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s390/smp: avoid concurrent write to sigp status field

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When a sigp instruction is issued it may store a status. This status is
currently stored in a per cpu field of the target cpu.
If multiple cpus issue a sigp instruction with the same target cpu
and a status is stored the result is not necessarily as expected.

Currently this is not an issue:
- on cpu hotplug no sigps, except "restart" and "sense" are sent to the
  target cpu.
- on external call we don't look at the status if it is stored
- on sense running the condition code "status stored" is sufficient to
  tell if a cpu is running or not

Signed-off-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
This commit is contained in:
Heiko Carstens 2012-08-30 14:24:42 +02:00 committed by Martin Schwidefsky
parent fbf3c54239
commit c5e3acd666
1 changed files with 7 additions and 6 deletions
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13
arch/s390/kernel/smp.c
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@ -66,7 +66,6 @@ struct pcpu {
unsigned long panic_stack; /* panic stack for the cpu */
unsigned long ec_mask; /* bit mask for ec_xxx functions */
int state; /* physical cpu state */
u32 status; /* last status received via sigp */
u16 address; /* physical cpu address */
};
@ -99,7 +98,7 @@ static inline int __pcpu_sigp_relax(u16 addr, u8 order, u32 parm, u32 *status)
int cc;
while (1) {
cc = __pcpu_sigp(addr, order, parm, status);
cc = __pcpu_sigp(addr, order, parm, NULL);
if (cc != SIGP_CC_BUSY)
return cc;
cpu_relax();
@ -111,7 +110,7 @@ static int pcpu_sigp_retry(struct pcpu *pcpu, u8 order, u32 parm)
int cc, retry;
for (retry = 0; ; retry++) {
cc = __pcpu_sigp(pcpu->address, order, parm, &pcpu->status);
cc = __pcpu_sigp(pcpu->address, order, parm, NULL);
if (cc != SIGP_CC_BUSY)
break;
if (retry >= 3)
@ -122,16 +121,18 @@ static int pcpu_sigp_retry(struct pcpu *pcpu, u8 order, u32 parm)
static inline int pcpu_stopped(struct pcpu *pcpu)
{
u32 status;
if (__pcpu_sigp(pcpu->address, SIGP_SENSE,
0, &pcpu->status) != SIGP_CC_STATUS_STORED)
0, &status) != SIGP_CC_STATUS_STORED)
return 0;
return !!(pcpu->status & (SIGP_STATUS_CHECK_STOP|SIGP_STATUS_STOPPED));
return !!(status & (SIGP_STATUS_CHECK_STOP|SIGP_STATUS_STOPPED));
}
static inline int pcpu_running(struct pcpu *pcpu)
{
if (__pcpu_sigp(pcpu->address, SIGP_SENSE_RUNNING,
0, &pcpu->status) != SIGP_CC_STATUS_STORED)
0, NULL) != SIGP_CC_STATUS_STORED)
return 1;
/* Status stored condition code is equivalent to cpu not running. */
return 0;