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s390/kernel: Fix smp_call_ipl_cpu() for offline CPUs

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If the IPL CPU is offline, currently the pcpu_delegate() function
used by smp_call_ipl_cpu() does not work because pcpu_delegate()
modifies the lowcore of the target CPU. In case of an offline
IPL CPU currently the prefix register is zero but pcpu->lowcore
still points to the old prefix page. Therefore the lowcore changes
done by pcpu_delegate() have no effect.

With this fix pcpu_delegate() now uses memcpy_absolute() and therefore
also prepares the absolute zero lowcore if the target CPU has prefix
register zero.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Michael Holzheu 2012-05-24 14:38:26 +02:00 committed by Martin Schwidefsky
parent 73bf463efa
commit 061da3dfb2
1 changed files with 10 additions and 9 deletions
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19
arch/s390/kernel/smp.c
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@ -297,26 +297,27 @@ static void pcpu_start_fn(struct pcpu *pcpu, void (*func)(void *), void *data)
static void pcpu_delegate(struct pcpu *pcpu, void (*func)(void *),
void *data, unsigned long stack)
{
struct _lowcore *lc = pcpu->lowcore;
unsigned short this_cpu;
struct _lowcore *lc = lowcore_ptr[pcpu - pcpu_devices];
struct {
unsigned long stack;
void *func;
void *data;
unsigned long source;
} restart = { stack, func, data, stap() };
__load_psw_mask(psw_kernel_bits);
this_cpu = stap();
if (pcpu->address == this_cpu)
if (pcpu->address == restart.source)
func(data); /* should not return */
/* Stop target cpu (if func returns this stops the current cpu). */
pcpu_sigp_retry(pcpu, sigp_stop, 0);
/* Restart func on the target cpu and stop the current cpu. */
lc->restart_stack = stack;
lc->restart_fn = (unsigned long) func;
lc->restart_data = (unsigned long) data;
lc->restart_source = (unsigned long) this_cpu;
memcpy_absolute(&lc->restart_stack, &restart, sizeof(restart));
asm volatile(
"0: sigp 0,%0,6 # sigp restart to target cpu\n"
" brc 2,0b # busy, try again\n"
"1: sigp 0,%1,5 # sigp stop to current cpu\n"
" brc 2,1b # busy, try again\n"
: : "d" (pcpu->address), "d" (this_cpu) : "0", "1", "cc");
: : "d" (pcpu->address), "d" (restart.source) : "0", "1", "cc");
for (;;) ;
}