Re: the s_lock_stuck on perform_spin_delay

Hi,

v6 attached which addressed all the items Robert suggested except the
following 2 open items. They are handled differently.

>
> Here is the summary of the open-items, it would be great that Andres and
> Matthias have a look at this when they have time.
>
>>> The LockBufHdr also used init_local_spin_delay / perform_spin_delay
>>> infrastruce and then it has the same issue like ${subject}, it is pretty
>>> like the code in s_lock; Based on my current knowledge, I think we
>>> should add the check there.
>>
>> I'd like to hear from Andres, if possible. @Andres: Should these
>> sanity checks apply only to spin locks per se, or also to buffer
>> header locks?

v6 is splitted into 2 commits, one for normal SpinLock and one for
LockBufHdr lock.

commit 6276d2f66b0760053e3fdfe259971be3abba3c63
Author: yizhi.fzh <yizhi(dot)fzh(at)alibaba-inc(dot)com>
Date: Fri Jan 19 13:52:07 2024 +0800

Detect more misuse of spin lock automatically

Spin lock are intended for *very* short-term locks, but it is possible
to be misused in many cases. e.g. Acquiring another LWLocks or regular
locks, memory allocation, errstart when holding a spin lock. this patch
would detect such misuse automatically in a USE_ASSERT_CHECKING build.

CHECK_FOR_INTERRUPTS should be avoided as well when holding a spin lock.
Depends on what signals are left to handle, PG may raise error/fatal
which would cause the code jump to some other places which is hardly to
release the spin lock anyway.

commit 590a0c6f767f62f6c83289d55de99973bc7da417 (HEAD -> s_stuck_v3)
Author: yizhi.fzh <yizhi(dot)fzh(at)alibaba-inc(dot)com>
Date: Fri Jan 19 13:57:46 2024 +0800

Treat (un)LockBufHdr as a SpinLock.

The LockBufHdr also used init_local_spin_delay / perform_spin_delay
infrastructure and so it is also possible that PANIC the system
when it can't be acquired in a short time, and its code is pretty
similar with s_lock. so treat it same as SPIN lock when regarding to
misuse of spinlock detection.

>>> they were put into spin.h in v1 but later move to miscadmin.h at [1].
>>> [1]
>>> https://www.postgresql.org/message-id/CAEze2WggP-2Dhocmdhp-LxBzic%3DMXRgGA_tmv1G_9n-PDt2MQg%40mail.gmail.com
>>
>> I'm not entirely sure what the right thing to do is here, and the
>> answer may depend on the previous question. But I disagree with
>> Matthias -- I don't think miscadmin.h can be the right answer
>> regardless.

I put it into spin.h this time in commit 1, and include the extern
function VerifyNoSpinLocksHeld in spin.c into miscadmin.h like what we
did for ProcessInterrupts. This will easy the miscadmin dependency. the
changes for '#include xxx' looks better than before.

--
Best Regards
Andy Fan