Merge commit '683b6c6f82a60fabf47012581c2cfbf1b037ab95' into stable/for-linus-3.15

This merge of the irq-core-for-linus branch broke the ARM build when
Xen is enabled.

Conflicts:
	drivers/xen/events/events_base.c

1 files changed, 12 insertions, 1 deletions

diff --git a/lib/random32.c b/lib/random32.c
index 1e5b2df44291..614896778700 100644
--- a/lib/random32.c
+++ b/lib/random32.c
@@ -244,8 +244,19 @@ static void __prandom_reseed(bool late)
         static bool latch = false;
         static DEFINE_SPINLOCK(lock);
 
+        /* Asking for random bytes might result in bytes getting
+         * moved into the nonblocking pool and thus marking it
+         * as initialized. In this case we would double back into
+         * this function and attempt to do a late reseed.
+         * Ignore the pointless attempt to reseed again if we're
+         * already waiting for bytes when the nonblocking pool
+         * got initialized.
+         */
+
         /* only allow initial seeding (late == false) once */
-        spin_lock_irqsave(&lock, flags);
+        if (!spin_trylock_irqsave(&lock, flags))
+                return;
+
         if (latch && !late)
                 goto out;
         latch = true;