linux-kernel - [PATCH V8 4/8] fork: Add USER_WORKER flag to ignore signals

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Date:   Wed,  9 Feb 2022 17:29:35 -0600
From:   Mike Christie <michael.christie@...cle.com>
To:     geert@...ux-m68k.org, hdanton@...a.com, hch@...radead.org,
        stefanha@...hat.com, jasowang@...hat.com, mst@...hat.com,
        sgarzare@...hat.com, virtualization@...ts.linux-foundation.org,
        christian.brauner@...ntu.com, axboe@...nel.dk,
        ebiederm@...ssion.com, linux-kernel@...r.kernel.org
Cc:     Mike Christie <michael.christie@...cle.com>,
        Christoph Hellwig <hch@....de>
Subject: [PATCH V8 4/8] fork: Add USER_WORKER flag to ignore signals

From: Christian Brauner <christian.brauner@...ntu.com>

Since:

commit 10ab825bdef8 ("change kernel threads to ignore signals instead of
blocking them")

kthreads have been ignoring signals by default, and the vhost layer has
never had a need to change that. This patch adds an option flag,
USER_WORKER_SIG_IGN, handled in copy_process() after copy_sighand()
and copy_signals() so vhost_tasks added in the next patches which are
based directly off task_structs instead of kthreads can continue to ignore
singals.

Signed-off-by: Christian Brauner <christian.brauner@...ntu.com>
Signed-off-by: Mike Christie <michael.christie@...cle.com>
Reviewed-by: Christoph Hellwig <hch@....de>
---
 include/linux/sched/task.h | 1 +
 kernel/fork.c              | 3 +++
 2 files changed, 4 insertions(+)

diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 706ca3dc3423..c001d0fa1426 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -21,6 +21,7 @@ struct css_set;
 #define USER_WORKER		BIT(0)
 #define USER_WORKER_IO		BIT(1)
 #define USER_WORKER_NO_FILES	BIT(2)
+#define USER_WORKER_SIG_IGN	BIT(3)
 
 struct kernel_clone_args {
 	u64 flags;
diff --git a/kernel/fork.c b/kernel/fork.c
index 81a1096d6ee9..6a04860fa1ae 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2185,6 +2185,9 @@ static __latent_entropy struct task_struct *copy_process(
 	if (retval)
 		goto bad_fork_cleanup_io;
 
+	if (args->worker_flags & USER_WORKER_SIG_IGN)
+		ignore_signals(p);
+
 	stackleak_task_init(p);
 
 	if (pid != &init_struct_pid) {
-- 
2.25.1