Horton

Re: Atomic operations within spinlocks

Tom Lane <tgl@sss.pgh.pa.us>

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From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
Cc: pgsql-hackers@lists.postgresql.org
Date: 2020-06-04T19:13:29Z
Lists: pgsql-hackers 
Andres Freund <andres@anarazel.de> writes:
> On 2020-06-04 14:50:40 -0400, Tom Lane wrote:
>> 2. The computed completePasses value would go backwards.  I bet
>> that wouldn't matter too much either, or at least we could teach
>> BgBufferSync to cope.  (I notice the comments therein suggest that
>> it is already designed to cope with completePasses wrapping around,
>> so maybe nothing needs to be done.)

> If we're not concerned about that, then we can remove the
> atomic-inside-spinlock, I think. The only reason for that right now is
> to avoid assuming a wrong pass number.

Hmm.  That might be a less-invasive path to a solution.  I can take
a look, if you don't want to.

			regards, tom lane

Commits

  1. Convert SpinLock* macros to static inline functions.

  2. Clean up includes of s_lock.h.

  3. Fix deadlock danger when atomic ops are done under spinlock.

  4. Add basic spinlock tests to regression tests.

  5. spinlock emulation: Fix bug when more than INT_MAX spinlocks are initialized.

  6. Avoid potential spinlock in a signal handler as part of global barriers.

  7. Make pg_stat_wal_receiver consistent with the WAL receiver's shmem info

  8. Improve 64bit atomics support.