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

From: Mike Christie
Date: Tue Sep 21 2021 - 17:53:39 EST


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@xxxxxxxxxx>
---
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