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

From: Sebastian Sewior
Date: Fri May 12 2017 - 12:04:10 EST


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

Signed-off-by: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
---
drivers/char/random.c | 12 ++++++++----
1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index ec886dda1b21..25ee319dc8e3 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -262,6 +262,7 @@
#include <linux/syscalls.h>
#include <linux/completion.h>
#include <linux/uuid.h>
+#include <linux/locallock.h>
#include <crypto/chacha20.h>

#include <asm/processor.h>
@@ -2052,6 +2053,7 @@ struct batched_entropy {
* goal of being quite fast and not depleting entropy.
*/
static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_long);
+static DEFINE_LOCAL_IRQ_LOCK(batched_entropy_long_lock);
unsigned long get_random_long(void)
{
unsigned long ret;
@@ -2060,13 +2062,13 @@ unsigned long get_random_long(void)
if (arch_get_random_long(&ret))
return ret;

- batch = &get_cpu_var(batched_entropy_long);
+ batch = &get_locked_var(batched_entropy_long_lock, batched_entropy_long);
if (batch->position % ARRAY_SIZE(batch->entropy_long) == 0) {
extract_crng((u8 *)batch->entropy_long);
batch->position = 0;
}
ret = batch->entropy_long[batch->position++];
- put_cpu_var(batched_entropy_long);
+ put_locked_var(batched_entropy_long_lock, batched_entropy_long);
return ret;
}
EXPORT_SYMBOL(get_random_long);
@@ -2078,6 +2080,8 @@ unsigned int get_random_int(void)
}
#else
static DEFINE_PER_CPU(struct batched_entropy, batched_entropy_int);
+static DEFINE_LOCAL_IRQ_LOCK(batched_entropy_int_lock);
+
unsigned int get_random_int(void)
{
unsigned int ret;
@@ -2086,13 +2090,13 @@ unsigned int get_random_int(void)
if (arch_get_random_int(&ret))
return ret;

- batch = &get_cpu_var(batched_entropy_int);
+ batch = &get_locked_var(batched_entropy_int_lock, batched_entropy_int);
if (batch->position % ARRAY_SIZE(batch->entropy_int) == 0) {
extract_crng((u8 *)batch->entropy_int);
batch->position = 0;
}
ret = batch->entropy_int[batch->position++];
- put_cpu_var(batched_entropy_int);
+ put_locked_var(batched_entropy_int_lock, batched_entropy_int);
return ret;
}
#endif
--
2.11.0