mirror of
https://github.com/torvalds/linux.git
synced 2024-12-29 14:21:47 +00:00
211baa7016
sched_clock is supposed to be initialized early - in the recently added init_early platform hook. However, in doing so we end up calling mod_timer() before the timer lists are initialized, resulting in an oops. Split the initialization in two - the part which the platform calls early which starts things off. The addition of the timer can be delayed until after we have more of the kernel initialized - when the normal time sources are initialized. Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
121 lines
3.4 KiB
C
121 lines
3.4 KiB
C
/*
|
|
* sched_clock.h: support for extending counters to full 64-bit ns counter
|
|
*
|
|
* This program is free software; you can redistribute it and/or modify
|
|
* it under the terms of the GNU General Public License version 2 as
|
|
* published by the Free Software Foundation.
|
|
*/
|
|
#ifndef ASM_SCHED_CLOCK
|
|
#define ASM_SCHED_CLOCK
|
|
|
|
#include <linux/kernel.h>
|
|
#include <linux/types.h>
|
|
|
|
struct clock_data {
|
|
u64 epoch_ns;
|
|
u32 epoch_cyc;
|
|
u32 epoch_cyc_copy;
|
|
u32 mult;
|
|
u32 shift;
|
|
};
|
|
|
|
#define DEFINE_CLOCK_DATA(name) struct clock_data name
|
|
|
|
static inline u64 cyc_to_ns(u64 cyc, u32 mult, u32 shift)
|
|
{
|
|
return (cyc * mult) >> shift;
|
|
}
|
|
|
|
/*
|
|
* Atomically update the sched_clock epoch. Your update callback will
|
|
* be called from a timer before the counter wraps - read the current
|
|
* counter value, and call this function to safely move the epochs
|
|
* forward. Only use this from the update callback.
|
|
*/
|
|
static inline void update_sched_clock(struct clock_data *cd, u32 cyc, u32 mask)
|
|
{
|
|
unsigned long flags;
|
|
u64 ns = cd->epoch_ns +
|
|
cyc_to_ns((cyc - cd->epoch_cyc) & mask, cd->mult, cd->shift);
|
|
|
|
/*
|
|
* Write epoch_cyc and epoch_ns in a way that the update is
|
|
* detectable in cyc_to_fixed_sched_clock().
|
|
*/
|
|
raw_local_irq_save(flags);
|
|
cd->epoch_cyc = cyc;
|
|
smp_wmb();
|
|
cd->epoch_ns = ns;
|
|
smp_wmb();
|
|
cd->epoch_cyc_copy = cyc;
|
|
raw_local_irq_restore(flags);
|
|
}
|
|
|
|
/*
|
|
* If your clock rate is known at compile time, using this will allow
|
|
* you to optimize the mult/shift loads away. This is paired with
|
|
* init_fixed_sched_clock() to ensure that your mult/shift are correct.
|
|
*/
|
|
static inline unsigned long long cyc_to_fixed_sched_clock(struct clock_data *cd,
|
|
u32 cyc, u32 mask, u32 mult, u32 shift)
|
|
{
|
|
u64 epoch_ns;
|
|
u32 epoch_cyc;
|
|
|
|
/*
|
|
* Load the epoch_cyc and epoch_ns atomically. We do this by
|
|
* ensuring that we always write epoch_cyc, epoch_ns and
|
|
* epoch_cyc_copy in strict order, and read them in strict order.
|
|
* If epoch_cyc and epoch_cyc_copy are not equal, then we're in
|
|
* the middle of an update, and we should repeat the load.
|
|
*/
|
|
do {
|
|
epoch_cyc = cd->epoch_cyc;
|
|
smp_rmb();
|
|
epoch_ns = cd->epoch_ns;
|
|
smp_rmb();
|
|
} while (epoch_cyc != cd->epoch_cyc_copy);
|
|
|
|
return epoch_ns + cyc_to_ns((cyc - epoch_cyc) & mask, mult, shift);
|
|
}
|
|
|
|
/*
|
|
* Otherwise, you need to use this, which will obtain the mult/shift
|
|
* from the clock_data structure. Use init_sched_clock() with this.
|
|
*/
|
|
static inline unsigned long long cyc_to_sched_clock(struct clock_data *cd,
|
|
u32 cyc, u32 mask)
|
|
{
|
|
return cyc_to_fixed_sched_clock(cd, cyc, mask, cd->mult, cd->shift);
|
|
}
|
|
|
|
/*
|
|
* Initialize the clock data - calculate the appropriate multiplier
|
|
* and shift. Also setup a timer to ensure that the epoch is refreshed
|
|
* at the appropriate time interval, which will call your update
|
|
* handler.
|
|
*/
|
|
void init_sched_clock(struct clock_data *, void (*)(void),
|
|
unsigned int, unsigned long);
|
|
|
|
/*
|
|
* Use this initialization function rather than init_sched_clock() if
|
|
* you're using cyc_to_fixed_sched_clock, which will warn if your
|
|
* constants are incorrect.
|
|
*/
|
|
static inline void init_fixed_sched_clock(struct clock_data *cd,
|
|
void (*update)(void), unsigned int bits, unsigned long rate,
|
|
u32 mult, u32 shift)
|
|
{
|
|
init_sched_clock(cd, update, bits, rate);
|
|
if (cd->mult != mult || cd->shift != shift) {
|
|
pr_crit("sched_clock: wrong multiply/shift: %u>>%u vs calculated %u>>%u\n"
|
|
"sched_clock: fix multiply/shift to avoid scheduler hiccups\n",
|
|
mult, shift, cd->mult, cd->shift);
|
|
}
|
|
}
|
|
|
|
extern void sched_clock_postinit(void);
|
|
|
|
#endif
|