Re: Printing backtrace of postgres processes

Hi,

On Sat, Jan 16, 2021, at 09:34, vignesh C wrote:
> On Sat, Jan 16, 2021 at 1:40 AM Andres Freund <andres@anarazel.de> wrote:
> >
> > On 2021-01-15 09:53:05 +0100, Peter Eisentraut wrote:
> > > On 2020-12-08 10:38, vignesh C wrote:
> > > > I have implemented printing of backtrace based on handling it in
> > > > CHECK_FOR_INTERRUPTS. This patch also includes the change to allow
> > > > getting backtrace of any particular process based on the suggestions.
> > > > Attached patch has the implementation for the same.
> > > > Thoughts?
> > >
> > > Are we willing to use up a signal for this?
> >
> > Why is a full signal needed? Seems the procsignal infrastructure should
> > suffice?
> 
> Most of the processes have access to ProcSignal, for these processes
> printing of callstack signal was handled by using ProcSignal. Pgstat
> process & syslogger process do not have access to ProcSignal,
> multiplexing with SIGUSR1 is not possible for these processes. So I
> handled the printing of callstack for pgstat process & syslogger using
> the SIGUSR2 signal.
> This is because shared memory is detached before pgstat & syslogger
> process is started by using the below:
> /* Drop our connection to postmaster's shared memory, as well */
> dsm_detach_all();
> PGSharedMemoryDetach();

Sure. But why is it important enough to support those that we are willing to dedicate a signal to the task? Their backtraces aren't often interesting, so I think we should just ignore them here.

Andres