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Message-ID: <20091012175233.GA8129@sgi.com>
Date: Mon, 12 Oct 2009 12:52:33 -0500
From: Dimitri Sivanich <sivanich@....com>
To: Ingo Molnar <mingo@...e.hu>
Cc: linux-kernel@...r.kernel.org, "H. Peter Anvin" <hpa@...or.com>,
Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86 UV: Fixes for UV rtc timers
On Mon, Oct 12, 2009 at 06:23:17PM +0200, Ingo Molnar wrote:
> hm, why is the (unnecessary seeming) pushing of the
> ack/exit_idle()/irq_enter()/irq_exit() sequence into the
> generic_interrupt_extension() function a cleanup?
It seems to make more sense to allow the users of generic_interrupt to
provide their own sequence, rather than being forced into this one.
>
> Also, the commit log is rather terse - what is being fixed and why isnt
> it separate from any cleanups?
>
I have added to the commit log. See below.
-------------------------------------------------------------------------------
Tune/fix early timer expiry handling and return correct early timeout value
for set_next_event.
Modify the irq_enter/ack_APIC_irq/irq_exit sequence and move it out of
smp_generic_interrupt to allow its users more flexibility.
Add clocksource only boot option.
Signed-off-by: Dimitri Sivanich <sivanich@....com>
---
arch/x86/kernel/irq.c | 10 +----
arch/x86/kernel/uv_time.c | 81 +++++++++++++++++++++++++++++-------------
2 files changed, 58 insertions(+), 33 deletions(-)
Index: linux/arch/x86/kernel/uv_time.c
===================================================================
--- linux.orig/arch/x86/kernel/uv_time.c 2009-10-08 11:31:05.000000000 -0500
+++ linux/arch/x86/kernel/uv_time.c 2009-10-09 07:49:05.000000000 -0500
@@ -25,6 +25,7 @@
#include <asm/uv/bios.h>
#include <asm/uv/uv.h>
#include <asm/apic.h>
+#include <asm/idle.h>
#include <asm/cpu.h>
#define RTC_NAME "sgi_rtc"
@@ -75,6 +76,7 @@ struct uv_rtc_timer_head {
static struct uv_rtc_timer_head **blade_info __read_mostly;
static int uv_rtc_enable;
+static int uv_rtc_evt_enable;
/*
* Hardware interface routines
@@ -123,7 +125,10 @@ static int uv_setup_intr(int cpu, u64 ex
/* Initialize comparator value */
uv_write_global_mmr64(pnode, UVH_INT_CMPB, expires);
- return (expires < uv_read_rtc(NULL) && !uv_intr_pending(pnode));
+ if (uv_read_rtc(NULL) <= expires)
+ return 0;
+
+ return !uv_intr_pending(pnode);
}
/*
@@ -223,6 +228,7 @@ static int uv_rtc_set_timer(int cpu, u64
next_cpu = head->next_cpu;
*t = expires;
+
/* Will this one be next to go off? */
if (next_cpu < 0 || bcpu == next_cpu ||
expires < head->cpu[next_cpu].expires) {
@@ -231,7 +237,7 @@ static int uv_rtc_set_timer(int cpu, u64
*t = ULLONG_MAX;
uv_rtc_find_next_timer(head, pnode);
spin_unlock_irqrestore(&head->lock, flags);
- return 1;
+ return -ETIME;
}
}
@@ -244,7 +250,7 @@ static int uv_rtc_set_timer(int cpu, u64
*
* Returns 1 if this timer was pending.
*/
-static int uv_rtc_unset_timer(int cpu)
+static int uv_rtc_unset_timer(int cpu, int force)
{
int pnode = uv_cpu_to_pnode(cpu);
int bid = uv_cpu_to_blade_id(cpu);
@@ -256,14 +262,15 @@ static int uv_rtc_unset_timer(int cpu)
spin_lock_irqsave(&head->lock, flags);
- if (head->next_cpu == bcpu && uv_read_rtc(NULL) >= *t)
+ if ((head->next_cpu == bcpu && uv_read_rtc(NULL) >= *t) || force)
rc = 1;
- *t = ULLONG_MAX;
-
- /* Was the hardware setup for this timer? */
- if (head->next_cpu == bcpu)
- uv_rtc_find_next_timer(head, pnode);
+ if (rc) {
+ *t = ULLONG_MAX;
+ /* Was the hardware setup for this timer? */
+ if (head->next_cpu == bcpu)
+ uv_rtc_find_next_timer(head, pnode);
+ }
spin_unlock_irqrestore(&head->lock, flags);
@@ -310,7 +317,7 @@ static void uv_rtc_timer_setup(enum cloc
break;
case CLOCK_EVT_MODE_UNUSED:
case CLOCK_EVT_MODE_SHUTDOWN:
- uv_rtc_unset_timer(ced_cpu);
+ uv_rtc_unset_timer(ced_cpu, 1);
break;
}
}
@@ -320,13 +327,21 @@ static void uv_rtc_interrupt(void)
struct clock_event_device *ced = &__get_cpu_var(cpu_ced);
int cpu = smp_processor_id();
+ exit_idle();
+
+ irq_enter();
+
+ ack_APIC_irq();
+
if (!ced || !ced->event_handler)
- return;
+ goto out;
- if (uv_rtc_unset_timer(cpu) != 1)
- return;
+ if (uv_rtc_unset_timer(cpu, 0) != 1)
+ goto out;
ced->event_handler(ced);
+out:
+ irq_exit();
}
static int __init uv_enable_rtc(char *str)
@@ -337,6 +352,14 @@ static int __init uv_enable_rtc(char *st
}
__setup("uvrtc", uv_enable_rtc);
+static int __init uv_enable_evt_rtc(char *str)
+{
+ uv_rtc_evt_enable = 1;
+
+ return 1;
+}
+__setup("uvrtcevt", uv_enable_evt_rtc);
+
static __init void uv_rtc_register_clockevents(struct work_struct *dummy)
{
struct clock_event_device *ced = &__get_cpu_var(cpu_ced);
@@ -353,24 +376,25 @@ static __init int uv_rtc_setup_clock(voi
if (!uv_rtc_enable || !is_uv_system() || generic_interrupt_extension)
return -ENODEV;
- generic_interrupt_extension = uv_rtc_interrupt;
-
clocksource_uv.mult = clocksource_hz2mult(sn_rtc_cycles_per_second,
clocksource_uv.shift);
rc = clocksource_register(&clocksource_uv);
- if (rc) {
- generic_interrupt_extension = NULL;
+ if (rc)
+ printk(KERN_INFO "UV RTC clocksource failed rc %d\n", rc);
+ else
+ printk(KERN_INFO "UV RTC clocksource registered freq %lu MHz\n",
+ sn_rtc_cycles_per_second/(unsigned long)1E6);
+
+ if (rc || !uv_rtc_evt_enable)
return rc;
- }
+
+ generic_interrupt_extension = uv_rtc_interrupt;
/* Setup and register clockevents */
rc = uv_rtc_allocate_timers();
- if (rc) {
- clocksource_unregister(&clocksource_uv);
- generic_interrupt_extension = NULL;
- return rc;
- }
+ if (rc)
+ goto error;
clock_event_device_uv.mult = div_sc(sn_rtc_cycles_per_second,
NSEC_PER_SEC, clock_event_device_uv.shift);
@@ -383,10 +407,17 @@ static __init int uv_rtc_setup_clock(voi
rc = schedule_on_each_cpu(uv_rtc_register_clockevents);
if (rc) {
- clocksource_unregister(&clocksource_uv);
- generic_interrupt_extension = NULL;
uv_rtc_deallocate_timers();
+ goto error;
}
+ printk(KERN_INFO "UV RTC clockevents registered\n");
+
+ return 0;
+
+error:
+ generic_interrupt_extension = NULL;
+ clocksource_unregister(&clocksource_uv);
+ printk(KERN_INFO "UV RTC clockevents failed rc %d\n", rc);
return rc;
}
Index: linux/arch/x86/kernel/irq.c
===================================================================
--- linux.orig/arch/x86/kernel/irq.c 2009-10-08 11:31:05.000000000 -0500
+++ linux/arch/x86/kernel/irq.c 2009-10-08 11:31:15.000000000 -0500
@@ -257,18 +257,12 @@ void smp_generic_interrupt(struct pt_reg
{
struct pt_regs *old_regs = set_irq_regs(regs);
- ack_APIC_irq();
-
- exit_idle();
-
- irq_enter();
-
inc_irq_stat(generic_irqs);
if (generic_interrupt_extension)
generic_interrupt_extension();
-
- irq_exit();
+ else
+ ack_APIC_irq();
set_irq_regs(old_regs);
}
--
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