Commit 4c1051e3 authored by Martin Schwidefsky's avatar Martin Schwidefsky
Browse files

[S390] rework idle code 



Whenever the cpu loads an enabled wait PSW it will appear as idle to the
underlying host system. The code in default_idle calls vtime_stop_cpu
which does the necessary voodoo to get the cpu time accounting right.
The udelay code just loads an enabled wait PSW. To correct this rework
the vtime_stop_cpu/vtime_start_cpu logic and move the difficult parts
to entry[64].S, vtime_stop_cpu can now be called from anywhere and
vtime_start_cpu is gone. The correction of the cpu time during wakeup
from an enabled wait PSW is done with a critical section in entry[64].S.
As vtime_start_cpu is gone, s390_idle_check can be removed as well.

Signed-off-by: default avatarMartin Schwidefsky <schwidefsky@de.ibm.com>
parent 8b646bd7

arch/s390/include/asm/cputime.h

+1 −8
Original line number Diff line number Diff line
@@ -170,24 +170,17 @@ struct s390_idle_data { 
	unsigned int sequence;

	unsigned long long idle_count;

	unsigned long long idle_enter;

	unsigned long long idle_exit;

	unsigned long long idle_time;

	int nohz_delay;

};



DECLARE_PER_CPU(struct s390_idle_data, s390_idle);



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(struct pt_regs *regs, __u64 int_clock,

				   __u64 enter_timer)

{

	if (regs->psw.mask & PSW_MASK_WAIT)

		vtime_start_cpu(int_clock, enter_timer);

}



static inline int s390_nohz_delay(int cpu)

{

	return __get_cpu_var(s390_idle).nohz_delay != 0;

arch/s390/include/asm/timer.h

+2 −2
Original line number Diff line number Diff line
@@ -33,8 +33,8 @@ struct vtimer_queue { 
	spinlock_t lock;

	__u64 timer;		/* last programmed timer */

	__u64 elapsed;		/* elapsed time of timer expire values */

	__u64 idle;		/* temp var for idle */

	int do_spt;		/* =1: reprogram cpu timer in idle */

	__u64 idle_enter;	/* cpu timer on idle enter */

	__u64 idle_exit;	/* cpu timer on idle exit */

};



extern void init_virt_timer(struct vtimer_list *timer);

arch/s390/kernel/asm-offsets.c

+8 −0
Original line number Diff line number Diff line
@@ -8,6 +8,8 @@ 


#include <linux/kbuild.h>

#include <linux/sched.h>

#include <asm/cputime.h>

#include <asm/timer.h>

#include <asm/vdso.h>

#include <asm/pgtable.h>

#include <asm/system.h>
@@ -70,6 +72,12 @@ int main(void) 
	DEFINE(__CLOCK_MONOTONIC, CLOCK_MONOTONIC);

	DEFINE(__CLOCK_REALTIME_RES, MONOTONIC_RES_NSEC);

	BLANK();

	/* idle data offsets */

	DEFINE(__IDLE_ENTER, offsetof(struct s390_idle_data, idle_enter));

	DEFINE(__IDLE_EXIT, offsetof(struct s390_idle_data, idle_exit));

	/* vtimer queue offsets */

	DEFINE(__VQ_IDLE_ENTER, offsetof(struct vtimer_queue, idle_enter));

	DEFINE(__VQ_IDLE_EXIT, offsetof(struct vtimer_queue, idle_exit));

	/* lowcore offsets */

	DEFINE(__LC_EXT_PARAMS, offsetof(struct _lowcore, ext_params));

	DEFINE(__LC_EXT_CPU_ADDR, offsetof(struct _lowcore, ext_cpu_addr));

arch/s390/kernel/entry.S

+70 −6
Original line number Diff line number Diff line
@@ -105,14 +105,14 @@ STACK_SIZE = 1 << STACK_SHIFT 


	.macro	ADD64 high,low,timer

	al	\high,\timer

	al	\low,\timer+4

	al	\low,4+\timer

	brc	12,.+8

	ahi	\high,1

	.endm



	.macro	SUB64 high,low,timer

	sl	\high,\timer

	sl	\low,\timer+4

	sl	\low,4+\timer

	brc	3,.+8

	ahi	\high,-1

	.endm
@@ -471,7 +471,6 @@ io_tif: 
	jnz	io_work			# there is work to do (signals etc.)

io_restore:

	mvc	__LC_RETURN_PSW(8),__PT_PSW(%r11)

	ni	__LC_RETURN_PSW+1,0xfd	# clean wait state bit

	stpt	__LC_EXIT_TIMER

	lm	%r0,%r15,__PT_R0(%r11)

	lpsw	__LC_RETURN_PSW
@@ -612,6 +611,26 @@ ext_skip: 
	basr	%r14,%r1		# call do_extint

	j	io_return



/*

 * Load idle PSW. The second "half" of this function is in cleanup_idle.

 */

ENTRY(psw_idle)

	st	%r4,__SF_EMPTY(%r15)

	basr	%r1,0

	la	%r1,psw_idle_lpsw+4-.(%r1)

	st	%r1,__SF_EMPTY+4(%r15)

	oi	__SF_EMPTY+4(%r15),0x80

	la	%r1,.Lvtimer_max-psw_idle_lpsw-4(%r1)

	stck	__IDLE_ENTER(%r2)

	ltr	%r5,%r5

	stpt	__VQ_IDLE_ENTER(%r3)

	jz	psw_idle_lpsw

	spt	0(%r1)

psw_idle_lpsw:

	lpsw	__SF_EMPTY(%r15)

	br	%r14

psw_idle_end:



__critical_end:



/*
@@ -673,7 +692,6 @@ mcck_skip: 
	TRACE_IRQS_ON

mcck_return:

	mvc	__LC_RETURN_MCCK_PSW(8),__PT_PSW(%r11) # move return PSW

	ni	__LC_RETURN_MCCK_PSW+1,0xfd # clear wait state bit

	tm	__LC_RETURN_MCCK_PSW+1,0x01 # returning to user ?

	jno	0f

	lm	%r0,%r15,__PT_R0(%r11)
@@ -748,6 +766,8 @@ cleanup_table: 
	.long	io_tif + 0x80000000

	.long	io_restore + 0x80000000

	.long	io_done + 0x80000000

	.long	psw_idle + 0x80000000

	.long	psw_idle_end + 0x80000000



cleanup_critical:

	cl	%r9,BASED(cleanup_table)	# system_call
@@ -766,6 +786,10 @@ cleanup_critical: 
	jl	cleanup_io_tif

	cl	%r9,BASED(cleanup_table+28)	# io_done

	jl	cleanup_io_restore

	cl	%r9,BASED(cleanup_table+32)	# psw_idle

	jl	0f

	cl	%r9,BASED(cleanup_table+36)	# psw_idle_end

	jl	cleanup_idle

0:	br	%r14



cleanup_system_call:
@@ -849,7 +873,6 @@ cleanup_io_restore: 
	jhe	0f

	l	%r9,12(%r11)		# get saved r11 pointer to pt_regs

	mvc	__LC_RETURN_PSW(8),__PT_PSW(%r9)

	ni	__LC_RETURN_PSW+1,0xfd	# clear wait state bit

	mvc	0(32,%r11),__PT_R8(%r9)

	lm	%r0,%r7,__PT_R0(%r9)

0:	lm	%r8,%r9,__LC_RETURN_PSW
@@ -857,11 +880,52 @@ cleanup_io_restore: 
cleanup_io_restore_insn:

	.long	io_done - 4 + 0x80000000



cleanup_idle:

	# copy interrupt clock & cpu timer

	mvc	__IDLE_EXIT(8,%r2),__LC_INT_CLOCK

	mvc	__VQ_IDLE_EXIT(8,%r3),__LC_ASYNC_ENTER_TIMER

	chi	%r11,__LC_SAVE_AREA_ASYNC

	je	0f

	mvc	__IDLE_EXIT(8,%r2),__LC_MCCK_CLOCK

	mvc	__VQ_IDLE_EXIT(8,%r3),__LC_MCCK_ENTER_TIMER

0:	# check if stck has been executed

	cl	%r9,BASED(cleanup_idle_insn)

	jhe	1f

	mvc	__IDLE_ENTER(8,%r2),__IDLE_EXIT(%r2)

	mvc	__VQ_IDLE_ENTER(8,%r3),__VQ_IDLE_EXIT(%r3)

	j	2f

1:	# check if the cpu timer has been reprogrammed

	ltr	%r5,%r5

	jz	2f

	spt	__VQ_IDLE_ENTER(%r3)

2:	# account system time going idle

	lm	%r9,%r10,__LC_STEAL_TIMER

	ADD64	%r9,%r10,__IDLE_ENTER(%r2)

	SUB64	%r9,%r10,__LC_LAST_UPDATE_CLOCK

	stm	%r9,%r10,__LC_STEAL_TIMER

	mvc	__LC_LAST_UPDATE_CLOCK(8),__IDLE_EXIT(%r2)

	lm	%r9,%r10,__LC_SYSTEM_TIMER

	ADD64	%r9,%r10,__LC_LAST_UPDATE_TIMER

	SUB64	%r9,%r10,__VQ_IDLE_ENTER(%r3)

	stm	%r9,%r10,__LC_SYSTEM_TIMER

	mvc	__LC_LAST_UPDATE_TIMER(8),__VQ_IDLE_EXIT(%r3)

	# prepare return psw

	n	%r8,BASED(cleanup_idle_wait)	# clear wait state bit

	l	%r9,24(%r11)			# return from psw_idle

	br	%r14

cleanup_idle_insn:

	.long	psw_idle_lpsw + 0x80000000

cleanup_idle_wait:

	.long	0xfffdffff



/*

 * Integer constants

 */

	.align	4

.Lnr_syscalls:		.long	NR_syscalls

.Lnr_syscalls:

	.long	NR_syscalls

.Lvtimer_max:

	.quad	0x7fffffffffffffff



/*

 * Symbol constants

arch/s390/kernel/entry.h

+4 −1
Original line number Diff line number Diff line
@@ -4,7 +4,8 @@ 
#include <linux/types.h>

#include <linux/signal.h>

#include <asm/ptrace.h>



#include <asm/cputime.h>

#include <asm/timer.h>



extern void (*pgm_check_table[128])(struct pt_regs *);

extern void *restart_stack;
@@ -16,6 +17,8 @@ void io_int_handler(void); 
void mcck_int_handler(void);

void restart_int_handler(void);

void restart_call_handler(void);

void psw_idle(struct s390_idle_data *, struct vtimer_queue *,

	      unsigned long, int);



asmlinkage long do_syscall_trace_enter(struct pt_regs *regs);

asmlinkage void do_syscall_trace_exit(struct pt_regs *regs);

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