linux-kernel - [PATCH 4/8] fork: move PF_IO_WORKER's kernel frame setup to new flag

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Message-Id: <20210916212051.6918-5-michael.christie@oracle.com>
Date:   Thu, 16 Sep 2021 16:20:47 -0500
From:   Mike Christie <michael.christie@...cle.com>
To:     stefanha@...hat.com, jasowang@...hat.com, mst@...hat.com,
        sgarzare@...hat.com, virtualization@...ts.linux-foundation.org,
        christian.brauner@...ntu.com, axboe@...nel.dk,
        linux-kernel@...r.kernel.org
Cc:     Mike Christie <michael.christie@...cle.com>
Subject: [PATCH 4/8] fork: move PF_IO_WORKER's kernel frame setup to new flag

The vhost worker threads need the same frame setup as io_uring's worker
threads, but do not handle signals and may not even be executing IO. This
moves the setup part to a new flag.

Signed-off-by: Mike Christie <michael.christie@...cle.com>
---
 arch/x86/kernel/process.c  | 4 ++--
 include/linux/sched.h      | 1 +
 include/linux/sched/task.h | 1 +
 kernel/fork.c              | 3 +++
 4 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index 1d9463e3096b..ccdec11cd120 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -178,9 +178,9 @@ int copy_thread(unsigned long clone_flags, unsigned long sp, unsigned long arg,
 	task_user_gs(p) = get_user_gs(current_pt_regs());
 #endif
 
-	if (unlikely(p->flags & PF_IO_WORKER)) {
+	if (unlikely(p->flags & PF_USER_WORKER)) {
 		/*
-		 * An IO thread is a user space thread, but it doesn't
+		 * An user worker thread is a user space thread, but it doesn't
 		 * return to ret_after_fork().
 		 *
 		 * In order to indicate that to tools like gdb,
diff --git a/include/linux/sched.h b/include/linux/sched.h
index e12b524426b0..817d3a7bec77 100644
--- a/include/linux/sched.h
+++ b/include/linux/sched.h
@@ -1664,6 +1664,7 @@ extern struct pid *cad_pid;
 #define PF_VCPU			0x00000001	/* I'm a virtual CPU */
 #define PF_IDLE			0x00000002	/* I am an IDLE thread */
 #define PF_EXITING		0x00000004	/* Getting shut down */
+#define PF_USER_WORKER		0x00000008	/* Userspace kernel worker */
 #define PF_IO_WORKER		0x00000010	/* Task is an IO worker */
 #define PF_WQ_WORKER		0x00000020	/* I'm a workqueue worker */
 #define PF_FORKNOEXEC		0x00000040	/* Forked but didn't exec */
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index d0b0872f56cc..4a6100a24894 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -33,6 +33,7 @@ struct kernel_clone_args {
 	int cgroup;
 	int io_thread;
 	int no_files;
+	int user_worker;
 	struct cgroup *cgrp;
 	struct css_set *cset;
 };
diff --git a/kernel/fork.c b/kernel/fork.c
index a0468e30b27e..1dda1d4ea77b 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2041,6 +2041,8 @@ static __latent_entropy struct task_struct *copy_process(
 		siginitsetinv(&p->blocked, sigmask(SIGKILL)|sigmask(SIGSTOP));
 	}
 
+	if (args->user_worker)
+		p->flags |= PF_USER_WORKER;
 	/*
 	 * This _must_ happen before we call free_task(), i.e. before we jump
 	 * to any of the bad_fork_* labels. This is to avoid freeing
@@ -2563,6 +2565,7 @@ struct task_struct *kernel_copy_process(int (*fn)(void *), void *arg, int node,
 		.stack_size	= (unsigned long)arg,
 		.io_thread	= io_thread,
 		.no_files	= no_files,
+		.user_worker	= 1,
 	};
 
 	return copy_process(NULL, 0, node, &args);
-- 
2.25.1