[RFC PATCH 3/8] fork/vhost_task: Switch to CLONE_THREAD and CLONE_SIGHAND

[Mike Christie]

This is a modified version of Linus's patch which has vhost_task
use CLONE_THREAD and CLONE_SIGHAND and allow SIGKILL and SIGSTOP.

I renamed the ignore_signals to block_signals based on Linus's comment
where it aligns with what we are doing with the siginitsetinv
p->blocked use and no longer calling ignore_signals.

Signed-off-by: Mike Christie <michael.christie@xxxxxxxxxx>
---
 include/linux/sched/task.h |  2 +-
 kernel/fork.c              | 12 +++---------
 kernel/vhost_task.c        |  5 +++--
 3 files changed, 7 insertions(+), 12 deletions(-)

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 537cbf9a2ade..249a5ece9def 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -29,7 +29,7 @@ struct kernel_clone_args {
 	u32 io_thread:1;
 	u32 user_worker:1;
 	u32 no_files:1;
-	u32 ignore_signals:1;
+	u32 block_signals:1;
 	unsigned long stack;
 	unsigned long stack_size;
 	unsigned long tls;
diff --git a/kernel/fork.c b/kernel/fork.c
index ed4e01daccaa..9e04ab5c3946 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2338,14 +2338,10 @@ __latent_entropy struct task_struct *copy_process(
 		p->flags |= PF_KTHREAD;
 	if (args->user_worker)
 		p->flags |= PF_USER_WORKER;
-	if (args->io_thread) {
-		/*
-		 * Mark us an IO worker, and block any signal that isn't
-		 * fatal or STOP
-		 */
+	if (args->io_thread)
 		p->flags |= PF_IO_WORKER;
+	if (args->block_signals)
 		siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
-	}
 
 	if (args->name)
 		strscpy_pad(p->comm, args->name, sizeof(p->comm));
@@ -2517,9 +2513,6 @@ __latent_entropy struct task_struct *copy_process(
 	if (retval)
 		goto bad_fork_cleanup_io;
 
-	if (args->ignore_signals)
-		ignore_signals(p);
-
 	stackleak_task_init(p);
 
 	if (pid != &init_struct_pid) {
@@ -2861,6 +2854,7 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
 		.fn_arg		= arg,
 		.io_thread	= 1,
 		.user_worker	= 1,
+		.block_signals	= 1,
 	};
 
 	return copy_process(NULL, 0, node, &args);
diff --git a/kernel/vhost_task.c b/kernel/vhost_task.c
index a661cfa32ba3..a11f036290cc 100644
--- a/kernel/vhost_task.c
+++ b/kernel/vhost_task.c
@@ -95,13 +95,14 @@ struct vhost_task *vhost_task_create(int (*fn)(void *), void *arg,
 				     const char *name)
 {
 	struct kernel_clone_args args = {
-		.flags		= CLONE_FS | CLONE_UNTRACED | CLONE_VM,
+		.flags		= CLONE_FS | CLONE_UNTRACED | CLONE_VM |
+				  CLONE_THREAD | CLONE_SIGHAND,
 		.exit_signal	= 0,
 		.fn		= vhost_task_fn,
 		.name		= name,
 		.user_worker	= 1,
 		.no_files	= 1,
-		.ignore_signals	= 1,
+		.block_signals	= 1,
 	};
 	struct vhost_task *vtsk;
 	struct task_struct *tsk;
-- 
2.25.1