This is a note to let you know that I've just added the patch titled
parisc: Switch to generic sched_clock implementation
to the 4.8-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
parisc-switch-to-generic-sched_clock-implementation.patch
and it can be found in the queue-4.8 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 43b1f6abd59063a088416a0df042b36450f91f75 Mon Sep 17 00:00:00 2001
From: Helge Deller <deller@xxxxxx>
Date: Tue, 22 Nov 2016 18:08:30 +0100
Subject: parisc: Switch to generic sched_clock implementation
From: Helge Deller <deller@xxxxxx>
commit 43b1f6abd59063a088416a0df042b36450f91f75 upstream.
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@xxxxxx>
Signed-off-by: Helge Deller <deller@xxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
arch/parisc/Kconfig | 4 ++-
arch/parisc/kernel/time.c | 57 ++++++++--------------------------------------
2 files changed, 14 insertions(+), 47 deletions(-)
--- a/arch/parisc/Kconfig
+++ b/arch/parisc/Kconfig
@@ -33,7 +33,9 @@ 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
--- a/arch/parisc/kernel/time.c
+++ b/arch/parisc/kernel/time.c
@@ -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(
*/
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 timesp
}
-/*
- * 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);
}
Patches currently in stable-queue which might be from deller@xxxxxx are
queue-4.8/parisc-fix-race-in-pci-dma.c.patch
queue-4.8/parisc-also-flush-data-tlb-in-flush_icache_page_asm.patch
queue-4.8/parisc-switch-to-generic-sched_clock-implementation.patch
queue-4.8/parisc-fix-races-in-parisc_setup_cache_timing.patch
--
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