linux-kernel - Re: [RFC][PATCH 3/4] locking/rtmutex: Add context analysis

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Message-ID: <20260121190144.GK166857@noisy.programming.kicks-ass.net>
Date: Wed, 21 Jan 2026 20:01:44 +0100
From: Peter Zijlstra <peterz@...radead.org>
To: Bart Van Assche <bvanassche@....org>
Cc: elver@...gle.com, linux-kernel@...r.kernel.org, bigeasy@...utronix.de,
	mingo@...nel.org, tglx@...utronix.de, will@...nel.org,
	boqun.feng@...il.com, longman@...hat.com, hch@....de,
	rostedt@...dmis.org, llvm@...ts.linux.dev
Subject: Re: [RFC][PATCH 3/4] locking/rtmutex: Add context analysis

On Wed, Jan 21, 2026 at 09:15:53AM -0800, Bart Van Assche wrote:
> On 1/21/26 3:07 AM, Peter Zijlstra wrote:
> > Add compiler context analysis annotations.
> > 
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
> > ---
> >   include/linux/mutex.h           |    2 +-
> >   include/linux/rtmutex.h         |    4 ++--
> >   kernel/locking/Makefile         |    2 ++
> >   kernel/locking/mutex.c          |    2 --
> >   kernel/locking/rtmutex.c        |   18 +++++++++++++++++-
> >   kernel/locking/rtmutex_api.c    |    3 +++
> >   kernel/locking/rtmutex_common.h |   22 ++++++++++++++++------
> >   kernel/locking/ww_mutex.h       |   18 +++++++++++++-----
> >   kernel/locking/ww_rt_mutex.c    |    1 +
> >   9 files changed, 55 insertions(+), 17 deletions(-)
> 
> The patch subject says "rtmutex" but this patch includes a change for
> the header file include/linux/mutex.h. Shouldn't that change be moved
> into the mutex patch?

Clearly I suffered from wandering hunks syndrome while doing these :/

> > --- a/kernel/locking/mutex.c
> > +++ b/kernel/locking/mutex.c
> > @@ -848,7 +848,6 @@ EXPORT_SYMBOL_GPL(mutex_lock_nested);
> >   void __sched
> >   _mutex_lock_nest_lock(struct mutex *lock, struct lockdep_map *nest)
> > -	__acquires(lock)
> >   {
> >   	__mutex_lock(lock, TASK_UNINTERRUPTIBLE, 0, nest, _RET_IP_);
> >   	__acquire(lock);
> 
> Shouldn't the "__acquires()" annotation be moved to the declaration in
> <linux/mutex.h>?

It is, but yeah, this should be in the previous patch.

> >   #define MUTEX		mutex
> >   #define MUTEX_WAITER	mutex_waiter
> > +#define MUST_HOLD_WAIT_LOCK	__must_hold(&lock->wait_lock)
> >   static inline struct mutex_waiter *
> >   __ww_waiter_first(struct mutex *lock)
> > @@ -97,9 +98,11 @@ static inline void lockdep_assert_wait_l
> >   #define MUTEX		rt_mutex
> >   #define MUTEX_WAITER	rt_mutex_waiter
> > +#define MUST_HOLD_WAIT_LOCK	__must_hold(&lock->rtmutex.wait_lock)
> 
> Is it really necessary to introduce these two macros? I prefer to see
> the __must_hold() annotations instead of the macro names.

You'd rather see something like:

	__must_hold(&lock->WAIT_LOCK)

? Can do I suppose.