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Date:   Wed, 25 Oct 2017 12:26:07 +0800
From:   Dou Liyang <douly.fnst@...fujitsu.com>
To:     Juergen Gross <jgross@...e.com>, <linux-kernel@...r.kernel.org>,
        <x86@...nel.org>
CC:     <hpa@...or.com>, <tglx@...utronix.de>, <mingo@...hat.com>,
        <arnd@...db.de>, <peterz@...radead.org>
Subject: Re: [PATCH] paravirt/locks: avoid modifying static key before
 jump_label_init()

Hi Juergen,

At 10/23/2017 09:49 PM, Juergen Gross wrote:
> Don't try to set the static virt_spin_lock_key to a value before
> jump_label_init() has been called, as this will result in a WARN().
>
> Solve the problem by introducing a new lock_init() hook called after
> jump_label_init() instead of doing the call inside of
> smp_prepare_boot_cpu().
>
> Signed-off-by: Juergen Gross <jgross@...e.com>
> ---
> Based on kernel/git/tip/tip.git locking/core

I also found that WARN() in tip tree.

IMO, adding a hook in start_kernel() is not elegant. It will
affect other arches and increase the complexity of the system.

I like your original method.
So, I try to fix it by moving the native_pv_lock_init() from
  native_smp_prepare_boot_cpu() to native_smp_prepare_cpus().

I hope it's useful to you.

Thanks,
	dou.

==================<
diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
index aed1460..6b1335a 100644
--- a/arch/x86/kernel/smpboot.c
+++ b/arch/x86/kernel/smpboot.c
@@ -1323,6 +1323,8 @@ void __init native_smp_prepare_cpus(unsigned int 
max_cpus)
         pr_info("CPU0: ");
         print_cpu_info(&cpu_data(0));

+       native_pv_lock_init();
+
         uv_system_init();

         set_mtrr_aps_delayed_init();
@@ -1350,7 +1352,6 @@ void __init native_smp_prepare_boot_cpu(void)
         /* already set me in cpu_online_mask in boot_cpu_init() */
         cpumask_set_cpu(me, cpu_callout_mask);
         cpu_set_state_online(me);
-       native_pv_lock_init();
  }

  void __init native_smp_cpus_done(unsigned int max_cpus)
diff --git a/arch/x86/xen/smp_pv.c b/arch/x86/xen/smp_pv.c
index 5147140..570b2bc 100644
--- a/arch/x86/xen/smp_pv.c
+++ b/arch/x86/xen/smp_pv.c
@@ -236,6 +236,8 @@ static void __init xen_pv_smp_prepare_cpus(unsigned 
int max_cpus)
                 xen_raw_printk(m);
                 panic(m);
         }
+       native_pv_lock_init();
+
         xen_init_lock_cpu(0);

         smp_store_boot_cpu_info();
> ---
>  arch/x86/include/asm/qspinlock.h | 5 +----
>  arch/x86/kernel/smpboot.c        | 1 -
>  include/asm-generic/qspinlock.h  | 6 ++++++
>  include/linux/spinlock.h         | 4 ++++
>  include/linux/spinlock_up.h      | 4 ++++
>  init/main.c                      | 2 ++
>  kernel/locking/spinlock.c        | 7 +++++++
>  7 files changed, 24 insertions(+), 5 deletions(-)
>
> diff --git a/arch/x86/include/asm/qspinlock.h b/arch/x86/include/asm/qspinlock.h
> index 308dfd0714c7..a53ef9ed0dc1 100644
> --- a/arch/x86/include/asm/qspinlock.h
> +++ b/arch/x86/include/asm/qspinlock.h
> @@ -49,6 +49,7 @@ static inline void queued_spin_unlock(struct qspinlock *lock)
>  #ifdef CONFIG_PARAVIRT
>  DECLARE_STATIC_KEY_TRUE(virt_spin_lock_key);
>
> +#define native_pv_lock_init native_pv_lock_init
>  void native_pv_lock_init(void) __init;
>
>  #define virt_spin_lock virt_spin_lock
> @@ -70,10 +71,6 @@ static inline bool virt_spin_lock(struct qspinlock *lock)
>
>  	return true;
>  }
> -#else
> -static inline void native_pv_lock_init(void)
> -{
> -}
>  #endif /* CONFIG_PARAVIRT */
>
>  #include <asm-generic/qspinlock.h>
> diff --git a/arch/x86/kernel/smpboot.c b/arch/x86/kernel/smpboot.c
> index 361f91674ce5..55a3121dd479 100644
> --- a/arch/x86/kernel/smpboot.c
> +++ b/arch/x86/kernel/smpboot.c
> @@ -1385,7 +1385,6 @@ void __init native_smp_prepare_boot_cpu(void)
>  	/* already set me in cpu_online_mask in boot_cpu_init() */
>  	cpumask_set_cpu(me, cpu_callout_mask);
>  	cpu_set_state_online(me);
> -	native_pv_lock_init();
>  }
>
>  void __init native_smp_cpus_done(unsigned int max_cpus)
> diff --git a/include/asm-generic/qspinlock.h b/include/asm-generic/qspinlock.h
> index 66260777d644..42784a353401 100644
> --- a/include/asm-generic/qspinlock.h
> +++ b/include/asm-generic/qspinlock.h
> @@ -111,6 +111,12 @@ static __always_inline bool virt_spin_lock(struct qspinlock *lock)
>  }
>  #endif
>
> +#ifndef native_pv_lock_init
> +static __always_inline void native_pv_lock_init(void)
> +{
> +}
> +#endif
> +
>  /*
>   * Remapping spinlock architecture specific functions to the corresponding
>   * queued spinlock functions.
> diff --git a/include/linux/spinlock.h b/include/linux/spinlock.h
> index 69e079c5ff98..6654ff285e5c 100644
> --- a/include/linux/spinlock.h
> +++ b/include/linux/spinlock.h
> @@ -420,4 +420,8 @@ extern int _atomic_dec_and_lock(atomic_t *atomic, spinlock_t *lock);
>  #define atomic_dec_and_lock(atomic, lock) \
>  		__cond_lock(lock, _atomic_dec_and_lock(atomic, lock))
>
> +#ifdef CONFIG_SMP
> +void lock_init(void) __init;
> +#endif
> +
>  #endif /* __LINUX_SPINLOCK_H */
> diff --git a/include/linux/spinlock_up.h b/include/linux/spinlock_up.h
> index 612fb530af41..bc4787900ad7 100644
> --- a/include/linux/spinlock_up.h
> +++ b/include/linux/spinlock_up.h
> @@ -80,4 +80,8 @@ static inline void arch_spin_unlock(arch_spinlock_t *lock)
>  #define arch_read_can_lock(lock)	(((void)(lock), 1))
>  #define arch_write_can_lock(lock)	(((void)(lock), 1))
>
> +static inline lock_init(void)
> +{
> +}
> +
>  #endif /* __LINUX_SPINLOCK_UP_H */
> diff --git a/init/main.c b/init/main.c
> index 0ee9c6866ada..e5c9f9bcd311 100644
> --- a/init/main.c
> +++ b/init/main.c
> @@ -88,6 +88,7 @@
>  #include <linux/io.h>
>  #include <linux/cache.h>
>  #include <linux/rodata_test.h>
> +#include <linux/spinlock.h>
>
>  #include <asm/io.h>
>  #include <asm/bugs.h>
> @@ -567,6 +568,7 @@ asmlinkage __visible void __init start_kernel(void)
>  	sort_main_extable();
>  	trap_init();
>  	mm_init();
> +	lock_init();
>
>  	ftrace_init();
>
> diff --git a/kernel/locking/spinlock.c b/kernel/locking/spinlock.c
> index 4b082b5cac9e..f086e444c2ac 100644
> --- a/kernel/locking/spinlock.c
> +++ b/kernel/locking/spinlock.c
> @@ -397,3 +397,10 @@ notrace int in_lock_functions(unsigned long addr)
>  	&& addr < (unsigned long)__lock_text_end;
>  }
>  EXPORT_SYMBOL(in_lock_functions);
> +
> +void __init lock_init(void)
> +{
> +#ifdef CONFIG_QUEUED_SPINLOCKS
> +	native_pv_lock_init();
> +#endif
> +}
>




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