From: Chen Zhongjin chenzhongjin@huawei.com

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 --- kernel/smp.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/kernel/smp.c b/kernel/smp.c index dd215f4394264..650810a6f29b3 100644 --- a/kernel/smp.c +++ b/kernel/smp.c @@ -174,9 +174,9 @@ static int __init csdlock_debug(char *str) if (val) static_branch_enable(&csdlock_debug_enabled);

- 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);