[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20220420133325.pdppfuc3ijggrgc4@wittgenstein>
Date: Wed, 20 Apr 2022 15:33:25 +0200
From: Christian Brauner <brauner@...nel.org>
To: 王洪亮 <wanghongliang@...ngson.cn>
Cc: musl@...ts.openwall.com
Subject: Re: Re: add loongarch64 port
On Wed, Apr 20, 2022 at 05:09:08PM +0800, 王洪亮 wrote:
>
> 在 2022/4/14 下午5:36, Christian Brauner 写道:
> > On Wed, Apr 13, 2022 at 10:09:31AM -0400, Rich Felker wrote:
> > > On Wed, Apr 13, 2022 at 03:25:05PM +0200, Arnd Bergmann wrote:
> > > > On Wed, Apr 13, 2022 at 11:04 AM Christian Brauner <brauner@...nel.org> wrote:
> > > > > On Wed, Apr 13, 2022 at 10:26:06AM +0200, Arnd Bergmann wrote:
> > > > > > The normal rule is that we don't define obsolete system calls in new
> > > > > > architectures when an improved variant has been added, e.g. oldoldstat,
> > > > > > oldstat, stat, newstat and stat64 have all been replaced by statx over
> > > > > > the decades. I was expecting the same to be true for clone(), but if
> > > > > > clone3() is not meant as a replacement, we can keep both around.
> > > > > No, I agree with you on this and would like to only implement clone3()
> > > > > on new architectures.
> > > > >
> > > > > What I'm asking is whether removing the size == 0 check is enough to
> > > > > unblock the missing behavior and whether you'd be on board with removing
> > > > > the check?
> > > > I think that's ok here, since we'd only rely on this for loongarch64 at the
> > > > moment. It would probably need to be documented in the man page
> > > > as a special case though.
> > > I'm okay with removing the check for size==0 (so size==0 will be
> > > allowed) and dropping __NR_clone on new archs, as long as it's noted
> > > in comments/documentation that size==0 is explicitly allowed so nobody
> > > breaks this in the future.
> > Ok, I'll try to have a patch ready early next week since I'm currently
> > out sick.
>
> Hi,
>
> I'm implementing __NR_clone3 syscall within __clone().
>
> I have another problem:CLONE_DETACHED
>
> in musl,internal call __clone()(such as __pthread_create()),the input
> parameter flags
>
> has been set CLONE_DETACHED ,in kernel,there is a check in
> clone3_args_valid(),
>
> if the condition met,return false.
>
> How to deal with this problem?
CLONE_DETACHED is meaningles since Linux on 2.6.2. There really should
be <=2.6.1 living kernel anywhere where CLONE_DETACHED does anything.
I've documented that in detail under [1] as:
CLONE_DETACHED (historical)
For a while (during the Linux 2.5 development series)
there was a CLONE_DETACHED flag, which caused the parent
not to receive a signal when the child terminated.
Ultimately, the effect of this flag was subsumed under the
CLONE_THREAD flag and by the time Linux 2.6.0 was
released, this flag had no effect. Starting in Linux
2.6.2, the need to give this flag together with
CLONE_THREAD disappeared.
This flag is still defined, but it is usually ignored when
calling clone(). However, see the description of
CLONE_PIDFD for some exceptions.
[1]: https://man7.org/linux/man-pages/man2/clone.2.html
Would it be possible to drop this flag from musl's pthread_create()
implementation? (Iirc, glibc dropped CLONE_DETACHED in 2004.)
>
> src/thread/pthread_create.c:
> int __pthread_create(pthread_t *restrict res, const pthread_attr_t *restrict
> attrp,
> void *(*entry)(void *), void *restrict arg)
> {
> unsigned flags = CLONE_VM | CLONE_FS | CLONE_FILES | CLONE_SIGHAND
> | CLONE_THREAD | CLONE_SYSVSEM | CLONE_SETTLS
> | CLONE_PARENT_SETTID | CLONE_CHILD_CLEARTID | CLONE_DETACHED;
> ...
> ret = __clone((c11 ? start_c11 : start), stack, flags, args, &new->tid,
> TP_ADJ(new), &__thread_list_lock);
> }
>
> kernel/fork.c:
> static bool clone3_args_valid(struct kernel_clone_args *kargs)
> {
> /*
> * - make the CLONE_DETACHED bit reusable for clone3
> * - make the CSIGNAL bits reusable for clone3
> */
> if (kargs->flags & (CLONE_DETACHED | CSIGNAL))
> return false;
> }
>
>
> Hongliang Wang
>
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
