Horton

Re: global barrier & atomics in signal handlers (Re: Atomic operations within spinlocks)

Robert Haas <robertmhaas@gmail.com>

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From: Robert Haas <robertmhaas@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2020-06-09T21:04:42Z
Lists: pgsql-hackers 
On Tue, Jun 9, 2020 at 3:37 PM Andres Freund <andres@anarazel.de> wrote:
> Hm. Looking at this again, perhaps the better fix would be to simply not
> look at the concrete values of the barrier inside the signal handler?
> E.g. we could have a new PROCSIG_GLOBAL_BARRIER, which just triggers
> ProcSignalBarrierPending to be set. And then have
> ProcessProcSignalBarrier do the check that's currently in
> CheckProcSignalBarrier()?

That seems like a good idea.

Also, I wonder if someone would be willing to set up a BF animal for this.

-- 
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company

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.