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

From: Lai Jiangshan
Date: Thu Apr 11 2013 - 22:53:38 EST

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In reply to: Sebastian Andrzej Siewior: "Re: [PATCH 2/3] kernel/SRCU: provide a static initializer"
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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@xxxxxxxxxxxxx>
> 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@xxxxxxxxxxxxx>
> Signed-off-by: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
> ---
> 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
>

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In reply to: Sebastian Andrzej Siewior: "Re: [PATCH 2/3] kernel/SRCU: provide a static initializer"
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