Re: ipc-daemon

Jason Tishler writes:

> 1. If ipc-daemon is not running, then cygipc's shmget() will return
> EACCES.
> 2. This causes PostgreSQL's InternalIpcMemoryCreate() to return
> NULL.
> 3. This causes PostgreSQL's PGSharedMemoryCreate() to spin looking
> for accessible shared memory which it will never find.

To me, this is a bug in PostgreSQL. A comment in
InternalIpcMemoryCreate() says

* Fail quietly if error indicates a collision with existing
* segment. One would expect EEXIST, given that we said IPC_EXCL,
* but perhaps we could get a permission violation instead?

I tend to think that the answer to that question is No.

> After reading the shmget() man page, I choose to return ENOSPC. Is
> there a better choice? Such as ENOMEM?

My first thought was ENOSYS (system call not implemented -- what BSD
kernels tend to return if you didn't compile them with SysV IPC support),
but that isn't a clearly superior choice either. Fixing PostgreSQL is
probably better and quicker to yield a return.

--
Peter Eisentraut peter_e(at)gmx(dot)net