Re: An example of bugs for Hot Standby - Mailing list pgsql-hackers

On Wed, 2010-01-20 at 11:04 +0100, Andres Freund wrote:
> On Wednesday 20 January 2010 10:52:24 Simon Riggs wrote:
> > On Wed, 2010-01-20 at 10:45 +0100, Andres Freund wrote:
> > > LWLockAcquire
> > 
> > I'm using spinlocks, not lwlocks.
> CancelDBBackends which is used in SendRecoveryConflictWithBufferPin which in 
> turn used by CheckStandbyTimeout triggered by SIGALRM acquires the lwlock.

Those are used in similar ways to deadlock detection.

> Now that case is a bit less dangerous because you would have to interrupt 
> yourself to trigger a deadlock there because the code sleeps soon after 
> setting up the handler.
> If ever two SIGALRM occur consecutive there is a problem. 

I'll protect against subsequent calls.

-- Simon Riggs           www.2ndQuadrant.com