diff options
| -rw-r--r-- | arch/powerpc/kernel/time.c | 25 | ||||
| -rw-r--r-- | include/asm-powerpc/system.h | 9 |
2 files changed, 26 insertions, 8 deletions
diff --git a/arch/powerpc/kernel/time.c b/arch/powerpc/kernel/time.c index 774c0a3c501..18e59e43d2b 100644 --- a/arch/powerpc/kernel/time.c +++ b/arch/powerpc/kernel/time.c @@ -417,7 +417,7 @@ static __inline__ void timer_check_rtc(void) /* * This version of gettimeofday has microsecond resolution. */ -static inline void __do_gettimeofday(struct timeval *tv, u64 tb_val) +static inline void __do_gettimeofday(struct timeval *tv) { unsigned long sec, usec; u64 tb_ticks, xsec; @@ -431,7 +431,12 @@ static inline void __do_gettimeofday(struct timeval *tv, u64 tb_val) * without a divide (and in fact, without a multiply) */ temp_varp = do_gtod.varp; - tb_ticks = tb_val - temp_varp->tb_orig_stamp; + + /* Sampling the time base must be done after loading + * do_gtod.varp in order to avoid racing with update_gtod. + */ + data_barrier(temp_varp); + tb_ticks = get_tb() - temp_varp->tb_orig_stamp; temp_tb_to_xs = temp_varp->tb_to_xs; temp_stamp_xsec = temp_varp->stamp_xsec; xsec = temp_stamp_xsec + mulhdu(tb_ticks, temp_tb_to_xs); @@ -464,7 +469,7 @@ void do_gettimeofday(struct timeval *tv) tv->tv_usec = usec; return; } - __do_gettimeofday(tv, get_tb()); + __do_gettimeofday(tv); } EXPORT_SYMBOL(do_gettimeofday); @@ -650,6 +655,7 @@ void timer_interrupt(struct pt_regs * regs) int next_dec; int cpu = smp_processor_id(); unsigned long ticks; + u64 tb_next_jiffy; #ifdef CONFIG_PPC32 if (atomic_read(&ppc_n_lost_interrupts) != 0) @@ -691,11 +697,14 @@ void timer_interrupt(struct pt_regs * regs) continue; write_seqlock(&xtime_lock); - tb_last_jiffy += tb_ticks_per_jiffy; - tb_last_stamp = per_cpu(last_jiffy, cpu); - do_timer(regs); - timer_recalc_offset(tb_last_jiffy); - timer_check_rtc(); + 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(); + } write_sequnlock(&xtime_lock); } diff --git a/include/asm-powerpc/system.h b/include/asm-powerpc/system.h index 7307aa77567..4c9f5229e83 100644 --- a/include/asm-powerpc/system.h +++ b/include/asm-powerpc/system.h @@ -53,6 +53,15 @@ #define smp_read_barrier_depends() do { } while(0) #endif /* CONFIG_SMP */ +/* + * This is a barrier which prevents following instructions from being + * started until the value of the argument x is known. For example, if + * x is a variable loaded from memory, this prevents following + * instructions from being executed until the load has been performed. + */ +#define data_barrier(x) \ + asm volatile("twi 0,%0,0; isync" : : "r" (x) : "memory"); + struct task_struct; struct pt_regs; |