In the transition from 5.10.158-rt77 to 5.10.162-rt78, the initialization of task_struct::wake_q_sleeper.next was dropped. Restore it. This appears to be only a problem in 5.10. 5.15 does not have wake_q_sleeper; 4.19 does have it but its initialization there is still present. The 5.10.162-rt78 patch that damaged fork.c is: 0170-locking-rtmutex-add-sleeping-lock-implementation.patch I do not have a simple test that brings out this problem. My test consists of a shell script and eight binaries, all of which were written in Ada. strace shows that it does a few thousand forks in rapid succession. One of the forks stalls out, after which no fork after that returns. Eventually the 122 second stallout occurs and a large number of threads are shown to be waiting for tasklist lock, either in do_exit or in copy_process. The kernel .config has rt and many debug features enabled, lockdep included. Signed-off-by: Joe Korty <joe.korty@xxxxxxxxxxxxxxxxx Index: b/kernel/fork.c =================================================================== --- a/kernel/fork.c +++ b/kernel/fork.c @@ -960,6 +960,7 @@ static struct task_struct *dup_task_stru tsk->splice_pipe = NULL; tsk->task_frag.page = NULL; tsk->wake_q.next = NULL; + tsk->wake_q_sleeper.next = NULL; tsk->pf_io_worker = NULL; account_kernel_stack(tsk, 1);
