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>

1 files changed, 7 insertions, 6 deletions

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 87be1024d91b..c88fe8569e62 100644
--- 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;