EXPORT_SYMBOL and __init is a bad combination because the .init.text section is freed up after the initialization. Hence, modules cannot use symbols annotated __init. The access to a freed symbol may end up with kernel panic. modpost used to detect it, but it had been broken for a decade. Commit 28438794aba4 ("modpost: fix section mismatch check for exported init/exit sections") fixed it so modpost started to warn it again, then this showed up: MODPOST vmlinux.symvers WARNING: modpost: vmlinux.o(___ksymtab_gpl+tick_nohz_full_setup+0x0): Section mismatch in reference from the variable __ksymtab_tick_nohz_full_setup to the function .init.text:tick_nohz_full_setup() The symbol tick_nohz_full_setup is exported and annotated __init Fix this by removing the __init annotation of tick_nohz_full_setup or drop the export. Drop the export because tick_nohz_full_setup() is only called from the built-in code in kernel/sched/isolation.c.
Unified · Split
| @@ -526,7 +526,6 @@ void __init tick_nohz_full_setup(cpumask_var_t cpumask) · 525 unmodified lines | ||
| 526 | 526 | cpumask_copy(tick_nohz_full_mask, cpumask); |
| 527 | 527 | tick_nohz_full_running = true; |
| 528 | 528 | } |
| 529 | −EXPORT_SYMBOL_GPL(tick_nohz_full_setup); | |
| 530 | 529 | |
| 531 | 530 | static int tick_nohz_cpu_down(unsigned int cpu) |
| 532 | 531 | { |