Horton

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

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Robert Haas <robertmhaas@gmail.com>
Cc: PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Tom Lane <tgl@sss.pgh.pa.us>
Date: 2020-06-11T17:31:28Z
Lists: pgsql-hackers 
Hi,

On 2020-06-10 13:37:59 -0400, Robert Haas wrote:
> On Tue, Jun 9, 2020 at 6:54 PM Andres Freund <andres@anarazel.de> wrote:
> > What do you think about my idea of having a BEGIN/END_SIGNAL_HANDLER?
> > That'd make it much easier to write assertions forbidding palloc, 64bit
> > atomics, ...
> 
> I must have missed the previous place where you suggested this, but I
> think it's a good idea.

https://www.postgresql.org/message-id/20200606023103.avzrctgv7476xj7i%40alap3.anarazel.de

It'd be neat if we could do that entirely within pqsignal(). But that'd
require some additional state (I think an array of handlers, indexed by
signum).

Greetings,

Andres Freund

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.