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authorHeiko Carstens <heiko.carstens@de.ibm.com>2010-11-25 09:52:45 +0100
committerMartin Schwidefsky <sky@mschwide.boeblingen.de.ibm.com>2010-11-25 09:52:59 +0100
commite8129c642155616d9e2160a75f103e127c8c3708 (patch)
treed863e72afaedfd89939c45ac95c9e02a2c585aa7
parent698fd6a2c3ca05ec796072defb5c415289a86cdc (diff)
downloadlinux-e8129c642155616d9e2160a75f103e127c8c3708.tar.gz
[S390] nmi: fix clock comparator revalidation
On each machine check all registers are revalidated. The save area for the clock comparator however only contains the upper most seven bytes of the former contents, if valid. Therefore the machine check handler uses a store clock instruction to get the current time and writes that to the clock comparator register which in turn will generate an immediate timer interrupt. However within the lowcore the expected time of the next timer interrupt is stored. If the interrupt happens before that time the handler won't be called. In turn the clock comparator won't be reprogrammed and therefore the interrupt condition stays pending which causes an interrupt loop until the expected time is reached. On NOHZ machines this can result in unresponsive machines since the time of the next expected interrupted can be a couple of days in the future. To fix this just revalidate the clock comparator register with the expected value. In addition the special handling for udelay must be changed as well. Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
-rw-r--r--arch/s390/kernel/nmi.c10
-rw-r--r--arch/s390/lib/delay.c14
2 files changed, 13 insertions, 11 deletions
diff --git a/arch/s390/kernel/nmi.c b/arch/s390/kernel/nmi.c
index ac151399ef3..1995c1712fc 100644
--- a/arch/s390/kernel/nmi.c
+++ b/arch/s390/kernel/nmi.c
@@ -95,7 +95,6 @@ EXPORT_SYMBOL_GPL(s390_handle_mcck);
static int notrace s390_revalidate_registers(struct mci *mci)
{
int kill_task;
- u64 tmpclock;
u64 zero;
void *fpt_save_area, *fpt_creg_save_area;
@@ -214,11 +213,10 @@ static int notrace s390_revalidate_registers(struct mci *mci)
: "0", "cc");
#endif
/* Revalidate clock comparator register */
- asm volatile(
- " stck 0(%1)\n"
- " sckc 0(%1)"
- : "=m" (tmpclock) : "a" (&(tmpclock)) : "cc", "memory");
-
+ if (S390_lowcore.clock_comparator == -1)
+ set_clock_comparator(S390_lowcore.mcck_clock);
+ else
+ set_clock_comparator(S390_lowcore.clock_comparator);
/* Check if old PSW is valid */
if (!mci->wp)
/*
diff --git a/arch/s390/lib/delay.c b/arch/s390/lib/delay.c
index 752b362bf65..7c37ec359ec 100644
--- a/arch/s390/lib/delay.c
+++ b/arch/s390/lib/delay.c
@@ -29,17 +29,21 @@ static void __udelay_disabled(unsigned long long usecs)
{
unsigned long mask, cr0, cr0_saved;
u64 clock_saved;
+ u64 end;
+ mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
+ end = get_clock() + (usecs << 12);
clock_saved = local_tick_disable();
- set_clock_comparator(get_clock() + (usecs << 12));
__ctl_store(cr0_saved, 0, 0);
cr0 = (cr0_saved & 0xffff00e0) | 0x00000800;
__ctl_load(cr0 , 0, 0);
- mask = psw_kernel_bits | PSW_MASK_WAIT | PSW_MASK_EXT;
lockdep_off();
- trace_hardirqs_on();
- __load_psw_mask(mask);
- local_irq_disable();
+ do {
+ set_clock_comparator(end);
+ trace_hardirqs_on();
+ __load_psw_mask(mask);
+ local_irq_disable();
+ } while (get_clock() < end);
lockdep_on();
__ctl_load(cr0_saved, 0, 0);
local_tick_enable(clock_saved);