From: Peter Zijlstra <peterz@infradead.org>
To: "Michał Mirosław" <mirq-linux@rere.qmqm.pl>
Cc: Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
Waiman Long <longman@redhat.com>,
Boqun Feng <boqun.feng@gmail.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] locking/mutex: remove redundant argument from __mutex_lock_common()
Date: Mon, 4 Sep 2023 15:18:53 +0200 [thread overview]
Message-ID: <20230904131853.GA12042@noisy.programming.kicks-ass.net> (raw)
In-Reply-To: <49c7163433999cc1fc9367311fbe6c6d5fd9f251.1693693823.git.mirq-linux@rere.qmqm.pl>
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).
next prev parent reply other threads:[~2023-09-04 13:19 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-02 22:33 [PATCH v2] locking/mutex: remove redundant argument from __mutex_lock_common() Michał Mirosław
2023-09-04 13:18 ` Peter Zijlstra [this message]
2023-09-04 19:08 ` Ingo Molnar
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