Date: Mon, 6 Jul 2026 10:47:03 -0500
From: Nathan Bossart <nathandbossart@gmail.com>
To: Heikki Linnakangas <hlinnaka@iki.fi>
Cc: pgsql-hackers@postgresql.org
Subject: Re: remove unnecessary volatile qualifiers
Message-ID: <akvN90hUZV70554F@nathan>
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On Mon, Jul 06, 2026 at 02:58:12PM +0300, Heikki Linnakangas wrote:
> On 01/07/2026 00:47, Nathan Bossart wrote:
>> I looked into some of these earlier [0], but ended up leaving them alone at
>> the time.  Here is a new patch that removes all of the volatile markers in
>> the tree that seemed obviously unnecessary to me.
> 
> Thanks!

Thanks for reviewing.

>> --- a/src/backend/access/transam/clog.c
>> +++ b/src/backend/access/transam/clog.c
>> @@ -450,7 +450,7 @@ static bool
>>  TransactionGroupUpdateXidStatus(TransactionId xid, XidStatus status,
>>  								XLogRecPtr lsn, int64 pageno)
>>  {
>> -	volatile PROC_HDR *procglobal = ProcGlobal;
>> +	PROC_HDR   *procglobal = ProcGlobal;
>>  	PGPROC	   *proc = MyProc;
>>  	uint32		nextidx;
>>  	uint32		wakeidx;
> 
> You might want to get rid of the local variable altogether and just refer to
> ProcGlobal directly..

Done.

>> @@ -512,7 +512,7 @@ ProcessProcSignalBarrier(void)
>>  {
>>  	uint64		local_gen;
>>  	uint64		shared_gen;
>> -	volatile uint32 flags;
>> +	uint32		flags;
>>  	Assert(MyProcSignalSlot);
> 
> Are you sure about this one? 'flags' is used in the PG_TRY/CATCH block that
> follows. It is modified in the PG_TRY(), here:
> 
>> 
>> 				/*
>> 				 * To avoid an infinite loop, we must always unset the bit in
>> 				 * flags.
>> 				 */
>> 				BARRIER_CLEAR_BIT(flags, type);
> 
> and read later in the PG_CATCH() block.

Whoops.  You are right.  I reverted this part.

-- 
nathan

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