[PATCH V2 7/9] fork: Add worker flag to ignore signals

[Mike Christie <michael.christie@oracle.com>]

The kthread API creates threads that ignore all signals by default so
modules like vhost that will move from that API to kernel_worker will
not be expecting them. This patch adds a worker flag that tells
kernel_worker to setup the task to ignore signals.

Signed-off-by: Mike Christie <michael.christie@oracle.com>
---
 include/linux/sched/task.h |  1 +
 kernel/fork.c              | 11 ++++++++++-
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 781abbc1c288..aefa0d221b57 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -21,6 +21,7 @@ struct css_set;
 #define KERN_WORKER_IO		BIT(0)
 #define KERN_WORKER_USER	BIT(1)
 #define KERN_WORKER_NO_FILES	BIT(2)
+#define KERN_WORKER_NO_SIGS	BIT(3)
 
 struct kernel_clone_args {
 	u64 flags;
diff --git a/kernel/fork.c b/kernel/fork.c
index 3f3fcabffa5f..34d3dca70cfb 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2555,6 +2555,8 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node)
 struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node,
 				  unsigned long clone_flags, u32 worker_flags)
 {
+	struct task_struct *tsk;
+
 	struct kernel_clone_args args = {
 		.flags		= ((lower_32_bits(clone_flags) | CLONE_VM |
 				   CLONE_UNTRACED) & ~CSIGNAL),
@@ -2564,7 +2566,14 @@ struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node,
 		.worker_flags	= KERN_WORKER_USER | worker_flags,
 	};
 
-	return copy_process(NULL, 0, node, &args);
+	tsk = copy_process(NULL, 0, node, &args);
+	if (IS_ERR(tsk))
+		return tsk;
+
+	if (worker_flags & KERN_WORKER_NO_SIGS)
+		ignore_signals(tsk);
+
+	return tsk;
 }
 EXPORT_SYMBOL_GPL(kernel_worker);
 
-- 
2.25.1