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 66d7ba61803c81899b6961d798a8417ecc6a8e65..659d99af91566de5229ecef142889a3cb7b14d9c 100644 (file)
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -885,24 +885,12 @@ static void __no_sanitize_address 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;