linux-kernel - Re: [BUG, PATCH] random: sleep in irq context

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Date:   Tue, 24 Apr 2018 10:40:36 +0200 (CEST)
From:   Sebastian Ott <sebott@...ux.ibm.com>
To:     "Theodore Ts'o" <tytso@....edu>
cc:     linux-kernel@...r.kernel.org
Subject: Re: [BUG, PATCH] random: sleep in irq context

On Mon, 23 Apr 2018, Sebastian Ott wrote:
> This happend once during boot and I could not reproduce this since, but I
> think the following patch should fix the issue:

I can now recreate the issue reliably. The following patch works for me:

------>8
>From 6bbfab86beae8fe8b6efeffd08c9ad43d1c2ba68 Mon Sep 17 00:00:00 2001
From: Sebastian Ott <sebott@...ux.ibm.com>
Date: Mon, 23 Apr 2018 14:59:20 +0200
Subject: [PATCH] random: don't sleep during allocations

Since numa_crng_init() can be called from irq context let's
use __GFP_ATOMIC for allocations.

Fixes: 8ef35c866f88 ("random: set up the NUMA crng instances...")
Signed-off-by: Sebastian Ott <sebott@...ux.ibm.com>
---
 drivers/char/random.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/char/random.c b/drivers/char/random.c
index 3cd3aae24d6d..98634b8025d5 100644
--- a/drivers/char/random.c
+++ b/drivers/char/random.c
@@ -795,10 +795,10 @@ static void numa_crng_init(void)
 	struct crng_state *crng;
 	struct crng_state **pool;
 
-	pool = kcalloc(nr_node_ids, sizeof(*pool), GFP_KERNEL|__GFP_NOFAIL);
+	pool = kcalloc(nr_node_ids, sizeof(*pool), __GFP_NOFAIL | GFP_ATOMIC);
 	for_each_online_node(i) {
 		crng = kmalloc_node(sizeof(struct crng_state),
-				    GFP_KERNEL | __GFP_NOFAIL, i);
+				    __GFP_NOFAIL | GFP_ATOMIC, i);
 		spin_lock_init(&crng->lock);
 		crng_initialize(crng);
 		pool[i] = crng;
-- 
2.13.4