Author: jhb
Date: Mon Feb 8 23:11:23 2016
New Revision: 295419
URL: https://svnweb.freebsd.org/changeset/base/295419
Log:
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 particular 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
MFC after: 1 week
Modified:
head/sys/kern/kern_fork.c
Modified: head/sys/kern/kern_fork.c
==============================================================================
--- head/sys/kern/kern_fork.c Mon Feb 8 23:06:27 2016 (r295418)
+++ head/sys/kern/kern_fork.c Mon Feb 8 23:11:23 2016 (r295419)
@@ -1040,7 +1040,7 @@ fork_exit(void (*callout)(void *, struct
if (p->p_flag & P_KTHREAD) {
printf("Kernel thread \"%s\" (pid %d) exited prematurely.\n",
td->td_name, p->p_pid);
- kproc_exit(0);
+ kthread_exit();
}
mtx_assert(&Giant, MA_NOTOWNED);
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