Horton

Re: [PATCH] Free memory allocated by waitonlock_error_callback()

Quan Zongliang <quanzongliang@yeah.net>

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From: Quan Zongliang <quanzongliang@yeah.net>
To: Aleksander Alekseev <aleksander@tigerdata.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Date: 2025-10-23T03:18:09Z
Lists: pgsql-hackers

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  1. Provide error context when an error is thrown within WaitOnLock().


On 9/19/25 7:16 PM, Aleksander Alekseev wrote:
> Hi,
> 
> Currently waitonlock_error_callback() allocates memory in ErrorContext
> and doesn't explicitly free it. Valgrind is not happy about it and
> generates multiple reports like this:
> 
> ```
> 2,048 bytes in 2 blocks are definitely lost in loss record 1,097 of 1,165
>     at 0x999539: palloc (mcxt.c:1389)
>     by 0x9DCBFD: initStringInfoInternal (stringinfo.c:45)
>     by 0x9DCC9D: initStringInfo (stringinfo.c:99)
>     by 0x73A807: waitonlock_error_callback (lock.c:2027)
>     by 0x94E1DE: errfinish (elog.c:510)
>     by 0x750394: ProcSleep (proc.c:1614)
>     by 0x73A720: WaitOnLock (lock.c:1979)
>     by 0x7391C2: LockAcquireExtended (lock.c:1221)
>     by 0x738360: LockAcquire (lock.c:814)
>     by 0x741064: VirtualXactLock (lock.c:4844)
>     by 0x3E9D93: WaitForOlderSnapshots (indexcmds.c:492)
>     by 0x3F155B: ReindexRelationConcurrently (indexcmds.c:4216)
> ```
> 
> I propose adding pfree().
> 
> waitonlock_error_callback() was added in:
> 
> ```
> commit f727b63e810724c7187f38b2580b2915bdbc3c9c
> Author: Tom Lane <tgl@sss.pgh.pa.us>
> Date:   Fri Aug 29 15:43:34 2025 -0400
> 
>      Provide error context when an error is thrown within WaitOnLock().
> ```
> 

LGTM

Improve the completeness of the code.