Re: [PATCH] mutex: nuke mutex_trylock_recursive

[Daniel Vetter]

On Tue, Feb 16, 2021 at 09:21:46AM +0100, Christian König wrote:
> The last user went away in the 5.11 cycle.
> 
> Signed-off-by: Christian König <christian.koenig@xxxxxxx>

Nice.

Reviewed-by: Daniel Vetter <daniel.vetter@xxxxxxxx>

I think would be good to still stuff this into 5.12 before someone
resurrects this zombie.
-Daniel


> ---
>  include/linux/mutex.h  | 25 -------------------------
>  kernel/locking/mutex.c | 10 ----------
>  scripts/checkpatch.pl  |  6 ------
>  3 files changed, 41 deletions(-)
> 
> diff --git a/include/linux/mutex.h b/include/linux/mutex.h
> index dcd185cbfe79..0cd631a19727 100644
> --- a/include/linux/mutex.h
> +++ b/include/linux/mutex.h
> @@ -199,29 +199,4 @@ extern void mutex_unlock(struct mutex *lock);
>  
>  extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
>  
> -/*
> - * These values are chosen such that FAIL and SUCCESS match the
> - * values of the regular mutex_trylock().
> - */
> -enum mutex_trylock_recursive_enum {
> -	MUTEX_TRYLOCK_FAILED    = 0,
> -	MUTEX_TRYLOCK_SUCCESS   = 1,
> -	MUTEX_TRYLOCK_RECURSIVE,
> -};
> -
> -/**
> - * mutex_trylock_recursive - trylock variant that allows recursive locking
> - * @lock: mutex to be locked
> - *
> - * This function should not be used, _ever_. It is purely for hysterical GEM
> - * raisins, and once those are gone this will be removed.
> - *
> - * Returns:
> - *  - MUTEX_TRYLOCK_FAILED    - trylock failed,
> - *  - MUTEX_TRYLOCK_SUCCESS   - lock acquired,
> - *  - MUTEX_TRYLOCK_RECURSIVE - we already owned the lock.
> - */
> -extern /* __deprecated */ __must_check enum mutex_trylock_recursive_enum
> -mutex_trylock_recursive(struct mutex *lock);
> -
>  #endif /* __LINUX_MUTEX_H */
> diff --git a/kernel/locking/mutex.c b/kernel/locking/mutex.c
> index 5352ce50a97e..adb935090768 100644
> --- a/kernel/locking/mutex.c
> +++ b/kernel/locking/mutex.c
> @@ -86,16 +86,6 @@ bool mutex_is_locked(struct mutex *lock)
>  }
>  EXPORT_SYMBOL(mutex_is_locked);
>  
> -__must_check enum mutex_trylock_recursive_enum
> -mutex_trylock_recursive(struct mutex *lock)
> -{
> -	if (unlikely(__mutex_owner(lock) == current))
> -		return MUTEX_TRYLOCK_RECURSIVE;
> -
> -	return mutex_trylock(lock);
> -}
> -EXPORT_SYMBOL(mutex_trylock_recursive);
> -
>  static inline unsigned long __owner_flags(unsigned long owner)
>  {
>  	return owner & MUTEX_FLAGS;
> diff --git a/scripts/checkpatch.pl b/scripts/checkpatch.pl
> index 92e888ed939f..15f7f4fa6b99 100755
> --- a/scripts/checkpatch.pl
> +++ b/scripts/checkpatch.pl
> @@ -7069,12 +7069,6 @@ sub process {
>  			}
>  		}
>  
> -# check for mutex_trylock_recursive usage
> -		if ($line =~ /mutex_trylock_recursive/) {
> -			ERROR("LOCKING",
> -			      "recursive locking is bad, do not use this ever.\n" . $herecurr);
> -		}
> -
>  # check for lockdep_set_novalidate_class
>  		if ($line =~ /^.\s*lockdep_set_novalidate_class\s*\(/ ||
>  		    $line =~ /__lockdep_no_validate__\s*\)/ ) {
> -- 
> 2.25.1
> 
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-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch