 jiffies_64_to_clock_t(u64 x); extern u64 nsec_to_clock_t(u64 x); extern u64 nsecs_to_jiffies64(u64 n); extern unsigned long nsecs_to_jiffies(u64 n); #define TIMESTAMP_SIZE … #endif
Codebase Browser
linux