[S390] idle time accounting vs. machine checks
A machine check can interrupt the i/o and external interrupt handler
anytime. If the machine check occurs while the interrupt handler is
waking up from idle vtime_start_cpu can get executed a second time
and the int_clock / async_enter_timer values in the lowcore get
clobbered. This can confuse the cpu time accounting.
To fix this problem two changes are needed. First the machine check
handler has to use its own copies of int_clock and async_enter_timer,
named mcck_clock and mcck_enter_timer. Second the nested execution
of vtime_start_cpu has to be prevented. This is done in s390_idle_check
by checking the wait bit in the program status word.
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
diff --git a/arch/s390/include/asm/cputime.h b/arch/s390/include/asm/cputime.h
index 258ba88..8b1a52a 100644
--- a/arch/s390/include/asm/cputime.h
+++ b/arch/s390/include/asm/cputime.h
@@ -188,15 +188,16 @@
DECLARE_PER_CPU(struct s390_idle_data, s390_idle);
-void vtime_start_cpu(void);
+void vtime_start_cpu(__u64 int_clock, __u64 enter_timer);
cputime64_t s390_get_idle_time(int cpu);
#define arch_idle_time(cpu) s390_get_idle_time(cpu)
-static inline void s390_idle_check(void)
+static inline void s390_idle_check(struct pt_regs *regs, __u64 int_clock,
+ __u64 enter_timer)
{
- if ((&__get_cpu_var(s390_idle))->idle_enter != 0ULL)
- vtime_start_cpu();
+ if (regs->psw.mask & PSW_MASK_WAIT)
+ vtime_start_cpu(int_clock, enter_timer);
}
static inline int s390_nohz_delay(int cpu)
diff --git a/arch/s390/include/asm/lowcore.h b/arch/s390/include/asm/lowcore.h
index f7e78c7..2c02d46 100644
--- a/arch/s390/include/asm/lowcore.h
+++ b/arch/s390/include/asm/lowcore.h
@@ -104,37 +104,39 @@
/* CPU time accounting values */
__u64 sync_enter_timer; /* 0x0250 */
__u64 async_enter_timer; /* 0x0258 */
- __u64 exit_timer; /* 0x0260 */
- __u64 user_timer; /* 0x0268 */
- __u64 system_timer; /* 0x0270 */
- __u64 steal_timer; /* 0x0278 */
- __u64 last_update_timer; /* 0x0280 */
- __u64 last_update_clock; /* 0x0288 */
+ __u64 mcck_enter_timer; /* 0x0260 */
+ __u64 exit_timer; /* 0x0268 */
+ __u64 user_timer; /* 0x0270 */
+ __u64 system_timer; /* 0x0278 */
+ __u64 steal_timer; /* 0x0280 */
+ __u64 last_update_timer; /* 0x0288 */
+ __u64 last_update_clock; /* 0x0290 */
/* Current process. */
- __u32 current_task; /* 0x0290 */
- __u32 thread_info; /* 0x0294 */
- __u32 kernel_stack; /* 0x0298 */
+ __u32 current_task; /* 0x0298 */
+ __u32 thread_info; /* 0x029c */
+ __u32 kernel_stack; /* 0x02a0 */
/* Interrupt and panic stack. */
- __u32 async_stack; /* 0x029c */
- __u32 panic_stack; /* 0x02a0 */
+ __u32 async_stack; /* 0x02a4 */
+ __u32 panic_stack; /* 0x02a8 */
/* Address space pointer. */
- __u32 kernel_asce; /* 0x02a4 */
- __u32 user_asce; /* 0x02a8 */
- __u32 user_exec_asce; /* 0x02ac */
+ __u32 kernel_asce; /* 0x02ac */
+ __u32 user_asce; /* 0x02b0 */
+ __u32 user_exec_asce; /* 0x02b4 */
/* SMP info area */
- __u32 cpu_nr; /* 0x02b0 */
- __u32 softirq_pending; /* 0x02b4 */
- __u32 percpu_offset; /* 0x02b8 */
- __u32 ext_call_fast; /* 0x02bc */
- __u64 int_clock; /* 0x02c0 */
- __u64 clock_comparator; /* 0x02c8 */
- __u32 machine_flags; /* 0x02d0 */
- __u32 ftrace_func; /* 0x02d4 */
- __u8 pad_0x02d8[0x0300-0x02d8]; /* 0x02d8 */
+ __u32 cpu_nr; /* 0x02b8 */
+ __u32 softirq_pending; /* 0x02bc */
+ __u32 percpu_offset; /* 0x02c0 */
+ __u32 ext_call_fast; /* 0x02c4 */
+ __u64 int_clock; /* 0x02c8 */
+ __u64 mcck_clock; /* 0x02d0 */
+ __u64 clock_comparator; /* 0x02d8 */
+ __u32 machine_flags; /* 0x02e0 */
+ __u32 ftrace_func; /* 0x02e4 */
+ __u8 pad_0x02e8[0x0300-0x02e8]; /* 0x02e8 */
/* Interrupt response block */
__u8 irb[64]; /* 0x0300 */
@@ -232,38 +234,40 @@
/* CPU accounting and timing values. */
__u64 sync_enter_timer; /* 0x02a0 */
__u64 async_enter_timer; /* 0x02a8 */
- __u64 exit_timer; /* 0x02b0 */
- __u64 user_timer; /* 0x02b8 */
- __u64 system_timer; /* 0x02c0 */
- __u64 steal_timer; /* 0x02c8 */
- __u64 last_update_timer; /* 0x02d0 */
- __u64 last_update_clock; /* 0x02d8 */
+ __u64 mcck_enter_timer; /* 0x02b0 */
+ __u64 exit_timer; /* 0x02b8 */
+ __u64 user_timer; /* 0x02c0 */
+ __u64 system_timer; /* 0x02c8 */
+ __u64 steal_timer; /* 0x02d0 */
+ __u64 last_update_timer; /* 0x02d8 */
+ __u64 last_update_clock; /* 0x02e0 */
/* Current process. */
- __u64 current_task; /* 0x02e0 */
- __u64 thread_info; /* 0x02e8 */
- __u64 kernel_stack; /* 0x02f0 */
+ __u64 current_task; /* 0x02e8 */
+ __u64 thread_info; /* 0x02f0 */
+ __u64 kernel_stack; /* 0x02f8 */
/* Interrupt and panic stack. */
- __u64 async_stack; /* 0x02f8 */
- __u64 panic_stack; /* 0x0300 */
+ __u64 async_stack; /* 0x0300 */
+ __u64 panic_stack; /* 0x0308 */
/* Address space pointer. */
- __u64 kernel_asce; /* 0x0308 */
- __u64 user_asce; /* 0x0310 */
- __u64 user_exec_asce; /* 0x0318 */
+ __u64 kernel_asce; /* 0x0310 */
+ __u64 user_asce; /* 0x0318 */
+ __u64 user_exec_asce; /* 0x0320 */
/* SMP info area */
- __u32 cpu_nr; /* 0x0320 */
- __u32 softirq_pending; /* 0x0324 */
- __u64 percpu_offset; /* 0x0328 */
- __u64 ext_call_fast; /* 0x0330 */
- __u64 int_clock; /* 0x0338 */
- __u64 clock_comparator; /* 0x0340 */
- __u64 vdso_per_cpu_data; /* 0x0348 */
- __u64 machine_flags; /* 0x0350 */
- __u64 ftrace_func; /* 0x0358 */
- __u8 pad_0x0368[0x0380-0x0360]; /* 0x0360 */
+ __u32 cpu_nr; /* 0x0328 */
+ __u32 softirq_pending; /* 0x032c */
+ __u64 percpu_offset; /* 0x0330 */
+ __u64 ext_call_fast; /* 0x0338 */
+ __u64 int_clock; /* 0x0340 */
+ __u64 mcck_clock; /* 0x0348 */
+ __u64 clock_comparator; /* 0x0350 */
+ __u64 vdso_per_cpu_data; /* 0x0358 */
+ __u64 machine_flags; /* 0x0360 */
+ __u64 ftrace_func; /* 0x0368 */
+ __u8 pad_0x0370[0x0380-0x0370]; /* 0x0370 */
/* Interrupt response block. */
__u8 irb[64]; /* 0x0380 */