[RFC][PATCH 2/2] xtime_lock vs update_process_times

From: Peter Zijlstra
Date: Mon Jan 28 2008 - 05:41:42 EST

move update_process_times() out from under xtime_lock.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
---
arch/alpha/kernel/time.c | 15 ++++++++-------
arch/arm/common/time-acorn.c | 2 --
arch/arm/mach-at91/at91sam926x_time.c | 3 ---
arch/arm/plat-iop/time.c | 4 ----
arch/arm/plat-s3c24xx/time.c | 2 --
arch/blackfin/kernel/time.c | 8 +++++---
arch/frv/kernel/time.c | 6 ++++--
arch/m68knommu/kernel/time.c | 12 +++++++-----
arch/sh/kernel/time.c | 19 +++++++++++++++----
arch/sh/kernel/timers/timer-cmt.c | 9 ---------
arch/sh/kernel/timers/timer-mtu2.c | 2 --
arch/sh64/kernel/time.c | 31 +++++++++++++++++--------------
arch/sparc/kernel/pcic.c | 2 +-
arch/sparc/kernel/time.c | 7 +++----
14 files changed, 60 insertions(+), 62 deletions(-)

Index: linux-2.6/arch/alpha/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/alpha/kernel/time.c
+++ linux-2.6/arch/alpha/kernel/time.c
@@ -119,13 +119,8 @@ irqreturn_t timer_interrupt(int irq, voi
state.partial_tick = delta & ((1UL << FIX_SHIFT) - 1);
nticks = delta >> FIX_SHIFT;

- while (nticks > 0) {
- do_timer(1);
-#ifndef CONFIG_SMP
- update_process_times(user_mode(get_irq_regs()));
-#endif
- nticks--;
- }
+ if (nticks)
+ do_timer(nticks);

/*
* If we have an externally synchronized Linux clock, then update
@@ -141,6 +136,12 @@ irqreturn_t timer_interrupt(int irq, voi
}

write_sequnlock(&xtime_lock);
+
+#ifndef CONFIG_SMP
+ while (nticks--)
+ update_process_times(user_mode(get_irq_regs()));
+#endif
+
return IRQ_HANDLED;
}

Index: linux-2.6/arch/arm/common/time-acorn.c
===================================================================
--- linux-2.6.orig/arch/arm/common/time-acorn.c
+++ linux-2.6/arch/arm/common/time-acorn.c
@@ -69,9 +69,7 @@ void __init ioctime_init(void)
static irqreturn_t
ioc_timer_interrupt(int irq, void *dev_id)
{
- write_seqlock(&xtime_lock);
timer_tick();
- write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
}

Index: linux-2.6/arch/arm/mach-at91/at91sam926x_time.c
===================================================================
--- linux-2.6.orig/arch/arm/mach-at91/at91sam926x_time.c
+++ linux-2.6/arch/arm/mach-at91/at91sam926x_time.c
@@ -49,8 +49,6 @@ static irqreturn_t at91sam926x_timer_int
volatile long nr_ticks;

if (at91_sys_read(AT91_PIT_SR) & AT91_PIT_PITS) { /* This is a shared interrupt */
- write_seqlock(&xtime_lock);
-
/* Get number to ticks performed before interrupt and clear PIT interrupt */
nr_ticks = PIT_PICNT(at91_sys_read(AT91_PIT_PIVR));
do {
@@ -58,7 +56,6 @@ static irqreturn_t at91sam926x_timer_int
nr_ticks--;
} while (nr_ticks);

- write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
} else
return IRQ_NONE; /* not handled */
Index: linux-2.6/arch/arm/plat-iop/time.c
===================================================================
--- linux-2.6.orig/arch/arm/plat-iop/time.c
+++ linux-2.6/arch/arm/plat-iop/time.c
@@ -57,8 +57,6 @@ unsigned long iop_gettimeoffset(void)
static irqreturn_t
iop_timer_interrupt(int irq, void *dev_id)
{
- write_seqlock(&xtime_lock);
-
write_tisr(1);

while ((signed long)(next_jiffy_time - read_tcr1())
@@ -67,8 +65,6 @@ iop_timer_interrupt(int irq, void *dev_i
next_jiffy_time -= ticks_per_jiffy;
}

- write_sequnlock(&xtime_lock);
-
return IRQ_HANDLED;
}

Index: linux-2.6/arch/arm/plat-s3c24xx/time.c
===================================================================
--- linux-2.6.orig/arch/arm/plat-s3c24xx/time.c
+++ linux-2.6/arch/arm/plat-s3c24xx/time.c
@@ -130,9 +130,7 @@ static unsigned long s3c2410_gettimeoffs
static irqreturn_t
s3c2410_timer_interrupt(int irq, void *dev_id)
{
- write_seqlock(&xtime_lock);
timer_tick();
- write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
}

Index: linux-2.6/arch/blackfin/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/blackfin/kernel/time.c
+++ linux-2.6/arch/blackfin/kernel/time.c
@@ -137,9 +137,6 @@ irqreturn_t timer_interrupt(int irq, voi

do_timer(1);

-#ifndef CONFIG_SMP
- update_process_times(user_mode(get_irq_regs()));
-#endif
profile_tick(CPU_PROFILING);

/*
@@ -161,6 +158,11 @@ irqreturn_t timer_interrupt(int irq, voi
last_rtc_update = xtime.tv_sec - 600;
}
write_sequnlock(&xtime_lock);
+
+#ifndef CONFIG_SMP
+ update_process_times(user_mode(get_irq_regs()));
+#endif
+
return IRQ_HANDLED;
}

Index: linux-2.6/arch/frv/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/frv/kernel/time.c
+++ linux-2.6/arch/frv/kernel/time.c
@@ -63,6 +63,7 @@ static irqreturn_t timer_interrupt(int i
/* last time the cmos clock got updated */
static long last_rtc_update = 0;

+ profile_tick(CPU_PROFILING);
/*
* Here we are in the timer irq handler. We just have irqs locally
* disabled but we don't know if the timer_bh is running on the other
@@ -73,8 +74,6 @@ static irqreturn_t timer_interrupt(int i
write_seqlock(&xtime_lock);

do_timer(1);
- update_process_times(user_mode(get_irq_regs()));
- profile_tick(CPU_PROFILING);

/*
* If we have an externally synchronized Linux clock, then update
@@ -99,6 +98,9 @@ static irqreturn_t timer_interrupt(int i
#endif /* CONFIG_HEARTBEAT */

write_sequnlock(&xtime_lock);
+
+ update_process_times(user_mode(get_irq_regs()));
+
return IRQ_HANDLED;
}

Index: linux-2.6/arch/m68knommu/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/m68knommu/kernel/time.c
+++ linux-2.6/arch/m68knommu/kernel/time.c
@@ -43,14 +43,12 @@ irqreturn_t arch_timer_interrupt(int irq
/* last time the cmos clock got updated */
static long last_rtc_update=0;

+ if (current->pid)
+ profile_tick(CPU_PROFILING);
+
write_seqlock(&xtime_lock);

do_timer(1);
-#ifndef CONFIG_SMP
- update_process_times(user_mode(get_irq_regs()));
-#endif
- if (current->pid)
- profile_tick(CPU_PROFILING);

/*
* If we have an externally synchronized Linux clock, then update
@@ -91,6 +89,10 @@ irqreturn_t arch_timer_interrupt(int irq
#endif /* CONFIG_HEARTBEAT */

write_sequnlock(&xtime_lock);
+
+#ifndef CONFIG_SMP
+ update_process_times(user_mode(get_irq_regs()));
+#endif
return(IRQ_HANDLED);
}

Index: linux-2.6/arch/sh/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/sh/kernel/time.c
+++ linux-2.6/arch/sh/kernel/time.c
@@ -120,10 +120,6 @@ static long last_rtc_update;
*/
void handle_timer_tick(void)
{
- do_timer(1);
-#ifndef CONFIG_SMP
- update_process_times(user_mode(get_irq_regs()));
-#endif
if (current->pid)
profile_tick(CPU_PROFILING);

@@ -133,6 +129,16 @@ void handle_timer_tick(void)
#endif

/*
+ * Here we are in the timer irq handler. We just have irqs locally
+ * disabled but we don't know if the timer_bh is running on the other
+ * CPU. We need to avoid to SMP race with it. NOTE: we don' t need
+ * the irq version of write_lock because as just said we have irq
+ * locally disabled. -arca
+ */
+ write_seqlock(&xtime_lock);
+ do_timer(1);
+
+ /*
* If we have an externally synchronized Linux clock, then update
* RTC clock accordingly every ~11 minutes. Set_rtc_mmss() has to be
* called as close as possible to 500 ms before the new second starts.
@@ -147,6 +153,11 @@ void handle_timer_tick(void)
/* do it again in 60s */
last_rtc_update = xtime.tv_sec - 600;
}
+ write_sequnlock(&xtime_lock);
+
+#ifndef CONFIG_SMP
+ update_process_times(user_mode(get_irq_regs()));
+#endif
}
#endif /* !CONFIG_GENERIC_CLOCKEVENTS */

Index: linux-2.6/arch/sh/kernel/timers/timer-cmt.c
===================================================================
--- linux-2.6.orig/arch/sh/kernel/timers/timer-cmt.c
+++ linux-2.6/arch/sh/kernel/timers/timer-cmt.c
@@ -98,16 +98,7 @@ static irqreturn_t cmt_timer_interrupt(i
timer_status &= ~0x80;
ctrl_outw(timer_status, CMT_CMCSR_0);

- /*
- * Here we are in the timer irq handler. We just have irqs locally
- * disabled but we don't know if the timer_bh is running on the other
- * CPU. We need to avoid to SMP race with it. NOTE: we don' t need
- * the irq version of write_lock because as just said we have irq
- * locally disabled. -arca
- */
- write_seqlock(&xtime_lock);
handle_timer_tick();
- write_sequnlock(&xtime_lock);

return IRQ_HANDLED;
}
Index: linux-2.6/arch/sh/kernel/timers/timer-mtu2.c
===================================================================
--- linux-2.6.orig/arch/sh/kernel/timers/timer-mtu2.c
+++ linux-2.6/arch/sh/kernel/timers/timer-mtu2.c
@@ -100,9 +100,7 @@ static irqreturn_t mtu2_timer_interrupt(
ctrl_outb(timer_status, MTU2_TSR_1);

/* Do timer tick */
- write_seqlock(&xtime_lock);
handle_timer_tick();
- write_sequnlock(&xtime_lock);

return IRQ_HANDLED;
}
Index: linux-2.6/arch/sh64/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/sh64/kernel/time.c
+++ linux-2.6/arch/sh64/kernel/time.c
@@ -285,15 +285,22 @@ static long last_rtc_update = 0;
static inline void do_timer_interrupt(void)
{
unsigned long long current_ctc;
+
+ if (current->pid)
+ profile_tick(CPU_PROFILING);
+
+ /*
+ * Here we are in the timer irq handler. We just have irqs locally
+ * disabled but we don't know if the timer_bh is running on the other
+ * CPU. We need to avoid to SMP race with it. NOTE: we don' t need
+ * the irq version of write_lock because as just said we have irq
+ * locally disabled. -arca
+ */
+ write_lock(&xtime_lock);
asm ("getcon cr62, %0" : "=r" (current_ctc));
ctc_last_interrupt = (unsigned long) current_ctc;

do_timer(1);
-#ifndef CONFIG_SMP
- update_process_times(user_mode(get_irq_regs()));
-#endif
- if (current->pid)
- profile_tick(CPU_PROFILING);

#ifdef CONFIG_HEARTBEAT
{
@@ -317,6 +324,11 @@ static inline void do_timer_interrupt(vo
else
last_rtc_update = xtime.tv_sec - 600; /* do it again in 60 s */
}
+ write_unlock(&xtime_lock);
+
+#ifndef CONFIG_SMP
+ update_process_times(user_mode(get_irq_regs()));
+#endif
}

/*
@@ -333,16 +345,7 @@ static irqreturn_t timer_interrupt(int i
timer_status &= ~0x100;
ctrl_outw(timer_status, TMU0_TCR);

- /*
- * Here we are in the timer irq handler. We just have irqs locally
- * disabled but we don't know if the timer_bh is running on the other
- * CPU. We need to avoid to SMP race with it. NOTE: we don' t need
- * the irq version of write_lock because as just said we have irq
- * locally disabled. -arca
- */
- write_lock(&xtime_lock);
do_timer_interrupt();
- write_unlock(&xtime_lock);

return IRQ_HANDLED;
}
Index: linux-2.6/arch/sparc/kernel/pcic.c
===================================================================
--- linux-2.6.orig/arch/sparc/kernel/pcic.c
+++ linux-2.6/arch/sparc/kernel/pcic.c
@@ -713,10 +713,10 @@ static irqreturn_t pcic_timer_handler (i
write_seqlock(&xtime_lock); /* Dummy, to show that we remember */
pcic_clear_clock_irq();
do_timer(1);
+ write_sequnlock(&xtime_lock);
#ifndef CONFIG_SMP
update_process_times(user_mode(get_irq_regs()));
#endif
- write_sequnlock(&xtime_lock);
return IRQ_HANDLED;
}

Index: linux-2.6/arch/sparc/kernel/time.c
===================================================================
--- linux-2.6.orig/arch/sparc/kernel/time.c
+++ linux-2.6/arch/sparc/kernel/time.c
@@ -128,10 +128,6 @@ irqreturn_t timer_interrupt(int irq, voi
clear_clock_irq();

do_timer(1);
-#ifndef CONFIG_SMP
- update_process_times(user_mode(get_irq_regs()));
-#endif
-

/* Determine when to update the Mostek clock. */
if (ntp_synced() &&
@@ -145,6 +141,9 @@ irqreturn_t timer_interrupt(int irq, voi
}
write_sequnlock(&xtime_lock);

+#ifndef CONFIG_SMP
+ update_process_times(user_mode(get_irq_regs()));
+#endif
return IRQ_HANDLED;
}


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