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Date: Thu, 18 Sep 2014 16:36:41 +0800 From: Lan Tianyu <tianyu.lan@...el.com> To: ego@...ux.vnet.ibm.com CC: peterz@...radead.org, mingo@...nel.org, rafael.j.wysocki@...el.com, srivatsa@....edu, akpm@...ux-foundation.org, laijs@...fujitsu.com, toshi.kani@...com, todd.e.brandt@...ux.intel.com, wangyun@...ux.vnet.ibm.com, fabf@...net.be, linux@....linux.org.uk, oleg@...hat.com, srivatsa.bhat@...ux.vnet.ibm.com, linux-kernel@...r.kernel.org Subject: Re: [RFC PATCH V2] PM/CPU: Parallel enalbing nonboot cpus with resume devices On 2014年09月17日 17:03, Gautham R Shenoy wrote: > Hi Lan, > > Sorry missed this repost! Couple of comments. > Np, Thanks for review :) > On Fri, Aug 22, 2014 at 04:33:40PM +0800, Lan Tianyu wrote: > > [.. snip ..] >> >> +static int _cpu_up_with_trace(int cpu) >> +{ >> + int error; >> + >> + trace_suspend_resume(TPS("CPU_ON"), cpu, true); >> + error = _cpu_up(cpu, 1); >> + trace_suspend_resume(TPS("CPU_ON"), cpu, false); >> + if (error) { >> + pr_warn("Error taking CPU%d up: %d\n", cpu, error); >> + return error; >> + } >> + >> + pr_info("CPU%d is up\n", cpu); >> + return 0; >> +} >> + >> +static int async_enable_nonboot_cpus(void *data) >> +{ >> + int cpu; >> + >> + cpu_maps_update_begin(); >> + arch_enable_nonboot_cpus_begin(); >> + >> + for_each_cpu(cpu, frozen_cpus) { >> + _cpu_up_with_trace(cpu); >> + } >> + >> + arch_enable_nonboot_cpus_end(); >> + cpumask_clear(frozen_cpus); >> + cpu_maps_update_done(); >> + return 0; >> +} >> + >> void __ref enable_nonboot_cpus(void) >> { >> + struct task_struct *tsk; >> int cpu, error; >> >> /* Allow everyone to use the CPU hotplug again */ >> @@ -563,22 +597,34 @@ void __ref enable_nonboot_cpus(void) >> >> pr_info("Enabling non-boot CPUs ...\n"); >> >> - arch_enable_nonboot_cpus_begin(); >> + cpu = cpumask_first(frozen_cpus); >> + cpumask_clear_cpu(cpu, frozen_cpus); >> >> - for_each_cpu(cpu, frozen_cpus) { >> - trace_suspend_resume(TPS("CPU_ON"), cpu, true); >> - error = _cpu_up(cpu, 1); >> - trace_suspend_resume(TPS("CPU_ON"), cpu, false); >> - if (!error) { >> - pr_info("CPU%d is up\n", cpu); >> - continue; >> + error = _cpu_up_with_trace(cpu); > > If cpu fails to come up, you need to add a pr_warn() citing the > reason why it failed to come up. Ok. > > >> + if (cpumask_empty(frozen_cpus)) >> + goto out; >> + >> + if (error) { >> + /* >> + * If fail to bring up the first frozen cpus, >> + * enable the rest frozen cpus on the boot cpu. >> + */ >> + arch_enable_nonboot_cpus_begin(); >> + for_each_cpu(cpu, frozen_cpus) { >> + _cpu_up_with_trace(cpu); >> } >> - pr_warn("Error taking CPU%d up: %d\n", cpu, error); >> - } >> + arch_enable_nonboot_cpus_end(); >> >> - arch_enable_nonboot_cpus_end(); >> + } else { >> + tsk = kthread_create_on_cpu(async_enable_nonboot_cpus, >> + NULL, cpu, "async-enable-nonboot-cpus"); >> + if (IS_ERR(tsk)) { >> + pr_err("Failed to create async enable nonboot cpus thread.\n"); >> + goto out; > > ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ This is not good. If you fail to > create a kthread on the first non-boot cpu, that means none of the > other non-boot cpus will be brought up. > > Hence you might want to consider reordering the code in such a manner > that if the first non-boot cpu fails to come up or if you fail to > create the kthread task, then the boot cpu will boot the remaining non > boot cpus. Yes, this sounds good and will do it in the new version. > > -- > Thanks and Regards > gautham. > -- Best regards Tianyu Lan -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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