Re: [PATCH v5 1/9] rv: Introduce DA_MON_ALLOCATION_STRATEGY
From: sashiko-bot@kernel.org
Date: 2026-08-19 18:30:07
Thank you for your contribution! Sashiko AI review found 1 potential issue(s) to consider: - [High] DA_ALLOC_POOL strategy causes lockdep 'Invalid wait context' warnings and crashes on PREEMPT_RT when used in tracepoints that hold raw spinlocks. --
--- Patch [1]: [PATCH v5 1/9] rv: Introduce DA_MON_ALLOCATION_STRATEGY ---commit e8961cb4205551f74e01ec6b7818734bafc846f3 Author: Wen Yang [off-list ref] rv: Introduce DA_MON_ALLOCATION_STRATEGY This patch introduces a compile-time selection for per-object deterministic automata (DA) monitor allocation strategies. It adds DA_ALLOC_AUTO, DA_ALLOC_POOL, and DA_ALLOC_MANUAL to handle contexts where dynamic memory allocation is problematic.
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diff --git a/include/rv/da_monitor.h b/include/rv/da_monitor.h index e3cf85c9ce556..48c534324cbb2 100644 --- a/include/rv/da_monitor.h +++ b/include/rv/da_monitor.h
[ ... ]
quoted hunk ↗ jump to hunk
@@ -543,6 +596,59 @@ static inline monitor_target da_get_target_by_id(da_id_type id) return mon_storage->target; } +/* + * Pre-allocated mempool for DA_ALLOC_POOL monitors: DA_MON_POOL_SIZE + * slots, eager-allocated at init. mempool_alloc_preallocated() pops a + * slot without touching the allocator (bounded start latency; NULL when + * exhausted). mempool_free() is safe from RCU-callback context. + * Non-pool monitors get a zero-initialised mempool_t; pool paths compile + * away. + */ +static mempool_t da_monitor_pool;
[ ... ]
+/*
+ * da_create_pool_storage - pop a free pool slot and insert it into the hash.
+ *
+ * Returns the new da_monitor, or NULL if the pool is exhausted. Finding
+ * an existing entry for the same id fires WARN_ON_ONCE (double-start bug).
+ *
+ * Caller must hold an RCU read-side CS and the monitor's serialisation lock.
+ */
+static inline struct da_monitor *
+da_create_pool_storage(da_id_type id, monitor_target target,
+ struct da_monitor *da_mon)
+{
+ struct da_monitor_storage *mon_storage, *existing;
+
+ if (da_mon)
+ return da_mon;
+
+ mon_storage = mempool_alloc_preallocated(&da_monitor_pool);[Severity: High] Will this cause an "Invalid wait context" lockdep warning or a kernel panic on PREEMPT_RT systems when executed from tracepoints holding raw spinlocks? The patch describes DA_ALLOC_POOL as being useful for contexts problematic for allocation, such as scheduling. If a monitor uses this pool strategy in a tracepoint like sched_switch, it will be called while holding a raw_spinlock_t (like rq->lock). Looking at mempool_alloc_preallocated(), it unconditionally acquires the pool lock, which is a spinlock_t. On PREEMPT_RT, spinlock_t maps to a sleepable rt_mutex. Acquiring a sleeping lock while holding a raw_spinlock_t is a strict wait-context locking violation. Is there a way to manage the pre-allocated pool in da_create_pool_storage() without relying on locks that sleep on PREEMPT_RT?
+ if (!mon_storage) + return NULL; + memset(mon_storage, 0, sizeof(*mon_storage)); + + mon_storage->id = id; + mon_storage->target = target;
[ ... ] -- Sashiko AI review · https://sashiko.dev/#/patchset/cover.1787161646.git.wen.yang@linux.dev?part=1