Re: [PATCH 2/3] kernel/SRCU: provide a static initializer

[Lai Jiangshan <laijs@cn.fujitsu.com>]

On 04/12/2013 01:04 AM, Sebastian Andrzej Siewior wrote:
> * Lai Jiangshan | 2013-04-09 09:09:56 [+0800]:
> 
>> If the percpu array can be defined in __SRCU_STRUCT_INIT(),
>> I'm happy to expose it. but it is not currently.
> 
> I have no idea how to achieve this.
> 
>> Why crypto can't use boot time initialization?
> 
> It would require something like this:
> --- linux-stable.orig/crypto/Kconfig
> +++ linux-stable/crypto/Kconfig
> @@ -13,7 +13,7 @@ source "crypto/async_tx/Kconfig"
>  # Cryptographic API Configuration
>  #
>  menuconfig CRYPTO
> -       tristate "Cryptographic API"
> +       bool "Cryptographic API"
>         help
>           This option provides the core Cryptographic API.

Why convert to "bool"?
srcu_init_notifier_head() can be called in module-load-time.

> 
> --- linux-stable.orig/crypto/api.c
> +++ linux-stable/crypto/api.c
> @@ -34,6 +34,13 @@ EXPORT_SYMBOL_GPL(crypto_alg_sem);
>  struct srcu_notifier_head crypto_chain;
>  EXPORT_SYMBOL_GPL(crypto_chain);
> 
> +static int __init crypto_api_init(void)
> +{
> +       srcu_init_notifier_head(&crypto_chain);
> +       return 0;
> +}
> +core_initcall(crypto_api_init);
> +
>  static inline struct crypto_alg *crypto_alg_get(struct crypto_alg *alg)
>  {
>         atomic_inc(&alg->cra_refcnt);

And again, why crypto can't use boot time nor module-load-time initialization?

> 
> and there is no need for this.
> 
>>> Do you have any idea how I could get it done without this? Do you want
>>> to move/merge header files?
>>
>> if crypto has to use static initialization, I will find out some way
>> or use your patch.
> 
> The crypto would like this:
> 
> Subject: crypto: Convert crypto notifier chain to SRCU
> From: Peter Zijlstra <peterz@infradead.org>
> Date: Fri, 05 Oct 2012 09:03:24 +0100
> 
> The crypto notifier deadlocks on RT. Though this can be a real deadlock
> on mainline as well due to fifo fair rwsems.
> 
> The involved parties here are:
> 
> [   82.172678] swapper/0       S 0000000000000001     0     1      0 0x00000000
> [   82.172682]  ffff88042f18fcf0 0000000000000046 ffff88042f18fc80 ffffffff81491238
> [   82.172685]  0000000000011cc0 0000000000011cc0 ffff88042f18c040 ffff88042f18ffd8
> [   82.172688]  0000000000011cc0 0000000000011cc0 ffff88042f18ffd8 0000000000011cc0
> [   82.172689] Call Trace:
> [   82.172697]  [<ffffffff81491238>] ? _raw_spin_unlock_irqrestore+0x6c/0x7a
> [   82.172701]  [<ffffffff8148fd3f>] schedule+0x64/0x66
> [   82.172704]  [<ffffffff8148ec6b>] schedule_timeout+0x27/0xd0
> [   82.172708]  [<ffffffff81043c0c>] ? unpin_current_cpu+0x1a/0x6c
> [   82.172713]  [<ffffffff8106e491>] ? migrate_enable+0x12f/0x141
> [   82.172716]  [<ffffffff8148fbbd>] wait_for_common+0xbb/0x11f
> [   82.172719]  [<ffffffff810709f2>] ? try_to_wake_up+0x182/0x182
> [   82.172722]  [<ffffffff8148fc96>] wait_for_completion_interruptible+0x1d/0x2e
> [   82.172726]  [<ffffffff811debfd>] crypto_wait_for_test+0x49/0x6b
> [   82.172728]  [<ffffffff811ded32>] crypto_register_alg+0x53/0x5a
> [   82.172730]  [<ffffffff811ded6c>] crypto_register_algs+0x33/0x72
> [   82.172734]  [<ffffffff81ad7686>] ? aes_init+0x12/0x12
> [   82.172737]  [<ffffffff81ad76ea>] aesni_init+0x64/0x66
> [   82.172741]  [<ffffffff81000318>] do_one_initcall+0x7f/0x13b
> [   82.172744]  [<ffffffff81ac4d34>] kernel_init+0x199/0x22c
> [   82.172747]  [<ffffffff81ac44ef>] ? loglevel+0x31/0x31
> [   82.172752]  [<ffffffff814987c4>] kernel_thread_helper+0x4/0x10
> [   82.172755]  [<ffffffff81491574>] ? retint_restore_args+0x13/0x13
> [   82.172759]  [<ffffffff81ac4b9b>] ? start_kernel+0x3ca/0x3ca
> [   82.172761]  [<ffffffff814987c0>] ? gs_change+0x13/0x13
> 
> [   82.174186] cryptomgr_test  S 0000000000000001     0    41      2 0x00000000
> [   82.174189]  ffff88042c971980 0000000000000046 ffffffff81d74830 0000000000000292
> [   82.174192]  0000000000011cc0 0000000000011cc0 ffff88042c96eb80 ffff88042c971fd8
> [   82.174195]  0000000000011cc0 0000000000011cc0 ffff88042c971fd8 0000000000011cc0
> [   82.174195] Call Trace:
> [   82.174198]  [<ffffffff8148fd3f>] schedule+0x64/0x66
> [   82.174201]  [<ffffffff8148ec6b>] schedule_timeout+0x27/0xd0
> [   82.174204]  [<ffffffff81043c0c>] ? unpin_current_cpu+0x1a/0x6c
> [   82.174206]  [<ffffffff8106e491>] ? migrate_enable+0x12f/0x141
> [   82.174209]  [<ffffffff8148fbbd>] wait_for_common+0xbb/0x11f
> [   82.174212]  [<ffffffff810709f2>] ? try_to_wake_up+0x182/0x182
> [   82.174215]  [<ffffffff8148fc96>] wait_for_completion_interruptible+0x1d/0x2e
> [   82.174218]  [<ffffffff811e4883>] cryptomgr_notify+0x280/0x385
> [   82.174221]  [<ffffffff814943de>] notifier_call_chain+0x6b/0x98
> [   82.174224]  [<ffffffff8108a11c>] ? rt_down_read+0x10/0x12
> [   82.174227]  [<ffffffff810677cd>] __blocking_notifier_call_chain+0x70/0x8d
> [   82.174230]  [<ffffffff810677fe>] blocking_notifier_call_chain+0x14/0x16
> [   82.174234]  [<ffffffff811dd272>] crypto_probing_notify+0x24/0x50
> [   82.174236]  [<ffffffff811dd7a1>] crypto_alg_mod_lookup+0x3e/0x74
> [   82.174238]  [<ffffffff811dd949>] crypto_alloc_base+0x36/0x8f
> [   82.174241]  [<ffffffff811e9408>] cryptd_alloc_ablkcipher+0x6e/0xb5
> [   82.174243]  [<ffffffff811dd591>] ? kzalloc.clone.5+0xe/0x10
> [   82.174246]  [<ffffffff8103085d>] ablk_init_common+0x1d/0x38
> [   82.174249]  [<ffffffff8103852a>] ablk_ecb_init+0x15/0x17
> [   82.174251]  [<ffffffff811dd8c6>] __crypto_alloc_tfm+0xc7/0x114
> [   82.174254]  [<ffffffff811e0caa>] ? crypto_lookup_skcipher+0x1f/0xe4
> [   82.174256]  [<ffffffff811e0dcf>] crypto_alloc_ablkcipher+0x60/0xa5
> [   82.174258]  [<ffffffff811e5bde>] alg_test_skcipher+0x24/0x9b
> [   82.174261]  [<ffffffff8106d96d>] ? finish_task_switch+0x3f/0xfa
> [   82.174263]  [<ffffffff811e6b8e>] alg_test+0x16f/0x1d7
> [   82.174267]  [<ffffffff811e45ac>] ? cryptomgr_probe+0xac/0xac
> [   82.174269]  [<ffffffff811e45d8>] cryptomgr_test+0x2c/0x47
> [   82.174272]  [<ffffffff81061161>] kthread+0x7e/0x86
> [   82.174275]  [<ffffffff8106d9dd>] ? finish_task_switch+0xaf/0xfa
> [   82.174278]  [<ffffffff814987c4>] kernel_thread_helper+0x4/0x10
> [   82.174281]  [<ffffffff81491574>] ? retint_restore_args+0x13/0x13
> [   82.174284]  [<ffffffff810610e3>] ? __init_kthread_worker+0x8c/0x8c
> [   82.174287]  [<ffffffff814987c0>] ? gs_change+0x13/0x13
> 
> [   82.174329] cryptomgr_probe D 0000000000000002     0    47      2 0x00000000
> [   82.174332]  ffff88042c991b70 0000000000000046 ffff88042c991bb0 0000000000000006
> [   82.174335]  0000000000011cc0 0000000000011cc0 ffff88042c98ed00 ffff88042c991fd8
> [   82.174338]  0000000000011cc0 0000000000011cc0 ffff88042c991fd8 0000000000011cc0
> [   82.174338] Call Trace:
> [   82.174342]  [<ffffffff8148fd3f>] schedule+0x64/0x66
> [   82.174344]  [<ffffffff814901ad>] __rt_mutex_slowlock+0x85/0xbe
> [   82.174347]  [<ffffffff814902d2>] rt_mutex_slowlock+0xec/0x159
> [   82.174351]  [<ffffffff81089c4d>] rt_mutex_fastlock.clone.8+0x29/0x2f
> [   82.174353]  [<ffffffff81490372>] rt_mutex_lock+0x33/0x37
> [   82.174356]  [<ffffffff8108a0f2>] __rt_down_read+0x50/0x5a
> [   82.174358]  [<ffffffff8108a11c>] ? rt_down_read+0x10/0x12
> [   82.174360]  [<ffffffff8108a11c>] rt_down_read+0x10/0x12
> [   82.174363]  [<ffffffff810677b5>] __blocking_notifier_call_chain+0x58/0x8d
> [   82.174366]  [<ffffffff810677fe>] blocking_notifier_call_chain+0x14/0x16
> [   82.174369]  [<ffffffff811dd272>] crypto_probing_notify+0x24/0x50
> [   82.174372]  [<ffffffff811debd6>] crypto_wait_for_test+0x22/0x6b
> [   82.174374]  [<ffffffff811decd3>] crypto_register_instance+0xb4/0xc0
> [   82.174377]  [<ffffffff811e9b76>] cryptd_create+0x378/0x3b6
> [   82.174379]  [<ffffffff811de512>] ? __crypto_lookup_template+0x5b/0x63
> [   82.174382]  [<ffffffff811e4545>] cryptomgr_probe+0x45/0xac
> [   82.174385]  [<ffffffff811e4500>] ? crypto_alloc_pcomp+0x1b/0x1b
> [   82.174388]  [<ffffffff81061161>] kthread+0x7e/0x86
> [   82.174391]  [<ffffffff8106d9dd>] ? finish_task_switch+0xaf/0xfa
> [   82.174394]  [<ffffffff814987c4>] kernel_thread_helper+0x4/0x10
> [   82.174398]  [<ffffffff81491574>] ? retint_restore_args+0x13/0x13
> [   82.174401]  [<ffffffff810610e3>] ? __init_kthread_worker+0x8c/0x8c
> [   82.174403]  [<ffffffff814987c0>] ? gs_change+0x13/0x13
> 
> cryptomgr_test spawns the cryptomgr_probe thread from the notifier
> call. The probe thread fires the same notifier as the test thread and
> deadlocks on the rwsem on RT.
> 
> Now this is a potential deadlock in mainline as well, because we have
> fifo fair rwsems. If another thread blocks with a down_write() on the
> notifier chain before the probe thread issues the down_read() it will
> block the probe thread and the whole party is dead locked.
> 
> Signed-off-by: Peter Zijlstra <peterz@infradead.org>
> Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> ---
>  crypto/algapi.c   |    4 ++--
>  crypto/api.c      |    6 +++---
>  crypto/internal.h |    4 ++--
>  3 files changed, 7 insertions(+), 7 deletions(-)
> 
> --- a/crypto/algapi.c
> +++ b/crypto/algapi.c
> @@ -683,13 +683,13 @@ EXPORT_SYMBOL_GPL(crypto_spawn_tfm2);
>  
>  int crypto_register_notifier(struct notifier_block *nb)
>  {
> -	return blocking_notifier_chain_register(&crypto_chain, nb);
> +	return srcu_notifier_chain_register(&crypto_chain, nb);
>  }
>  EXPORT_SYMBOL_GPL(crypto_register_notifier);
>  
>  int crypto_unregister_notifier(struct notifier_block *nb)
>  {
> -	return blocking_notifier_chain_unregister(&crypto_chain, nb);
> +	return srcu_notifier_chain_unregister(&crypto_chain, nb);
>  }
>  EXPORT_SYMBOL_GPL(crypto_unregister_notifier);
>  
> --- a/crypto/api.c
> +++ b/crypto/api.c
> @@ -31,7 +31,7 @@ EXPORT_SYMBOL_GPL(crypto_alg_list);
>  DECLARE_RWSEM(crypto_alg_sem);
>  EXPORT_SYMBOL_GPL(crypto_alg_sem);
>  
> -BLOCKING_NOTIFIER_HEAD(crypto_chain);
> +SRCU_NOTIFIER_HEAD(crypto_chain);
>  EXPORT_SYMBOL_GPL(crypto_chain);
>  
>  static inline struct crypto_alg *crypto_alg_get(struct crypto_alg *alg)
> @@ -237,10 +237,10 @@ int crypto_probing_notify(unsigned long
>  {
>  	int ok;
>  
> -	ok = blocking_notifier_call_chain(&crypto_chain, val, v);
> +	ok = srcu_notifier_call_chain(&crypto_chain, val, v);
>  	if (ok == NOTIFY_DONE) {
>  		request_module("cryptomgr");
> -		ok = blocking_notifier_call_chain(&crypto_chain, val, v);
> +		ok = srcu_notifier_call_chain(&crypto_chain, val, v);
>  	}
>  
>  	return ok;
> --- a/crypto/internal.h
> +++ b/crypto/internal.h
> @@ -48,7 +48,7 @@ struct crypto_larval {
>  
>  extern struct list_head crypto_alg_list;
>  extern struct rw_semaphore crypto_alg_sem;
> -extern struct blocking_notifier_head crypto_chain;
> +extern struct srcu_notifier_head crypto_chain;
>  
>  #ifdef CONFIG_PROC_FS
>  void __init crypto_init_proc(void);
> @@ -136,7 +136,7 @@ static inline int crypto_is_moribund(str
>  
>  static inline void crypto_notify(unsigned long val, void *v)
>  {
> -	blocking_notifier_call_chain(&crypto_chain, val, v);
> +	srcu_notifier_call_chain(&crypto_chain, val, v);
>  }
>  
>  #endif	/* _CRYPTO_INTERNAL_H */
> 
>> Thanks,
>> Lai
> 
> Sebastian
>