Commit eb36c288 authored by Paul Mackerras's avatar Paul Mackerras Committed by Linus Torvalds
Browse files

[PATCH] ppc32: fix last_jiffy time comparison 



This fixes a hang on ppc32.

The problem was that I was comparing a 32-bit quantity with a 64-bit
quantity, and consequently time wasn't advancing.  This makes us use a
64-bit quantity on all platforms, which ends up simplifying the code
since we can now get rid of the tb_last_stamp variable (which actually
fixes another bug that Ben H and I noticed while going carefully through
the code).

This works fine on my G4 tibook.  Let me know how it goes on your
machines.

Acked-by: default avatarOlaf Hering <olaf@aepfle.de>
Acked-by: default avatarMikael Pettersson <mikpe@it.uu.se>
Signed-off-by: default avatarLinus Torvalds <torvalds@osdl.org>
parent 98a3c781

arch/powerpc/kernel/time.c

+8 −17
Original line number Diff line number Diff line
@@ -125,15 +125,8 @@ static long timezone_offset; 
unsigned long ppc_proc_freq;

unsigned long ppc_tb_freq;



u64 tb_last_jiffy __cacheline_aligned_in_smp;

unsigned long tb_last_stamp;



/*

 * Note that on ppc32 this only stores the bottom 32 bits of

 * the timebase value, but that's enough to tell when a jiffy

 * has passed.

 */

DEFINE_PER_CPU(unsigned long, last_jiffy);

static u64 tb_last_jiffy __cacheline_aligned_in_smp;

static DEFINE_PER_CPU(u64, last_jiffy);



#ifdef CONFIG_VIRT_CPU_ACCOUNTING

/*
@@ -458,7 +451,7 @@ void do_gettimeofday(struct timeval *tv) 
		do {

			seq = read_seqbegin_irqsave(&xtime_lock, flags);

			sec = xtime.tv_sec;

			nsec = xtime.tv_nsec + tb_ticks_since(tb_last_stamp);

			nsec = xtime.tv_nsec + tb_ticks_since(tb_last_jiffy);

		} while (read_seqretry_irqrestore(&xtime_lock, seq, flags));

		usec = nsec / 1000;

		while (usec >= 1000000) {
@@ -700,7 +693,6 @@ void timer_interrupt(struct pt_regs * regs) 
		tb_next_jiffy = tb_last_jiffy + tb_ticks_per_jiffy;

		if (per_cpu(last_jiffy, cpu) >= tb_next_jiffy) {

			tb_last_jiffy = tb_next_jiffy;

			tb_last_stamp = per_cpu(last_jiffy, cpu);

			do_timer(regs);

			timer_recalc_offset(tb_last_jiffy);

			timer_check_rtc();
@@ -749,7 +741,7 @@ void __init smp_space_timers(unsigned int max_cpus) 
	int i;

	unsigned long half = tb_ticks_per_jiffy / 2;

	unsigned long offset = tb_ticks_per_jiffy / max_cpus;

	unsigned long previous_tb = per_cpu(last_jiffy, boot_cpuid);

	u64 previous_tb = per_cpu(last_jiffy, boot_cpuid);



	/* make sure tb > per_cpu(last_jiffy, cpu) for all cpus always */

	previous_tb -= tb_ticks_per_jiffy;
@@ -830,7 +822,7 @@ int do_settimeofday(struct timespec *tv) 
	 * and therefore the (jiffies - wall_jiffies) computation

	 * has been removed.

	 */

	tb_delta = tb_ticks_since(tb_last_stamp);

	tb_delta = tb_ticks_since(tb_last_jiffy);

	tb_delta = mulhdu(tb_delta, do_gtod.varp->tb_to_xs); /* in xsec */

	new_nsec -= SCALE_XSEC(tb_delta, 1000000000);
@@ -950,8 +942,7 @@ void __init time_init(void) 
	if (__USE_RTC()) {

		/* 601 processor: dec counts down by 128 every 128ns */

		ppc_tb_freq = 1000000000;

		tb_last_stamp = get_rtcl();

		tb_last_jiffy = tb_last_stamp;

		tb_last_jiffy = get_rtcl();

	} else {

		/* Normal PowerPC with timebase register */

		ppc_md.calibrate_decr();
@@ -959,7 +950,7 @@ void __init time_init(void) 
		       ppc_tb_freq / 1000000, ppc_tb_freq % 1000000);

		printk(KERN_DEBUG "time_init: processor frequency   = %lu.%.6lu MHz\n",

		       ppc_proc_freq / 1000000, ppc_proc_freq % 1000000);

		tb_last_stamp = tb_last_jiffy = get_tb();

		tb_last_jiffy = get_tb();

	}



	tb_ticks_per_jiffy = ppc_tb_freq / HZ;
@@ -1036,7 +1027,7 @@ void __init time_init(void) 
	do_gtod.varp = &do_gtod.vars[0];

	do_gtod.var_idx = 0;

	do_gtod.varp->tb_orig_stamp = tb_last_jiffy;

	__get_cpu_var(last_jiffy) = tb_last_stamp;

	__get_cpu_var(last_jiffy) = tb_last_jiffy;

	do_gtod.varp->stamp_xsec = (u64) xtime.tv_sec * XSEC_PER_SEC;

	do_gtod.tb_ticks_per_sec = tb_ticks_per_sec;

	do_gtod.varp->tb_to_xs = tb_to_xs;

include/asm-powerpc/time.h

+0 −4
Original line number Diff line number Diff line
@@ -30,10 +30,6 @@ extern unsigned long tb_ticks_per_usec; 
extern unsigned long tb_ticks_per_sec;

extern u64 tb_to_xs;

extern unsigned      tb_to_us;

extern unsigned long tb_last_stamp;

extern u64 tb_last_jiffy;



DECLARE_PER_CPU(unsigned long, last_jiffy);



struct rtc_time;

extern void to_tm(int tim, struct rtc_time * tm);

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