From 3a2c0ba5ad00c018c0bef39a2224aca950aa33f2 Mon Sep 17 00:00:00 2001 From: Rusty Russell Date: Mon, 8 Dec 2014 16:50:37 +0800 Subject: hwrng: use reference counts on each struct hwrng. current_rng holds one reference, and we bump it every time we want to do a read from it. This means we only hold the rng_mutex to grab or drop a reference, so accessing /sys/devices/virtual/misc/hw_random/rng_current doesn't block on read of /dev/hwrng. Using a kref is overkill (we're always under the rng_mutex), but a standard pattern. This also solves the problem that the hwrng_fillfn thread was accessing current_rng without a lock, which could change (eg. to NULL) underneath it. Signed-off-by: Rusty Russell Signed-off-by: Amos Kong Signed-off-by: Herbert Xu --- include/linux/hw_random.h | 2 ++ 1 file changed, 2 insertions(+) (limited to 'include/linux/hw_random.h') diff --git a/include/linux/hw_random.h b/include/linux/hw_random.h index 914bb08cd738..c212e71ea886 100644 --- a/include/linux/hw_random.h +++ b/include/linux/hw_random.h @@ -14,6 +14,7 @@ #include #include +#include /** * struct hwrng - Hardware Random Number Generator driver @@ -44,6 +45,7 @@ struct hwrng { /* internal. */ struct list_head list; + struct kref ref; }; /** Register a new Hardware Random Number Generator driver. */ -- cgit v1.2.3-59-g8ed1b