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-rw-r--r--drivers/char/random.c24
1 files changed, 16 insertions, 8 deletions
diff --git a/drivers/char/random.c b/drivers/char/random.c
index 73e52b7796f..35487e8ded5 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -865,16 +865,24 @@ static size_t account(struct entropy_store *r, size_t nbytes, int min,
if (r->entropy_count / 8 < min + reserved) {
nbytes = 0;
} else {
+ int entropy_count, orig;
+retry:
+ entropy_count = orig = ACCESS_ONCE(r->entropy_count);
/* If limited, never pull more than available */
- if (r->limit && nbytes + reserved >= r->entropy_count / 8)
- nbytes = r->entropy_count/8 - reserved;
-
- if (r->entropy_count / 8 >= nbytes + reserved)
- r->entropy_count -= nbytes*8;
- else
- r->entropy_count = reserved;
+ if (r->limit && nbytes + reserved >= entropy_count / 8)
+ nbytes = entropy_count/8 - reserved;
+
+ if (entropy_count / 8 >= nbytes + reserved) {
+ entropy_count -= nbytes*8;
+ if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+ goto retry;
+ } else {
+ entropy_count = reserved;
+ if (cmpxchg(&r->entropy_count, orig, entropy_count) != orig)
+ goto retry;
+ }
- if (r->entropy_count < random_write_wakeup_thresh)
+ if (entropy_count < random_write_wakeup_thresh)
wakeup_write = 1;
}