llext: Allow multiple DP instances of same module

[jsarha]

The LL userspace changes broke support of multiple instances of same DP module. This is a quick remedy to fix that. The fix has a down side that it does not allow having both LL and DP instances of the same module within a same configuration.

This fixes #11133

[Copilot]

Pull request overview

Fixes regression where multiple DP (Data Processing) instances of the same LLEXT module could not be safely used after recent LL userspace changes, by ensuring module segments are added to each DP instance’s memory domain even when the underlying LLEXT is already refcounted.

Changes:

• Treat DP modules as a special case when deciding whether to add module partitions to a memory domain (don’t skip on use_count > 1).
• Document the known limitation that mixed LL+DP instances of the same module in one configuration are not supported by this quick remedy.

Suppressed comments (1)

src/library_manager/llext_manager.c:854

• This change intentionally makes mixed LL+DP instances of the same module unsupported, but the code currently may still proceed in such a configuration and later fault (e.g., llext_manager_add_domain() can return success while skipping all partition additions when mctx->domain_dp is false and the module is already refcounted). Consider failing fast when a new instance’s ipc_config->proc_domain conflicts with the already-mapped module’s mctx->domain_dp (e.g., in llext_manager_allocate_module()), returning an error and logging a clear message instead of allowing a hard-to-debug crash.

	 * NOTE: This approach will make it impossible to have one module
	 *       to have both LL and DP instances within one configuration.
	 *       This will be fixed in future.
	 */
	if (!mctx->domain_dp && ext->use_count > 1 && mctx->n_dependent != 1)

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