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Message-ID: <20120603082507.GA16829@zhy>
Date: Sun, 3 Jun 2012 16:25:07 +0800
From: Yong Zhang <yong.zhang0@...il.com>
To: "Srivatsa S. Bhat" <srivatsa.bhat@...ux.vnet.ibm.com>
Cc: tglx@...utronix.de, peterz@...radead.org,
paulmck@...ux.vnet.ibm.com, rusty@...tcorp.com.au,
mingo@...nel.org, akpm@...ux-foundation.org,
vatsa@...ux.vnet.ibm.com, rjw@...k.pl, linux-arch@...r.kernel.org,
linux-kernel@...r.kernel.org, nikunj@...ux.vnet.ibm.com,
Ralf Baechle <ralf@...ux-mips.org>,
Eric Dumazet <eric.dumazet@...il.com>,
Mike Frysinger <vapier@...too.org>,
David Howells <dhowells@...hat.com>,
Arun Sharma <asharma@...com>, linux-mips@...ux-mips.org
Subject: Re: [PATCH 10/27] mips, smpboot: Use generic SMP booting
infrastructure
On Fri, Jun 01, 2012 at 02:42:32PM +0530, Srivatsa S. Bhat wrote:
> Convert mips to use the generic framework to boot secondary CPUs.
>
> Notes:
> 1. The boot processor was setting the secondary cpu in cpu_online_mask!
> Instead, leave it up to the secondary cpu (... and it will be done by the
> generic code now).
>
> 2. Make the boot cpu wait for the secondary cpu to be set in cpu_online_mask
> before returning.
We don't need to wait for both cpu_callin_map (The code above yours)
any more.
>
> 3. Don't enable interrupts in cmp_smp_finish() and vsmp_smp_finish().
> Do it much later, in generic code.
Hmmm... the bad thing is that some board enable irq more early than
->smp_finish(), I have sent patches for that (by moving irq enable
to smp_finish() and delaying smp_finish()).
Please check patch#0001~patch#0004 in
http://marc.info/?l=linux-mips&m=133758022710973&w=2
>
> 4. In synchronise_count_slave(), use local_save_flags() instead of
> local_irq_save() because irqs are still disabled.
We can just remove local_irq_save()/local_irq_restore() like:
http://marc.info/?l=linux-mips&m=133758046211043&w=2
Thanks,
Yong
>
> Cc: Ralf Baechle <ralf@...ux-mips.org>
> Cc: Andrew Morton <akpm@...ux-foundation.org>
> Cc: Eric Dumazet <eric.dumazet@...il.com>
> Cc: Mike Frysinger <vapier@...too.org>
> Cc: David Howells <dhowells@...hat.com>
> Cc: Arun Sharma <asharma@...com>
> Cc: Thomas Gleixner <tglx@...utronix.de>
> Cc: Rusty Russell <rusty@...tcorp.com.au>
> Cc: linux-mips@...ux-mips.org
> Signed-off-by: Srivatsa S. Bhat <srivatsa.bhat@...ux.vnet.ibm.com>
> ---
>
> arch/mips/kernel/smp-cmp.c | 8 ++++----
> arch/mips/kernel/smp-mt.c | 2 --
> arch/mips/kernel/smp.c | 23 +++++++++++++++--------
> arch/mips/kernel/sync-r4k.c | 3 ++-
> 4 files changed, 21 insertions(+), 15 deletions(-)
>
> diff --git a/arch/mips/kernel/smp-cmp.c b/arch/mips/kernel/smp-cmp.c
> index e7e03ec..7ecd6db 100644
> --- a/arch/mips/kernel/smp-cmp.c
> +++ b/arch/mips/kernel/smp-cmp.c
> @@ -108,7 +108,9 @@ static void cmp_init_secondary(void)
>
> static void cmp_smp_finish(void)
> {
> - pr_debug("SMPCMP: CPU%d: %s\n", smp_processor_id(), __func__);
> + unsigned int cpu = smp_processor_id();
> +
> + pr_debug("SMPCMP: CPU%d: %s\n", cpu, __func__);
>
> /* CDFIXME: remove this? */
> write_c0_compare(read_c0_count() + (8 * mips_hpt_frequency / HZ));
> @@ -116,10 +118,8 @@ static void cmp_smp_finish(void)
> #ifdef CONFIG_MIPS_MT_FPAFF
> /* If we have an FPU, enroll ourselves in the FPU-full mask */
> if (cpu_has_fpu)
> - cpu_set(smp_processor_id(), mt_fpu_cpumask);
> + cpumask_set_cpu(cpu, &mt_fpu_cpumask);
> #endif /* CONFIG_MIPS_MT_FPAFF */
> -
> - local_irq_enable();
> }
>
> static void cmp_cpus_done(void)
> diff --git a/arch/mips/kernel/smp-mt.c b/arch/mips/kernel/smp-mt.c
> index ff17868..25f7b09 100644
> --- a/arch/mips/kernel/smp-mt.c
> +++ b/arch/mips/kernel/smp-mt.c
> @@ -171,8 +171,6 @@ static void __cpuinit vsmp_smp_finish(void)
> if (cpu_has_fpu)
> cpu_set(smp_processor_id(), mt_fpu_cpumask);
> #endif /* CONFIG_MIPS_MT_FPAFF */
> -
> - local_irq_enable();
> }
>
> static void vsmp_cpus_done(void)
> diff --git a/arch/mips/kernel/smp.c b/arch/mips/kernel/smp.c
> index 71a95f5..4453d4d 100644
> --- a/arch/mips/kernel/smp.c
> +++ b/arch/mips/kernel/smp.c
> @@ -33,6 +33,7 @@
> #include <linux/cpu.h>
> #include <linux/err.h>
> #include <linux/ftrace.h>
> +#include <linux/smpboot.h>
>
> #include <linux/atomic.h>
> #include <asm/cpu.h>
> @@ -98,8 +99,11 @@ __cpuinit void register_smp_ops(struct plat_smp_ops *ops)
> */
> asmlinkage __cpuinit void start_secondary(void)
> {
> - unsigned int cpu;
> + smpboot_start_secondary(NULL);
> +}
>
> +void __cpuinit __cpu_pre_starting(void *unused)
> +{
> #ifdef CONFIG_MIPS_MT_SMTC
> /* Only do cpu_probe for first TC of CPU */
> if ((read_c0_tcbind() & TCBIND_CURTC) == 0)
> @@ -116,20 +120,22 @@ asmlinkage __cpuinit void start_secondary(void)
> */
>
> calibrate_delay();
> - preempt_disable();
> - cpu = smp_processor_id();
> - cpu_data[cpu].udelay_val = loops_per_jiffy;
> + cpu_data[smp_processor_id()].udelay_val = loops_per_jiffy;
> +}
>
> - notify_cpu_starting(cpu);
> +void __cpuinit __cpu_pre_online(void *unused)
> +{
> + unsigned int cpu = smp_processor_id();
>
> mp_ops->smp_finish();
> set_cpu_sibling_map(cpu);
>
> cpu_set(cpu, cpu_callin_map);
> +}
>
> +void __cpuinit __cpu_post_online(void *unused)
> +{
> synchronise_count_slave();
> -
> - cpu_idle();
> }
>
> /*
> @@ -196,7 +202,8 @@ int __cpuinit __cpu_up(unsigned int cpu, struct task_struct *tidle)
> while (!cpu_isset(cpu, cpu_callin_map))
> udelay(100);
>
> - set_cpu_online(cpu, true);
> + while (!cpu_online(cpu))
> + udelay(100);
>
> return 0;
> }
> diff --git a/arch/mips/kernel/sync-r4k.c b/arch/mips/kernel/sync-r4k.c
> index 99f913c..7f43069 100644
> --- a/arch/mips/kernel/sync-r4k.c
> +++ b/arch/mips/kernel/sync-r4k.c
> @@ -46,7 +46,8 @@ void __cpuinit synchronise_count_master(void)
> printk(KERN_INFO "Synchronize counters across %u CPUs: ",
> num_online_cpus());
>
> - local_irq_save(flags);
> + /* IRQs are already disabled. So just save the flags */
> + local_save_flags(flags);
>
> /*
> * Notify the slaves that it's time to start
--
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