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parisc: Switch to generic sched_clock implementation

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Drop the open-coded sched_clock() function and replace it by the provided
GENERIC_SCHED_CLOCK implementation.  We have seen quite some hung tasks in the
past, which seem to be fixed by this patch.

Signed-off-by: Helge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # v4.7+
Signed-off-by: Helge Deller <deller@gmx.de>
This commit is contained in:
Helge Deller 2016-11-22 18:08:30 +01:00
parent 741dc7bf1c
commit 43b1f6abd5
2 changed files with 14 additions and 47 deletions
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4
arch/parisc/Kconfig
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@ -34,7 +34,9 @@ config PARISC
select HAVE_ARCH_HASH
select HAVE_ARCH_SECCOMP_FILTER
select HAVE_ARCH_TRACEHOOK
select HAVE_UNSTABLE_SCHED_CLOCK if (SMP || !64BIT)
select GENERIC_SCHED_CLOCK
select HAVE_UNSTABLE_SCHED_CLOCK if SMP
select GENERIC_CLOCKEVENTS
select ARCH_NO_COHERENT_DMA_MMAP
select CPU_NO_EFFICIENT_FFS

57
arch/parisc/kernel/time.c
View File

@ -14,6 +14,7 @@
#include <linux/module.h>
#include <linux/rtc.h>
#include <linux/sched.h>
#include <linux/sched_clock.h>
#include <linux/kernel.h>
#include <linux/param.h>
#include <linux/string.h>
@ -39,18 +40,6 @@
static unsigned long clocktick __read_mostly; /* timer cycles per tick */
#ifndef CONFIG_64BIT
/*
* The processor-internal cycle counter (Control Register 16) is used as time
* source for the sched_clock() function. This register is 64bit wide on a
* 64-bit kernel and 32bit on a 32-bit kernel. Since sched_clock() always
* requires a 64bit counter we emulate on the 32-bit kernel the higher 32bits
* with a per-cpu variable which we increase every time the counter
* wraps-around (which happens every ~4 secounds).
*/
static DEFINE_PER_CPU(unsigned long, cr16_high_32_bits);
#endif
/*
* We keep time on PA-RISC Linux by using the Interval Timer which is
* a pair of registers; one is read-only and one is write-only; both
@ -121,12 +110,6 @@ irqreturn_t __irq_entry timer_interrupt(int irq, void *dev_id)
*/
mtctl(next_tick, 16);
#if !defined(CONFIG_64BIT)
/* check for overflow on a 32bit kernel (every ~4 seconds). */
if (unlikely(next_tick < now))
this_cpu_inc(cr16_high_32_bits);
#endif
/* Skip one clocktick on purpose if we missed next_tick.
* The new CR16 must be "later" than current CR16 otherwise
* itimer would not fire until CR16 wrapped - e.g 4 seconds
@ -208,7 +191,7 @@ EXPORT_SYMBOL(profile_pc);
/* clock source code */
static cycle_t read_cr16(struct clocksource *cs)
static cycle_t notrace read_cr16(struct clocksource *cs)
{
return get_cycles();
}
@ -287,26 +270,9 @@ void read_persistent_clock(struct timespec *ts)
}
/*
* sched_clock() framework
*/
static u32 cyc2ns_mul __read_mostly;
static u32 cyc2ns_shift __read_mostly;
u64 sched_clock(void)
static u64 notrace read_cr16_sched_clock(void)
{
u64 now;
/* Get current cycle counter (Control Register 16). */
#ifdef CONFIG_64BIT
now = mfctl(16);
#else
now = mfctl(16) + (((u64) this_cpu_read(cr16_high_32_bits)) << 32);
#endif
/* return the value in ns (cycles_2_ns) */
return mul_u64_u32_shr(now, cyc2ns_mul, cyc2ns_shift);
return get_cycles();
}
@ -316,17 +282,16 @@ u64 sched_clock(void)
void __init time_init(void)
{
unsigned long current_cr16_khz;
unsigned long cr16_hz;
current_cr16_khz = PAGE0->mem_10msec/10; /* kHz */
clocktick = (100 * PAGE0->mem_10msec) / HZ;
/* calculate mult/shift values for cr16 */
clocks_calc_mult_shift(&cyc2ns_mul, &cyc2ns_shift, current_cr16_khz,
NSEC_PER_MSEC, 0);
start_cpu_itimer(); /* get CPU 0 started */
cr16_hz = 100 * PAGE0->mem_10msec; /* Hz */
/* register at clocksource framework */
clocksource_register_khz(&clocksource_cr16, current_cr16_khz);
clocksource_register_hz(&clocksource_cr16, cr16_hz);
/* register as sched_clock source */
sched_clock_register(read_cr16_sched_clock, BITS_PER_LONG, cr16_hz);
}