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

[Peter Zijlstra <a.p.zijlstra@chello.nl>]

[-- Attachment #1: xtime-foo.patch --]
[-- Type: text/plain, Size: 12116 bytes --]

move update_process_times() out from under xtime_lock.

Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
---
 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;
 }
 

--