From: Sven Schnelle svens@linux.ibm.com
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
--- arch/s390/kernel/smp.c | 18 +++--------------- 1 file changed, 3 insertions(+), 15 deletions(-)
--- a/arch/s390/kernel/smp.c +++ b/arch/s390/kernel/smp.c @@ -864,24 +864,12 @@ static void smp_start_secondary(void *cp /* 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;