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Commit 43b1f6ab authored by Helge Deller's avatar Helge Deller
Browse files

parisc: Switch to generic sched_clock implementation 



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: default avatarHelge Deller <deller@gmx.de>
Cc: <stable@vger.kernel.org> # v4.7+
Signed-off-by: default avatarHelge Deller <deller@gmx.de>
parent 741dc7bf

arch/parisc/Kconfig

+3 −1
Original line number Diff line number Diff line
@@ -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

arch/parisc/kernel/time.c

+11 −46
Original line number Diff line number Diff line
@@ -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);

}