Messages in this thread Patch in this message | | | From | HuKeping <> | Subject | [PATCH] ARM: kexec: Fix validating CPU hotplug support | Date | Sat, 25 Oct 2014 17:20:55 +0800 |
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Due to commit:2103f6cba61a8b8bea3fc1b63661d830a2125e76, there is a hotplug checking in machine_kexec_prepare(), but it will lead a failure when loading the crash-kernel in some cases.
Kexec utility can load the crash kernel by two ways: 1. kexec -l kernel-image --append=command-line-options --initrd=initrd-image 2. kexec -p kernel-image --append=command-line-options --initrd=initrd-image
In case #1, it's ok to do the hotplug checking things, for it will cut off cpus in _cpu_down() later when command "kexec -e" be sended, function _cpu_down() needs the support of cpu hotplug.
In case #2, it is no need to do the checking, because we actually do not shut the cpus down, but just keep them invoking cpu_relax(), the whole routing has no business with cpu cutting off. That means, even if the CONFIG_HOTPLUG_CPU was not selected, it can also load and reboot the crash-kernel successfully if we use "kexec -p ..." and then a crash came to trigger the kexec.
Prior to this patch, if the first kernel is not support the CPU hotplug, we can not use kexec utility.
Signed-off-by: Hu Keping <hukeping@huawei.com> --- arch/arm/kernel/machine_kexec.c | 18 +++++++++++++----- 1 file changed, 13 insertions(+), 5 deletions(-)
diff --git a/arch/arm/kernel/machine_kexec.c b/arch/arm/kernel/machine_kexec.c index 8cf0996..1e5620f 100644 --- a/arch/arm/kernel/machine_kexec.c +++ b/arch/arm/kernel/machine_kexec.c @@ -41,12 +41,20 @@ int machine_kexec_prepare(struct kimage *image) int i, err; /* - * Validate that if the current HW supports SMP, then the SW supports - * and implements CPU hotplug for the current HW. If not, we won't be - * able to kexec reliably, so fail the prepare operation. + * When it is a * crash * triggered the kexec, we do not really shut the + * cpus down but just let them keep invoking cpu_relax(), so there is no need + * to do the hotplug checking things. */ - if (num_possible_cpus() > 1 && !platform_can_cpu_hotplug()) - return -EINVAL; + if (image->type != KEXEC_TYPE_CRASH) + { + /* + * Validate that if the current HW supports SMP, then the SW supports + * and implements CPU hotplug for the current HW. If not, we won't be + * able to kexec reliably, so fail the prepare operation. + */ + if (num_possible_cpus() > 1 && !platform_can_cpu_hotplug()) + return -EINVAL; + } /* * No segment at default ATAGs address. try to locate -- 1.8.5.5
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