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Jinliang Zheng says: ==================== macsec: use rcu_work to fix crypto cleanup in softirq context From: Jinliang Zheng <alexjlzheng@tencent.com> crypto_free_aead() can internally call vunmap() (e.g. via dma_free_attrs() in hardware crypto drivers like hisi_sec2), which must not be invoked from softirq context. Both free_rxsa() and free_txsa() are RCU callbacks that run in softirq, causing a kernel crash on affected hardware. This series fixes the issue by deferring the actual cleanup to a workqueue using rcu_work, which combines the RCU grace period and workqueue dispatch into a single primitive. Two design decisions worth noting: 1. rcu_work instead of schedule_work() + synchronize_rcu() An alternative would be to call schedule_work() directly from macsec_rxsa_put()/macsec_txsa_put(), then call synchronize_rcu() at the start of the work handler to replace the grace period previously provided by call_rcu(). However, synchronize_rcu() blocks the worker thread for the duration of a full RCU grace period. Under high SA churn (e.g. tearing down an interface with many SAs), each SA would occupy a worker thread while waiting, and multiple concurrent calls cannot share the same grace period — leading to unnecessary latency and resource waste. rcu_work uses call_rcu_hurry() internally, which is fully asynchronous: the worker thread is only dispatched after the grace period has elapsed, and multiple concurrent queue_rcu_work() calls naturally batch under the same grace period via the RCU subsystem's existing coalescing mechanism. 2. Dedicated workqueue instead of system_wq Using a dedicated workqueue (macsec_wq) allows macsec_exit() to drain exactly the work items belonging to this module — by calling destroy_workqueue() after rcu_barrier(). If system_wq were used, flush_scheduled_work() would drain all pending work items across the entire system, creating unnecessary coupling with unrelated subsystems and potentially causing unexpected delays. The dedicated workqueue provides a clean, contained teardown path. ==================== Link: https://patch.msgid.link/20260511153102.2640368-1-alexjlzheng@tencent.com Signed-off-by: Jakub Kicinski <kuba@kernel.org>
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