s390/smp: perform initial CPU reset also for SMT siblings

commit b5e438ebd7e808d1d2435159ac4742e01a94b8da upstream.

Not resetting the SMT siblings might leave them in unpredictable
state. One of the observed problems was that the CPU timer wasn't
reset and therefore large system time values where accounted during
CPU bringup.

Cc: <stable@kernel.org> # 4.0
Fixes: 10ad34bc76dfb ("s390: add SMT support")
Reviewed-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Sven Schnelle <svens@linux.ibm.com>
Signed-off-by: Heiko Carstens <hca@linux.ibm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 808f4fbe869e7bc59fed410fbf12b05721e18a3a..40946c8587a5418d35c59272eae3717cb23e146a 100644 (file)
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -864,24 +864,12 @@ static void smp_start_secondary(void *cpuvoid)
 /* Upping and downing of CPUs */
 int __cpu_up(unsigned int cpu, struct task_struct *tidle)
 {
-       struct pcpu *pcpu;
-       int base, i, rc;
+       struct pcpu *pcpu = pcpu_devices + cpu;
+       int rc;
 
-       pcpu = pcpu_devices + cpu;
        if (pcpu->state != CPU_STATE_CONFIGURED)
                return -EIO;
-       base = smp_get_base_cpu(cpu);
-       for (i = 0; i <= smp_cpu_mtid; i++) {
-               if (base + i < nr_cpu_ids)
-                       if (cpu_online(base + i))
-                               break;
-       }
-       /*
-        * If this is the first CPU of the core to get online
-        * do an initial CPU reset.
-        */
-       if (i > smp_cpu_mtid &&
-           pcpu_sigp_retry(pcpu_devices + base, SIGP_INITIAL_CPU_RESET, 0) !=
+       if (pcpu_sigp_retry(pcpu, SIGP_INITIAL_CPU_RESET, 0) !=
            SIGP_CC_ORDER_CODE_ACCEPTED)
                return -EIO;