commit 8589b4e00e352f983259140f25a262d973be6bc5
author David Howells <dhowells@redhat.com> Thu Jun 23 22:00:53 2005 -0700
committer Linus Torvalds <torvalds@ppc970.osdl.org> Fri Jun 24 00:05:18 2005 -0700
tree d53c9b43ee0aaa2d7518a023c4b6373422117506
parent 7888e7ff4ee579442128d7d12a9c9dbf2cf7de6a

[PATCH] Keys: Use RCU to manage session keyring pointer

The attached patch uses RCU to manage the session keyring pointer in struct
signal_struct.  This means that searching need not disable interrupts and get
a the sighand spinlock to access this pointer.  Furthermore, by judicious use
of rcu_read_(un)lock(), this patch also avoids the need to take and put
refcounts on the session keyring itself, thus saving on even more atomic ops.

Signed-Off-By: David Howells <dhowells@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

security/keys/request_key.c

diff --git a/security/keys/request_key.c b/security/keys/request_key.c
index 1919540..54aa7b7 100644
--- a/security/keys/request_key.c
+++ b/security/keys/request_key.c
@@ -175,13 +175,12 @@
 	key->expiry = now.tv_sec + key_negative_timeout;
 
 	if (current->signal->session_keyring) {
-		unsigned long flags;
 		struct key *keyring;
 
-		spin_lock_irqsave(&current->sighand->siglock, flags);
-		keyring = current->signal->session_keyring;
+		rcu_read_lock();
+		keyring = rcu_dereference(current->signal->session_keyring);
 		atomic_inc(&keyring->usage);
-		spin_unlock_irqrestore(&current->sighand->siglock, flags);
+		rcu_read_unlock();
 
 		key_link(keyring, key);
 		key_put(keyring);