Re: [PATCH tip/core/rcu 02/20] x86: Use common outgoing-CPU-notification code

Paul E. McKenney
2015-03-05T22:00:52Z

On Thu, Mar 05, 2015 at 04:17:59PM -0500, Boris Ostrovsky wrote:
> On 03/04/2015 10:25 AM, Paul E. McKenney wrote:
> >On Wed, Mar 04, 2015 at 09:55:11AM -0500, Boris Ostrovsky wrote:
>
> >>The simple solution is to stop calling native_cpu_die() above but
> >>I'd like to use common code in native_cpu_die(). I'll see if I can
> >>carve it out without too much damage to x86.
> >
> >Very good, thank you! I look forward to seeing your patch.
>
> How about something like this, on top of your original 02/20 patch
> (this is copy-paste but hopefully it can be applied):

Unfortunately, no joy. :-(

I was able to fix a couple of whitespace problems, but it still didn't
like this hunk: "@@ -766,12 +778,6 @@".

Could you please send the patch as an attachment, post it on the web
somewhere, or otherwise get me a clean copy it it?

Thanx, Paul

> arch/x86/include/asm/smp.h | 1 +
> arch/x86/kernel/smpboot.c | 12 +++++++++++-
> arch/x86/xen/smp.c | 34 ++++++++++++++++++++--------------
> 3 files changed, 32 insertions(+), 15 deletions(-)
>
> diff --git a/arch/x86/include/asm/smp.h b/arch/x86/include/asm/smp.h
> index 8cd27e0..a5cb4f6 100644
> --- a/arch/x86/include/asm/smp.h
> +++ b/arch/x86/include/asm/smp.h
> @@ -155,6 +155,7 @@ void native_smp_prepare_cpus(unsigned int max_cpus);
> void native_smp_cpus_done(unsigned int max_cpus);
> int native_cpu_up(unsigned int cpunum, struct task_struct *tidle);
> int native_cpu_disable(void);
> +int common_cpu_die(unsigned int cpu);
> void native_cpu_die(unsigned int cpu);
> void native_play_dead(void);
> void play_dead_common(void);
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index ff24fbd..c8fa349 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -1345,8 +1345,10 @@ int native_cpu_disable(void)
> return 0;
> }
>
> -void native_cpu_die(unsigned int cpu)
> +int common_cpu_die(unsigned int cpu)
> {
> + int ret = 0;
> +
> /* We don't do anything here: idle task is faking death itself. */
>
> /* They ack this in play_dead() by setting CPU_DEAD */
> @@ -1355,7 +1357,15 @@ void native_cpu_die(unsigned int cpu)
> pr_info("CPU %u is now offline\n", cpu);
> } else {
> pr_err("CPU %u didn't die...\n", cpu);
> + ret = -1;
> }
> +
> + return ret;
> +}
> +
> +void native_cpu_die(unsigned int cpu)
> +{
> + common_cpu_die(cpu);
> }
>
> void play_dead_common(void)
> diff --git a/arch/x86/xen/smp.c b/arch/x86/xen/smp.c
> index e2c7389..1c5e760 100644
> --- a/arch/x86/xen/smp.c
> +++ b/arch/x86/xen/smp.c
> @@ -455,7 +455,10 @@ static int xen_cpu_up(unsigned int cpu, struct
> task_struct *idle)
> xen_setup_timer(cpu);
> xen_init_lock_cpu(cpu);
>
> - /* Xen outgoing CPUs need help cleaning up, so -EBUSY is an error. */
> + /*
> + * PV VCPUs are always successfully taken down (see 'while' loop
> + * in xen_cpu_die()), so -EBUSY is an error.
> + */
> rc = cpu_check_up_prepare(cpu);
> if (rc)
> return rc;
> @@ -508,12 +511,11 @@ static void xen_cpu_die(unsigned int cpu)
> schedule_timeout(HZ/10);
> }
>
> - (void)cpu_wait_death(cpu, 5);
> - /* FIXME: Are the below calls really safe in case of timeout? */
> -
> - xen_smp_intr_free(cpu);
> - xen_uninit_lock_cpu(cpu);
> - xen_teardown_timer(cpu);
> + if (common_cpu_die(cpu) == 0) {
> + xen_smp_intr_free(cpu);
> + xen_uninit_lock_cpu(cpu);
> + xen_teardown_timer(cpu);
> + }
> }
>
> static void xen_play_dead(void) /* used only with HOTPLUG_CPU */
> @@ -745,6 +747,16 @@ static void __init
> xen_hvm_smp_prepare_cpus(unsigned int max_cpus)
> static int xen_hvm_cpu_up(unsigned int cpu, struct task_struct *tidle)
> {
> int rc;
> +
> + /*
> + * This can happen if CPU was offlined earlier and
> + * offlining timed out in common_cpu_die().
> + */
> + if (cpu_report_state(cpu) == CPU_DEAD_FROZEN) {
> + xen_smp_intr_free(cpu);
> + xen_uninit_lock_cpu(cpu);
> + }
> +
> /*
> * xen_smp_intr_init() needs to run before native_cpu_up()
> * so that IPI vectors are set up on the booting CPU before
> @@ -766,12 +778,6 @@ static int xen_hvm_cpu_up(unsigned int cpu,
> struct task_struct *tidle)
> return rc;
> }
>
> -static void xen_hvm_cpu_die(unsigned int cpu)
> -{
> - xen_cpu_die(cpu);
> - native_cpu_die(cpu);
> -}
> -
> void __init xen_hvm_smp_init(void)
> {
> if (!xen_have_vector_callback)
> @@ -779,7 +785,7 @@ void __init xen_hvm_smp_init(void)
> smp_ops.smp_prepare_cpus = xen_hvm_smp_prepare_cpus;
> smp_ops.smp_send_reschedule = xen_smp_send_reschedule;
> smp_ops.cpu_up = xen_hvm_cpu_up;
> - smp_ops.cpu_die = xen_hvm_cpu_die;
> + smp_ops.cpu_die = xen_cpu_die;
> smp_ops.send_call_func_ipi = xen_smp_send_call_function_ipi;
> smp_ops.send_call_func_single_ipi =
> xen_smp_send_call_function_single_ipi;
> smp_ops.smp_prepare_boot_cpu = xen_smp_prepare_boot_cpu;
> --
> 1.7.7.6
>
>