Re: [PATCH v2] locking/mutex: remove redundant argument from __mutex_lock_common()

[Peter Zijlstra]

On Sun, Sep 03, 2023 at 12:33:19AM +0200, Michał Mirosław wrote:
> use_ww_ctx is equivalent to ww_ctx != NULL. The one case where
> use_ww_ctx was true but ww_ctx == NULL leads to the same
> __mutex_add_waiter() call via __ww_mutex_add_waiter().
> 
> Since now __ww_mutex_add_waiter() is called only with ww_ctx != NULL
> (from both regular and PREEMPT_RT implementations), remove the
> branch there.
> 

There were compilers that failed to constant propagate the ww_ctx==NULL
thing properly and generated crap code, the use_ww_ctx thing fixed that.

I can't remember which compilers that were (my brain is saying <gcc-6 or
something, but I could be totally wrong) and if we still care about
people using them (probably not).