git: 4690e20eed17 - main - tools/uma/smrstress: fix kthread exit

The branch main has been updated by kib:

URL: https://cgit.FreeBSD.org/src/commit/?id=4690e20eed17a6e79a67a8d10874fdc67a1c4ccf

commit 4690e20eed17a6e79a67a8d10874fdc67a1c4ccf
Author:     Konstantin Belousov <kib@FreeBSD.org>
AuthorDate: 2022-07-30 18:54:34 +0000
Commit:     Konstantin Belousov <kib@FreeBSD.org>
CommitDate: 2022-07-30 21:40:12 +0000

    tools/uma/smrstress: fix kthread exit
    
    By convention, kernel threads must call kthread_exit() instead of
    blindly returning from the thread function.  We have some safety measure
    in fork_exit(), which checks for the P_KPROC p_flag and does
    kthread_exit() for kernel thread that forgot to do it itself.
    
    But this workaround only works for kernel threads belonging to the
    kernel process.  If a kernel thread is attached to the normal process
    with live userspace, and does not call kthread_exit(), then the
    workaround is not activated, and for amd64 at least, the return from the
    thread function/fork_exit() results in the return to userspace with the
    copy of frame from the thread that did kthread_add().
    
    Practically for smrstress, this destroys the user stack of the still
    active frame in the other thread, which was the caller of kthread_add().
    
    Fix it by adding kthread_exit() to the thread function.
    
    Reported and tested by: pho
    Reviewed by:    markj
    Sponsored by:   The FreeBSD Foundation
    MFC after:      1 week
    Differential revision:  https://reviews.freebsd.org/D35999
---
 tools/uma/smrstress/smrstress.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/uma/smrstress/smrstress.c b/tools/uma/smrstress/smrstress.c
index 7e7ee4ea065c..2cf5f50ffae4 100644
--- a/tools/uma/smrstress/smrstress.c
+++ b/tools/uma/smrstress/smrstress.c
@@ -123,6 +123,7 @@ smrs_thread(void *arg)
 	else
 		smrs_read();
 	atomic_add_int(&smrs_completed, 1);
+	kthread_exit();
 }
 
 static void