linux-kernel - Re: [PATCH 15/15] seqlock: drop seqcount_ww_mutex

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Date:   Thu, 7 Apr 2022 13:48:45 +0200
From:   Christian König <christian.koenig@....com>
To:     Christian König <ckoenig.leichtzumerken@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-media@...r.kernel.org,
        linaro-mm-sig@...ts.linaro.org, intel-gfx@...ts.freedesktop.org,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Waiman Long <longman@...hat.com>,
        Boqun Feng <boqun.feng@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 15/15] seqlock: drop seqcount_ww_mutex_t

Am 07.04.22 um 11:19 schrieb Daniel Vetter:
> On Thu, Apr 07, 2022 at 10:59:46AM +0200, Christian König wrote:
>> Daniel pointed out that this series removes the last user of
>> seqcount_ww_mutex_t, so let's drop this.
>>
>> Signed-off-by: Christian König <christian.koenig@....com>
>> Cc: Peter Zijlstra <peterz@...radead.org>
>> Cc: Ingo Molnar <mingo@...hat.com>
>> Cc: Will Deacon <will@...nel.org>
>> Cc: Waiman Long <longman@...hat.com>
>> Cc: Boqun Feng <boqun.feng@...il.com>
>> Cc: linux-kernel@...r.kernel.org
> Yeah I don't think we'll ever need this again, ww_mutex aren't common and
> the ww_mutex+seqlock thing wasn't the brighest idea.
>
> Peter/Ingo, assuming you agree, can you ack this for merging through
> drm-misc, or want to pick this up later on when the last user disappeared
> in Linus' tree?

Mpf, I didn't noticed that removing ww_mutex.h from seqlock.h is causing 
a problem for futex.h.

Just send out a patch to fix this because the build servers are pointing 
out now that drm-misc-next is broken.

Please review ASAP,
Christian.

>
> Cheers, Daniel
>
>> ---
>>   include/linux/seqlock.h | 8 ++------
>>   1 file changed, 2 insertions(+), 6 deletions(-)
>>
>> diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
>> index 37ded6b8fee6..3926e9027947 100644
>> --- a/include/linux/seqlock.h
>> +++ b/include/linux/seqlock.h
>> @@ -17,7 +17,6 @@
>>   #include <linux/kcsan-checks.h>
>>   #include <linux/lockdep.h>
>>   #include <linux/mutex.h>
>> -#include <linux/ww_mutex.h>
>>   #include <linux/preempt.h>
>>   #include <linux/spinlock.h>
>>   
>> @@ -164,7 +163,7 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s)
>>    * static initializer or init function. This enables lockdep to validate
>>    * that the write side critical section is properly serialized.
>>    *
>> - * LOCKNAME:	raw_spinlock, spinlock, rwlock, mutex, or ww_mutex.
>> + * LOCKNAME:	raw_spinlock, spinlock, rwlock or mutex
>>    */
>>   
>>   /*
>> @@ -184,7 +183,6 @@ static inline void seqcount_lockdep_reader_access(const seqcount_t *s)
>>   #define seqcount_spinlock_init(s, lock)		seqcount_LOCKNAME_init(s, lock, spinlock)
>>   #define seqcount_rwlock_init(s, lock)		seqcount_LOCKNAME_init(s, lock, rwlock)
>>   #define seqcount_mutex_init(s, lock)		seqcount_LOCKNAME_init(s, lock, mutex)
>> -#define seqcount_ww_mutex_init(s, lock)		seqcount_LOCKNAME_init(s, lock, ww_mutex)
>>   
>>   /*
>>    * SEQCOUNT_LOCKNAME()	- Instantiate seqcount_LOCKNAME_t and helpers
>> @@ -277,7 +275,6 @@ SEQCOUNT_LOCKNAME(raw_spinlock, raw_spinlock_t,  false,    s->lock,        raw_s
>>   SEQCOUNT_LOCKNAME(spinlock,     spinlock_t,      __SEQ_RT, s->lock,        spin,     spin_lock(s->lock))
>>   SEQCOUNT_LOCKNAME(rwlock,       rwlock_t,        __SEQ_RT, s->lock,        read,     read_lock(s->lock))
>>   SEQCOUNT_LOCKNAME(mutex,        struct mutex,    true,     s->lock,        mutex,    mutex_lock(s->lock))
>> -SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mutex, ww_mutex_lock(s->lock, NULL))
>>   
>>   /*
>>    * SEQCNT_LOCKNAME_ZERO - static initializer for seqcount_LOCKNAME_t
>> @@ -304,8 +301,7 @@ SEQCOUNT_LOCKNAME(ww_mutex,     struct ww_mutex, true,     &s->lock->base, ww_mu
>>   	__seqprop_case((s),	raw_spinlock,	prop),			\
>>   	__seqprop_case((s),	spinlock,	prop),			\
>>   	__seqprop_case((s),	rwlock,		prop),			\
>> -	__seqprop_case((s),	mutex,		prop),			\
>> -	__seqprop_case((s),	ww_mutex,	prop))
>> +	__seqprop_case((s),	mutex,		prop))
>>   
>>   #define seqprop_ptr(s)			__seqprop(s, ptr)
>>   #define seqprop_sequence(s)		__seqprop(s, sequence)
>> -- 
>> 2.25.1
>>