linux-kernel - Re: [PATCH] Locking: Let PREEMPT_RT compile again with new rwsem asserts.

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Message-ID: <20240319141506.DUd9NKl4@linutronix.de>
Date: Tue, 19 Mar 2024 15:15:06 +0100
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: Matthew Wilcox <willy@...radead.org>
Cc: linux-kernel@...r.kernel.org, Boqun Feng <boqun.feng@...il.com>,
	Ingo Molnar <mingo@...hat.com>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Waiman Long <longman@...hat.com>, Will Deacon <will@...nel.org>,
	Clark Williams <williams@...hat.com>
Subject: Re: [PATCH] Locking: Let PREEMPT_RT compile again with new rwsem
 asserts.

On 2024-03-19 13:38:06 [+0000], Matthew Wilcox wrote:
> On Tue, Mar 19, 2024 at 08:05:50AM +0100, Sebastian Andrzej Siewior wrote:
> > -static inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem)
> > +static __always_inline bool rwsem_held_write(const struct rw_semaphore *sem)
> 
> The locking maintainers were very clear that this predicate Should Not
> Exist.  It encourages people to write bad code.  Assertions only!

What do you refer to? The inline vs __always_inline or
rwsem_held_write() should not exists and it should invoke directly
rw_base_is_write_locked()?

> >  {
> > -	rw_base_assert_held_write(sem);
> > +	return rw_base_is_write_locked(&sem->rwbase);
> > +}
> > +
> > +static __always_inline void rwsem_assert_held_write_nolockdep(const struct rw_semaphore *sem)
> > +{
> > +	WARN_ON(!rwsem_held_write(sem));
> >  }
> >  
> >  static __always_inline int rwsem_is_contended(struct rw_semaphore *sem)

Sebastian