On 6/27/2025 8:30 AM, Huang, Kai wrote:
[...]
And I am not 100% sure whether this issue exists, since allowing CPU hotplug
during kexec doesn't seem reasonable to me at least on x86, despite it is
indeed enabled kernel_kexec() common code:
/*
* 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.
*/
cpu_hotplug_enable();
pr_notice("Starting new kernel\n");
machine_shutdown();
I tried to git blame to find clue but failed since the history is lost
during file move/renaming etc. I suspect it is for other ARCHs.
Had a check in git history, it's related to powerpc kexec code.
First, commit e8e5c2155b00 ("powerpc/kexec: Fix orphaned offline CPUs across kexec")
add the code to online each present CPU.
Later, commit011e4b02f1da (" powerpc, kexec: Fix "Processor X is stuck" issue
during kexec from ST mode") add the code in the common code kernel_kexec() to
enable hotplug to fix the stuck issue.
