[PATCH RT 02/13] random: avoid preempt_disable()ed section

[Steven Rostedt]

3.18.91-rt98-rc1 stable review patch.
If anyone has any objections, please let me know.

------------------

From: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>

extract_crng() will use sleeping locks while in a preempt_disable()
section due to get_cpu_var().
Work around it with local_locks.

Cc: stable-rt@xxxxxxxxxxxxxxx # where it applies to
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Signed-off-by: Steven Rostedt (VMware) <rostedt@xxxxxxxxxxx>
---
 drivers/char/random.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index acb8e7c218d1..06c4b06fcea0 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -260,6 +260,7 @@
 #include <linux/irq.h>
 #include <linux/syscalls.h>
 #include <linux/completion.h>
+#include <linux/locallock.h>
 
 #include <asm/processor.h>
 #include <asm/uaccess.h>
@@ -1712,6 +1713,7 @@ int random_int_secret_init(void)
 
 static DEFINE_PER_CPU(__u32 [MD5_DIGEST_WORDS], get_random_int_hash)
 		__aligned(sizeof(unsigned long));
+static DEFINE_LOCAL_IRQ_LOCK(hash_entropy_int_lock);
 
 /*
  * Get a random word for internal kernel use only. Similar to urandom but
@@ -1727,12 +1729,12 @@ unsigned int get_random_int(void)
 	if (arch_get_random_int(&ret))
 		return ret;
 
-	hash = get_cpu_var(get_random_int_hash);
+	hash = get_locked_var(hash_entropy_int_lock, get_random_int_hash);
 
 	hash[0] += current->pid + jiffies + random_get_entropy();
 	md5_transform(hash, random_int_secret);
 	ret = hash[0];
-	put_cpu_var(get_random_int_hash);
+	put_locked_var(hash_entropy_int_lock, get_random_int_hash);
 
 	return ret;
 }
@@ -1749,12 +1751,12 @@ unsigned long get_random_long(void)
 	if (arch_get_random_long(&ret))
 		return ret;
 
-	hash = get_cpu_var(get_random_int_hash);
+	hash = get_locked_var(hash_entropy_int_lock, get_random_int_hash);
 
 	hash[0] += current->pid + jiffies + random_get_entropy();
 	md5_transform(hash, random_int_secret);
 	ret = *(unsigned long *)hash;
-	put_cpu_var(get_random_int_hash);
+	put_locked_var(hash_entropy_int_lock, get_random_int_hash);
 
 	return ret;
 }
-- 
2.13.2