Re: [PATCH AUTOSEL 6.17-6.1] ftrace: Fix softlockup in ftrace_module_enable

On Sat, 25 Oct 2025 12:00:16 -0400 Sasha Levin sashal@kernel.org wrote:

• The change inserts `cond_resched()` inside the inner iteration over every ftrace record (`kernel/trace/ftrace.c:7538`). That loop holds the ftrace mutex and, for each record, invokes heavy helpers like `test_for_valid_rec()` which in turn calls `kallsyms_lookup()` (`kernel/trace/ftrace.c:4289`). On huge modules (e.g. amdgpu) this can run for tens of milliseconds with preemption disabled, triggering the

It got the "preemption disabled" wrong. Well maybe when running PREEMPT_NONE it is, but the description doesn't imply that.

-- Steve

documented soft lockup/panic during module load.

• `ftrace_module_enable()` runs only in process context via `prepare_coming_module()` (`kernel/module/main.c:3279`), so adding a voluntary reschedule point is safe; the same pattern already exists in other long-running ftrace loops (see commits d0b24b4e91fc and 42ea22e754ba), so this brings consistency without changing control flow or semantics.
• No data structures or interfaces change, and the code still executes under the same locking (`ftrace_lock`, `text_mutex` when the arch overrides `ftrace_arch_code_modify_prepare()`), so the risk of regression is minimal: the new call simply yields CPU if needed while keeping the locks held, preventing watchdog-induced crashes but otherwise behaving identically.