bpf: replace use of system_wq with system_percpu_wq

Currently if a user enqueue a work item using schedule_delayed_work() the
used wq is "system_wq" (per-cpu wq) while queue_delayed_work() use
WORK_CPU_UNBOUND (used when a cpu is not specified). The same applies to
schedule_work() that is using system_wq and queue_work(), that makes use
again of WORK_CPU_UNBOUND.

This lack of consistentcy cannot be addressed without refactoring the API.

system_wq is a per-CPU worqueue, yet nothing in its name tells about that
CPU affinity constraint, which is very often not required by users. Make
it clear by adding a system_percpu_wq.

queue_work() / queue_delayed_work() mod_delayed_work() will now use the
new per-cpu wq: whether the user still stick on the old name a warn will
be printed along a wq redirect to the new one.

This patch add the new system_percpu_wq except for mm, fs and net
subsystem, whom are handled in separated patches.

The old wq will be kept for a few release cylces.

Suggested-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Marco Crivellari <marco.crivellari@suse.com>
Link: https://lore.kernel.org/r/20250905085309.94596-2-marco.crivellari@suse.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

diff --git a/kernel/bpf/cgroup.c b/kernel/bpf/cgroup.c
index 9912c7b9a266043dbd7b9c99cb534c0f78040f8d..dde605c9415a34e60352d301c80e644bdb1f88dd 100644 (file)
--- a/kernel/bpf/cgroup.c
+++ b/kernel/bpf/cgroup.c
@@ -27,7 +27,7 @@ EXPORT_SYMBOL(cgroup_bpf_enabled_key);
 /*
  * cgroup bpf destruction makes heavy use of work items and there can be a lot
  * of concurrent destructions.  Use a separate workqueue so that cgroup bpf
- * destruction work items don't end up filling up max_active of system_wq
+ * destruction work items don't end up filling up max_active of system_percpu_wq
  * which may lead to deadlock.
  */
 static struct workqueue_struct *cgroup_bpf_destroy_wq;

diff --git a/kernel/bpf/cpumap.c b/kernel/bpf/cpumap.c
index b2b7b8ec2c2a1c6d6af58b031991d9b8f10256dd..a9b347ccbec29870a2c9a079e9240f60504e6865 100644 (file)
--- a/kernel/bpf/cpumap.c
+++ b/kernel/bpf/cpumap.c
@@ -550,7 +550,7 @@ static void __cpu_map_entry_replace(struct bpf_cpu_map *cmap,
        old_rcpu = unrcu_pointer(xchg(&cmap->cpu_map[key_cpu], RCU_INITIALIZER(rcpu)));
        if (old_rcpu) {
                INIT_RCU_WORK(&old_rcpu->free_work, __cpu_map_entry_free);
-               queue_rcu_work(system_wq, &old_rcpu->free_work);
+               queue_rcu_work(system_percpu_wq, &old_rcpu->free_work);
        }
 }