Huacai Chen <chenhuacai@xxxxxxxxxx> writes: > Hi, Eric, > > On Tue, Sep 12, 2023 at 9:59 AM Eric W. Biederman <ebiederm@xxxxxxxxxxxx> wrote: >> >> Huacai Chen <chenhuacai@xxxxxxxxxx> writes: >> >> > Hi, all, >> > >> > Friendly ping again? >> > >> > >> > Huacai >> > >> > On Sun, Jul 23, 2023 at 10:13 PM Huacai Chen <chenhuacai@xxxxxxxxxx> wrote: >> >> >> >> Hi, Eric, >> >> >> >> On Tue, Jul 18, 2023 at 8:43 PM Huacai Chen <chenhuacai@xxxxxxxxxx> wrote: >> >> > >> >> > Hi, Luis, >> >> > >> >> > On Sat, Jul 1, 2023 at 7:25 AM Luis Chamberlain <mcgrof@xxxxxxxxxx> wrote: >> >> > > >> >> > > On Sun, Jun 25, 2023 at 04:55:33PM +0800, Huacai Chen wrote: >> >> > > > Friendly ping? >> >> > > >> >> > > You want to cc the folks who Nacked your patch. Until then, this >> >> > > probably can't go further. >> >> > Thank you very much. Eric and Andrew are already in the CC list, so >> >> > add Thomas now. >> >> > >> >> > My brain is a little old-fashioned so I insisted that "a thread >> >> > without mm_struct should be a kernel thread" in the previous patch. >> >> > Unfortunately this makes Eric and Thomas unhappy, I'm very sorry for >> >> > that. >> >> > >> >> > During the discussion of the previous patch I know I made some >> >> > mistakes about some basic concepts, but I also found the name >> >> > "user_mode_thread()" is somewhat confusing. I think rename it to >> >> > kmuser_thread() is better, because: >> >> > 1, it identify init and umh as user threads; >> >> > 2, it points out that init and umh are special user threads that run >> >> > in kernel mode before loading a user program. >> >> > >> >> > Sorry for my rudeness again. >> >> Excuse me, but could you please tell me what your opinion is. In my >> >> opinion a typical user thread is created by >> >> pthread_create()/sys_clone(), it is better to distinguish typical user >> >> threads from init and umh. >> >> If we want to emphasize that it is a kernel concept I am happy with >> renaming user_mode_thread to user_mode_task. That is more accurate. >> >> But all threads from the kernel perspective are tasks. Further >> all threads have times when they run code in the kernel (aka system >> calls) and times when they run code in userspace. >> >> Linux kernel tasks created with user_mode_thread() are exactly like >> other user mode tasks, and have all treated exactly the same was by the >> system as any the tasks created by pthread_create() and sys_clone(). >> >> The only oddity is that there is no user mode code to execute until >> after execve is called. >> >> When running code in the kernel, user space threads never logically >> do not use the user space page tables. >> >> They are different in some significant ways from tasks created with >> kernel_thread(). Tasks created with kernel_thread do not support >> calling execve, among other things. >> >> But deeply and fundamentally I think you are trying to make a >> distinction that is not there. All user space threads run code >> in the kernel before they run code in userspace. Most often >> it is from the system calls fork/clone/exec. For init and umh it >> is effectively a special dedicated system call that includes >> an execve. >> >> Let me ask what difference are you trying to high light that callers >> of user_mode_thread need to be aware of? What problem in thinking >> do you think that the name user_mode_thread creates? I am asking >> because I might just be missing your point. > 1, My first key point is “intuition”, by intuition > sys_clone()/pthread_create() creates a user thread, but init and umh > are more or less different (special user thread). My point is the entire point of the name is to point out your intuition is probably wrong in this context. > 2, My second key point is "symmetry", for symmetry ‘kernel_thread’ is > a counterpart of ‘user_thread’, while ‘user_mode_thread’ is a > counterpart of ‘kernel_mode_thread’. If we keep the ‘kernel_thread’ > name, then we can only rename the ‘user_mode_thread’. Frankly they could just as well be named user_mode_process, and user_mode_task. All are equally accurate. kernel_thread is a bit different. Strictly speaking they are all processes that share the same address space. But because they all share the same address space and userspace can't touch them thread is a perfectly adequate term. > As discussed > before, init and umh are user threads, but they are special user > threads run in kernel mode before kernel_execve, so I want to rename > it to ‘user_thread’ with a 'km' prefix, so ‘kmuser_thread’. My deep and fundamental question to you is what technically makes umh and init special? What are you trying to point out to the rest of us with an improved name? I want to point out that people need to treat umh and init as user space processes, and very much not as kernel threads. That none of the kernel_thread infrastructure works on them. Eric
