Re: [PATCH net-next v2] rds: synchronize info callbacks with module unload
From: Paolo Abeni <pabeni@redhat.com>
Date: 2026-07-30 10:02:05
Also in:
linux-rdma, lkml
Hi, It looks like I was too optimistic in my previous reply. On 7/27/26 7:48 PM, Chengfeng Ye wrote:
quoted hunk ↗ jump to hunk
@@ -78,8 +80,13 @@ void rds_info_register_func(int optname, rds_info_func func) BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST); spin_lock(&rds_info_lock); - BUG_ON(rds_info_funcs[offset]); - rds_info_funcs[offset] = func; + /* Validate the latest published slot value. */ + if (WARN_ON_ONCE(smp_load_acquire(&rds_info_funcs[offset]))) {
This read is under the same lock that perform the store. It's totally unclear why smp_load_acquire() would be needed here. Very reasonably it's not.
quoted hunk ↗ jump to hunk
+ spin_unlock(&rds_info_lock); + return; + } + /* Pair with lockless callback lookup. */ + smp_store_release(&rds_info_funcs[offset], func); spin_unlock(&rds_info_lock); } EXPORT_SYMBOL_GPL(rds_info_register_func);@@ -91,9 +98,15 @@ void rds_info_deregister_func(int optname, rds_info_func func) BUG_ON(optname < RDS_INFO_FIRST || optname > RDS_INFO_LAST); spin_lock(&rds_info_lock); - BUG_ON(rds_info_funcs[offset] != func); - rds_info_funcs[offset] = NULL; + /* Validate the latest published slot value. */ + if (WARN_ON_ONCE(smp_load_acquire(&rds_info_funcs[offset]) != func)) {
Same here. /P