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  1. Fix ProcWakeup() resetting wrong waitStart field.

  1. Fix bug of clearing of waitStart in ProcWakeup()

    Chao Li <li.evan.chao@gmail.com> — 2026-02-24T06:28:15Z

    Hi,

I just noticed this while reviewing patch [1]. It looks like this is caused by a simple typo.

In ProcWakeup():
```
PGPROC *
ProcWakeup(PGPROC *proc, ProcWaitStatus waitStatus)
{
	PGPROC	   *retProc;

	/* Proc should be sleeping ... */
	if (proc->links.prev == NULL ||
		proc->links.next == NULL)
		return NULL;
	Assert(proc->waitStatus == PROC_WAIT_STATUS_WAITING);

	/* Save next process before we zap the list link */
	retProc = (PGPROC *) proc->links.next;

	/* Remove process from wait queue */
	SHMQueueDelete(&(proc->links));
	(proc->waitLock->waitProcs.size)--;

	/* Clean up process' state and pass it the ok/fail signal */
	proc->waitLock = NULL;
	proc->waitProcLock = NULL;
	proc->waitStatus = waitStatus;
	pg_atomic_write_u64(&MyProc->waitStart, 0); <== Here, it should operate on proc

	/* And awaken it */
	SetLatch(&proc->procLatch);

	return retProc;
}
```

Since this function is clearly operating on the parameter proc, the only statement that touches MyProc looks suspicious. It should reset proc->waitStart, not MyProc->waitStart.

As written, it will incorrectly clear the caller’s waitStart instead of the awakened backend’s, potentially leaving a stale waitStart value in the target PGPROC.

[1] https://postgr.es/m/CAHGQGwGw4LhNwOGQT3nbw3uWy8gL94_MB4T39Wfr4_Vgopuovg@mail.gmail.com

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/

  2. Re: Fix bug of clearing of waitStart in ProcWakeup()

    ji xu <thanksgreed@gmail.com> — 2026-02-24T07:31:06Z

    Chao Li <li.evan.chao@gmail.com> 于2026年2月24日周二 14:29写道：

> Hi,
>
> I just noticed this while reviewing patch [1]. It looks like this is
> caused by a simple typo.
>
> In ProcWakeup():
> ```
> PGPROC *
> ProcWakeup(PGPROC *proc, ProcWaitStatus waitStatus)
> {
>         PGPROC     *retProc;
>
>         /* Proc should be sleeping ... */
>         if (proc->links.prev == NULL ||
>                 proc->links.next == NULL)
>                 return NULL;
>         Assert(proc->waitStatus == PROC_WAIT_STATUS_WAITING);
>
>         /* Save next process before we zap the list link */
>         retProc = (PGPROC *) proc->links.next;
>
>         /* Remove process from wait queue */
>         SHMQueueDelete(&(proc->links));
>         (proc->waitLock->waitProcs.size)--;
>
>         /* Clean up process' state and pass it the ok/fail signal */
>         proc->waitLock = NULL;
>         proc->waitProcLock = NULL;
>         proc->waitStatus = waitStatus;
>         pg_atomic_write_u64(&MyProc->waitStart, 0); <== Here, it should
> operate on proc
>
>         /* And awaken it */
>         SetLatch(&proc->procLatch);
>
>         return retProc;
> }
> ```
>
> Since this function is clearly operating on the parameter proc, the only
> statement that touches MyProc looks suspicious. It should reset
> proc->waitStart, not MyProc->waitStart.
>
> As written, it will incorrectly clear the caller’s waitStart instead of
> the awakened backend’s, potentially leaving a stale waitStart value in the
> target PGPROC.
>
> [1]
> https://postgr.es/m/CAHGQGwGw4LhNwOGQT3nbw3uWy8gL94_MB4T39Wfr4_Vgopuovg@mail.gmail.com
>
> Best regards,
> --
> Chao Li (Evan)
> HighGo Software Co., Ltd.
> https://www.highgo.com/
>
>
>
>
>
>
>
Hi ,

The fix looks correct to me. I applied it locally and build and "make
check" passed from my side.

Regards,
ji xu

  3. Re: Fix bug of clearing of waitStart in ProcWakeup()

    Fujii Masao <masao.fujii@gmail.com> — 2026-02-24T15:41:03Z

    On Tue, Feb 24, 2026 at 4:31 PM ji xu <thanksgreed@gmail.com> wrote:
>
>
> Chao Li <li.evan.chao@gmail.com> 于2026年2月24日周二 14:29写道：
>>
>> Since this function is clearly operating on the parameter proc, the only statement that touches MyProc looks suspicious. It should reset proc->waitStart, not MyProc->waitStart.
>>
>> As written, it will incorrectly clear the caller’s waitStart instead of the awakened backend’s, potentially leaving a stale waitStart value in the target PGPROC.

Thanks for the report!

You’re right. This leaves proc->waitStart unreset for a backend that has
woken up from a lock wait. In practice this doesn't seem to cause
user-visible issues, since pg_locks.waitstart is reported as NULL
when pg_locks.granted is true, regardless of proc->waitStart.

That said, the behavior is incorrect, so I'm feeling inclined to backpatch
a fix. Thoughts?


> The fix looks correct to me. I applied it locally and build and "make check" passed from my side.

Sounds good to me.

Regards,

-- 
Fujii Masao

  4. Re: Fix bug of clearing of waitStart in ProcWakeup()

    Álvaro Herrera <alvherre@kurilemu.de> — 2026-02-24T16:12:41Z

    On 2026-Feb-24, ji xu wrote:

> Chao Li <li.evan.chao@gmail.com> 于2026年2月24日周二 14:29写道：
> 
> > ```
> > PGPROC *
> > ProcWakeup(PGPROC *proc, ProcWaitStatus waitStatus)
> > {

> >         pg_atomic_write_u64(&MyProc->waitStart, 0); <== Here, it should
> > operate on proc

I agree that this looks wrong.  AFAICS it comes from 46d6e5f56790.

-- 
Álvaro Herrera               48°01'N 7°57'E  —  https://www.EnterpriseDB.com/
[…] indem ich in meinem Leben oft an euch gedacht, euch glücklich zu machen. Seyd es!
A menudo he pensado en vosotros, en haceros felices. ¡Sedlo, pues!
		Heiligenstädter Testament, L. v. Beethoven, 1802
		https://de.wikisource.org/wiki/Heiligenstädter_Testament

  5. Re: Fix bug of clearing of waitStart in ProcWakeup()

    Fujii Masao <masao.fujii@gmail.com> — 2026-02-24T16:37:13Z

    On Wed, Feb 25, 2026 at 1:12 AM Álvaro Herrera <alvherre@kurilemu.de> wrote:
>
> On 2026-Feb-24, ji xu wrote:
>
> > Chao Li <li.evan.chao@gmail.com> 于2026年2月24日周二 14:29写道：
> >
> > > ```
> > > PGPROC *
> > > ProcWakeup(PGPROC *proc, ProcWaitStatus waitStatus)
> > > {
>
> > >         pg_atomic_write_u64(&MyProc->waitStart, 0); <== Here, it should
> > > operate on proc
>
> I agree that this looks wrong.  AFAICS it comes from 46d6e5f56790.

Yes, it's my mistake...

For the record, patch attached.

Regards,

-- 
Fujii Masao

  6. Re: Fix bug of clearing of waitStart in ProcWakeup()

    Chao Li <li.evan.chao@gmail.com> — 2026-02-24T22:03:14Z

    
> On Feb 24, 2026, at 23:41, Fujii Masao <masao.fujii@gmail.com> wrote:
> 
> On Tue, Feb 24, 2026 at 4:31 PM ji xu <thanksgreed@gmail.com> wrote:
>> 
>> 
>> Chao Li <li.evan.chao@gmail.com> 于2026年2月24日周二 14:29写道：
>>> 
>>> Since this function is clearly operating on the parameter proc, the only statement that touches MyProc looks suspicious. It should reset proc->waitStart, not MyProc->waitStart.
>>> 
>>> As written, it will incorrectly clear the caller’s waitStart instead of the awakened backend’s, potentially leaving a stale waitStart value in the target PGPROC.
> 
> Thanks for the report!
> 

I just realized that I forgot to attach the patch file. Anyway, that’s just a one-line change.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/

  7. Re: Fix bug of clearing of waitStart in ProcWakeup()

    Fujii Masao <masao.fujii@gmail.com> — 2026-02-26T00:08:58Z

    On Wed, Feb 25, 2026 at 7:03 AM Chao Li <li.evan.chao@gmail.com> wrote:
>
>
>
> > On Feb 24, 2026, at 23:41, Fujii Masao <masao.fujii@gmail.com> wrote:
> >
> > On Tue, Feb 24, 2026 at 4:31 PM ji xu <thanksgreed@gmail.com> wrote:
> >>
> >>
> >> Chao Li <li.evan.chao@gmail.com> 于2026年2月24日周二 14:29写道：
> >>>
> >>> Since this function is clearly operating on the parameter proc, the only statement that touches MyProc looks suspicious. It should reset proc->waitStart, not MyProc->waitStart.
> >>>
> >>> As written, it will incorrectly clear the caller’s waitStart instead of the awakened backend’s, potentially leaving a stale waitStart value in the target PGPROC.
> >
> > Thanks for the report!
> >
>
> I just realized that I forgot to attach the patch file. Anyway, that’s just a one-line change.

I've pushed the patch. Thanks!

Regards,

-- 
Fujii Masao

  8. Re: Fix bug of clearing of waitStart in ProcWakeup()

    Chao Li <li.evan.chao@gmail.com> — 2026-02-26T01:04:01Z

    
> On Feb 26, 2026, at 08:08, Fujii Masao <masao.fujii@gmail.com> wrote:
> 
> On Wed, Feb 25, 2026 at 7:03 AM Chao Li <li.evan.chao@gmail.com> wrote:
>> 
>> 
>> 
>>> On Feb 24, 2026, at 23:41, Fujii Masao <masao.fujii@gmail.com> wrote:
>>> 
>>> On Tue, Feb 24, 2026 at 4:31 PM ji xu <thanksgreed@gmail.com> wrote:
>>>> 
>>>> 
>>>> Chao Li <li.evan.chao@gmail.com> 于2026年2月24日周二 14:29写道：
>>>>> 
>>>>> Since this function is clearly operating on the parameter proc, the only statement that touches MyProc looks suspicious. It should reset proc->waitStart, not MyProc->waitStart.
>>>>> 
>>>>> As written, it will incorrectly clear the caller’s waitStart instead of the awakened backend’s, potentially leaving a stale waitStart value in the target PGPROC.
>>> 
>>> Thanks for the report!
>>> 
>> 
>> I just realized that I forgot to attach the patch file. Anyway, that’s just a one-line change.
> 
> I've pushed the patch. Thanks!
> 
> Regards,
> 
> -- 
> Fujii Masao

Hi Fujii-san, thank you very much for taking care of this patch.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/