Patch-mainline: v6.0-rc1
Git-commit: 9c9b26b0df270d4f9246e483a44686fca951a29c
References: git-fixes
From: Chen Zhongjin <chenzhongjin@huawei.com>
Date: Tue, 10 May 2022 17:46:39 +0800
Subject: [PATCH] locking/csd_lock: Change csdlock_debug from early_param to
 __setup

The csdlock_debug kernel-boot parameter is parsed by the
early_param() function csdlock_debug().  If set, csdlock_debug()
invokes static_branch_enable() to enable csd_lock_wait feature, which
triggers a panic on arm64 for kernels built with CONFIG_SPARSEMEM=y and
CONFIG_SPARSEMEM_VMEMMAP=n.

With CONFIG_SPARSEMEM_VMEMMAP=n, __nr_to_section is called in
static_key_enable() and returns NULL, resulting in a NULL dereference
because mem_section is initialized only later in sparse_init().

This is also a problem for powerpc because early_param() functions
are invoked earlier than jump_label_init(), also resulting in
static_key_enable() failures.  These failures cause the warning "static
key 'xxx' used before call to jump_label_init()".

Thus, early_param is too early for csd_lock_wait to run
static_branch_enable(), so changes it to __setup to fix these.

Fixes: 8d0968cc6b8f ("locking/csd_lock: Add boot parameter for controlling CSD lock debugging")
Cc: stable@vger.kernel.org
Reported-by: Chen jingwen <chenjingwen6@huawei.com>
Signed-off-by: Chen Zhongjin <chenzhongjin@huawei.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
Signed-off-by: Juergen Gross <jgross@suse.com>
---
 kernel/smp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c
index dd215f439426..650810a6f29b 100644
--- a/kernel/smp.c
+++ b/kernel/smp.c
@@ -174,9 +174,9 @@ static int __init csdlock_debug(char *str)
 	if (val)
 		enable_csdlock_debug = true;
 
-	return 0;
+	return 1;
 }
-early_param("csdlock_debug", csdlock_debug);
+__setup("csdlock_debug=", csdlock_debug);
 
 static DEFINE_PER_CPU(call_single_data_t *, cur_csd);
 static DEFINE_PER_CPU(smp_call_func_t, cur_csd_func);
-- 
2.35.3