Messages in this thread | | | Date | Tue, 5 Oct 2021 14:50:18 +0200 | From | Christian Brauner <> | Subject | Re: [PATCH V3 5/9] fork: add helper to clone a process |
| |
On Mon, Oct 04, 2021 at 02:21:24PM -0500, Mike Christie wrote: > The vhost layer has similar requirements as io_uring where its worker > threads need to access the userspace thread's memory, want to inherit the > parents's cgroups and namespaces, and be checked against the parent's > RLIMITs. Right now, the vhost layer uses the kthread API which has > kthread_use_mm for mem access, and those threads can use > cgroup_attach_task_all for v1 cgroups, but there are no helpers for the > other items. > > This adds a helper to clone a process so we can inherit everything we > want in one call. It's a more generic version of create_io_thread which > will be used by the vhost layer and io_uring in later patches in this set. > > Signed-off-by: Mike Christie <michael.christie@oracle.com> > Acked-by: Christian Brauner <christian.brauner@ubuntu.com> > --- > include/linux/sched/task.h | 6 ++++- > kernel/fork.c | 48 ++++++++++++++++++++++++++++++++++++++ > 2 files changed, 53 insertions(+), 1 deletion(-) > > diff --git a/include/linux/sched/task.h b/include/linux/sched/task.h > index e165cc67fd3c..ba0499b6627c 100644 > --- a/include/linux/sched/task.h > +++ b/include/linux/sched/task.h > @@ -87,7 +87,11 @@ extern void exit_files(struct task_struct *); > extern void exit_itimers(struct signal_struct *); > > extern pid_t kernel_clone(struct kernel_clone_args *kargs); > -struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node); > +struct task_struct *create_io_thread(int (*fn)(void *i), void *arg, int node); > +struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node, > + unsigned long clone_flags, u32 worker_flags); > +__printf(2, 3) > +void kernel_worker_start(struct task_struct *tsk, const char namefmt[], ...); > struct task_struct *fork_idle(int); > struct mm_struct *copy_init_mm(void); > extern pid_t kernel_thread(int (*fn)(void *), void *arg, unsigned long flags); > diff --git a/kernel/fork.c b/kernel/fork.c > index 98264cf1d6a6..3f3fcabffa5f 100644 > --- a/kernel/fork.c > +++ b/kernel/fork.c > @@ -2540,6 +2540,54 @@ struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node) > return copy_process(NULL, 0, node, &args); > } > > +/** > + * kernel_worker - create a copy of a process to be used by the kernel > + * @fn: thread stack > + * @arg: data to be passed to fn > + * @node: numa node to allocate task from > + * @clone_flags: CLONE flags > + * @worker_flags: KERN_WORKER flags > + * > + * This returns a created task, or an error pointer. The returned task is > + * inactive, and the caller must fire it up through kernel_worker_start(). If > + * this is an PF_IO_WORKER all singals but KILL and STOP are blocked. > + */ > +struct task_struct *kernel_worker(int (*fn)(void *), void *arg, int node, > + unsigned long clone_flags, u32 worker_flags) > +{ > + struct kernel_clone_args args = { > + .flags = ((lower_32_bits(clone_flags) | CLONE_VM | > + CLONE_UNTRACED) & ~CSIGNAL), > + .exit_signal = (lower_32_bits(clone_flags) & CSIGNAL), > + .stack = (unsigned long)fn, > + .stack_size = (unsigned long)arg, > + .worker_flags = KERN_WORKER_USER | worker_flags, > + }; > + > + return copy_process(NULL, 0, node, &args); > +} > +EXPORT_SYMBOL_GPL(kernel_worker); > + > +/** > + * kernel_worker_start - Start a task created with kernel_worker > + * @tsk: task to wake up > + * @namefmt: printf-style format string for the thread name > + * @arg: arguments for @namefmt > + */ > +void kernel_worker_start(struct task_struct *tsk, const char namefmt[], ...) > +{ > + char name[TASK_COMM_LEN]; > + va_list args;
You could think about reporting an error from this function if KERN_WORK_USER isn't set or only call the below when KERN_WORK_USER is set. Both options are fine.
> + > + va_start(args, namefmt); > + vsnprintf(name, sizeof(name), namefmt, args); > + set_task_comm(tsk, name); > + va_end(args); > + > + wake_up_new_task(tsk); > +} > +EXPORT_SYMBOL_GPL(kernel_worker_start); > + > /* > * Ok, this is the main fork-routine. > * > -- > 2.25.1 >
| |