[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/kernel/entry.S b/arch/s390/kernel/entry.S
index 07d8499..0e2b162 100644
--- a/arch/s390/kernel/entry.S
+++ b/arch/s390/kernel/entry.S
@@ -742,15 +742,14 @@
.globl mcck_int_handler
mcck_int_handler:
- stck __LC_INT_CLOCK
+ stck __LC_MCCK_CLOCK
spt __LC_CPU_TIMER_SAVE_AREA # revalidate cpu timer
lm %r0,%r15,__LC_GPREGS_SAVE_AREA # revalidate gprs
SAVE_ALL_BASE __LC_SAVE_AREA+32
la %r12,__LC_MCK_OLD_PSW
tm __LC_MCCK_CODE,0x80 # system damage?
bo BASED(mcck_int_main) # yes -> rest of mcck code invalid
- mvc __LC_SAVE_AREA+52(8),__LC_ASYNC_ENTER_TIMER
- mvc __LC_ASYNC_ENTER_TIMER(8),__LC_CPU_TIMER_SAVE_AREA
+ mvc __LC_MCCK_ENTER_TIMER(8),__LC_CPU_TIMER_SAVE_AREA
tm __LC_MCCK_CODE+5,0x02 # stored cpu timer value valid?
bo BASED(1f)
la %r14,__LC_SYNC_ENTER_TIMER
@@ -764,7 +763,7 @@
bl BASED(0f)
la %r14,__LC_LAST_UPDATE_TIMER
0: spt 0(%r14)
- mvc __LC_ASYNC_ENTER_TIMER(8),0(%r14)
+ mvc __LC_MCCK_ENTER_TIMER(8),0(%r14)
1: tm __LC_MCCK_CODE+2,0x09 # mwp + ia of old psw valid?
bno BASED(mcck_int_main) # no -> skip cleanup critical
tm __LC_MCK_OLD_PSW+1,0x01 # test problem state bit
@@ -786,9 +785,9 @@
bno BASED(mcck_no_vtime) # no -> skip cleanup critical
tm SP_PSW+1(%r15),0x01 # interrupting from user ?
bz BASED(mcck_no_vtime)
- UPDATE_VTIME __LC_EXIT_TIMER,__LC_ASYNC_ENTER_TIMER,__LC_USER_TIMER
+ UPDATE_VTIME __LC_EXIT_TIMER,__LC_MCCK_ENTER_TIMER,__LC_USER_TIMER
UPDATE_VTIME __LC_LAST_UPDATE_TIMER,__LC_EXIT_TIMER,__LC_SYSTEM_TIMER
- mvc __LC_LAST_UPDATE_TIMER(8),__LC_ASYNC_ENTER_TIMER
+ mvc __LC_LAST_UPDATE_TIMER(8),__LC_MCCK_ENTER_TIMER
mcck_no_vtime:
l %r9,__LC_THREAD_INFO # load pointer to thread_info struct
la %r2,SP_PTREGS(%r15) # load pt_regs
@@ -811,7 +810,6 @@
mcck_return:
mvc __LC_RETURN_MCCK_PSW(8),SP_PSW(%r15) # move return PSW
ni __LC_RETURN_MCCK_PSW+1,0xfd # clear wait state bit
- mvc __LC_ASYNC_ENTER_TIMER(8),__LC_SAVE_AREA+52
tm __LC_RETURN_MCCK_PSW+1,0x01 # returning to user ?
bno BASED(0f)
lm %r0,%r15,SP_R0(%r15) # load gprs 0-15
@@ -934,15 +932,16 @@
cleanup_system_call:
mvc __LC_RETURN_PSW(8),0(%r12)
- c %r12,BASED(.Lmck_old_psw)
- be BASED(0f)
- la %r12,__LC_SAVE_AREA+16
- b BASED(1f)
-0: la %r12,__LC_SAVE_AREA+32
-1:
clc __LC_RETURN_PSW+4(4),BASED(cleanup_system_call_insn+4)
bh BASED(0f)
+ mvc __LC_SYNC_ENTER_TIMER(8),__LC_MCCK_ENTER_TIMER
+ c %r12,BASED(.Lmck_old_psw)
+ be BASED(0f)
mvc __LC_SYNC_ENTER_TIMER(8),__LC_ASYNC_ENTER_TIMER
+0: c %r12,BASED(.Lmck_old_psw)
+ la %r12,__LC_SAVE_AREA+32
+ be BASED(0f)
+ la %r12,__LC_SAVE_AREA+16
0: clc __LC_RETURN_PSW+4(4),BASED(cleanup_system_call_insn+8)
bhe BASED(cleanup_vtime)
clc __LC_RETURN_PSW+4(4),BASED(cleanup_system_call_insn)
@@ -984,16 +983,19 @@
cleanup_sysc_restore:
clc 4(4,%r12),BASED(cleanup_sysc_restore_insn)
be BASED(2f)
+ mvc __LC_EXIT_TIMER(8),__LC_MCCK_ENTER_TIMER
+ c %r12,BASED(.Lmck_old_psw)
+ be BASED(0f)
mvc __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
- clc 4(4,%r12),BASED(cleanup_sysc_restore_insn+4)
+0: clc 4(4,%r12),BASED(cleanup_sysc_restore_insn+4)
be BASED(2f)
mvc __LC_RETURN_PSW(8),SP_PSW(%r15)
c %r12,BASED(.Lmck_old_psw)
- bne BASED(0f)
- mvc __LC_SAVE_AREA+32(16),SP_R12(%r15)
- b BASED(1f)
-0: mvc __LC_SAVE_AREA+16(16),SP_R12(%r15)
-1: lm %r0,%r11,SP_R0(%r15)
+ la %r12,__LC_SAVE_AREA+32
+ be BASED(1f)
+ la %r12,__LC_SAVE_AREA+16
+1: mvc 0(16,%r12),SP_R12(%r15)
+ lm %r0,%r11,SP_R0(%r15)
l %r15,SP_R15(%r15)
2: la %r12,__LC_RETURN_PSW
br %r14
@@ -1009,19 +1011,15 @@
cleanup_io_restore:
clc 4(4,%r12),BASED(cleanup_io_restore_insn)
- be BASED(2f)
- mvc __LC_EXIT_TIMER(8),__LC_ASYNC_ENTER_TIMER
+ be BASED(1f)
+ mvc __LC_EXIT_TIMER(8),__LC_MCCK_ENTER_TIMER
clc 4(4,%r12),BASED(cleanup_io_restore_insn+4)
- be BASED(2f)
+ be BASED(1f)
mvc __LC_RETURN_PSW(8),SP_PSW(%r15)
- c %r12,BASED(.Lmck_old_psw)
- bne BASED(0f)
mvc __LC_SAVE_AREA+32(16),SP_R12(%r15)
- b BASED(1f)
-0: mvc __LC_SAVE_AREA+16(16),SP_R12(%r15)
-1: lm %r0,%r11,SP_R0(%r15)
+ lm %r0,%r11,SP_R0(%r15)
l %r15,SP_R15(%r15)
-2: la %r12,__LC_RETURN_PSW
+1: la %r12,__LC_RETURN_PSW
br %r14
cleanup_io_restore_insn:
.long io_done - 4 + 0x80000000