From: Karl Mehltretter Date: Sat, 23 May 2026 18:51:22 +0000 (+0200) Subject: lockdep/selftests: Restore migrate_disable() state on PREEMPT_RT X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=d8c897b20bf4d4cbb1e935a8ceb666bcc0f82580;p=thirdparty%2Flinux.git lockdep/selftests: Restore migrate_disable() state on PREEMPT_RT The lockdep selftests deliberately run unbalanced locking patterns. dotest() restores the task state they leave behind before running the next testcase. On PREEMPT_RT, spin_lock() uses migrate_disable() instead of disabling preemption. dotest() cleans up the resulting migration-disabled state, but that cleanup is still guarded by CONFIG_SMP. That used to match the scheduler data model, where migration_disabled was also CONFIG_SMP-only. The commit referenced below made SMP scheduler state unconditional, so CONFIG_SMP=n PREEMPT_RT kernels with CONFIG_DEBUG_LOCKING_API_SELFTESTS=y report success from the selftests and then trip over stale current->migration_disabled state: releasing a pinned lock bad: scheduling from the idle thread! Kernel panic - not syncing: Fatal exception Save and restore current->migration_disabled for every PREEMPT_RT build. Fixes: cac5cefbade9 ("sched/smp: Make SMP unconditional") Assisted-by: Codex:gpt-5 Signed-off-by: Karl Mehltretter Signed-off-by: Peter Zijlstra (Intel) Reviewed-by: Sebastian Andrzej Siewior Link: https://patch.msgid.link/20260523185123.17482-2-kmehltretter@gmail.com --- diff --git a/lib/locking-selftest.c b/lib/locking-selftest.c index d939403331b5a..cb806b628352b 100644 --- a/lib/locking-selftest.c +++ b/lib/locking-selftest.c @@ -1431,9 +1431,7 @@ static void dotest(void (*testcase_fn)(void), int expected, int lockclass_mask) { int saved_preempt_count = preempt_count(); #ifdef CONFIG_PREEMPT_RT -#ifdef CONFIG_SMP int saved_mgd_count = current->migration_disabled; -#endif int saved_rcu_count = current->rcu_read_lock_nesting; #endif @@ -1471,10 +1469,8 @@ static void dotest(void (*testcase_fn)(void), int expected, int lockclass_mask) preempt_count_set(saved_preempt_count); #ifdef CONFIG_PREEMPT_RT -#ifdef CONFIG_SMP while (current->migration_disabled > saved_mgd_count) migrate_enable(); -#endif while (current->rcu_read_lock_nesting > saved_rcu_count) rcu_read_unlock();