[PATCH 6/6] kernel: add a kernel_wait helper

[Christoph Hellwig]

On Fri, Jun 19, 2020 at 09:17:00PM +0000, Luis Chamberlain wrote:
> On Thu, Jun 18, 2020 at 04:46:27PM +0200, Christoph Hellwig wrote:
> > --- a/kernel/exit.c
> > +++ b/kernel/exit.c
> > @@ -1626,6 +1626,22 @@ long kernel_wait4(pid_t upid, int __user *stat_addr, int options,
> >  	return ret;
> >  }
> >  
> > +int kernel_wait(pid_t pid, int *stat)
> > +{
> > +	struct wait_opts wo = {
> > +		.wo_type	= PIDTYPE_PID,
> > +		.wo_pid		= find_get_pid(pid),
> > +		.wo_flags	= WEXITED,
> > +	};
> > +	int ret;
> > +
> > +	ret = do_wait(&wo);
> > +	if (ret > 0 && wo.wo_stat)
> > +		*stat = wo.wo_stat;
> 
> Since all we care about is WEXITED, that could be simplified
> to something like this:
> 
> if (ret > 0 && KWIFEXITED(wo.wo_stat)
>  	*stat = KWEXITSTATUS(wo.wo_stat)
> 
> Otherwise callers have to use W*() wrappers.
> 
> > +	put_pid(wo.wo_pid);
> > +	return ret;
> > +}
> 
> Then we don't get *any* in-kernel code dealing with the W*() crap.
> I just unwrapped this for the umh [0], given that otherwise we'd
> have to use KW*() callers elsewhere. Doing it upshot one level
> further would be even better.
> 
> [0] https://lkml.kernel.org/r/20200610154923.27510-1-mcgrof@kernel.org              
Do you just want to pick this patch up, add your suggested bits and
add it to the beginning of your series?  That should clean the whole
thing up a bit.  Nothing else in this series depends on the patch.