On Thu, 2010-01-07 at 14:45 +0100, Joachim Wieland wrote: > On Thu, Dec 31, 2009 at 6:40 PM, Simon Riggs <si...@2ndquadrant.com> wrote: > >> Building racy infrastructure when it can be avoided with a little care > >> still seems not to be the best path to me. > > > > Doing that will add more complexity in an area that is hard to test > > effectively. I think the risk of introducing further bugs while trying > > to fix this rare condition is high. Right now the conflict processing > > needs more work and is often much less precise than this, so improving > > this aspect of it would not be a priority. I've added it to the TODO > > though. Thank you for your research. > > > > Patch implements recovery conflict signalling using SIGUSR1 > > multiplexing, then uses a SessionCancelPending mode similar to Joachim's > > TransactionCancelPending. > > I have reworked Simon's patch a bit and attach the result.
Oh dear, this is exactly what I've been working on... > Quick facts: > > - Hot Standby only uses SIGUSR1 > - SIGINT behaves as it did before: it only cancels running statements > - pg_cancel_backend() continues to use SIGINT > - I added pg_cancel_idle_transaction() to cancel an idle transaction via > SIGUSR1 > - One central function HandleCancelAction() sets the flags before calling > ProcessInterrupts(), it is called from the different signal handlers and > receives parameters about what it should do > - If a SIGUSR1 reason is used that will cancel something, ProcArrayLock is > acquired until the signal has been sent to make sure that we won't signal > the > wrong backend. Does this sufficiently cover the concerns of Andres Freund > discussed upthread? > > As there were so many boolean SomethingCancelPending variables I changed them > to be bitmasks and merged all of them into a single variable. However I am not > sure if we can change the name and type of especially InterruptPending that > easily as it was marked with PGDLLIMPORT... > > @Simon: Is there a reason why you have not yet removed recoveryConflictMode > from PGPROC? -- Simon Riggs www.2ndQuadrant.com -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
