linux-kernel - Re: linux-next: Tree for Dec 6 (objtool, lots in btrfs)

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Date:   Tue, 17 Dec 2019 16:29:54 +0100
From:   David Sterba <dsterba@...e.cz>
To:     Josh Poimboeuf <jpoimboe@...hat.com>
Cc:     Randy Dunlap <rdunlap@...radead.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Linux Next Mailing List <linux-next@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Btrfs <linux-btrfs@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: linux-next: Tree for Dec 6 (objtool, lots in btrfs)

On Fri, Dec 13, 2019 at 11:45:15PM -0600, Josh Poimboeuf wrote:
> On Fri, Dec 13, 2019 at 04:04:58PM -0800, Randy Dunlap wrote:
> > > diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> > > index b2e8fd8a8e59..bbd68520f5f1 100644
> > > --- a/fs/btrfs/ctree.h
> > > +++ b/fs/btrfs/ctree.h
> > > @@ -3110,14 +3110,16 @@ do {								\
> > >  	rcu_read_unlock();					\
> > >  } while (0)
> > >  
> > > -__cold
> > > +#ifdef CONFIG_BTRFS_ASSERT
> > > +__cold __unlikely
> > 
> > what provides __unlikely?  It is causing build errors.
> > 
> > and if I remove the "__unlikely", I still see the objtool warnings
> > (unreachable instructions).
> 
> Ha, not sure how that happened... Should be __noreturn instead of
> __unlikely.  Cheers...
> 
> diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
> index b2e8fd8a8e59..398bd010dfc5 100644
> --- a/fs/btrfs/ctree.h
> +++ b/fs/btrfs/ctree.h
> @@ -3110,14 +3110,16 @@ do {								\
>  	rcu_read_unlock();					\
>  } while (0)
>  
> -__cold
> +#ifdef CONFIG_BTRFS_ASSERT
> +__cold __noreturn
>  static inline void assfail(const char *expr, const char *file, int line)
>  {
> -	if (IS_ENABLED(CONFIG_BTRFS_ASSERT)) {
> -		pr_err("assertion failed: %s, in %s:%d\n", expr, file, line);
> -		BUG();
> -	}
> +	pr_err("assertion failed: %s, in %s:%d\n", expr, file, line);
> +	BUG();
>  }
> +#else
> +static inline void assfail(const char *expr, const char *file, int line) {}
> +#endif
>  
>  #define ASSERT(expr)	\
>  	(likely(expr) ? (void)0 : assfail(#expr, __FILE__, __LINE__))

Separating the definitions by #ifdef looks ok, I'd rather do separate
definitions of ASSERT too, to avoid the ternary operator. I'll send the
patch.