Re: Andres Freund 2014-05-19 <20140519141221.gc5...@alap3.anarazel.de> > On 2014-05-19 09:53:11 -0400, Tom Lane wrote: > > I think throwing an error out of a SIGBUS handler is right out. There > > would be no way to know exactly what code we were interrupting. It's > > the same reason we don't let, eg, the SIGALRM handler throw a timeout > > error directly (in most places anyway).
Right. I just mentioned that for completeness. > Agreed. I think if we really, really feel the need to do something about > this - which I don't - we could allocate a separate stack very early on > and use that. Hmm, that'd be an extension of the other idea, "write something deep in the stack on startup". This is probably less evil, though I agree it's a big hammer for solving something that should probably be fixed elsewhere. > > >> * PostgreSQL allocates lots of heap using brk() instead of mmap() > > > > > It doesn't really do that, btw. It's the libc's mmap that makes those > > > decisions, not postgres. > > > > It occurs to me that maybe this is a glibc bug, not a kernel bug? > > You think malloc() should try to be careful when calling brk() and check > beforehand wether it'll conflict with stack_base + RLIMIT_STACK? That's > not a bad argument, but it still seems a really bad choice to leave that > little space for the heap. Especially when it's dependant on -pie being > used. It's probably both, the default ASLR layout providing too little heap, plus malloc() running into the stack area - I'm not sure if the former is the kernel's fault or libc/ld.so's, probably they need to work together on that anyway. Disabling -pie for all 32bit archs seems to be the way to go for us now. Does this topic warrant being mentioned in the docs? Christoph -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
