linux-kernel - Re: [PATCH v8 13/19] locking/rwsem: Make rwsem->owner an atomic_long

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Message-ID: <0d4d11c4-80e8-f75f-fae8-b653481db260@redhat.com>
Date:   Tue, 4 Jun 2019 11:44:46 -0400
From:   Waiman Long <longman@...hat.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will.deacon@....com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Borislav Petkov <bp@...en8.de>,
        "H. Peter Anvin" <hpa@...or.com>, linux-kernel@...r.kernel.org,
        x86@...nel.org, Davidlohr Bueso <dave@...olabs.net>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Tim Chen <tim.c.chen@...ux.intel.com>,
        huang ying <huang.ying.caritas@...il.com>
Subject: Re: [PATCH v8 13/19] locking/rwsem: Make rwsem->owner an
 atomic_long_t

On 6/4/19 4:52 AM, Peter Zijlstra wrote:
> On Mon, May 20, 2019 at 04:59:12PM -0400, Waiman Long wrote:
>> +static inline struct task_struct *rwsem_read_owner(struct rw_semaphore *sem)
>> +{
>> +	return (struct task_struct *)(atomic_long_read(&sem->owner) &
>> +					~RWSEM_OWNER_FLAGS_MASK);
>> +}
>> +
>> +/*
>> + * Return the real task structure pointer of the owner and the embedded
>> + * flags in the owner. pflags must be non-NULL.
>> + */
>> +static inline struct task_struct *
>> +rwsem_read_owner_flags(struct rw_semaphore *sem, long *pflags)
>> +{
>> +	long owner = atomic_long_read(&sem->owner);
>> +
>> +	*pflags = owner & RWSEM_OWNER_FLAGS_MASK;
>> +	return (struct task_struct *)(owner & ~RWSEM_OWNER_FLAGS_MASK);
>> +}
> I got confused by the 'read' part in those nanes, I initially thought
> they paired with rwsem_set_reader_owned().

Sorry for the confusion. I initially use "get", but I am afraid that it
may get confused with "get/put" for reference counting. So I used read
instead.


> So I've done 's/rwsem_read_owner/rwsem_owner/g on it.

I am fine with getting rid of the "read" from the function names.

Cheers,
Longman