Messages in this thread | | | Subject | Re: [PATCH] MIPS: No need to check CPU 0 in {loongson3,bmips,octeon}_cpu_disable() | From | Tiezhu Yang <> | Date | Tue, 15 Dec 2020 12:10:31 +0800 |
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On 12/15/2020 11:26 AM, liwei (GF) wrote: > Hi, > > On 2020/11/25 18:11, Tiezhu Yang wrote: >> After commit 9cce844abf07 ("MIPS: CPU#0 is not hotpluggable"), > Why CPU#0 is not hotpluggable on MIPS? Does that unrealizable?
The early discussion is here: https://patchwork.kernel.org/project/linux-mips/patch/1594896024-16624-1-git-send-email-chenhc@lemote.com/
As Jiaxun said, it seems that this is a software limitation. I think the initial aim of commit 9cce844abf07 ("MIPS: CPU#0 is not hotpluggable") is to solve ltp test failure.
> >> c->hotpluggable is 0 for CPU 0 and it will not generate a control >> file in sysfs for this CPU: >> >> [root@linux loongson]# cat /sys/devices/system/cpu/cpu0/online >> cat: /sys/devices/system/cpu/cpu0/online: No such file or directory >> [root@linux loongson]# echo 0 > /sys/devices/system/cpu/cpu0/online >> bash: /sys/devices/system/cpu/cpu0/online: Permission denied >> >> So no need to check CPU 0 in {loongson3,bmips,octeon}_cpu_disable(), > missing cps_cpu_disable()?
Yes, thank you, let me send a patch to do it.
Thanks, Tiezhu
> > Thanks, > Wei > >> just remove them. >> >> Signed-off-by: Tiezhu Yang <yangtiezhu@loongson.cn> >> --- >> arch/mips/cavium-octeon/smp.c | 3 --- >> arch/mips/kernel/smp-bmips.c | 3 --- >> arch/mips/loongson64/smp.c | 3 --- >> 3 files changed, 9 deletions(-) >> >> diff --git a/arch/mips/cavium-octeon/smp.c b/arch/mips/cavium-octeon/smp.c >> index 076db9a..66ce552 100644 >> --- a/arch/mips/cavium-octeon/smp.c >> +++ b/arch/mips/cavium-octeon/smp.c >> @@ -290,9 +290,6 @@ static int octeon_cpu_disable(void) >> { >> unsigned int cpu = smp_processor_id(); >> >> - if (cpu == 0) >> - return -EBUSY; >> - >> if (!octeon_bootloader_entry_addr) >> return -ENOTSUPP; >> >> diff --git a/arch/mips/kernel/smp-bmips.c b/arch/mips/kernel/smp-bmips.c >> index 1dbfb5a..359b176 100644 >> --- a/arch/mips/kernel/smp-bmips.c >> +++ b/arch/mips/kernel/smp-bmips.c >> @@ -362,9 +362,6 @@ static int bmips_cpu_disable(void) >> { >> unsigned int cpu = smp_processor_id(); >> >> - if (cpu == 0) >> - return -EBUSY; >> - >> pr_info("SMP: CPU%d is offline\n", cpu); >> >> set_cpu_online(cpu, false); >> diff --git a/arch/mips/loongson64/smp.c b/arch/mips/loongson64/smp.c >> index aa0cd72..b8c1fc3 100644 >> --- a/arch/mips/loongson64/smp.c >> +++ b/arch/mips/loongson64/smp.c >> @@ -544,9 +544,6 @@ static int loongson3_cpu_disable(void) >> unsigned long flags; >> unsigned int cpu = smp_processor_id(); >> >> - if (cpu == 0) >> - return -EBUSY; >> - >> set_cpu_online(cpu, false); >> calculate_cpu_foreign_map(); >> local_irq_save(flags); >>
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