s390/smp: avoid concurrent write to sigp status field

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>

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 87be1024d91b7eb31defdaa235b90cb7f90a6908..c88fe8569e62e35f8db5550f71b16e8227ca0224 100644 (file)
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -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;