From 221a97fa10ec668d02e3ab059f5d6136f88f6fac Mon Sep 17 00:00:00 2001 From: jhb Date: Tue, 16 Feb 2016 21:36:48 +0000 Subject: MFC 295418,295419: Fix hangs or panics when misbehaved kernel threads return from their main function. 295418: Mark proc0 as a kernel process via the P_KTHREAD flag. All other kernel processes have this flag set and all threads in proc0 (including thread0) have the similar TDP_KTHREAD flag set. 295419: Call kthread_exit() rather than kproc_exit() for a premature kthread exit. Kernel threads (and processes) are supposed to call kthread_exit() (or kproc_exit()) to terminate. However, the kernel includes a fallback in fork_exit() to force a kthread exit if a kernel thread's "main" routine returns. This fallback was added back when the kernel only had processes and was not updated to call kthread_exit() instead of kproc_exit() when threads were added to the kernel. This mistake was particularly exciting when the errant thread belonged to proc0. Due to the missing P_KTHREAD flag the fallback did not kick in and instead tried to return to userland via whatever garbage was in the trapframe. With P_KTHREAD set it tried to terminate proc0 resulting in other amusements. PR: 204999 Approved by: re (glebius) --- sys/kern/init_main.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'sys/kern/init_main.c') diff --git a/sys/kern/init_main.c b/sys/kern/init_main.c index 201680a..ae6bd3a 100644 --- a/sys/kern/init_main.c +++ b/sys/kern/init_main.c @@ -479,7 +479,7 @@ proc0_init(void *dummy __unused) session0.s_leader = p; p->p_sysent = &null_sysvec; - p->p_flag = P_SYSTEM | P_INMEM; + p->p_flag = P_SYSTEM | P_INMEM | P_KTHREAD; p->p_flag2 = 0; p->p_state = PRS_NORMAL; knlist_init_mtx(&p->p_klist, &p->p_mtx); -- cgit v1.1