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[PATCH] ppc32: fix last_jiffy time comparison

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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: Olaf Hering <olaf@aepfle.de>
Acked-by: Mikael Pettersson <mikpe@it.uu.se>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
This commit is contained in:
Paul Mackerras 2006-08-30 16:13:16 +10:00 committed by Linus Torvalds
parent 98a3c78105
commit eb36c2884a
2 changed files with 8 additions and 21 deletions
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25
arch/powerpc/kernel/time.c
View file

@ -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;

4
include/asm-powerpc/time.h
View file

@ -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);