Hi All, I am building lttng-modules-2.10.x/2.9.10 against Linux-4.14.69-rt43 as out-of-tree modules and have been noticing the error/warning as shown below: Build warning: -------------------------------------------------------------------------------------------- WARNING: "__migrate_disabled" [/home/builder/lttng-modules/lttng-modules-2.10.7/lttng-tracer.ko] undefined! -------------------------------------------------------- Runtime issue: -------------------------------------------------------- debian at debian:~$ sudo dmesg | grep -i migrate [ 10.721478] lttng_tracer: Unknown symbol __migrate_disabled (err 0) -------------------------------------------------------- Impact: LTTng Kernel tracing not working, Lttng modules are not loaded. Reference: https://lists.lttng.org/pipermail/lttng-dev/2018-September/028216.html RT code which affects external modules build is: File: include/linux/preempt.h ------------------------------------------- #if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) extern void migrate_disable(void); extern void migrate_enable(void); int __migrate_disabled(struct task_struct *p) #elif !defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) ------------------------------------------- The kernel has both SMP & PREEMPT_RT_BASE/FULL enabled, Since I am building LTTNG as module i.e. CONFIG_LTTNG=m, I see this warning and LTTng kernel tracing isnt working anymore. OTOH, If I modify the condition as shown below, then no warning is seen and the Lttng builds and runs fine. -------------------------------------------- -#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) +#if defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) && defined(CONFIG_MODULES) extern void migrate_disable(void); extern void migrate_enable(void); int __migrate_disabled(struct task_struct *p); -#elif !defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) +#elif !defined(CONFIG_SMP) && defined(CONFIG_PREEMPT_RT_BASE) && defined(CONFIG_MODULES) -------------------------------------------- Kindly suggest if there is a better approach to fix this issue ? Thanks in Advance! -- Srikanth
