linux-kernel - [PATCH RT] Revert "crypto: Convert crypto notifier chain to SRCU"

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Date:   Fri, 27 Jul 2018 14:59:43 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     linux-rt-users@...r.kernel.org
Cc:     tglx@...utronix.de, rostedt@...dmis.org,
        Peter Zilstra <peterz@...radead.org>,
        linux-kernel@...r.kernel.org,
        Herbert Xu <herbert@...dor.apana.org.au>
Subject: [PATCH RT] Revert "crypto: Convert crypto notifier chain to SRCU"

This reverts commit Revert "crypto: Convert crypto notifier chain to
SRCU".
This is not longer required because the rwsem is now multi reader
capable on RT.
The other concern was a deadlock because the rwsem is fifo writer fair
in regard to incoming reader. This is currently not an issue because we
have only one crypto_register_notifier() user, which is invoked before
the reader (blocking_notifier_call_chain()) are coming.

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 crypto/algapi.c   | 4 ++--
 crypto/api.c      | 6 +++---
 crypto/internal.h | 4 ++--
 3 files changed, 7 insertions(+), 7 deletions(-)

diff --git a/crypto/algapi.c b/crypto/algapi.c
index 99ed1c74217f..395b082d03a9 100644
--- a/crypto/algapi.c
+++ b/crypto/algapi.c
@@ -726,13 +726,13 @@ EXPORT_SYMBOL_GPL(crypto_spawn_tfm2);
 
 int crypto_register_notifier(struct notifier_block *nb)
 {
-	return srcu_notifier_chain_register(&crypto_chain, nb);
+	return blocking_notifier_chain_register(&crypto_chain, nb);
 }
 EXPORT_SYMBOL_GPL(crypto_register_notifier);
 
 int crypto_unregister_notifier(struct notifier_block *nb)
 {
-	return srcu_notifier_chain_unregister(&crypto_chain, nb);
+	return blocking_notifier_chain_unregister(&crypto_chain, nb);
 }
 EXPORT_SYMBOL_GPL(crypto_unregister_notifier);
 
diff --git a/crypto/api.c b/crypto/api.c
index d4bbeba587f9..70a894e52ff3 100644
--- a/crypto/api.c
+++ b/crypto/api.c
@@ -32,7 +32,7 @@ EXPORT_SYMBOL_GPL(crypto_alg_list);
 DECLARE_RWSEM(crypto_alg_sem);
 EXPORT_SYMBOL_GPL(crypto_alg_sem);
 
-SRCU_NOTIFIER_HEAD(crypto_chain);
+BLOCKING_NOTIFIER_HEAD(crypto_chain);
 EXPORT_SYMBOL_GPL(crypto_chain);
 
 static struct crypto_alg *crypto_larval_wait(struct crypto_alg *alg);
@@ -237,10 +237,10 @@ int crypto_probing_notify(unsigned long val, void *v)
 {
 	int ok;
 
-	ok = srcu_notifier_call_chain(&crypto_chain, val, v);
+	ok = blocking_notifier_call_chain(&crypto_chain, val, v);
 	if (ok == NOTIFY_DONE) {
 		request_module("cryptomgr");
-		ok = srcu_notifier_call_chain(&crypto_chain, val, v);
+		ok = blocking_notifier_call_chain(&crypto_chain, val, v);
 	}
 
 	return ok;
diff --git a/crypto/internal.h b/crypto/internal.h
index 998a6af375d4..5ac27fba10e8 100644
--- a/crypto/internal.h
+++ b/crypto/internal.h
@@ -44,7 +44,7 @@ struct crypto_larval {
 
 extern struct list_head crypto_alg_list;
 extern struct rw_semaphore crypto_alg_sem;
-extern struct srcu_notifier_head crypto_chain;
+extern struct blocking_notifier_head crypto_chain;
 
 #ifdef CONFIG_PROC_FS
 void __init crypto_init_proc(void);
@@ -139,7 +139,7 @@ static inline int crypto_is_moribund(struct crypto_alg *alg)
 
 static inline void crypto_notify(unsigned long val, void *v)
 {
-	srcu_notifier_call_chain(&crypto_chain, val, v);
+	blocking_notifier_call_chain(&crypto_chain, val, v);
 }
 
 #endif	/* _CRYPTO_INTERNAL_H */
-- 
2.18.0