[S390] Force PSW restart on online CPU

PSW restart can be triggered on offline CPUs. If this happens, currently
the PSW restart code fails, because functions like smp_processor_id()
do not work on offline CPUs. This patch fixes this as follows:

If PSW restart is triggered on an offline CPU, the PSW restart (sigp restart)
is done a second time on another CPU that is online and the old CPU is
stopped afterwards.

Signed-off-by: Michael Holzheu <holzheu@linux.vnet.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>

diff --git a/arch/s390/include/asm/smp.h b/arch/s390/include/asm/smp.h
index 045e009fc16443e1ed6816c6d2375abbbbeeae4b..ab47a69fdf071de639bf12914b83316488105d93 100644 (file)
--- a/arch/s390/include/asm/smp.h
+++ b/arch/s390/include/asm/smp.h
@@ -33,6 +33,7 @@ extern struct save_area *zfcpdump_save_areas[NR_CPUS + 1];
 extern void smp_switch_to_ipl_cpu(void (*func)(void *), void *);
 extern void smp_switch_to_cpu(void (*)(void *), void *, unsigned long sp,
                              int from, int to);
+extern void smp_restart_with_online_cpu(void);
 extern void smp_restart_cpu(void);
 
 /*
@@ -64,6 +65,10 @@ static inline void smp_switch_to_ipl_cpu(void (*func)(void *), void *data)
        func(data);
 }
 
+static inline void smp_restart_with_online_cpu(void)
+{
+}
+
 #define smp_vcpu_scheduled     (1)
 
 #endif /* CONFIG_SMP */

diff --git a/arch/s390/kernel/ipl.c b/arch/s390/kernel/ipl.c
index 48c710206366308270e70a846c268c9e5cc8ea9f..90769b4bc7f643063075fbde1f38566cd5f955fb 100644 (file)
--- a/arch/s390/kernel/ipl.c
+++ b/arch/s390/kernel/ipl.c
@@ -1738,6 +1738,7 @@ static struct kobj_attribute on_restart_attr =
 
 void do_restart(void)
 {
+       smp_restart_with_online_cpu();
        smp_send_stop();
        on_restart_trigger.action->fn(&on_restart_trigger);
        stop_run(&on_restart_trigger);

diff --git a/arch/s390/kernel/smp.c b/arch/s390/kernel/smp.c
index 6ab16ac64d294687b90815328f90060362abc8de..e4572601e91e0cf2d7f1d22103406b5761845399 100644 (file)
--- a/arch/s390/kernel/smp.c
+++ b/arch/s390/kernel/smp.c
@@ -97,6 +97,29 @@ static inline int cpu_stopped(int cpu)
        return raw_cpu_stopped(cpu_logical_map(cpu));
 }
 
+/*
+ * Ensure that PSW restart is done on an online CPU
+ */
+void smp_restart_with_online_cpu(void)
+{
+       int cpu;
+
+       for_each_online_cpu(cpu) {
+               if (stap() == __cpu_logical_map[cpu]) {
+                       /* We are online: Enable DAT again and return */
+                       __load_psw_mask(psw_kernel_bits & ~PSW_MASK_MCHECK);
+                       return;
+               }
+       }
+       /* We are not online: Do PSW restart on an online CPU */
+       while (sigp(cpu, sigp_restart) == sigp_busy)
+               cpu_relax();
+       /* And stop ourself */
+       while (raw_sigp(stap(), sigp_stop) == sigp_busy)
+               cpu_relax();
+       for (;;);
+}
+
 void smp_switch_to_ipl_cpu(void (*func)(void *), void *data)
 {
        struct _lowcore *lc, *current_lc;