Re: [PATCH stable-rc queue/4.9 1/1] futex: Provide distinct return value when owner is exiting

[Xiaoming Ni]

On 2021/2/22 18:16, Greg KH wrote:
> On Mon, Feb 22, 2021 at 03:03:28PM +0800, Xiaoming Ni wrote:
> > From: Thomas Gleixner<tglx@xxxxxxxxxxxxx>
> >
> > commit ac31c7ff8624409ba3c4901df9237a616c187a5d upstream.
> This commit is already in the 4.9 tree.  If the backport was incorrect,
> say that here, and describe what went wrong and why this commit fixes
> it.
>
> Also state what commit this fixes as well, otherwise this changelog just
> looks like it is being applied again to the tree, which doesn't make
> much sense.
>
> thanks,
>
> greg k-h
> .

I wrote a cover for it. but forgot to adjust the title of the cover:

https://lore.kernel.org/lkml/20210222070328.102384-1-nixiaoming@xxxxxxxxxx/


I found a dead code in the queue/4.9 branch of the stable-rc repository.

2021-02-03:
commit c27f392040e2f6 ("futex: Provide distinct return value when
 owner is exiting")
	The function handle_exit_race does not exist. Therefore, the
	change in handle_exit_race() is ignored in the patch round.

2021-02-22:
commit e55cb811e612 ("futex: Cure exit race")
	Define the handle_exit_race() function,
	but no branch in the function returns EBUSY.
	As a result, dead code occurs in the attach_to_pi_owner():

		int ret = handle_exit_race(uaddr, uval, p);
		...
		if (ret == -EBUSY)
			*exiting = p; /* dead code */

To fix the dead code, modify the commit e55cb811e612 ("futex: Cure exit 
race"),
or install a patch to incorporate the changes in handle_exit_race().

I am unfamiliar with the processing of the stable-rc queue branch,
and I cannot find the patch mail of the current branch in
	https://lore.kernel.org/lkml/?q=%22futex%3A+Cure+exit+race%22
Therefore, I re-integrated commit ac31c7ff8624 ("futex: Provide distinct
 return value when owner is exiting").
 And wrote a cover (but forgot to adjust the title of the cover):

https://lore.kernel.org/lkml/20210222070328.102384-1-nixiaoming@xxxxxxxxxx/

Thanks
Xiaoming Ni