Dear RT folks!

I'm pleased to announce the v5.17-rc3-rt6 patch set. 

Changes since v5.17-rc3-rt5:

  - Update John's printk series. It supports now direct printing from
    irqwork.

  - Correct atomic access to a variable in printk. Patch by John Ogness.

  - Add a warning if there is a ksoftirqd wakeup from idle.

  - Jason A. Donenfeld patches against the random subsystem were updated
    to v4. There is an additional RT related change on top.

  - The known issue
      netconsole triggers WARN.
    has been removed from the list since it also triggers with
    CONFIG_PREEMPT and v5.17-rc3 (without the PREEMPT_RT patch).

Known issues
     - Valentin Schneider reported a few splats on ARM64, see
          https://lkml.kernel.org/r/20210810134127.1394269-1-valentin.schneider@xxxxxxx

The delta patch against v5.17-rc3-rt5 is appended below and can be found here:
 
     https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.17/incr/patch-5.17-rc3-rt5-rt6.patch.xz

You can get this release via the git tree at:

    git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git v5.17-rc3-rt6

The RT patch against v5.17-rc3 can be found here:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.17/older/patch-5.17-rc3-rt6.patch.xz

The split quilt queue is available at:

    https://cdn.kernel.org/pub/linux/kernel/projects/rt/5.17/older/patches-5.17-rc3-rt6.tar.xz

Sebastian

diff --git a/drivers/char/random.c b/drivers/char/random.c
index afcedefb0c1c8..e4bde9c917654 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -404,7 +404,7 @@ struct fast_pool {
 	struct work_struct mix;
 	unsigned long last;
 	u32 pool[4];
-	atomic_t count;
+	unsigned int count;
 	u16 reg_idx;
 };
 #define FAST_POOL_MIX_INFLIGHT (1U << 31)
@@ -1045,25 +1045,33 @@ static u32 get_reg(struct fast_pool *f, struct pt_regs *regs)
 static void mix_interrupt_randomness(struct work_struct *work)
 {
 	struct fast_pool *fast_pool = container_of(work, struct fast_pool, mix);
+	u8 pool[sizeof(fast_pool->pool)];
 
-	fast_pool->last = jiffies;
+	if (unlikely(crng_init == 0)) {
+		size_t ret;
 
-	/* Since this is the result of a trip through the scheduler, xor in
+		ret = crng_fast_load((u8 *)fast_pool->pool, sizeof(fast_pool->pool));
+		if (ret) {
+			WRITE_ONCE(fast_pool->count, 0);
+			fast_pool->last = jiffies;
+			return;
+		}
+	}
+
+	/*
+	 * Since this is the result of a trip through the scheduler, xor in
 	 * a cycle counter. It can't hurt, and might help.
 	 */
 	fast_pool->pool[3] ^= random_get_entropy();
+	/* Copy the pool to the stack so that the mixer always has a consistent view. */
+	memcpy(pool, fast_pool->pool, sizeof(pool));
+	/* We take care to zero out the count only after we're done reading the pool. */
+	WRITE_ONCE(fast_pool->count, 0);
+	fast_pool->last = jiffies;
 
-	if (unlikely(crng_init == 0)) {
-		if (crng_fast_load((u8 *)&fast_pool->pool, sizeof(fast_pool->pool)) > 0)
-			atomic_set(&fast_pool->count, 0);
-		else
-			atomic_and(~FAST_POOL_MIX_INFLIGHT, &fast_pool->count);
-		return;
-	}
-
-	mix_pool_bytes(&fast_pool->pool, sizeof(fast_pool->pool));
-	atomic_set(&fast_pool->count, 0);
+	mix_pool_bytes(pool, sizeof(pool));
 	credit_entropy_bits(1);
+	memzero_explicit(pool, sizeof(pool));
 }
 
 void add_interrupt_randomness(int irq)
@@ -1089,15 +1097,33 @@ void add_interrupt_randomness(int irq)
 
 	fast_mix(fast_pool);
 	add_interrupt_bench(cycles);
+	new_cou