workqueue: introduce BPF iterators for workqueues, worker pools and pending work - #8523
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…ues list
Add bpf_iter_workqueue_{new,next,destroy} kfuncs so BPF programs can walk
every workqueue on the global workqueues list.
The workqueues list is RCU-protected for reads and each workqueue_struct
is freed via call_rcu(), so the iterator is KF_RCU_PROTECTED i.e. the
caller must hold bpf_rcu_read_lock() across new()..destroy(), which keeps
the list and each returned wq alive between next() calls.
The kfuncs live in kernel/workqueue.c because struct workqueue_struct's
list anchor and the workqueues root are local to this file.
Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
Add a 'workqueue' BPF iterator target (bpftool-iter / pinnable) that reuses the open-coded bpf_iter_workqueue_next(). Since the open-coded next() is KF_RCU_PROTECTED, the seq path supplies the RCU section: seq_start() takes rcu_read_lock() and holds it across the read chunk, so the returned workq and the cursor stay alive while the program runs and next() steps; position is re-derived from *pos on each start, so the cursor is never dereferenced across the RCU gap between chunks. Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
Add bpf_iter_worker_pool_{new,next,destroy} kfuncs so BPF programs can
walk every worker_pool in the system via worker_pool_idr, in ascending
pool-id order.
This mirrors the pool enumeration in the drgn tools/workqueue/wq_dump.py
script.
The idr walk (idr_get_next) runs as kernel C, so no BPF-side idr support
is needed. worker_pool_idr is RCU-readable and each worker_pool is freed
via call_rcu(), so the iterator is KF_RCU_PROTECTED, like the workqueue
iterator: the caller holds bpf_rcu_read_lock() across new()..destroy().
Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
Add a 'worker_pool' BPF iterator target, backed by the open-coded bpf_iter_worker_pool_next() via a shared union, using the same RCU-per-chunk scheme as the workqueue seq iterator. Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
Add a seq_file BPF iterator ("workqueue_pending_work") that walks the
pending work items of every worker_pool. Unlike the workqueue and
worker_pool iterators this is deliberately not open-coded because
pool->worklist is protected by pool->lock and struct work_struct has
neither a refcount nor RCU-freeing, so a pending work cannot be kept alive
for a suspended open-coded iterator.
Instead, for each pool a bounded snapshot of its pending works (pool id,
work address, work function) is copied out while pool->lock is held and
the BPF program runs over the stable snapshot with no lock held.
worker_pool(s) are visited in worker_pool_idr order.
Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
Cover both the open-coded and seq_file forms of the workqueue and worker_pool iterators, plus the pending-work seq iterator: - count_workqueues / count_worker_pools drive the open-coded iterators (inside bpf_rcu_read_lock()); userspace checks the counts are non-zero. - dump_workqueues / dump_worker_pools attach the seq forms and drain them, exercising the RCU-per-chunk seq path that reuses the open-coded next(). - dump_pending attaches the workqueue_pending_work seq iterator and drains it, exercising the per-pool snapshot path. - wq_iter_fail.c checks the verifier rejects the RCU-protected open-coded iterators when used outside an RCU critical section. Also declare the open-coded iterator kfuncs in bpf_experimental.h. Signed-off-by: Imran Khan <imran.f.khan@oracle.com>
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Pull request for series with
subject: workqueue: introduce BPF iterators for workqueues, worker pools and pending work
version: 1
url: https://patchwork.kernel.org/project/netdevbpf/list/?series=1135671