lua-lsm: fix unregister and module lifetime handling#16
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chenzongyao200127 wants to merge 5 commits into
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lua-lsm: fix unregister and module lifetime handling#16chenzongyao200127 wants to merge 5 commits into
chenzongyao200127 wants to merge 5 commits into
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Lua-LSM publishes module pointers under modules_ss SRCU. The unregister path removes a module from the list before freeing it, but readers that already entered the SRCU read-side critical section may still hold the old pointer. Wait for an SRCU grace period after unlinking the module and before freeing its storage. Signed-off-by: Zongyao Chen <ZongYao.Chen@linux.alibaba.com>
shared[name] caches a Lua userdata that can outlive module unregister. The userdata used to hold a raw kvcache_dict pointer, while unregister freed the backing shared dict before every loaded VM was purged. If unregister left the module busy, later shared-dict access could dereference freed memory. Store a refcounted shared-dict wrapper in the userdata, tombstone shared dicts when unregister starts, and drop the module list reference only once unregister can finish. Signed-off-by: Zongyao Chen <ZongYao.Chen@linux.alibaba.com>
newshdict() allocates Lua userdata and can raise a Lua allocation error before any userdata exists to run the shared-dict __gc method. Allocate the userdata slot before taking the per-userdata shared-dict reference. Once the userdata exists, store the referenced shdict in it so later GC can drop the reference even if the following table update fails. Signed-off-by: Zongyao Chen <ZongYao.Chen@linux.alibaba.com>
task_call_func() may run callbacks under pi_lock and, for runnable tasks, the runqueue lock. The unregister path used it to remove modules from other tasks' Lua VMs, which updates Lua tables and can run a full Lua GC. Stop doing remote task VM teardown from task_call_func(). Unregister now purges only the current task and per-cpu Lua VMs directly; other task VMs purge unloading modules lazily when they next enter Lua-LSM. Modules that still have loaded VMs remain zombie and unregister returns -EBUSY until the remaining VMs have purged them. Signed-off-by: Zongyao Chen <ZongYao.Chen@linux.alibaba.com>
Lazy unload can drop a module's last VM-local reference after unregister() has already returned -EBUSY. In that case the module used to stay on the unloading list until another unregister() retried the final teardown. Queue a worker when lazy purge or task teardown drains nloaded to zero. The worker detaches the drained zombie under modules_mutex, waits for the modules_ss SRCU grace period, and then frees the module outside the mutex. Also skip purge attempts once nloaded is already zero and make lua_modules_free() explicitly rely on the caller's existing SRCU read-side protection. Signed-off-by: Zongyao Chen <ZongYao.Chen@linux.alibaba.com>
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Lua-LSM module unregister has to coordinate several lifetimes at once: the global module list protected by modules_ss SRCU, per-VM loaded module references, shared dictionaries cached in Lua userdata, and the contexts where VM teardown is allowed to run.
This series keeps those pieces ordered so unregister no longer frees state that can still be reached from an existing Lua VM, and so lazy unload can finish modules once the last VM-local reference is gone.
The series contains these commits:
Main fixes:
Please use Rebase and merge, or another merge mode that preserves the individual commits. Please do not squash this PR, since each commit has its own kernel-style subject and message.
Validation:
Signed-off-by: Zongyao Chen ZongYao.Chen@linux.alibaba.com