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Message-Id: <20230603015302.1768127-1-chenhuacai@loongson.cn>
Date: Sat, 3 Jun 2023 09:53:02 +0800
From: Huacai Chen <chenhuacai@...ngson.cn>
To: Luis Chamberlain <mcgrof@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
"Eric W . Biederman" <ebiederm@...ssion.com>
Cc: Kees Cook <keescook@...omium.org>, chenhuacai@...nel.org,
linux-mm@...ck.org, linux-kernel@...r.kernel.org,
Huacai Chen <chenhuacai@...ngson.cn>
Subject: [PATCH V1] kthread: Unify kernel_thread() and user_mode_thread()
Commit 343f4c49f2438d8 ("kthread: Don't allocate kthread_struct for init
and umh") introduces a new function user_mode_thread() for init and umh.
init and umh are different from typical kernel threads since the don't
need a "kthread" struct and they will finally become user processes by
calling kernel_execve(), but on the other hand, they are also different
from typical user mode threads (they have no "mm" structs at creation
time, which is traditionally used to distinguish a user thread and a
kernel thread).
So I think it is reasonable to treat init and umh as "special kernel
threads". Then let's unify the kernel_thread() and user_mode_thread()
to kernel_thread() again, and add a new 'user' parameter for init and
umh.
This also makes code simpler.
Signed-off-by: Huacai Chen <chenhuacai@...ngson.cn>
---
RFC -> V1: Update commit message and change "user" from int to bool.
include/linux/sched/task.h | 3 +--
init/main.c | 4 ++--
kernel/fork.c | 20 ++------------------
kernel/kthread.c | 2 +-
kernel/umh.c | 6 +++---
5 files changed, 9 insertions(+), 26 deletions(-)
diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h
index 537cbf9a2ade..02eb953bc809 100644
--- a/include/linux/sched/task.h
+++ b/include/linux/sched/task.h
@@ -98,8 +98,7 @@ struct task_struct *copy_process(struct pid *pid, int trace, int node,
struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node);
struct task_struct *fork_idle(int);
extern pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
- unsigned long flags);
-extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags);
+ unsigned long flags, bool user);
extern long kernel_wait4(pid_t, int __user *, int, struct rusage *);
int kernel_wait(pid_t pid, int *stat);
diff --git a/init/main.c b/init/main.c
index af50044deed5..469cebbd35e0 100644
--- a/init/main.c
+++ b/init/main.c
@@ -697,7 +697,7 @@ noinline void __ref __noreturn rest_init(void)
* the init task will end up wanting to create kthreads, which, if
* we schedule it before we create kthreadd, will OOPS.
*/
- pid = user_mode_thread(kernel_init, NULL, CLONE_FS);
+ pid = kernel_thread(kernel_init, NULL, NULL, CLONE_FS, true);
/*
* Pin init on the boot CPU. Task migration is not properly working
* until sched_init_smp() has been run. It will set the allowed
@@ -710,7 +710,7 @@ noinline void __ref __noreturn rest_init(void)
rcu_read_unlock();
numa_default_policy();
- pid = kernel_thread(kthreadd, NULL, NULL, CLONE_FS | CLONE_FILES);
+ pid = kernel_thread(kthreadd, NULL, NULL, CLONE_FS | CLONE_FILES, false);
rcu_read_lock();
kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns);
rcu_read_unlock();
diff --git a/kernel/fork.c b/kernel/fork.c
index ed4e01daccaa..f91696904252 100644
--- a/kernel/fork.c
+++ b/kernel/fork.c
@@ -2965,7 +2965,7 @@ pid_t kernel_clone(struct kernel_clone_args *args)
* Create a kernel thread.
*/
pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
- unsigned long flags)
+ unsigned long flags, bool user)
{
struct kernel_clone_args args = {
.flags = ((lower_32_bits(flags) | CLONE_VM |
@@ -2974,23 +2974,7 @@ pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name,
.fn = fn,
.fn_arg = arg,
.name = name,
- .kthread = 1,
- };
-
- return kernel_clone(&args);
-}
-
-/*
- * Create a user mode thread.
- */
-pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags)
-{
- struct kernel_clone_args args = {
- .flags = ((lower_32_bits(flags) | CLONE_VM |
- CLONE_UNTRACED) & ~CSIGNAL),
- .exit_signal = (lower_32_bits(flags) & CSIGNAL),
- .fn = fn,
- .fn_arg = arg,
+ .kthread = !user,
};
return kernel_clone(&args);
diff --git a/kernel/kthread.c b/kernel/kthread.c
index 490792b1066e..5f025569eb38 100644
--- a/kernel/kthread.c
+++ b/kernel/kthread.c
@@ -400,7 +400,7 @@ static void create_kthread(struct kthread_create_info *create)
#endif
/* We want our own signal handler (we take no signals by default). */
pid = kernel_thread(kthread, create, create->full_name,
- CLONE_FS | CLONE_FILES | SIGCHLD);
+ CLONE_FS | CLONE_FILES | SIGCHLD, false);
if (pid < 0) {
/* Release the structure when caller killed by a fatal signal. */
struct completion *done = xchg(&create->done, NULL);
diff --git a/kernel/umh.c b/kernel/umh.c
index 60aa9e764a38..b0ead7cce761 100644
--- a/kernel/umh.c
+++ b/kernel/umh.c
@@ -130,7 +130,7 @@ static void call_usermodehelper_exec_sync(struct subprocess_info *sub_info)
/* If SIGCLD is ignored do_wait won't populate the status. */
kernel_sigaction(SIGCHLD, SIG_DFL);
- pid = user_mode_thread(call_usermodehelper_exec_async, sub_info, SIGCHLD);
+ pid = kernel_thread(call_usermodehelper_exec_async, sub_info, NULL, SIGCHLD, true);
if (pid < 0)
sub_info->retval = pid;
else
@@ -169,8 +169,8 @@ static void call_usermodehelper_exec_work(struct work_struct *work)
* want to pollute current->children, and we need a parent
* that always ignores SIGCHLD to ensure auto-reaping.
*/
- pid = user_mode_thread(call_usermodehelper_exec_async, sub_info,
- CLONE_PARENT | SIGCHLD);
+ pid = kernel_thread(call_usermodehelper_exec_async, sub_info,
+ NULL, CLONE_PARENT | SIGCHLD, true);
if (pid < 0) {
sub_info->retval = pid;
umh_complete(sub_info);
--
2.39.1
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