From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pingfan Liu Date: Tue, 25 Jan 2022 11:39:13 +0800 Subject: [PATCH] kexec: disable cpu hotplug until the rebooting cpu is stable Message-ID: <20220125033913.15374-1-kernelfans@gmail.com> List-Id: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: kexec@lists.infradead.org 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 Cc: Eric Biederman Cc: Peter Zijlstra Cc: Thomas Gleixner Cc: Valentin Schneider Cc: Vincent Donnefort Cc: Ingo Molnar Cc: Mark Rutland Cc: YueHaibing Cc: Baokun Li Cc: Randy Dunlap Cc: kexec at lists.infradead.org To: linux-kernel@vger.kernel.org --- 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