The following identical code piece appears in both
migrate_to_reboot_cpu() and smp_shutdown_nonboot_cpus():
if (!cpu_online(primary_cpu))
primary_cpu = cpumask_first(cpu_online_mask);
Although the kexec-reboot task can get through a cpu_down() on its cpu,
this code looks a little confusing.
Make things straight forward by keep cpu hotplug disabled until
smp_shutdown_nonboot_cpus() holds cpu_add_remove_lock. By this way, the
rebooting cpu can keep unchanged.
Signed-off-by: Pingfan Liu <[email protected]>
Cc: Eric Biederman <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Valentin Schneider <[email protected]>
Cc: Vincent Donnefort <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Mark Rutland <[email protected]>
Cc: YueHaibing <[email protected]>
Cc: Baokun Li <[email protected]>
Cc: Randy Dunlap <[email protected]>
Cc: [email protected]
To: [email protected]
---
kernel/cpu.c | 16 ++++++++++------
kernel/kexec_core.c | 10 ++++------
2 files changed, 14 insertions(+), 12 deletions(-)
diff --git a/kernel/cpu.c b/kernel/cpu.c
index 407a2568f35e..bc687d59ca90 100644
--- a/kernel/cpu.c
+++ b/kernel/cpu.c
@@ -1227,20 +1227,24 @@ int remove_cpu(unsigned int cpu)
}
EXPORT_SYMBOL_GPL(remove_cpu);
+/* primary_cpu keeps unchanged after migrate_to_reboot_cpu() */
void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
{
unsigned int cpu;
int error;
+ /*
+ * Block other cpu hotplug event, so primary_cpu is always online if
+ * it is not touched by us
+ */
cpu_maps_update_begin();
-
/*
- * Make certain the cpu I'm about to reboot on is online.
- *
- * This is inline to what migrate_to_reboot_cpu() already do.
+ * migrate_to_reboot_cpu() disables CPU hotplug assuming that
+ * no further code needs to use CPU hotplug (which is true in
+ * the reboot case). However, the kexec path depends on using
+ * CPU hotplug again; so re-enable it here.
*/
- if (!cpu_online(primary_cpu))
- primary_cpu = cpumask_first(cpu_online_mask);
+ __cpu_hotplug_enable();
for_each_online_cpu(cpu) {
if (cpu == primary_cpu)
diff --git a/kernel/kexec_core.c b/kernel/kexec_core.c
index 68480f731192..db4fa6b174e3 100644
--- a/kernel/kexec_core.c
+++ b/kernel/kexec_core.c
@@ -1168,14 +1168,12 @@ int kernel_kexec(void)
kexec_in_progress = true;
kernel_restart_prepare("kexec reboot");
migrate_to_reboot_cpu();
-
/*
- * migrate_to_reboot_cpu() disables CPU hotplug assuming that
- * no further code needs to use CPU hotplug (which is true in
- * the reboot case). However, the kexec path depends on using
- * CPU hotplug again; so re-enable it here.
+ * migrate_to_reboot_cpu() disables CPU hotplug. If an arch
+ * relies on the cpu teardown to achieve reboot, it needs to
+ * re-enable CPU hotplug there.
*/
- cpu_hotplug_enable();
+
pr_notice("Starting new kernel\n");
machine_shutdown();
}
--
2.31.1
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